Co-reporter:Chao Li, Yaqin Tao, Yi Yang, Yang Xiang, and Genxi Li
Analytical Chemistry May 2, 2017 Volume 89(Issue 9) pp:5003-5003
Publication Date(Web):April 3, 2017
DOI:10.1021/acs.analchem.7b00329
The interaction between protein and DNA elements controls a variety of functions of genomes. The development of a convenient and cost-effective method for investigating the sequence specificity of DNA-binding proteins represents an important challenge. In response, we have introduced an electrochemical assay in this work for specific and sensitive analysis of interaction between protein and nucleic acid in nucleic extracts, based on the protein-induced distinctive motion behavior of DNA deoxyribozyme (DNAzyme) on an electrode surface. As a proof of principle, we have also presented assays for the rapid, sensitive, and selective detection of three transcription factors (NF-κB, SP6 RNA polymerase, and HNF-4α), as well as the analysis of binding affinity of the mutated protein-binding sequence, and even screening of the binding sequence of HNF-4α protein in vitro. This work may open new opportunity for in-depth profiling of the sequence specificity of DNA-binding proteins and study of nucleotide polymorphisms in known protein-binding sites.
Co-reporter:Chang Feng, Xiaoxia Mao, Hai Shi, Bing Bo, Xiaoxia Chen, Tianshu Chen, Xiaoli Zhu, and Genxi Li
Analytical Chemistry June 20, 2017 Volume 89(Issue 12) pp:6631-6631
Publication Date(Web):May 29, 2017
DOI:10.1021/acs.analchem.7b00850
Laborious and costly detection of miRNAs has brought challenges to its practical applications, especially for home health care, rigorous military medicine, and the third world. In this work, we present a pH-responsive miRNA amplification method, which allows the detection of miRNA just using a pH test paper. The operation is easy and no other costly instrument is involved, making the method very friendly. In our strategy, a highly efficient isothermal amplification of miRNA is achieved using an improved netlike rolling circle amplification (NRCA) technique. Large amounts of H+ can be produced as a byproduct during the amplification to induce significant changes of pH, which can be monitored directly using a pH test paper or pH-sensitive indicators. The degree of color changes depends on the amount of miRNA, making it possible for quantitative analysis. As an example, the method is successfully applied to quantify a miRNA (miR-21) in cancer cells. The results agree well with that from the prevalent qRT-PCR analysis. It is the first time that a paper-based point-of-care testing (POCT) is developed for the detection of miRNAs, which might promote the popularization of miRNAs working as biomarkers for diagnostic purposes.
Co-reporter:Juan Zhang, Xiaonan Wang, Tingjun Chen, Chang Feng, and Genxi Li
Analytical Chemistry December 19, 2017 Volume 89(Issue 24) pp:13245-13245
Publication Date(Web):November 22, 2017
DOI:10.1021/acs.analchem.7b03197
In this work, a new strategy for electrochemical analysis of enzyme has been proposed based on a self-assembled lipid bilayer on an electrode surface mediated by hydrazone chemistry. Taking aldolase as an example, the enzyme can catalyze the formation of products containing carbonyl groups. These groups can react with hydrazine groups of the functional lipid derivative, resulting in the self-assembly of a lipid bilayer on a guanidinium modified electrode surface. The lipid bilayer will then prevent the movement of hydrophilic electrochemical probes. Consequently, the catalytic reaction of the enzyme may result in the change of the obtained electrochemical peak current. Experimental results reveal that aldolase activity can be analyzed over a widely linear detection range from 5 mU/L to 100 U/L with a low detection limit of 1 mU/L. Meanwhile, the method can exhibit good precision and reproducibility and it can be applied for real sample analysis. What is more, because the lipid bilayer is the universal basis for cell-membrane structure, while hydrazone chemistry is popular in nature, this work may also provide a new insight for the development of electrochemical analysis and electrochemical biosensors.
Co-reporter:Xiaoli Zhu, Yaoyao Chen, Chang Feng, Wei Wang, Bing Bo, Ruixin Ren, and Genxi Li
Analytical Chemistry April 4, 2017 Volume 89(Issue 7) pp:4131-4131
Publication Date(Web):February 28, 2017
DOI:10.1021/acs.analchem.6b05177
Passivation of electrode surface and tedious reconstruction of biosensing architectures have long plagued researchers for the development of electrochemical biosensors. Here, we report a novel self-cleaning electrode by modifying the commonly used working electrode with superhydrophobic and conductive nanocomposite. Owing to the superhydrophobicity and the chemical stability, the electrode avoids passivation result from both adsorption of molecules and oxidation in air. The high conductivity and the high effective area also allow the achievement of enhanced electrochemical signals. On the basis of comprehensive studies on this novel electrode, we have applied it in the fabrication of refreshable electrochemical biosensors for both electro-active and electro-inactive targets. For both cases, detection of the targets can be well performed, and the self-cleaning electrode can be refreshed by simply washing and applied for successive measurements in a long period.
Co-reporter:Tao Gao, Shiyu Gu, Chaoli Mu, Meiling Zhang, Jie Yang, Ping Liu, Genxi Li
Electrochimica Acta 2017 Volume 252(Volume 252) pp:
Publication Date(Web):20 October 2017
DOI:10.1016/j.electacta.2017.08.190
Lipid phosphorylation plays central regulatory roles in diverse fundamental cellular processes. However, there are still many challenges remained to investigate these effector enzymes, lipid kinase. So we report a simple, sensitive and effective electrochemical method assisted by liposome that can provide biomimetic membrane environment. In this work, the liposome is designed to not only provide favorable catalytic environment for the assay of lipid kinase, but also act as a carrier of abundant signal molecules to enhance the electrochemical signal. So, the problems involved in lipid kinase assay can be addressed, and very high sensitivity of the assay is ensured owing to the enrichment of signal molecules (methylene blue, MB). Compared with the currently-used methods, this new method avoids complex treatments of lipid substrats/products, thus fewer steps of the assay procedure are required. In this work, a vital lipid kinase, sphingosine kinase 1 (SphK1), has been selected as the assay target. Facilitated by liposome-based electrochemical signal amplification, a relative wide detection range from 10 pmol min−1 mg−1 to 12 nmol min−1 mg−1 and a low limit of detection (LOD) down to 2.33 pmol min−1 mg−1 have been achieved. This method can be effectively utilized for SphK1 detection, and further employments may also hold great promise for the analysis of other lipid kinases and even lipid metabolites in the future.A liposome-based electrochemical biosensor has been first proposed for lipid kinase activity, which ensures simplicity, sensitivity and efficiency.Download high-res image (119KB)Download full-size image
Co-reporter:Xiaonan Wang, Ying Liu, Juan Zhang, Genxi Li
Sensors and Actuators B: Chemical 2017 Volume 242() pp:687-693
Publication Date(Web):April 2017
DOI:10.1016/j.snb.2016.11.099
•A new strategy has been introduced for the fabrication of electrochemical biosensor.•The strategy is based on the covalent capturing of molecules on electrode interface through oxime chemistry.•Guanidinium recognization contributes to the excellent performance of the electrochemical biosensor.•The strategy has been applied for the detection of aldolase activity.•The established biosensor may be extended to other substances with chemoselective groups.A new strategy to fabricate electrochemical biosensor is proposed based on the covalent capturing of molecules on electrode interface through oxime chemistry and the loading of signal probes via guanidinium-phosphate electronic interaction with a “covalent-like” stability. Taking aldolase as an example, enzyme analysis can be achieved through the covalent loading of the catalyzed products on the aminooxy modified gold electrode surface and subsequent immobilization of guanidinium functionalized sliver nanoparticles. Different from adolase substrate, the hydrolyzed products contain both carbonyl groups and phosphate acid groups in their structures. The carbonyl groups can chemoselectively react with aminoxy groups on the electrode surface to form oxime, resulting in the exposure of phosphate groups. Subsequently, signal probe can be loaded onto electrode surface through guanidinium recognition, giving a electrochemical current value. So the number of enzyme catalyzed products determines the amount of signal probes on the electrode surface, and aldolase activity can be analyzed. For the proposed method, the chemoselective oxime ligation and highly stable guanidinium recognition improve the accuracy, selectivity and stability of enzyme analysis. The established method may be extended to the analysis of other related substances containing carbonyl groups.
Co-reporter:Jinlong Li, Tao Gao, Shiyu Gu, Jun Zhi, Jie Yang, Genxi Li
Biosensors and Bioelectronics 2017 Volume 87() pp:352-357
Publication Date(Web):15 January 2017
DOI:10.1016/j.bios.2016.08.071
•A novel electrochemical method for AFP-L3detection is developed.•Multifunctional silver nanoprobes have been synthesized.•Simple and sensitive detection of AFP-L3 can be achieved.•AFP-L3 is detected effectively in complex serum samples.•This method may have potential applications in clinical practice.The detection of alpha-fetoprotein-L3 (AFP-L3) is of great importance for hepatocellular carcinoma (HCC) diagnosis, but remains unsatisfactory owing to poor sensitivity and complex operating steps. In this work, a simple and sensitive method has been proposed for the detection of AFP-L3. Firstly, biotinylated Lens culinaris agglutinin-integrated silver nanoparticles (B-LCA-AgNPs) is fabricated. Owing to the specific interaction between Lens culinaris agglutinin and AFP-L3, AFP-L3 can be detected directly through the electrochemical signal readout of AgNPs, avoiding separated steps used in clinical practice. Furthermore, after the recognition between B-LCA-AgNPs and AFP-L3, large amount of AgNPs can be gathered at the binding site through avidin-biotin interactions, which can amplify the signal. Therefore, detection of AFP-L3 can be sensitively achieved. Moreover, compared with the other approaches, this new method has a better linear correlation (25–15,000 pg/mL) and a lower detection limit (12 pg/mL). Also, the new method developed in this work has been demonstrated to have good stability and reproducibility for the assay of AFP-L3 in human serum samples, so, it may hold a great application prospect in clinical diagnostics.
Co-reporter:Xiaolu Hu;Chao Li;Chang Feng;Xiaoxia Mao;Yang Xiang
Chemical Communications 2017 vol. 53(Issue 34) pp:4692-4694
Publication Date(Web):2017/04/25
DOI:10.1039/C7CC00687J
A simple colorimetric assay is developed for the sensitive and selective detection of an antibody, which combines a protein binding-induced signaling approach with a novel DNAzyme-based conformational switching strategy.
Co-reporter:Xiaoli Zhu;Xiaoxia Chen;Fangfang Ban;Ya Cao;Jing Zhao;Guifang Chen
Chemical Communications 2017 vol. 53(Issue 76) pp:10504-10507
Publication Date(Web):2017/09/21
DOI:10.1039/C7CC05174C
We report a novel mechanical wave-like DNA nanomachine. A successive stem-loop structure is involved, which will rearrange successively from one side to the opposite side upon binding with an input activator just like the motion of a mechanical wave, and thereby achieving diverse functions.
Co-reporter:Xiaoli Zhu;Xiaoxia Mao;Zihan Wang;Chang Feng;Guifang Chen
Nano Research 2017 Volume 10( Issue 3) pp:959-970
Publication Date(Web):2017 March
DOI:10.1007/s12274-016-1354-9
Nanozymes have received great attention owing to the advantages of easy preparation and low cost. Unlike natural enzymes that readily adapt to physiological environments, artificial nanozymes are apt to passivate in complex clinical samples (e.g., serum), which may damage the catalytic capability and consequently limit the application in biomedical analysis. To conquer this problem, in this study, we fabricated novel nanozyme@DNA hydrogel architecture by incorporating nanozymes into a pure DNA hydrogel. Gold nanoparticles (AuNPs) were adopted as a model nanozyme. Results indicate that AuNPs incorporated in the DNA hydrogel retain their catalytic capability in serum as they are protected by the hydrogel, whereas AuNPs alone totally lose the catalytic capability in serum. The detection of hydrogen peroxide and glucose in serum based on the catalysis of the AuNPs@DNA hydrogel was achieved. The detection limit of each reaches 1.7 and 38 μM, respectively, which is equal to the value obtained using natural enzymes. Besides the mechanisms, some other advantages, such as recyclability and availability, have also been explored. This nanozyme@DNA hydrogel architecture may have a great potential for the utilization of nanozymes as well as the application of nanozymes for biomedical analysis in complex physiological samples.
Co-reporter:Chao Li, Yucai Yang, Dan Wu, Tianqi Li, Yongmei Yin and Genxi Li
Chemical Science 2016 vol. 7(Issue 5) pp:3011-3016
Publication Date(Web):2016/02/03
DOI:10.1039/C5SC04256A
An enzyme-linked immunosorbent assay that is dependent on enzyme amplification has dominated the current field of protein detection; however, limited multiple detection ability and susceptible enzymatic reactions, and low sensitivity may severely hinder its application. Here, we report a new signal amplification scheme based on allochroic molecule modified carboxyl graphene oxide (cGO), which can be used to develop a multicolor immunoassay named as allochroic-cGO linked immunosorbent assay (ALISA). Thanks to high adsorption levels and a wide selection of allochroic molecules, the simultaneous colorimetric detection of diagnostic biomarkers at a picogram level can be successfully achieved for the first time. In addition, the color change triggered by acidic or basic water can provide a simple, rapid, stable and economical signal output, further meeting the growing biodetection requirements. Moreover, with the help of ALISA, we demonstrate that the combined detection of three tumor biomarkers, including carcino-embryonic antigen, neuron-specific enolase, and cytokeratin-19 fragment, is more valuable for differentiating lung cancer patients than the detection of a single biomarker, further manifesting the superiority of ALISA. All in all, this straightforward approach not only opens up new prospects for multicolor immunoassays, but also has great potential for applications in resource-constrained settings.
Co-reporter:Chao Li, Jiehua Ma, Qiongxuan Fan, Yaqin Tao and Genxi Li
Chemical Communications 2016 vol. 52(Issue 50) pp:7850-7853
Publication Date(Web):24 May 2016
DOI:10.1039/C6CC02633H
A novel dynamic light scattering (DLS)-based immunoassay that utilizes manganese dioxide nanosheet-modified gold nanoparticles (MnO2–GNPs) as an activatable nanoprobe has been developed to detect tumor markers down to femtomolar levels.
Co-reporter:Luming Wei, Xiaoying Wang, Dan Wu, Chao Li, Yongmei Yin and Genxi Li
Chemical Communications 2016 vol. 52(Issue 32) pp:5633-5636
Publication Date(Web):18 Mar 2016
DOI:10.1039/C6CC00205F
A novel colourimetric method for protein assays is proposed based on proximity ligation induced assembly of Mg2+-dependent DNAzymes, which may offer simple, cost-effective, sensitive and selective detection of the target protein.
Co-reporter:Hao Li, Yue Huang, Yue Yu, Genxi Li, and Yannis Karamanos
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 4) pp:2833
Publication Date(Web):January 11, 2016
DOI:10.1021/acsami.5b11567
In this work, a new strategy of biosensor design is developed based on the assembly of amyloid beta and its multiple interactions with other bioactive species. These interactions can enable amyloid beta peptide as a multifunctional sensing element, so the immobilization of sensing probe and the step-by-step modification of the sensing interface have all been dispensed with. Instead, the kinetics of the assembly of a peptide-based catalytic network serves to convert the quantity of analyte into amplified signal readout. The designed dynamic assembling and biosensing system has also been successfully applied in detecting the activity of polyglutamylation, an essential post translation modification controlling cell skeleton and cell cycle, in biological complex samples. Further studies reveal that the serum abundance of a polyglutamylase, tubulin tyrosine ligase-like protein 12, may show parallel with the degree of development of prostate cancer and the discrimination between early cancerous development and benign conditions. And the obtained result is more distinct than that based on PSA detection, the current gold standard. This study may also point to the prospective of extending this design strategy to broader range of biosensing applications in the future.Keywords: amyloid-beta peptide; catalytically self-propagating assembly; nanozyme; peptide self-assembly; peptide-based biosensing;
Co-reporter:Yue Huang, Hao Li, Lei Wang, Xiaoxia Mao, and Genxi Li
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 41) pp:28202
Publication Date(Web):September 29, 2016
DOI:10.1021/acsami.6b09270
In this work, we have successfully designed a smart and flexible signal amplification method based on a newly synthesized hybrid nanocomposite with switchable enzyme activity for specific and sensitive protein detection. The smart hybrid nanocomposite synthesized here is initially loaded with quenched fluorophore and a unique aptamer-inhibited DNA polymerase. It then undergoes target protein-triggered release of the fluorophore and activation of the DNA polymerase, which can thereby promote multiple catalytic reactions and recycled use of the target protein, resulting in the generation of highly amplified signals. Therefore, a small amount of target protein can lead to a large amount of signal without being consumed. In addition, the programmable control of DNA polymerase activity may effectively reduce background signal and avoid false positive results, which may further facilitate an efficient detection of small amounts of protein. By taking the detection of human stress-induced phosphoprotein 1 (STIP1) as an example, the excellent performance of this method has been verified. Furthermore, the proposed method has been used to analyze serum STIP1 from patients of ovarian cancer, showing promising application in clinical practice.Keywords: clinical application; hybrid nanocomposite; signal amplification; STIP1; switchable enzyme activity
Co-reporter:Tao Gao, Liudi Li, Bei Wang, Jun Zhi, Yang Xiang, and Genxi Li
Analytical Chemistry 2016 Volume 88(Issue 20) pp:9996
Publication Date(Web):September 16, 2016
DOI:10.1021/acs.analchem.6b02156
Artificial control of cell adhesion on smart surface is an on-demand technique in areas ranging from tissue engineering, stem cell differentiation, to the design of cell-based diagnostic system. In this paper, we report an electrochemical system for dynamic control of cell catch-and-release, which is based on the redox-controlled host–guest interaction. Experimental results reveal that the interaction between guest molecule (ferrocene, Fc) and host molecule (β-cyclodextrin, β-CD) is highly sensitive to electrochemical stimulus. By applying a reduction voltage, the uncharged Fc can bind to β-CD that is immobilized at the electrode surface. Otherwise, it is disassociated from the surface as a result of electrochemical oxidation, thus releasing the captured cells. The catch-and-release process on this voltage-responsive surface is noninvasive with the cell viability over 86%. Moreover, because Fc can act as an electrochemical probe for signal readout, the integration of this property has further extended the ability of this system to cell detection. Electrochemical signal has been greatly enhanced for cell detection by introducing branched polymer scaffold that are carrying large quantities of Fc moieties. Therefore, a minimum of 10 cells can be analyzed. It is anticipated that such redox-controlled system can be an important tool in biological and biomedical research, especially for electrochemical stimulated tissue engineering and cell-based clinical diagnosis.
Co-reporter:Chao Li, Dan Wu, Xiaolu Hu, Yang Xiang, Yongqian Shu, and Genxi Li
Analytical Chemistry 2016 Volume 88(Issue 15) pp:7583
Publication Date(Web):July 4, 2016
DOI:10.1021/acs.analchem.6b01250
Electrochemistry-based nucleic acid sensors have long been plagued by the limited accessibility of target molecules to the capture probes immobilized on heterogeneous surfaces, which largely hinders their practical application. In this work, we find that dual-thiolated hairpin DNA immobilized on an electrode surface as the capture probe cannot only efficiently bind with target molecule as well as the signal probe but also process impressive protein-repelling ability, which allows us to directly detect as few as attomolar targets (∼300 copies in 100 μL sample) with single-base discrimination ability. Meanwhile, the preparation of functional electrode surface becomes simple (one step), fast (30 min), and homogeneous (just one probe modified surface without small molecules coassembled). These advantages are attributed to the unique probe design, where the stem of the capture probe can act as rigid scaffold to keep it upright, and the loop of the capture probe may provide an enclosed platform for target and signal probe binding. More importantly, through tuning the distance between enzyme and the electrode surface (from 8.5 to 13.6 nm), we find that the performance of the sensor can be favorably controlled. Furthermore, taking advantage of this new binding model, different complex samples including polymerase chain reaction (PCR) product, mRNA, and micro RNA can be conveniently analyzed, which may hold great potential for real application.
Co-reporter:Yue Yu, Hao Li, Luming Wei, Liudi Li, Yitao Ding, and Genxi Li
Analytical Chemistry 2016 Volume 88(Issue 7) pp:3879
Publication Date(Web):March 4, 2016
DOI:10.1021/acs.analchem.6b00037
Pro-metastatic cell signaling controls the switch to distant metastasis and the final cancer death. In hepatocellular carcinoma (HCC), this death switch is turned on by the multiprotein interactions of β-catenin with many transcription factors, so a method to assay the bioactivity of β-catenin to participate in these pro-metastatic protein/protein interactions has been proposed in this work. This method employs cost-effective peptide-based protein targeting ligands, while the electrochemical catalytic cross-linking in this method also “finalize” the noncovalent molecular recognition, so that the robustness can be improved to enable detection of relatively more complex biosamples. In studying clinical samples with the proposed method, the cellular distribution and overall expression of β-catenin show a parallel with the pathological grade of the sample, particularly, nuclear translocation. The pro-metastatic activation of β-catenin can also be observed as evidently correlated with higher-grade cases, suggesting the active role of β-catenin in promoting metastasis. According to these results, the proposed method may have the prospective use as a prognostic tool for evaluating the potential of invasion and metastasis in cancer.
Co-reporter:Hao Li, Weiwei Li, Fengzhen Liu, Zhaoxia Wang, Genxi Li, and Yannis Karamanos
Analytical Chemistry 2016 Volume 88(Issue 7) pp:3662
Publication Date(Web):March 3, 2016
DOI:10.1021/acs.analchem.5b04423
Inspired by the structural and functional features of proteins in cell signaling, a switchable peptide is designed in this work. This switchable peptide is named a “peptamer,” and it can react to ligand binding with conformational change and activation/deactivation of catalytic ability. The peptamer is constructed by elaborately integrating several different peptide motifs with targeting and catalytic abilities. Thus, targeted binding of the peptamer to an integrin can be regulated by a synthetic ligand. Moreover, the conformational rearrangement of the peptamer induced by both integrin and the synthetic ligand can resolve in altered affinity of the peptamer for a catalytic cofactor, cupric ion. This leads to greatly contrasted efficiency of catalysis in the presence/absence of integrin. This distinct switching on/off of catalytic activity also enables a bioassay of tissue integrin expression in clinical samples of thyroid carcinoma. Experimental results reveal that the detected integrin level parallels the state of lymph node metastasis. Therefore, this simple peptide model may help to understand the structural reconfiguration of proteins involved in cellular signal transduction, as well as to provide a new means to assess protein activity under pathological conditions such as cancer.
Co-reporter:Weiwei Li, Hao Li, Shuai Wu, Chang Feng, Genxi Li
Electrochemistry Communications 2016 Volume 71() pp:84-88
Publication Date(Web):October 2016
DOI:10.1016/j.elecom.2016.08.011
•DNAzyme circular cleavage of substrate on the electrode•DNAzyme cleavage induced exposure of artificial DNA phosphate end.•Zirconia nanoparticles with phosphate group affinity as signal carrierIn this work, a new method for the sensitive detection of proteins has been developed by combining the highly efficient DNAzyme cycling processing of DNA with nanoparticles which have an affinity for DNA. Specifically, DNAzymes are designed to be activated after recognition between the target protein and its aptamer, pre-hybridized with a DNAzyme sequence. In the meantime, DNAzyme substrates are pre-modified on an electrode surface so as to expose their 5′ phosphate end to conjugate with zirconia nanoparticles (ZrNPs), which have strong phosphoric affinity. The nanoparticles are also decorated with a large amount of signal molecule, peptide GHK. Consequently, a greatly amplified electrochemical signal can be achieved for the assay of the target protein. In addition to high sensitivity and simplicity, this strategy is also versatile, because it can easily be adapted to assay a large spectrum of targets simply by changing the sequence of the aptamer. Thus it holds great potential for the development of ultrasensitive biosensors in clinical bioanalysis.
Co-reporter:Dan Wu, Tao Gao, Lin Lei, Dawei Yang, Xiaoxia Mao, Genxi Li
Analytica Chimica Acta 2016 Volume 942() pp:68-73
Publication Date(Web):26 October 2016
DOI:10.1016/j.aca.2016.09.010
•A colorimetric strategy for protein detection has been developed.•The detection relies on recognition between VEGF and its aptamer leading to the activation the DNAzyme.•The proposed method is not only simple, efficient but also convenient to be operated.•The principle of this proposed new method can be extended as a universal assay method.The detection of protein is vital to fundamental research as well as practical applications. However, most detection methods depend on antibody-based assays which are faced with many shortcomings. Herein, we propose a colorimetric method for protein assays based on target-triggered activation of aptazyme, which may offer simple, rapid and cost-effective detection of the target protein. In this method, the conformation change of aptazyme induced by target protein is designed to be associated with aptazyme activation. Consequently, in the presence of the target protein, the designed DNA linkers will be cleaved into two fragments that fail to cross-link gold nanoparticles (GNPs), thus the color of GNP solution remains red, while the color will be changed in the absence of the target. Because of the advantages of aptazyme such as economic synthesis, stable, easy modification and its ability to accomplish signal recognition and signal amplification simultaneously, the method is thermostable, simple and cost-efficient. In this work, we have taken the detection of vascular endothelial growth factor (VEGF) as an example, which can present an analytical performance with as low as 0.1 nM detection limit, spanning a detection range of 3 orders of magnitude. What is more, the principle of this proposed new method can be extended as a universal assay method not only for the detection of analytes which have an aptamer but also for those analytes that have ligands.
Co-reporter:Dan Wu, Chao Li, Xiaolu Hu, Xiaoxia Mao, Genxi Li
Analytica Chimica Acta 2016 Volume 924() pp:29-34
Publication Date(Web):14 June 2016
DOI:10.1016/j.aca.2016.04.013
•A novel electrochemical strategy for DNA 3´-phosphatases detection has been developed.•The detection relies on TdT mediated signal amplification.•The proposed method is not only simple, sensitive but also convenient to be operated.•The sensing system provides a detection limit of T4PNKP as low as 1 mU mL−1Determination of DNA dephosphorylation is of great value due to its vital role in many cellular processes. Here we report a surface-extended DNA nanotail strategy for simple and ultrasensitive detection of DNA 3′-phosphatases by terminal deoxynucleotidyl transferase (TdT) mediated signal amplification. In this work, DNA probes labeled with thiols at their 5′ terminals and phosphoryls at 3′ terminals are immobilized on gold electrode and are used as substrates for DNA 3′-phosphatases, taking T4 polynucleotide kinase phosphatase (T4PNKP) as an example. T4PNKP can catalyze the dephosphorylation reaction of the substrate DNA, followed by the formation of a long DNA strand by TdT on its 3′ terminal hydroxyl, leading to an evident chronocoulometry signal enhancement. The proposal presents a considerable analytical performance with low detection limit and wide linear range, making it promise to be applied in the fields of DNA dephosphorylation related processes, drug discovery, and clinical diagnostics.
Co-reporter:Tao Gao, Shiyu Gu, Fengzhen Liu, Liudi Li, Zhaoxia Wang, Jie Yang, Genxi Li
Analytica Chimica Acta 2016 Volume 905() pp:66-71
Publication Date(Web):28 January 2016
DOI:10.1016/j.aca.2015.12.011
•Mismatch-based DNA chain elongation strategy (MB-DCE) is firstly proposed.•MutT Homolog 1 (MTH1) is critical important for biomedical cancer research.•An electrochemical method is developed for MTH1 activity based on MB-DCE.•This method can reveal MTH1 activity in normal and breast cancer cell lines.Accumulation and misincorporation of oxidative damaged 8-oxo-7,8-dihydroguanine triphosphates (8-oxo-dGTP) in genomic DNA may cause serious cellular function disorders. MutT Homolog 1 (MTH1), a protein enzyme that can help to prevent 8-oxo-dGTP misincorporation, plays critical roles in oxidative stress neutralization, oncogene-associated tumor malignancy, and anticancer therapies. So, in this work, a simple and function-oriented method is developed for the assay of MTH1 activity. Specifically, a mismatch-based (“8-oxoG: A” mismatch) DNA chain elongation strategy (MB-DCE) is firstly proposed to reveal the misincorporation efficiency of 8-oxo-dGTP. Then, further coupled with the inherent activity of MTH1 to prevent 8-oxo-dGTP misincorporation, a relationship can be established to reveal the activity of MTH1 through MB-DCE. As the method is designed directly towards the cellular function of MTH1, activity of MTH1 in different breast cancer cell lines has been detected, implying the potential application of this assay method for biomedical research and clinical diagnose in the future.
Co-reporter:Chang Feng, Xiaoxia Mao, Yucai Yang, Xiaoli Zhu, Yongmei Yin, Genxi Li
Journal of Electroanalytical Chemistry 2016 Volume 781() pp:223-232
Publication Date(Web):15 November 2016
DOI:10.1016/j.jelechem.2016.07.008
•Amplified electrochemical signals are vital for biomedical applications.•Rolling circle amplification (RCA) is a favorable signal amplification approach.•RCA provides a feasible and versatile platform for electrochemical biosensors.Signal amplification is vital in biosensor fabrication, especially for the sensitive analysis of target molecules. Rolling circle amplification (RCA) is an isothermal nucleic acid amplification technique. In a typical RCA process, a short DNA or RNA primer is extended under the catalysis of a polymerase to form a long single stranded DNA or RNA using a circular DNA template. In recent years, various approaches have been proposed to improve the RCA technique, so this nucleic acid amplification technique has become an attractive tool for biosensor fabrication, especially for the development of electrochemical biosensors with biomedical applications. Owing to the accumulation of RCA products on electrode surface, the electrochemical signal can be greatly amplified after an elaborated design so as to improve the detection sensitivity. Therefore, a variety of biomolecular targets such as genes, microRNAs, proteins, with ultra-low abundance have been successfully detected using the developed RCA-based electrochemical biosensors. In this review, we will summarize the improvement of the RCA technique and its application for the development of electrochemical biosensors with biomedical applications. We will also comment on the recent progress of RCA-based electrochemical biosensors, making an outlook on the trends of the related research fields in the future.
Co-reporter:Yue Huang, Hao Li, Qiongxuan Fan, Lei Wang, Yao Wang, Genxi Li
Biosensors and Bioelectronics 2016 Volume 83() pp:85-90
Publication Date(Web):15 September 2016
DOI:10.1016/j.bios.2016.04.045
•A novel electrochemical method for TGM2 assay is developed.•The nanocatalyst synthesized here is multifunctional.•Simple and sensitive detection of TGM2 can be achieved.•TGM2 is detected effectively in complex serum samples.•This method may have potential applications in clinical diagnosis of HCC.Tissue transglutaminase 2 (TGM2) is a novel tumor marker, which can be used as the complementary marker for alpha-fetoprotein to improve overall diagnostic performance of hepatocellular carcinoma at the clinical level. In this work, we have developed a multifunctional nanocatalyst-based electrochemical method for TGM2 assay with an ultrahigh sensitivity. Here we firstly functionalize carboxyl-modified graphene oxide with poly-lysine and copper ion to form an electrochemical nanocatalyst. On the one hand, the nanocatalyst can function as the substrate of TGM2. On the other, the nanocatalyst can be applied for signal amplification to enable high sensitivity of the detection. With the specific glutamine-donor-peptide of TGM2 modified on the electrode, the exertion of the transamidation activity by TGM2 can lead to the tethering of the nanocatalyst with the peptide on the electrode, inducing obvious changes of the electrochemical signals. Therefore, simple and sensitive detection of TGM2 can be achieved. Moreover, TGM2 is also detected effectively in complex serum samples, suggesting potential diagnostic applications of the new method proposed in this work.
Co-reporter:Qiongxuan Fan, Chao Li, Yaqin Tao, Xiaoxia Mao, Genxi Li
Talanta 2016 Volume 160() pp:144-147
Publication Date(Web):1 November 2016
DOI:10.1016/j.talanta.2016.07.009
•An electrochemical method is developed for screening the G-quadruplex ligands.•This method is simple and fast, which may have great application.•The inhibited electron transfer is due to the formation of G-quadruplex by ligand.Small molecules that may facilitate and stabilize the formation of G-quadruplexes can be used for cancer treatments, because the G-quadruplex structure can inhibit the activity of telomerase, an enzyme over-expressed in many cancer cells. Therefore, there is considerable interest in developing a simple and high-performance method for screening small molecules binding to G-quadruplex. Here, we have designed a simple electrochemical approach to screen such ligands based on the fact that the formation and stabilization of G-quadruplex by ligand may inhibit electron transfer of redox species to electrode surface. As a proof-of-concept study, two types of classical G-quadruplex ligands, TMPyP4 and BRACO-19, are studied in this work, which demonstrates that this method is fast and robust and it may be applied to screen G-quadruplex ligands for anticancer drugs testing and design in the future.
Co-reporter:Juan Zhang;Yangyang Chen;Defeng Li;Ya Cao;Zhaoxia Wang
Microchimica Acta 2016 Volume 183( Issue 2) pp:659-665
Publication Date(Web):2016 February
DOI:10.1007/s00604-015-1687-1
The article describes the preparation of gold nanoparticles functionalized with resveratrol (Res-AuNPs) in a single step and by integrating synthesis and modification. By using Res-AuNPs, we have established a colorimetric method for the determination of fibrillar islet amyloid polypeptides (IAPP) and its inhibitors. It is based on the specific recognition of resveratrol by IAPP fibrils. This results in a decrease in the concentration of Res-AuNPs in the supernatant and a corresponding reduction in absorbance at 537 nm. This finding was exploited to design a simple and sensitive colorimetric assay for IAPP fibrils. The analytical range extends from 30 to 400 μM, and the limit of detection is as low as 1.2 μM. In addition, the inhibitory effects of caffeic acid and caffein on the formation of fibrillar IAPP were evaluated. The method is simple and effective, and therefore is perceived to represent a promising scheme for determination of fibrillar IAPPs and their inhibitors.
Co-reporter:Chao Li, Xiaoxi Li, Luming Wei, Muyun Liu, Yangyang Chen and Genxi Li
Chemical Science 2015 vol. 6(Issue 7) pp:4311-4317
Publication Date(Web):05 May 2015
DOI:10.1039/C5SC00891C
Various strategies have been proposed for the detection of disease protein biomarkers; however, most methods are too expensive, cumbersome or limited in sensitivity for clinical use. Here, we report that a fabricated complex can be used as a powerful tool to detect trace proteins in complex samples. In this strategy, a DNA–protein complex that comprises of one target molecule and two or more deoxyribozyme-containing probes can exhibit autonomous cleavage behavior on the surface of the substrate DNA modified electrode. In the meantime, the complex can remove the cleaved DNA fragment from the electrode surface by taking advantage of the proximity effect. The proposed approach allows one-step and highly sensitive detection of a variety of targets based on the changes of the direct electrochemical readout. Moreover, this method may also have considerable advantages over the commonly reported DNA amplification-assisted immunoassays, particularly in terms of assay simplicity and cost, which may hold great potential for application in resource-constrained regions.
Co-reporter:Yue Huang, Hao Li, Yuanyuan Zhang, Weiwei Li, Lizhou Sun and Genxi Li
Chemical Communications 2015 vol. 51(Issue 55) pp:11004-11007
Publication Date(Web):26 May 2015
DOI:10.1039/C5CC03700J
This communication reports a novel strategy for the detection of proteins based on the integration of three signal amplification reactions via sharing a specially designed DNA sequence. This strategy has been demonstrated by the assay of human TNF-α in the serum of ovarian cancer patients, showing potential clinical applications.
Co-reporter:Xiaoli Zhu, Yalan Shen, Jiepei Cao, Li Yin, Fangfang Ban, Yongqian Shu and Genxi Li
Chemical Communications 2015 vol. 51(Issue 49) pp:10002-10005
Publication Date(Web):01 May 2015
DOI:10.1039/C5CC02039E
Here we report a reduced graphene oxide-assisted rolling circle amplification for the detection of miRNA SNPs. The difference of the signal of a miRNA SNP reaches 100 fold, a value over 10 times larger than some current methodologies, which allows the discrimination of a SNP even with the naked eye.
Co-reporter:Xiaoli Zhu, Bin Zhang, Zonghuang Ye, Hai Shi, Yalan Shen and Genxi Li
Chemical Communications 2015 vol. 51(Issue 4) pp:640-643
Publication Date(Web):05 Nov 2014
DOI:10.1039/C4CC07990F
Here, we report a graphene oxide–aptamer–nanochannel architecture for the fabrication of a novel stimuli-responsive gate. The gate is switched OFF in the absence of ATP, and is switched ON when ATP is present. The concept we proposed may contribute to a versatile platform for the development of stimuli-responsive gates.
Co-reporter:Yue Yu, Hao Li, Bin Zhang, Xiaoshu Pan, Xiaoli Zhu, Yitao Ding, and Genxi Li
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 7) pp:4401
Publication Date(Web):January 28, 2015
DOI:10.1021/am5089378
In this work, a surface-confined peptide network that can exhibit distinct structural features under protease cleavage and electrochemical treatment is developed as a highly sensitive biosensor for clinical detection of kallikrein 6 (KLK6). KLK6 is a serine protease of the tissue-remodeling process determining the development of hepatocellular carcinoma (HCC). The peptide network, immobilized on the electrode surface by a Au–S bond, loses its integrity upon KLK6 cleavage and is removed from the electrode by electrochemical desorption of thiol groups, while the network without protease cleavage can remain attached by a few intact Au–S bonds. In this manner, distinct conductivity of the electrode surface in the presence/absence of protease can result in a large signal-to-background ratio, enabling KLK6 detection in clinical samples. The detected KLK6 abundance can manifest the correlation between up-regulated KLK6 activity and the progress of HCC. These results suggest a potential future use of this peptide network as a biosensor to provide diagnostic information for better administration of HCC.Keywords: electrochemical detection; extracellular matrix; hepatocellular carcinoma; kallikrein 6; peptide network
Co-reporter:Tao Gao, Fengzhen Liu, Dawei Yang, Yue Yu, Zhaoxia Wang, and Genxi Li
Analytical Chemistry 2015 Volume 87(Issue 11) pp:5683
Publication Date(Web):April 30, 2015
DOI:10.1021/acs.analchem.5b00816
In nature, cellular molecule sensing is usually achieved at the environment/membrane interface. In the meantime, rapid growth of nanotechnology is increasingly pushing engineered nanomaterials to interact with biological surfaces. Herein, inspired by trans-membrane signal transduction, a nano–bio interface has been constructed in this work for biosensing application. The interface is formed between a selective biomembrane mimetic surface (SBMMS) and a function-oriented 2D nanohybrid. Based on the design, target recognition can be performed in a biologically favorable environment, and the nano–bio interaction can be transduced into amplified electrochemical readouts. Furthermore, this sensing platform can be used to analyze various kinds of targets, including proteins, nucleic acids, and small molecules, just by changing the biorecognition element. Low detection limits and wide detection ranges can also be obtained. So, this nano–bio interface may provide a new platform for bioanalytical research in the future.
Co-reporter:Hao Li, Yue Huang, Yue Yu, Weiwei Li, Yongmei Yin, and Genxi Li
Analytical Chemistry 2015 Volume 87(Issue 18) pp:9251
Publication Date(Web):August 24, 2015
DOI:10.1021/acs.analchem.5b01750
Detection of metastatic activity before the onset of the actual metastasis can be a promising method to combat metastasis, the foremost cause of death in cancer. Therefore, in this work, we have developed an assay method for the detection of metastatic tumor cells in primary tumor, by using a protein of the metastatic cell signaling as the biomarker. In this assay, a peptide-based probe targeting the marker protein and a sensitive nanoparticle doped graphene nanolabel are combined to enable the detection of metastatic cells. Consequently, the metastatic cells can be specifically detected and discriminated from primary tumor cells. By applying this assay method to clinical samples of primary tumor, a low amount of metastatic activity can be detected in the tumor sites, which may suggest the activity of local metastatic transformation. So, these results may point to the prospect of using the proposed method for controlling metastatic cancer.
Co-reporter:Yuanyuan Zhang, Hao Li, Yue Huang, Tingting Yin, Lizhou Sun, Genxi Li
Analytica Chimica Acta 2015 Volume 882() pp:27-31
Publication Date(Web):2 July 2015
DOI:10.1016/j.aca.2015.05.006
•A new assay for direct serum detection of protein or hormone markers is developed.•PNA-coupled DNA cycling reactions with dual amplification is adopted.•The sensing system provides a detection limit of insulin as low as 1 pM.•The assay of blood sample can discriminate GDM patients from the normal ones.Serum level of disease markers may provide important guidance for diagnosis and prognosis. In this work, a sensitive and specific method suitable for direct serum detection of biomarkers is developed based on peptide nucleic acid (PNA)-coupled DNA cycling reactions with dual amplification. In this method, PNA released from a target-triggered homogeneous DNA cycling is employed to initiate an interface DNA cycling, and both of the cycling reactions are based on polymerase-assisted strand displacement reaction. Consequently, two PNA-coupled DNA cycling steps can take place simultaneously in one-pot, leading to greatly enhanced limit of detection and simplified operation. This method has also been successfully applied for evaluating serum insulin in pregnant women as an indicator of gestational diabetes mellitus. So the application of this method in real bio-samples may allow it to hold considerable potential in clinical practice. In addition, since there is no requirement for specific sequence of aptamer, the strategy proposed can be extended for the detection of many other protein markers and peptide-hormones in the future.
Co-reporter:Dawei Yang, Liming Ning, Tao Gao, Zonghuang Ye, Genxi Li
Electrochemistry Communications 2015 Volume 58() pp:33-36
Publication Date(Web):September 2015
DOI:10.1016/j.elecom.2015.06.001
•An electrochemical method has been developed for ultra-sensitive protein detection.•The assay can realize low detection limit through the dual amplification strategy.•The assay is relatively simple and cheap due to the enzyme-free process.•Excellent performance in serum sample shows high selectivity of this method.In this work, we present an enzyme-free electrochemical assay method that can detect target protein with ultra-high sensitivity through dual amplification. Firstly, target protein is specifically captured by its aptamer, and then is released due to toehold-mediated click chemical ligation (the first round of recycling) via DNA strand displacement reaction. Secondly, the overhang of aptamer on the electrode surface can hybridize with RP DNA and trigger hybridization chain reaction (the second round of recycling). Consequently, large amount of electrochemical species hexaammineruthenium (III) chloride ([Ru(NH3)6]3 +) can be embedded into double-stranded DNA to produce a remarkable electrochemical signal, thus the target protein can be quantified with ultra-high sensitivity. Taken thrombin as a model analyte, a wide linear dynamic range from 100 fM to 10 nM and a detection limit of 30 fM (S/N = 3) can be obtained. Meanwhile, since no enzyme is required for the measurement, the assay is relatively simple and inexpensive. Therefore, the protein assay method proposed in this work may have a great potential for clinical diagnosis and biomedical research in the future.
Co-reporter:Juan Zhang, Jun Lv, Xiaonan Wang, Defeng Li, Zhaoxia Wang and Genxi Li
Analyst 2015 vol. 140(Issue 16) pp:5716-5723
Publication Date(Web):24 Jun 2015
DOI:10.1039/C5AN00970G
Inhibitors of protein tyrosine phosphatase 1B (PTP1B) are promising agents for the treatment of type 2 diabetes and obesity, so a colorimetric method has been developed in this work for PTP1B assay and screening of its inhibitors. The method is based on the chelation effect of zirconium (Zr4+) ions on the phosphate group, which may induce aggregation of 4-aminophenylphosphate-functionalized gold nanoparticles (APP/AuNPs) and the corresponding color change of the testing solution. Owing to the dephosphorylation of PTP1B, the aggregation of AuNPs will be influenced by PTP1B since there is no coordination reactivity between Zr4+ ions and 4-aminophenol, the hydrolyzed product of APP catalyzed by the enzyme. Therefore, a simple colorimetric method for the assay of PTP1B activity can be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 650 nm to that at 522 nm vary linearly with the PTP1B activity in the range from 0.005 to 0.18 U mL−1 with the lowest detection limit of 0.0017 U mL−1. Moreover, using this proposed method, the inhibition effect of 6-chloro-3-formyl-7-methylchromone, betulinic acid, ursolic acid, and sodium orthovanadate on PTP1B activity can be tested with IC50 values of 10, 13, 9, and 1.1 μM, respectively. Therefore, this new method has great potential not only for the detection of PTP1B activity but also for the screening of the inhibitors.
Co-reporter:Xiaoli Zhu, Chang Feng, Bin Zhang, Hui Tong, Tao Gao and Genxi Li
Analyst 2015 vol. 140(Issue 1) pp:74-78
Publication Date(Web):04 Nov 2014
DOI:10.1039/C4AN01711K
A nucleic acid amplification technique termed as netlike rolling circle amplification is proposed by introducing a nicking enzyme into the existing hyperbranched rolling circle amplification system. Surprisingly dense and uniform network morphology is observed; and cubic amplification is achieved for the sensitive detection of a sequence from HIV.
Co-reporter:Jing Zhao, Suisui Hu, Ya Cao, Bin Zhang, Genxi Li
Biosensors and Bioelectronics 2015 Volume 66() pp:327-331
Publication Date(Web):15 April 2015
DOI:10.1016/j.bios.2014.11.039
•Terminal protection can protect probe DNA from Exo I-catalyzed degradation.•Probe DNA can trigger hybridization chain reaction on the electrode surface.•CuNPs can be formed by using long duplex DNA oligomers from HCR as template.•The method can sensitively detect FR by electrochemical characterization of CuNPs.In this paper, we report an electrochemical method for highly sensitive and specific detection of protein based on hybridization chain reaction (HCR)-assisted formation of copper nanoparticles by using small molecule such as folate-linked DNA as probe. In the presence of target protein, taking folate receptor (FR) as the model protein in this study, its binding with folate can protect the probe DNA from exonuclease I-catalyzed degradation, thus the probe DNA can be immobilized onto the electrode surface through the hybridization with capture DNA, triggering HCR on the electrode surface. Subsequently, copper nanoparticles can be formed on the electrode surface by using long duplex DNA oligomers from HCR as templates. Furthermore, copper ions released from acid-dissolution of copper nanoparticles can catalyze the oxidation of ο-phenylenediamine by dissolved oxygen, leading to significant electrochemical responses. As a result, our method can sensitively detect FR in the linear range from 0.01 ng/mL to 100 ng/mL with a detection limit of 3 pg/mL. It can also specifically distinguish the target protein in both buffer and complex serum samples. Since many other proteins can be assayed by changing the corresponding small molecule, this method may be promising for the development of the technique for protein detections.
Co-reporter:Juan Zhang;Jun Lv;Xiaonan Wang;Defeng Li;Zhaoxia Wang
Nano Research 2015 Volume 8( Issue 12) pp:3853-3863
Publication Date(Web):2015 December
DOI:10.1007/s12274-015-0885-9
Here we developed a saccharic colorimetric method based on the combination of chemoselective ligation and enzyme-specific catalysis using aminooxy/hydrazine-functionalized gold nanoparticles (AO/AuNPs or H/AuNPs). In the detection of galactose (Gal), galactohexodialdose (GHDA), the galactose oxidase (GalOx)-catalyzed product, has an aldehyde group, which allows it to chemoselectively react with an aminooxy or hydrazine group at the outer layer of AO/AuNPs or H/AuNPs by oxime/hydrazone click chemistry to form oxime or hydrozone. Consequently, through the specific recognition of 1,4-phenylenediboronic acid (PDBA) on cis-diols, GHDA, which contains two pairs of hydroxyls in the cis form, can bind not only with AO/AuNPs or H/AuNPs, but also with PDBA to form boronate diester, thereby triggering the aggregation of AuNPs and causing the corresponding color change. As GalOx catalyzed specific substrates, the amount of Gal correlated with the production of GHDA and the extent of AuNPs aggregation, thus allowing a simple and easily operatable colorimetric method for Gal detection to be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 617 nm to that at 536 nm vary linearly with the logarithmic values of Gal concentrations within a wide range of 500 nM to 5 mM. Moreover, this colorimetric method shows anti-interference capability and high sensitivity with a detection limit of 21 nM. Thus, a universal platform for accurate and specific colorimetric analysis can be established through the integration of chemoselective ligation with enzyme specific catalysis.
Co-reporter:Luming Wei, Xiaoying Wang, Chao Li, Xiaoxi Li, Yongmei Yin, Genxi Li
Biosensors and Bioelectronics 2015 Volume 71() pp:348-352
Publication Date(Web):15 September 2015
DOI:10.1016/j.bios.2015.04.072
•A new colorimetric assay using peptides as recognition elements has been firstly developed.•The assay method offer not only easy handing but also considerable sensitivity and selectivity for protein detection.•This study may provide new insight for transducing protein–peptide interaction to colorimetric signal and might be of potential for further clinical applications.•The approach may have universal applicability.•Take full advantage of the properties of both CB[8] and peptide modified GNPs.Small peptide can be used as an effective biological recognition element and provide an alternative tool for protein detection. However, the development of peptide-based detecting strategy still remains elusive due to the difficulty of signal transduction. Herein, we report a peptide-based colorimetric strategy for the detection of disease biomarker by using vascular endothelial growth factor receptor 1 (Flt-1) as an example. In this strategy, N-terminal aromatic residue-containing peptide modified gold nanoparticles (GNPs) can form bulky aggregate by the introduction of cucurbit[8]uril (CB[8]) that can selectively accommodate two N-terminal aromatic residue of peptides simultaneously regardless of their sequences. However, in the presence of Flt-1, the peptide can specifically bind to the protein molecule and the N-terminal aromatic residue will be occupied, resulting in little aggregation of GNPs. By taking advantage of the highly affinitive peptide and efficiency cross-linking effect of CB[8] to GNPs, colorimetric assay for protein detection can be achieved with a detection limit of 0.2 nM, which is comparable with traditional methods. The feasibility of our method has also been demonstrated in spiked serum sample, indicating potential application in the future.
Co-reporter:Juan Zhang;Ying Liu;Jun Lv
Nano Research 2015 Volume 8( Issue 3) pp:920-930
Publication Date(Web):2015 March
DOI:10.1007/s12274-014-0573-1
A colorimetric method has been established for α-glucosidase activity assay and its inhibitor screening. The method is based on the specific recognition between 1,4-phenylenediboronic acid (PDBA) and 4-aminophenyl-α-d-glucopyranoside (pAPG), which may induce aggregation of pAPG-functionalized gold nanoparticles (AuNPs) to achieve color change of the test solution. Because pAPG is the substrate of α-glucosidase, the aggregation of AuNPs will be influenced by α-glucosidase since there is no coordination reactivity between PDBA and 4-aminobenzene, the hydrolyzed product of pAPG catalyzed by the enzyme. Therefore, a simple and easily-operated colorimetric method for the assay of α-glucosidase activity can be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 650 nm to that at 520 nm vary linearly with the α-glucosidase activity within a range from 0.05 to 1.1 U/mL with a lowest detection limit of 0.004 U/mL. Moreover, using the proposed method, the inhibition effect of gallic acid and quercetin on α-glucosidase activity can be tested with IC50 values of 1.16 mM and 1.82 μM, respectively. Thus, the method has a great potential not only for the detection of α-glucosidase activity, but also for the screening of its inhibitors.
Co-reporter:Juan Zhang, Ying Liu, Xiaonan Wang, Yangyang Chen, Genxi Li
Biosensors and Bioelectronics 2015 Volume 74() pp:666-672
Publication Date(Web):15 December 2015
DOI:10.1016/j.bios.2015.07.023
•An electrochemical method is established for α-glucosidase and the inhibitors.•The method can be directly used in cell medium.•Competitive coordination of AgNPs/DA and MNPs/pAPG with PBA/GE is utilized.•The method may be extended to other proteases and their inhibitors as well.An electrochemical method is established in this work for the assay of α-glucosidase activity and the inhibitor screening through one-step displacement reaction, which can be directly used in cell medium. The displacement reaction can be achieved via strong binding of 4-aminophenyl-α-d-glucopyranoside (pAPG)/magnetic nanoparticles (MNPs) to pyrene boric acid (PBA) immobilized on the surface of graphite electrode (GE), compared to that of dopamine (DA)/sliver nanoparticles (AgNPs). Since α-glucosidase can specifically catalyze MNPs/pAPG into MNPs/pAP which has no binding capacity with PBA, the activity of both isolated and membrane bound enzyme can be well evaluated by using this proposed method. Meanwhile, signal amplification can be accomplished via the immobilization of DA at the outer layer of AgNPs, and the accuracy can be strengthened through magnetic separation. Moreover, this method can also be utilized for inhibitor screening not only in the medium containing the enzyme but also in cell medium. With good precision and accuracy, it may be extended to other proteases and their inhibitors as well.
Co-reporter:Limin Ning, Dawei Yang, Tao Gao, Shan Lu, Yongmei Yin, Genxi Li
Talanta 2015 Volume 143() pp:414-418
Publication Date(Web):1 October 2015
DOI:10.1016/j.talanta.2015.05.016
•A new method to evaluate trinucleotide length polymorphism has been developed.•The method is based on the secondary structure with doxorubicin as fluorescent probe.•With doxorubicin as fluorescent probe, the method introduces no fluorophores and quenchers.Trinucleotide repeats (TNRs) are involved in a number of debilitating diseases and disorders, the length of which usually indicates disease severity at gene level. Herein we have developed a novel fluorescent method in this work to evaluate TNRs length polymorphism based on its DNA secondary structure with doxorubicin (Dox) as fluorescent probe. This new method makes use of the fact that TNRs rich in guanine (G) and cytosine (C) are susceptible to forming stable intramolecular structures, resulting in the formation of double-stranded 5’-GC-3’ or 5’-CG-3’ sequences. So, intercalating of these sequences by Dox, fluorescence quenching of Dox occurs. Consequently, the length polymorphism of TNRs can be evaluated. Taking the study of CAG for an example, a linear relationship between fluorescence intensity and the sequences ranging from 10 to 35 CAG repeats has been obtained, and the assay of the TNRs length polymorphism for PCR products has been realized. Therefore, without the necessity to introduce fluorophores and quenchers by chemical modifications, this new method is simple, cost-effective and convenient to be operated, so it may hold great promise in the diagnosis of diseases arouse from the triplet expansion.
Co-reporter:Tao Gao, Dawei Yang, Limin Ning, Lin Lei, Zonghuang Ye and Genxi Li
Nanoscale 2014 vol. 6(Issue 24) pp:14828-14835
Publication Date(Web):29 Sep 2014
DOI:10.1039/C4NR04283B
The strong coupling of inorganic nanocrystals with 2D nanosheets to produce function-enhanced nano-materials with uniform size, dispersion, and high coverage density has long been of interest to scientists from various research fields. Here, a simple and effective method has been described to fabricate ultrafine and well dispersed silver nanocrystals (AgNCs) on graphene oxide (GO), based on a facial-induced co-reduction strategy. The synthesized nanohybrid has shown uniform and well dispersed AgNCs (2.9 ± 1.4 nm), individually separated GO sheets, as well as highly covered surface (5250 nanocrystals per square micrometer), indicating the formation of a high-quality GO-based nanohybrid. Moreover, this material shows excellent catalytic activity for oxygen reduction reactions (ORRs) and exhibits enhanced signal readout for molecular sensing, demonstrating the potential application of this newly synthesized inorganic hybrid with strong synergistic coupling effects on advanced functional systems.
Co-reporter:Haona Xie, Hao Li, Yue Huang, Xiaoying Wang, Yongmei Yin, and Genxi Li
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 1) pp:459
Publication Date(Web):December 12, 2013
DOI:10.1021/am404506g
In this work, a novel method for a protein assay is proposed which uses the specific protein-binding peptide of the target protein and sequence-specific DNA to interact with the target as the capture and detection probe, respectively. Meanwhile, since the DNA sequence can be coupled with gold nanoparticles to amplify the signal readout, a sensitive and easily operated method for protein assay is developed. We have also employed a transcription factor named as cysteine-rich intestinal protein 1 (CRIP1), which has been identified as an ideal biomarker for staging of breast cancer, as the model protein for this study. With the proposed method, CRIP1 can be determined in a linear range from 1.25 to 10.13 ng/mL, with a detection limit of 1.25 ng/mL. Furthermore, the proposed method can be directly used to assay CRIP1 in tissue samples. Owing to its desirable sensitivity, excellent reproducibility, and high selectivity, the proposed method may hold great potential in clinical practice in the future.Keywords: breast cancer; cyclic peptide; cysteine-rich intestinal protein 1; electrochemistry; gold nanoparticles;
Co-reporter:Yucai Yang, Chao Li, Li Yin, Muyun Liu, Zhaoxia Wang, Yongqian Shu, and Genxi Li
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 10) pp:7579
Publication Date(Web):April 15, 2014
DOI:10.1021/am500912m
Rational utilization of nanomaterials to construct electrochemical nucleic acid sensors has attracted large attention in recent years. In this work, we systematically interrogate the interaction between gold nanoparticles (GNPs) and single-strand DNA (ssDNA) immobilized on an electrode surface and then take advantage of the ultrahigh charge-transfer efficiency of GNPs to develop a novel DNA sensing method. Specifically, ssDNA modified gold electrode can adsorb GNPs because of the interaction between gold and nitrogen-containing bases; thus, the negative electrochemical species [Fe(CN)6]3–/4– may transfer electrons to electrode through adsorbed GNPs. In the presence of target DNA, the formed double-strand DNA (dsDNA) cannot capture GNPs onto the electrode surface and the dsDNA may result in a large charge-transfer resistance owing to the negatively charged phosphate backbones of DNA. So a simple but sensitive method for the detection of target DNA can be developed by using GNPs without any requirement of modification. Experimental results demonstrate that the electrochemical method we have proposed in this work can detect as low as 1 pM breast cancer gene BRCA1 in a 10 μL sample volume without any signal amplification process or the involvement of other synthesized complex, which may provide an alternative for cancer DNA detection. This method may also be generalized for detecting a spectrum of targets using functional DNA (aptamer, metal-specific oligonucleotide, or DNAzyme) in the future.Keywords: biosensor; charge transfer; DNA; electrochemical impedance spectroscopy; gold nanoparticle;
Co-reporter:Jing Zhao, Suisui Hu, Weidong Zhong, Jiguang Wu, Zhongming Shen, Zhong Chen, and Genxi Li
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 10) pp:7070
Publication Date(Web):May 1, 2014
DOI:10.1021/am502053d
In this paper, we have proposed a new electrochemical aptasensor based on a novel ligase-assisted Exo III-catalyzed degradation reaction (LAECDR), which consists of DNA ligase-catalyzed ligation of thrombin-binding aptamer (TBA) with an extension strand (E-strand) and Exo III-catalyzed selective degradation of probe DNA, by using an improved target-induced strand displacement strategy. As a result of LAECDR, methylene blue (MB)-labeled mononucleotides can be released from the 3′-terminal of probe DNA and captured by cucurbit[7]uril-functionalized electrode to induce noticeable electrochemical response. Nevertheless, in the presence of the target protein, thrombin, the TBA that is partially complementary to probe DNA is preferentially binding with the target protein, thereby inhibiting LAECDR from taking place. The remaining intact probe DNA will prevent the terminal-attached MB from approaching to the electrode surface due to strong electrostatic repulsion, so the electrochemical response will be changed by thrombin. By tracing the electrochemical response of adsorbed MB, our aptasensor can exhibit high sensitivity for thrombin detection with a wide linear range from 100 fM to 1 nM and an extremely low detection limit of 33 fM, which can also easily distinguish thrombin in the complex serum samples with high specificity. Therefore, our aptasensor might have great potential in clinical applications in the future.Keywords: cucurbit[7]uril; DNA ligase; electrochemical aptasensor; exonuclease III; thrombin;
Co-reporter:Hao Li, Yue Huang, Bin Zhang, Xiaoshu Pan, Xiaoli Zhu, and Genxi Li
Analytical Chemistry 2014 Volume 86(Issue 24) pp:12138
Publication Date(Web):November 17, 2014
DOI:10.1021/ac503077f
We report a new method to study stoichiometry of protein post-translational modification (PTM) via manipulating small-molecule labels. Such labels can simultaneously bind with all the modified amino acids in a target protein, resulting in a large signal. However, if the small-molecule labels are previously attached with a macromolecule comparable to the target protein in size, binding of one such label will prevent subsequent binding of more labels of its kind; thus, only one of the modified amino acids in the target protein can be bound with the label, resulting in a small signal. Therefore, the stoichiometric number of PTM can be determined by a ratio of the two signals. The proposed method can analyze nitration of several essential regulatory proteins of cellular life, all of which are found to have an integer stoichiometric number indicating regulated site-specific nitration. These results validate the efficacy of our method to provide detailed information on PTMs with biological significance.
Co-reporter:Limin Ning, Xiaoxi Li, Dawei Yang, Peng Miao, Zonghuang Ye, and Genxi Li
Analytical Chemistry 2014 Volume 86(Issue 16) pp:8042
Publication Date(Web):July 22, 2014
DOI:10.1021/ac500141p
Intracellular pH (pHi) is a fundamental modulator of cell function. Minute changes in pHi may cause great effects in many cellular activities such as metabolism and signal transduction. Herein we report an electrochemical pHi sensor based on viral-coat proteins–DNA nanotubes modified gold electrode. The sensor is pH-sensitive as a result of the pH-dependent electrochemical property of methylene blue (MB) and cell permeable owing to the polyarginine domain of the cowpea chlorotic mottle virus (CCMV) coat protein. Moreover, because the pH sensor can be translocated into cells without any further operations, the measurement of pHi changes can be greatly simplified. The pH sensor has a broad pH spectrum in the pH range from 4.0 to 9.0 and responds rapidly to the pH changes of cells, so it may hold great potential to be a valuable tool to study pH-dependent biological and pathological processes in the future.
Co-reporter:Ya Cao, Dehu Chen, Weiwei Chen, Jiacui Yu, Zhong Chen, Genxi Li
Analytica Chimica Acta 2014 Volume 812() pp:45-49
Publication Date(Web):17 February 2014
DOI:10.1016/j.aca.2014.01.008
•A novel electrochemical strategy for protein detection has been established.•The detection strategy relies on a homogeneous aptamer-binding assay format.•Supramolecular principle is introduced into the procedure to improve sensitivity.•The method displays excellent performance for the detection of osteopontin.A new strategy for homogeneous protein detection is developed based on a cucurbit[7]uril (CB[7]) functionalized electrode. The analytical procedure consists of the binding of target protein to its aptamer in the test solution, followed by an exonuclease-catalyzed digestion of methylene blue (MB) tag labeled DNA oligonucleotides. Since CB[7] molecules immobilized on the electrode may efficiently capture the released MB-labeled nucleotides, the MB tags are concentrated to the electrode surface and subsequently yield highly sensitive electrochemical signal, which is related to the concentration of the target protein. The method combines the host–guest properties of CB[7] with the immobilization-free homogeneous assay, providing a powerful tool for protein detection. Taking the detection of osteopontin as an example, the proposed method can have a linear response to the target protein in a range from 50 to 500 ng mL−1 with a detection limit of 10.7 ng mL−1. It can also show high specificity and good reproducibility, and can be used directly for the assay of osteopontin in serum samples.
Co-reporter:Guifang Chen, Hui Tong, Tao Gao, Yangyang Chen, Genxi Li
Analytica Chimica Acta 2014 Volume 849() pp:1-6
Publication Date(Web):7 November 2014
DOI:10.1016/j.aca.2014.08.011
•A novel one-pot colloidal AuNPs-based electrochemical biosensor was fabricated.•AuNPs were first adopted directly as the electrolyte.•Sensitive detection of glucose and single-nucleotide polymorphism was achieved.•Without need to modify the electrode, this system can be regenerated easily.Gold nanoparticles (AuNPs) have been widely employed for the fabrication of electrochemical biosensors. In most cases, AuNPs are immobilized on the surface of an electrode, so they are difficult to be regenerated, making the use of the biosensor unfriendly. In this work, by adopting AuNPs directly as the electrolytes, we have developed a novel AuNPs-based electrochemical detection system. In brief, AuNPs-catalyzed oxidation of glucose is combined with a HRP-catalyzed reaction as well as an electrocatalytic reaction to compose cascade reactions in the electrolyte. Thus, the intensity of the electrocatalytic signals has quantitative relation with the concentration of glucose, and favors the sensitive detection of glucose. Furthermore, because the catalysis of AuNPs may be blocked under the interaction with single-stranded DNA and unblocked in the presence of a complementary sequence, detection of DNA and even single-nucleotide polymorphism can thereby been achieved. This one-pot detection system can be operated and regenerated very easily, since all the components are integrated in the electrolytes of AuNPs, and the unmodified electrode can be reused after being rinsed. This concept by integrating the advantages of sensitive electrochemical detection with the easy-to-operate nanocolloidal system may also promote the development of other kinds of electrochemical biosensors.Gold nanoparticles (AuNPs) have been widely employed for the fabrication of electrochemical biosensors; AuNPs are usually immobilized on the surface of an electrode, so they are difficult to be regenerated, making use of the unfriendly biosensor. In this work, by adopting AuNPs directly as the electrolytes, we have developed a novel AuNPs-based electrochemical detection system. Moreover, the catalytic property of AuNPs is allowed to be associated with the electrochemical reaction to realize cascade reactions. To demonstrate the principle of this design, sensitive detection of glucose as well as single-nucleotide polymorphism has thereby been achieved. This one-pot detection system can be operated and regenerated very easily, since all the components are integrated in the electrolytes of AuNPs, and the unmodified electrode can be reused after being rinsed. This concept by integrating the advantages of sensitive electrochemical detection with the easy-to-operate nanocolloidal system may also promote the development of other kinds of electrochemical biosensors.
Co-reporter:Nana Yang, Hao Li, Tingting Yin, Yue Huang, Lizhou Sun, Genxi Li
Analytica Chimica Acta 2014 Volume 838() pp:31-36
Publication Date(Web):1 August 2014
DOI:10.1016/j.aca.2014.05.045
•A novel electrochemical method has been established for hypoxia-inducible factor-1.•The sensitivity of the method surpasses that of current immunoassays.•The assay of placenta sample can be used to evaluate the severity of preeclampsia.Hypoxia-inducible factor-1 (HIF-1) is among the most important indicators of hypoxia in evaluating severity of many diseases. In this work, a novel method for HIF-1 detection is proposed by using electrochemical techniques based on small molecule binding DNA. In this method, since the designed DNA sequence can specifically bind with either an electroactive small molecule or HIF-1, the signal readout is inversely proportional to HIF-1 concentration, thus a simple and easily-operated method for HIF-1 detection can be developed. With the proposed method, HIF-1 can be determined in a linear range from 5 to 25 nM with a detection limit of 2.8 nM. Furthermore, the proposed method can be directly used to assay HIF-1 in placenta tissue, and the assay results can reliably reflect the severity of preeclampsia, a very dangerous condition during pregnancy. The proposed method also shows desirable sensitivity, high selectivity and excellent reproducibility, so this method can have potential applications in clinical practice.A novel method for HIF-1 detection is proposed by using electrochemical techniques based on small molecule binding DNA. The proposed method can be directly used to assay HIF-1 in placenta tissue, and the assay results can reliably reflect the severity of preeclampsia, a very dangerous condition during pregnancy.
Co-reporter:Yue Yu, Tao Gao, Hao Li, Zonghuang Ye, Zhong Chen, Genxi Li
Electrochemistry Communications 2014 Volume 42() pp:6-8
Publication Date(Web):May 2014
DOI:10.1016/j.elecom.2014.01.021
•An electrochemical immunosensor assay for GP73 has been developed.•The combination of graphene oxide and CdSe QDs enables high sensitivity.•Patient serum assay of GP73 can be realized.In this work, we have developed an electrochemical immunosensor for the assay of Golgi Protein 73 (GP73), which is a newly-established and highly sensitive biomarker for biliary tract cancer. Intrinsic specificity and sensitivity of this immunosensor can be achieved due to the good conductivity of electrochemically reduced graphene oxide, and the prominent electrochemical signal of quantum dots. So, our sensor can enable a limit of detection as low as 12 pM, and it can make direct serum assay possible, the results of which may clearly predict the effect of surgical removal of the primary tumor, indicating potential clinical application of our sensor in the future.
Co-reporter:Xiaoying Wang, Hao Li, Xiaoxi Li, Yangyang Chen, Yongmei Yin, Genxi Li
Electrochemistry Communications 2014 Volume 39() pp:12-14
Publication Date(Web):February 2014
DOI:10.1016/j.elecom.2013.12.003
•A peptide-based assay that detects melanoma biomarker down to 0.1 nM is developed.•High sensitivity is achieved by signal amplification via Cu chelating peptide.•The melanoma biomarker can be reliably detected in human serum.We report here an electrochemical assay to detect S100B, a serum biomarker of melanoma. This assay takes advantage of the 1:2 binding between S100B and its specific binding peptide. The first peptide immobilized on a gold electrode can capture S100B, while a second peptide modified with Gly–His–Lys copper ion chelating motif can generate signal. The chelated copper ion can also amplify the signal by catalyzing the oxidation of o-phenylenediamine (OPD) to electroactive 3-diaminophenazine (DAP). By using square wave voltammetry, a limit of detection as low as 0.1 nM can be achieved. This method has also demonstrated favorable recovery in the complex serum sample, indicating potential clinical application in the future.
Co-reporter:Dianyuan Zheng, Zonghuang Ye, Shiya Yang, Yun Li, Xiaomei He, Genxi Li
Electrochemistry Communications 2014 Volume 49() pp:30-33
Publication Date(Web):December 2014
DOI:10.1016/j.elecom.2014.09.022
•An electrochemical method to study p53 C-terminal domain acetylation is developed.•p53 C-terminal domain acetylation on its DNA binding ability is studied.•This design is simple and easy to operate, and may have potential application.In this work, an electrochemical method has been developed to evaluate the DNA binding efficiency of p53 C-terminal domain (CTD) after acetylation. Firstly, peptides derived from the CTD of p53 with single or multiple acetylated lysine residues are immobilized on an electrode surface. Then, ferrocene (Fc) labeled dsDNA probe bind with the p53 CTD and give different electrochemical response corresponding to the acetylation degree. Consequently, the electrochemical signals can clearly distinguish a different extent of p53 CTD acetylation on its DNA binding ability. Experimental results also show that acetylation of p53 CTD may enhance its DNA binding ability which is positively correlated with the acetylated lysine residue numbers. This electrochemical method is simple, which may provide a novel method to study protein modifications in the future.
Co-reporter:Chao Li, Luming Wei, Xinjian Liu, Lin Lei, Genxi Li
Analytica Chimica Acta 2014 Volume 831() pp:60-64
Publication Date(Web):11 June 2014
DOI:10.1016/j.aca.2014.05.001
•A novel colorimetric strategy for lead ion detection has been established.•The detection relies on DNAzyme functionalized gold nanoparticles.•Target-induced cleavage can mediate assembly of graphene oxide.•The method displays excellent performance for the detection of lead ion.In this paper, we report a novel colorimetric strategy for the detection of small molecules by using Pb2+ ion as an example. In this strategy, DNAzyme duplex modified gold nanoparticles (GNPs) are designed to be unable to interact with graphene oxide (GO). However, in the presence of Pb2+, the substrate strand of the DNAzyme is cleaved at its cleavage site, resulting in the disassembly of the DNAzyme duplex modified GNPs into three parts, i.e., the 3′- and 5′-fragments of substrate strand and the DNAzyme strand modified GNPs. By taking advantage of the efficient cross-linking effect of ssDNA-GNPs to GO, colorimetric sensor for the detection of the metal ion can be fabricated with a detection limit of 100 pM, which is much lower than the previous reports. This colorimetric method has also been used for the determination of Pb2+ in the tap water of the local city and the water from a reservoir with satisfactory results, so it may have potential applications in the future.
Co-reporter:Yue Huang, Hao Li, Tao Gao, Xinjian Liu and Genxi Li
Analyst 2014 vol. 139(Issue 15) pp:3744-3747
Publication Date(Web):09 Jun 2014
DOI:10.1039/C4AN00599F
In this work, we propose a sensitive method to detect proteins by using a peptide-based nano-label. This label is fabricated by attaching the streptavidin-specific peptide to a streptavidin-coated gold nanoparticle. In the meantime, the nano-label is used in combination with a capture probe prepared by using the specific peptide of the target protein and biotin. In the detection procedure, the target proteins can specifically bind with the biotinylated capture probes which have been previously immobilized on an electrode surface, thus the probes can be protected from thermolysin cleavage. Consequently, the capture probes can be tethered with the nano-labels through the robust biotin–streptavidin interaction, resulting in facile electron transfer between the nano-labels and the electrode. Taking the detection of human glypican-3 (GPC3), a valuable biomarker for hepatocellular carcinoma (HCC), as an example, experimental results demonstrate that the proposed method can show excellent performance. Moreover, based on the serum level of GPC3 detected by our method, HCC can be efficiently differentiated from benign hepatic disorders. Owing to its analytical merits and acceptable applications in real samples, the proposed method may hold great potential in clinical practice in the future.
Co-reporter:Juan Zhang, Junhui Cui, Ying Liu, Yangyang Chen and Genxi Li
Analyst 2014 vol. 139(Issue 13) pp:3429-3433
Publication Date(Web):16 Apr 2014
DOI:10.1039/C3AN01839C
In this paper, we report a novel electrochemical method that can be developed as a biosensor for simple and direct determination of α-amylase activity. The method is based on the hydrolysis of maltopentaose, the substrate of the enzyme, which is immobilized on the surface of a gold electrode, and the induced charge changes of the substrate-modified electrode. Specifically, the substrate maltopentaose is immobilized onto a gold electrode surface via a simple and direct immobilization technique that involves a one-step and site-specific attachment of unmodified maltopentaose to the hydrazide-derivatized surface. So, by analyzing the electrochemical signal obtained from the electro-active molecule [Ru(NH3)5Cl]2+ during the hydrolysis of maltopentaose, the determination of α-amylase activity is achieved. Under optimized conditions, α-amylase activity can be assayed with a detection limit of 0.022 U mL−1. The biosensor exhibits a rapid response, good stability and anti-interference ability. Furthermore, the biosensor has also been successfully applied to detect α-amylase in human serum, which shows acceptable accuracy compared to the currently used clinical method. The proposed method in this work may also have potential application of α-amylase determination in real blood samples, diagnostics and food production in the future.
Co-reporter:Juan Zhang, Lin Xiao, Yucai Yang, Zhaoxia Wang, Genxi Li
Food Chemistry 2014 Volume 149() pp:99-106
Publication Date(Web):15 April 2014
DOI:10.1016/j.foodchem.2013.10.067
•Lignin can bind to pancreatic lipase (PL) to form 1:1 complex.•Hydrophobic and electrostatic interactions induce the complex formation.•The effect of lignin on PL is depended on reaction medium and substrate used.In this paper, we find that the effect of lignin on pancreatic lipase (PL) is dependent on reaction medium and substrate used. Experimental results reveal that lignin can gradually bind to PL to form a PL–lignin complex, resulting in an increased activity of the enzyme. The binding process is spontaneous and the PL–lignin complex formation is an endothermic reaction induced by hydrophobic and electrostatic interaction. There is a non-radiation energy transfer from PL to lignin during the binding process, and the binding of lignin to PL conforms to a secondary exponential decay function. Moreover, the α-helix content of the enzyme will be changed and the rigidity of its side chain will be enhanced due to the formation of lignin–PL complex. This study has not only provided the activation effect of lignin on PL, but also given an insight into the interaction between lignin and the enzyme, which would benefit the application of lignin in the pharmacy and food industry, as well as other fields.
Co-reporter:Xiaoli Zhu, Huihui Zhang, Chang Feng, Zonghuang Ye and Genxi Li
RSC Advances 2014 vol. 4(Issue 5) pp:2421-2426
Publication Date(Web):17 Oct 2013
DOI:10.1039/C3RA44033H
In this work, by employing graphene together with a peroxidase-mimic DNAzyme, we have developed a novel dual-colorimetric strategy for DNA detection. In this strategy, a bi-functional probe DNA with both the sequence to have peroxidase activity and the sequence to be complementary to the target DNA is designed. Through π–π stacking, the probe DNA can interact with graphene; however, when the target DNA is present, the graphene-probe DNA interaction will be interrupted, resulting in the peroxidase activity being transferred from the precipitated graphene to the supernatant under centrifugation. Consequently, colorimetric signals can be obtained due to the catalytic reactions by the formed peroxidase-mimic DNAzyme. By observing the changes of the color depth of either the precipitate or the supernate, we are able to detect the target DNA very easily and sensitively with the naked eye. The dual colorimetric signals (signal-off for the precipitate and signal-on for the supernate) can also be integrated through mathematical operations, which may greatly improve the performance of the sensing platform.
Co-reporter:Hongxia Chen, Jiangjiang Zhang, Xinjian Liu, Yanmin Gao, Zonghuang Ye and Genxi Li
Analytical Methods 2014 vol. 6(Issue 8) pp:2580-2585
Publication Date(Web):27 Jan 2014
DOI:10.1039/C3AY42211A
Detection of heavy metal ions has attracted great attention, and the colorimetric assay has remarkable advantages, such as convenient, efficient, free-equipment and always visible. Herein, we report a highly sensitive and selective colorimetric sensor for the determination of copper(II) ions based on the conformational change of Cu2+-binding peptides immobilized onto the surface of gold nanoparticles. In the presence of copper(II) ions, the peptides modified gold nanoparticles (p-AuNPs) will cooperatively bind together, resulting in aggregation and precipitation of the p-AuNPs, thus color change can be observed from wine red to colorless. Nevertheless, other cations like Mg2+, Ca2+, Zn2+, Fe3+, Pb2+, Mn2+, Ba2+, Ni2+, Co2+, K+ and Ag+ cannot have such an effect, so no obvious disturbance occurs in the same concentration to Cu2+. With this well-designed sensing platform, the detection range of copper(II) ions is found to be 10–150 μM, which falls into the maximum accepted level of 1.3 ppm (∼20 μM) as set by the US Environmental Protection Agency. Moreover, modification of AuNPs with differential binding peptides may provide new and simple platforms for the detection of other heavy metal ions, so the strategy proposed for the detection of Cu2+ in this work can be extended for more applications in the future.
Co-reporter:Shan Lu;Limin Ning;Tao Gao;Xiaolan Wu
Chemical Research in Chinese Universities 2014 Volume 30( Issue 3) pp:437-440
Publication Date(Web):2014 June
DOI:10.1007/s40242-014-4153-4
Multidrug resistance(MDR) is a main factor to make the failure of chemotherapy. It is closely related to the over-expression of P-glycoprotein(P-gp), multidrug resistance protein(MRP) and breast cancer resistance protein( BCRP). Herein we reported a novel method to characterize MDR, taking advantage of the electrochemical property of chemotherapeutic drugs. Meanwhile, the definition of accumulation phase and retention phase has been improved. Furthermore, with specific modulators introduced to inhibit the relevant efflux pumps, the exact protein that mainly works in the cells employed in this study can be identified.
Co-reporter:Hongxia Chen, Yafei Hou, Fangjie Qi, Jiangjiang Zhang, Kwangnak Koh, Zhongming Shen, Genxi Li
Biosensors and Bioelectronics 2014 Volume 61() pp:83-87
Publication Date(Web):15 November 2014
DOI:10.1016/j.bios.2014.05.005
•A highly sensitive and selective VEGF sensor based on RCA enhanced SPR has been reported.•Two DNA aptamers targeting VEGF have been used as capture and detection probe, respectively.•Carboxyl-coated polystyrene microspheres have been used to load aptamer and primer for further RCA process.Vascular endothelial growth factor (VEGF) is a major regulator of angiogenesis. It has been identified as an ideal biomarker for staging of many kinds of cancers, so more specific and intense signal is desirable for VEGF biosensors so that the sensors may have more valuable clinical application. Herein, we report a highly sensitive and selective surface plasmon resonance (SPR) sensor for VEGF detection by using two DNA aptamers which target different VEGF domains used as the capture and detection probe, respectively. Moreover, by making use of carboxyl-coated polystyrene microspheres, 3′–NH2 immobilized aptamer and 3′–NH2 modified primer DNA are loaded through amidation onto the sensing layer for further rolling circle amplification (RCA) process to amplify the SPR signal. With the well-designed sensing platform, VEGF can be determined in a linear range from 100 pg mL−1 to 1 μg mL−1 with a detection limit of 100 pg mL−1. Due to its high specificity and desirable sensitivity, this RCA assisted SPR method may be a useful tool for the assay of VEGF in the future. What is more, by replacing the sensing element, i.e., the aptamer of VEGF used in this work, more biosensors for sensitive detection of other biomarkers proteins can be fabricated based on the strategy proposed in this study.
Co-reporter:Tingting Yin, Hao Li, Nana Yang, Tao Gao, Lizhou Sun, Genxi Li
Biosensors and Bioelectronics 2014 Volume 56() pp:1-5
Publication Date(Web):15 June 2014
DOI:10.1016/j.bios.2013.12.057
•A new assay that can detect CREB phosphorylation down to 0.25 nM is developed.•High sensitivity is attained by Zr4+ mediated signal amplification.•Assays in human placenta tissues can reliably indicate progress of preeclampsia.Phosphorylation of protein plays a vital regulatory role in a variety of biological processes. We herein report a novel method to assay the level of phosphorylated cAMP-response element binding protein (CREB) via Zr4+ mediated signal amplification using gold nanoparticle/DNA/methylene blue (GNP/DNA/MB) nanocomposites. In this method the probe DNA immobilized at a gold electrode surface can specifically and efficiently recognize the phosphorylated target protein CREB. Then Zr4+ links the phosphorylated CREB with GNP/DNA/MB nanocomposites by coordinating the phosphate groups on both CREB and the nanocomposites. Since the nanocomposites can provide high sensitivity (limit of detection: 0.25 nM) for the detection, efficient and highly sensitive bioanalysis of the expression level of phosphorylated protein CREB in human placenta tissues has also been conducted in this work. Our method is reported which shows acceptable stability, reproducibility for assaying of the protein phosphorylation states in real biosamples under physiological and pathological conditions with great potential for clinical applications in future.
Co-reporter:Hao Li, Haona Xie, Yue Huang, Bing Bo, Xiaoli Zhu, Yongqian Shu and Genxi Li
Chemical Communications 2013 vol. 49(Issue 84) pp:9848-9850
Publication Date(Web):02 Sep 2013
DOI:10.1039/C3CC45529G
A novel probe with catalytic activity is used for highly sensitive MDM2 detection.
Co-reporter:Chao Li, Zhaoyin Wang, Tao Gao, Aiping Duan and Genxi Li
Chemical Communications 2013 vol. 49(Issue 36) pp:3760-3762
Publication Date(Web):19 Mar 2013
DOI:10.1039/C3CC40543E
A new strategy to fabricate an aptamer-protein nanowire at an electrode surface is reported in this paper, and a simple electrochemical method to determine the concentration of a protein is proposed with high sensitivity and selectivity.
Co-reporter:Hao Li, Haona Xie, Nana Yang, Yue Huang, Lizhou Sun and Genxi Li
Chemical Communications 2013 vol. 49(Issue 47) pp:5387-5389
Publication Date(Web):09 May 2013
DOI:10.1039/C3CC42353K
A bi-functional peptide is designed to incorporate protein recognition and signal amplification functions into a single short peptide sequence.
Co-reporter:Hao Li, Haona Xie, Ya Cao, Xiaorong Ding, Yongmei Yin, and Genxi Li
Analytical Chemistry 2013 Volume 85(Issue 2) pp:1047
Publication Date(Web):December 13, 2012
DOI:10.1021/ac302906c
Protein-binding peptide is recently recognized as an effective artificial affinity reagent for protein assays. However, its application is hampered by the limited choices of available signal readout methods. Herein, we report a general electrochemical signal readout method for protein-binding peptides exploiting the host–guest chemistry of cucurbituril. Via the formation of supermolecules among cucurbituril, electrochemical reporter, and the peptide, a protein-binding peptide can be noncovalently coupled with the electrochemical reporter. To assay the target protein, the protein-binding peptides are first self-assembled in the sensing layer, and after the capturing of the target protein, a portion of the peptides become protein-bound. The protein-free peptides are then coupled with the electrochemical reporter to yield a signal readout inversely proportional to the amount of the captured target proteins. Since the only requirement of supermolecule formation is the incorporation of aromatic amino acids in the peptide sequence, this strategy is universally applicable to many protein-binding peptides. The generality and target specificity of the proposed method are successfully demonstrated in the assays of two kinds of target proteins: tumor necrosis factor-α and amyloid β 1-42 soluble oligomer, respectively. The feasibility of our method is also tested in the monitoring of tumor necrosis factor-α secretion activity of HL-60 cells. These results indicate that our method can have great use in protein detection in the future.
Co-reporter:Bing Bo, Peng Miao, Yuanyuan Xu, Yongqian Shu, Genxi Li
Electrochemistry Communications 2013 Volume 34() pp:142-145
Publication Date(Web):September 2013
DOI:10.1016/j.elecom.2013.06.002
•A sensitive biosensor for Dicer activity is developed.•Methylene blue labeled DNA is used as the signal reporter.•It has potential utility for functional studies of Dicer and RNAi.Dicer cleaves long double strand RNA (dsRNA) into short ones and initiates RNA interference (RNAi), a sequence-specific post-transcriptional gene silencing process. Moreover, it is also involved in the development of cancers. Herein, we report an electrochemical method to study the ribonuclease activity of Dicer for the first time. The designed dsRNA which is thiolated at one end is firstly immobilized on a gold electrode. Square wave voltammetry is then employed to characterize the ribonuclease activity of Dicer after the enzyme digestion of the dsRNA and the subsequent hybridization between short denatured RNA on the electrode and DNA molecules labeled with electrochemical species. This proposed method shows desirable sensitivity and reproducibility, demonstrating the great potential utility for functional studies of Dicer and RNAi in the future.
Co-reporter:Dehu Chen, Min Shen, Ya Cao, Bing Bo, Zhong Chen, Yongqian Shu, Genxi Li
Electrochemistry Communications 2013 Volume 27() pp:38-41
Publication Date(Web):February 2013
DOI:10.1016/j.elecom.2012.10.042
Hepatocellular carcinoma (HCC) is one of the most prevalent malignant tumors throughout the world, generally leading to death within 6–20 months. Since there is no effective therapy for patients with advanced HCC, early diagnosis of HCC is crucial. In this paper, we report a novel method for detecting human cervical cancer oncoprotein-1 (HCCR-1) overexpressed in early-stage HCC, which is of great value for early-stage HCC identification. Specifically, calixarene derivative is immobilized on a gold electrode surface. Then, HCCR-1 antibody is further loaded on the electrode surface, which may capture HCCR-1 in serum. Since the recognition of HCCR-1 in serum can be monitored by electrochemical impedance spectroscopy (EIS), and the experimental results may show a different EIS response between the patients with HCC and the healthy subjects, HCC can be easily identified by our approach. Moreover, due to its simple and convenient operation, the proposed method in this work may have considerable potential for early-stage HCC diagnosis in the future.Highlights► An impedimetric method is proposed for the assay of HCCR-1. ► ProLinker B is used to immobilize HCCR-1 antibody in a favorable orientation. ► HCCR-1 can be directly detected in serum. ► Patients with HCC can be distinguished from healthy subjects by the EIS response.
Co-reporter:Limin Ning, Peng Miao, Tao Gao, Haiyan Wang, Genxi Li
Electrochimica Acta 2013 Volume 111() pp:499-503
Publication Date(Web):30 November 2013
DOI:10.1016/j.electacta.2013.08.008
•The complex of collagen and DNA has been prepared on the electrode surface.•The prepared tubular complex was developed to be a new platform for protein analysis.•A simple but sensitive electrochemical biosensor for assays of MMP-2 was developed.•Entrapment of target proteins onto the electrode was achieved.In this work, we have prepared collagen–DNA complex on the surface of an electrode through electrostatic interaction and hydrogen bonding between collagen triple helix and DNA double helix. The prepared tubular material is then deposited on the electrode surface to form a film. Due to the excellent biocompatibility of collagen and DNA, the prepared biomaterial can provide a new platform for protein analysis. On the one hand, since collagen in the complex is the substrate of matrix metalloproteinases-2 (MMP-2), a new kind of electrochemical biosensor for the detection of MMP-2 can be developed. On the other, the collagen–DNA complex can be used to entrap proteins onto the electrode surface with the activity of the target proteins being well maintained, thus further analysis can be conducted on the target proteins.
Co-reporter:Tao Gao, Limin Ning, Chao Li, Haiyan Wang, Genxi Li
Analytica Chimica Acta 2013 Volume 788() pp:171-176
Publication Date(Web):25 July 2013
DOI:10.1016/j.aca.2013.06.029
•Our method converted the detection of protein to the colorimetric detection of DNA with considerable sensitivity and selectivity.•The obtained signal was amplified with the help of exonuclease III-assisted DNA cleavage cycles.•Target proteins can bind to DNA aptamer or specific DNA sequences with high affinity and selectivity, thus can block the cleavage cycle.•Our method has been utilized for the assay of anti-dsDNA antibodies, which are specific serological markers for systemic lupus erythematosus (SLE).Taking advantage of exonuclease III (Exo III)-assisted signal attenuation strategy and the protection of DNA from Exo III-mediated digestion by specific DNA–protein interaction, a colorimetric method is proposed in this paper for protein assay. Specifically, in the absence of target protein, Exo III-assisted signal attenuation can be achieved by digesting the report DNA in a complex formed by the hybridization of a report DNA and a probe DNA. Nevertheless, in the presence of target protein, the binding of the analyte to the probe DNA will inhibit the Exo III-assisted nucleotides cleavage, so that cyclic signal attenuation is blocked. Therefore, a bridge can be established between the concentration of target protein and the degree of the attenuation of the obtained signal, and the relationship can be shown by the surface plasmon changes caused by the report DNA-induced aggregation of DNA-modified gold nanoparticles (AuNPs). Our method can also have considerable sensitivity and selectivity, which has been demonstrated by the assay of human α-thrombin. Furthermore, by simply changing the sequence of the probe DNA, we can expand the application of our method to not only aptamer binding proteins but also DNA binding proteins, thus we have also used this method to analyze a specific serological marker for systemic lupus erythematosus (SLE) in this study. With a broad detection range of 1.3–133 nM and a detection limit of 0.61 nM (S/N = 3), it may hold great promise for clinical application.A novel colorimetric method for protein assay is proposed in this work based on Exo III-assisted signal attenuation strategy and specific DNA–protein interaction. This method offers easy handling, broad application scope, as well as considerable sensitivity and selectivity.
Co-reporter:Xiaoli Zhu, Jinghua Yang, Min Liu, Yao Wu, Zhongming Shen, Genxi Li
Analytica Chimica Acta 2013 Volume 764() pp:59-63
Publication Date(Web):18 February 2013
DOI:10.1016/j.aca.2012.12.024
Breast cancer is one of the most critical threats to the health of women, and the development of new methods for early diagnosis is urgently required, so this paper reports a method to detect Michigan cancer foundation-7 (MCF-7) human breast cancer cells with considerable sensitivity and selectivity by using electrochemical technique. In this method, a mucin 1 (MUC1)-binding aptamer is adopted to recognize MCF-7 human breast cancer cells, while enzyme labeling is employed to produce amplified catalytic signals. The molecular recognition and the signal amplification are elaborately integrated by fabricating an aptamer–cell–aptamer sandwich architecture on an electrode surface, thus a biosensor for the detection of MCF-7 is fabricated based on the architecture. The detection range can be from 100 to 1 × 107 cells, and the detection limit can be as low as 100 cells. The method is also cost-effective and conveniently operated, implying potential help for the development of early diagnosis of breast cancer.Graphical abstractHighlights► An electrochemical biosensor for the detection of MCF-7 cells was fabricated. ► An aptamer–cell–aptamer sandwich architecture was constructed on an electrode. ► Dual-recognition and enzyme-linked amplification were well integrated. ► Favorable sensitivity and selectivity can be achieved.
Co-reporter:Juan Zhang, Jun-Hui Cui, Tingting Yin, Lizhou Sun, Genxi Li
Food Chemistry 2013 Volume 141(Issue 3) pp:2229-2237
Publication Date(Web):1 December 2013
DOI:10.1016/j.foodchem.2013.05.047
•As a new kind of activator, lignin can greatly increase α-amylase activity.•Lignin may interact with α-amylase to form 1:1 complex.•Hydrogen bonding plays a key role in the process of the binding.This paper reports a new kind of activator of α-amylase, lignin, which can greatly increase α-amylase activity. The promoted ratio of lignin is even much higher than that of chloride ion, the traditional activator of α-amylase. Further experimental results reveal that lignin may interact with α-amylase to form a 1:1 complex with a binding constant of 4.47 × 105 M−1. The binding is spontaneous and lignin/α-amylase complex formation is an exothermal reaction. Hydrogen bonding plays a key role and non-radiation energy transfers from α-amylase to lignin in the binding process. Lignin, combining with α-amylase, conforms to a first-order exponential decay function. The formation of the lignin/α-amylase complex results in the reduction of α-helical content from 57.7% to 53.9%, the increase of the polarity around tryptophan residues, the decrease of the hydrophobicity, and the enlargement of protein granule volume. This work will give a deeper insight into lignin as a kind of dietary fibre, known as an important food functional factor. Furthermore, it also contributes to the exploration of an activator of α-amylase, used in the food industry.
Co-reporter:Dianyuan Zheng, Xiaoli Zhu, Xuejun Zhu, Bing Bo, Yongmei Yin and Genxi Li
Analyst 2013 vol. 138(Issue 6) pp:1886-1890
Publication Date(Web):09 Jan 2013
DOI:10.1039/C3AN36590E
Oxytetracycline (OTC), a broad-spectrum antibiotic, has been extensively used as a food additive for livestock. Its extensive use has greatly increased the risk of chronic drug abuse and has also increased the risk of the resulting diseases. Therefore, in light of this emerging situation, the detection of OTC in both food and livestock is very important to reduce the risks and for diagnosis purposes . In this work, we have proposed an electrochemical aptasensor to quantify OTC. The biosensor shows considerable sensitivity and selectivity, and it can be easily operated and regenerated. Furthermore, for the first time, we have shown that an electrochemical aptasensor can be directly used to detect OTC in mouse blood serum and urine. This biosensor has the potential to aid in the analysis of residual OTC levels, as well as providing more pharmacokinetic information in the future.
Co-reporter:Hongxia Chen, Qiaohan Mei, Yafei Hou, Xiaoli Zhu, Kwangnak Koh, Xiaoxi Li and Genxi Li
Analyst 2013 vol. 138(Issue 19) pp:5757-5761
Publication Date(Web):05 Jul 2013
DOI:10.1039/C3AN01137B
Diagnosis of apoptosis is essential to the early detection of therapy efficiency and the evaluation of disease progression. Caspase-3 is supposed to be closely related to cellular apoptosis. We describe here a label-free surface plasmon resonance (SPR) detection of apoptosis based on caspase-3 activity assay through enzyme digestion. An artificial peptide sequence was designed as a substrate of caspase-3 and immobilized on a gold disk through covalent binding. The 4Lys part at the end of the pentadecyl-peptide was designed to form a unique peptide array through electrostatic repulsion. The immobilization of the peptide on the gold surface was carefully characterized by SPR and atomic force microscopy. The catalytic conditions of caspase-3 were optimized with electrochemical impedance spectroscopy. The detection limit of caspase-3 was found at a concentration of 1 pg mL−1. The activity of caspase-3 in apoptotic cells could also be measured sensitively by the one-step and intuitional SPR response decrease. The fabricated simple and convenient caspase-3 sensor is proposed for application in clinical analysis.
Co-reporter:Xiaoli Zhu, Liya Sun, Yangyang Chen, Zonghuang Ye, Zhongming Shen, Genxi Li
Biosensors and Bioelectronics 2013 Volume 47() pp:32-37
Publication Date(Web):15 September 2013
DOI:10.1016/j.bios.2013.02.039
Graphene, a single atom thick and two dimensional carbon nano-material, has been proven to possess many unique properties, one of which is the recent discovery that it can interact with single-stranded DNA through noncovalent π–π stacking. In this work, we demonstrate that a new strategy to fabricate many kinds of biosensors can be developed by combining this property with cascade chemical reactions. Taking the fabrication of glucose sensor as an example, while the detection target, glucose, may regulate the graphene–DNA interaction through three cascade chemical reactions, electrochemical techniques are employed to detect the target-regulated graphene–DNA interaction. Experimental results show that in a range from 5 μM to 20 mM, the glucose concentration is in a natural logarithm with the logarithm of the amperometric response, suggesting a best detection limit and detection range. The proposed biosensor also shows favorable selectivity, and it has the advantage of no need for labeling. What is more, by controlling the cascade chemical reactions, detection of a variety of other targets may be achieved, thus the strategy proposed in this work may have a wide application potential in the future.Highlights► Combination of cascade chemical reactions with graphene–DNA interaction. ► A broader scope for the application of graphene in biosensing can be achieved. ► Development of electrochemical study on target-regulated graphene–DNA interaction. ► Glucose can be well detected with a superior detection limit and detection range.
Co-reporter:Ya Cao, Jiacui Yu, Bing Bo, Yongqian Shu, Genxi Li
Biosensors and Bioelectronics 2013 Volume 45() pp:1-5
Publication Date(Web):15 July 2013
DOI:10.1016/j.bios.2012.12.061
Proteases are involved in a large number of serious disease processes, while the assay of proteolytic activity can be used for clinical diagnostics. In this paper we report a simple electrochemical method to assay protease activity. This method makes use of an unlabeled peptide that comprises the specific substrate domain of a protease, which can be easily operated and generalized for assay of various kinds of proteases. Specifically, the peptide is immobilized onto a gold electrode surface via the chemical adsorption of the C-terminal cysteine residue, forming a positively charged interface derived from the N-terminal cationic residue. Therefore, the positive electrochemical probes [Ru(NH3)5Cl]2+ cannot get across to the electrode to generate signal. Nevertheless, the proteolytic digestion of the peptide will decrease the number of positive charges on the electrode surface and weaken the blocking effect against the positive electrochemical species, resulting in an increased electrochemical signal. Under optimized conditions, the activity of the model protease, trypsin, can be assayed with a detection limit of 0.026 U/mL. The method may also allow the determination of trypsin activity in serum samples. Moreover, since this approach can be used for the assay of other proteases by simply changing the substrate domain of the peptide, it may have great potential in biomedical applications in the future.Highlights► A simple electrochemical biosensor is proposed for the assay of protease activity. ► The detection bases on proteolytic digestion of unlabeled peptide substrates. ► Trypsin is detected as a model analyte with a detection limit of 0.05 U/mL. ► This method is applicable to other proteases with a suitable peptide substrate.
Co-reporter:GenXi Li;ZengYi Chang
Science China Life Sciences 2013 Volume 56( Issue 12) pp:1154-1155
Publication Date(Web):2013 December
DOI:10.1007/s11427-013-4571-4
Co-reporter:Xiaorong Ding, Hao Li, Haona Xie, Yue Huang, Yafei Hou, Yongmei Yin, Genxi Li
Biosensors and Bioelectronics 2013 Volume 47() pp:75-79
Publication Date(Web):15 September 2013
DOI:10.1016/j.bios.2013.02.042
In this work, we have proposed a novel method to specifically assay the molecular chaperone activity of HSP70 based on the HSP70-substrate peptide interaction. By selectively labeling the substrate peptide of HSP70 via host–guest interaction with two different cucurbituril species, the HSP70-substrate peptide interaction can be transduced into detectable signal readout. By using the signal readout, assay of the molecular chaperone activity of HSP70 can be achieved. Moreover, by using our method, chaperone activity of HSP70 can serve as a reliable indicator of drug resistance in cancer treatment. The experimental results reveal that enhanced chaperone activity of HSP70 is observed in both drug-resistant cancer cell line and the serum of cancer victim subject to anti-cancer therapy. Therefore, the proposed method to assay the molecular chaperone activity of HSP70 can be a tool of efficiency in evaluating therapeutic response in HSP70-targeted cancer treatment.► A new assay method for the molecular chaperone activity of HSP70 is developed. ► The method is based on selective labeling of substrate peptide by cucurbiturils. ► Patient serum is assayed to evaluate drug resistance in cancer treatment.
Co-reporter:Bing Bo, Xuejun Zhu, Peng Miao, Dong Pei, Bo Jiang, Yue Lou, Yongqian Shu, Genxi Li
Talanta 2013 Volume 113() pp:36-40
Publication Date(Web):15 September 2013
DOI:10.1016/j.talanta.2013.03.056
•A sensitive biosensor for clenbuterol is developed using platinum nanoparticles.•It can be used to unequivocally diagnose clenbuterol food poisoning.•It has potentials to develop next-generation strategies for pharmacokinetic study.Clenbuterol is a member of β2 adrenergic agonists, which is widely used not only as a food additive for livestocks, but also a kind of stimulant for athletes; however, the abuse of clenbuterol may pose a significant negative impact on human health. Since it is highly required to develop fast, sensitive and cost-effective method to determine clenbuterol level in the suspected urine or blood, we herein have fabricated an electrochemical biosensor for the determination of clenbuterol. Measurement of the species with the proposed biosensor can also have the advantages of simplicity, high sensitivity and selectivity. Moreover, the sensor can be directly used for clenbuterol determination in rat urine. We have further studied the pharmacokinetics of clenbuterol by using this proposed electrochemical biosensor, so a new tool to investigate pharmacokinetic is developed in this work.Graphical abstract
Co-reporter:AiPing Duan;LiMin Ning;Chao Li;YaFei Hou;NaNa Yang
Science China Life Sciences 2013 Volume 56( Issue 4) pp:293-297
Publication Date(Web):2013 April
DOI:10.1007/s11427-013-4468-2
Hepatitis C virus (HCV), a positive single-stranded RNA virus, is a major cause of liver disease in humans. Herein we report a novel strategy to inhibit the reproduction and translation of HCV using a short RNA, named an Additional RNA, to activate the endonuclease activity of Argonaute 2 (Ago2). In the presence of the Additional RNA, the HCV genome RNA has the requisite 12 nucleotides of base-pairing with microRNA-122. This activates the endonuclease activity of Ago2, resulting in cleavage and release of the HCV genome RNA from Ago2 and microRNA-122. The free HCV genome RNA would be susceptible to intracellular degradation, effectively inhibiting its reproduction and translation. This study presents a new method to inhibit HCV that may hold great potential for HCV treatment in the future.
Co-reporter:Dianyuan Zheng, Xuejun Zhu, Xiaorong Ding, Xiaoli Zhu, Yongmei Yin, Genxi Li
Talanta 2013 Volume 105() pp:187-191
Publication Date(Web):15 February 2013
DOI:10.1016/j.talanta.2012.11.060
Cluster of differentiation 147 (CD147), also known as extracellular matrix metalloproteinase inducer (EMMPRIN), plays an essential role in tumor progression and metastasis, the expression of which on cell surface is a critical clinical testing index for cancer therapy. In this work, an electrochemical method to assay CD147/EMMPRIN expression on tumor cell surface is proposed. While the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) catalyzed by horseradish peroxidase (HRP) can be employed for electrochemical measurement, the signal enhancement amplified by gold nanoparticles (GNPs) can be also utilized in this study. Therefore, under optimized conditions, the fabricated biosensor responds linearly to the CD147/EMMPRIN concentration from 125 to 1000 pg/mL with a detection limit as low as 52 pg/mL. High sensitivity can also be achieved for the quantification of breast cancer cells in a linear range from 6.2×104 to 6.25×105 cells/mL. Moreover, the CD147/EMMPRIN expressed on a single breast cancer cell can be calculated as 2.57×104 molecules/cell. The proposed strategy in this study is considerably potential for monitoring the dynamic protein expression on cancer cells and for the effective cancer diagnosis and treatment in the future.Highlights► A method is proposed to assay CD147/EMMPRIN and its expression on cancer cells. ► The biosensor can sensitively detect CD147/EMMPRIN with a very low detection limit. ► The biosensor can also quantify the cancer cells with CD147/EMMPRIN expressed. ► The expression of CD147/EMMPRIN on single cancer cell surface can be determined.
Co-reporter:Jing Zhao, Qi Fan, Sha Zhu, Aiping Duan, Yongmei Yin, Genxi Li
Biosensors and Bioelectronics 2013 Volume 39(Issue 1) pp:183-186
Publication Date(Web):15 January 2013
DOI:10.1016/j.bios.2012.07.073
Ag+ ions are greatly toxic to a lot of algae, fungi, viruses and bacteria, which can also induce harmful side-effects to environments and human health. Herein we report an ultra-sensitive method for the selective detection of Ag+ ions with electrochemical technique based on Ag+-assisted isothermal exponential degradation reaction. In the presence of Ag+, mismatched trigger DNA can transiently bind to template DNA immobilized on an electrode surface through the formation of C–Ag+–C base pair, which then initiates the isothermal exponential degradation reaction. As a result, the mismatched trigger DNA may melt off the cleaved template DNA to trigger rounds of elongation and cutting. After the cyclic degradation reactions, removal of the template DNA immobilized on the electrode surface can be efficiently monitored by using electrochemical technique to show the status of the electrode surface, which can be then used to determine the presence of Ag+. Further studies reveal that the proposed method can be ultra-sensitive to detect Ag+ at a picomolar level. The selectivity of the detection can also be satisfactory, thus the proposed method for the Ag+ ions detection may be potentially useful in the future.Highlights► Ag+-assisted isothermal exponential degradation reaction is proposed. ► Ag+ ion can be ultra-sensitively detected with high selectivity. ► Metal-mediated base pair is further employed for electroanalysis.
Co-reporter:Jing Zhao, Tao Gao, Yalin Yan, Guifang Chen, Genxi Li
Electrochemistry Communications 2013 30() pp: 26-28
Publication Date(Web):
DOI:10.1016/j.elecom.2013.01.019
Co-reporter:Jing Zhao, Li Zhu, Chao Guo, Tao Gao, Xiaoli Zhu, Genxi Li
Biosensors and Bioelectronics 2013 Volume 49() pp:329-333
Publication Date(Web):15 November 2013
DOI:10.1016/j.bios.2013.05.044
•Small molecule-linked DNA has been immobilized on the electrode surface as the probe.•Folate can specially bind to folate receptor over-expressed on the surface of cancer cells.•Cancer cells can be sensitively detected based on the principle of terminal protection.•Proposed biosensor can easily distinguish the folate receptor-negative normal cells.•The method can also be feasible to determinate MCF-7 cells in complex serum samples.Sensitive and accurate detection of cancer cells plays a crucial role in clinical diagnosis, treatment and prognosis of tumors. In this paper, we report a new electrochemical method for highly selective and sensitive detection of cancer cells by using small molecule-linked DNA as probes. The methodology is based on the fact that exonuclease I can catalyze the digestion of folate-linked DNA probes that are immobilized on an electrode surface; however, in the presence of the target cells, such as human breast cancer MCF-7 cells, the probes can be protected from digestion upon the binding with folate receptor that is over-expressed on the cell surface. Consequently, cancer cells can be efficiently detected by monitoring the status of the probe DNA with electrochemical techniques. In this study, the protection to exonuclease I-catalyzed digestion has also been proven by electrochemical studies. Moreover, the proposed method has been proven to linearly detect MCF-7 cells in a wide range from 102–106 cell mL−1 with a low detection limit of 67 cell mL−1, which can also easily distinguish the folate receptor-negative normal cells, for instance, islet β cells. The reproduction of the detection is also satisfactory, since the relative standard deviations for three independent measurements of different concentration of MCF-7 cells are all within 10%. By replacing the small molecules linked on the DNA probe, other cancer cells can also be detected by making use of this proposed method. Therefore, our cytosensor may have great potential in clinical applications.
Co-reporter:Zhaoyin Wang, Limin Ning, Aiping Duan, Xiaoli Zhu, Haiyan Wang and Genxi Li
Chemical Communications 2012 vol. 48(Issue 60) pp:7507-7509
Publication Date(Web):08 Jun 2012
DOI:10.1039/C2CC33088A
A G-quadruplex–hemin complex assembled at an electrode surface may exhibit “smart” behaviors under benign conditions, which can be further used in fabricating a set of logic gates. Desirably, these logic gates can be integrated into a logic network with the advantages of integrity, unification and reversibility.
Co-reporter:Nana Yang, Ya Cao, Ping Han, Xuejun Zhu, Lizhou Sun, and Genxi Li
Analytical Chemistry 2012 Volume 84(Issue 5) pp:2492-2497
Publication Date(Web):January 26, 2012
DOI:10.1021/ac2032854
Mammalian Argonaute2 (Ago2) protein is the key player of RNA-induced silencing complexes (RISCs), regulating gene function through RNA interference. In this paper, a method to investigate the RNA endonuclease activity of Ago2 is reported using electrochemical technique with G-quadruplex–hemin complexes as signal transduction probes. Experimental results reveal that Ago2 may exhibit its slicer activity without any biological partners or ATP in wide pH and temperature ranges; thus, a method to assay the activity of the enzyme is proposed. For purified samples, the endonuclease activity of Ago2 can be quantified in the range from 6.25 to 25 nM with a detection limit of 5.02 nM. In the case of porcine cardiocyte lysates which contain a certain amount of Ago2, a linear correlation can be also obtained between the electrochemical signal and the dilution radio of the lysates. The proposed method shows desirable sensitivity, high selectivity, and excellent reproducibility, implying that this method may hold considerable potential for functional studies of Ago2 and clinical diagnosis in the future.
Co-reporter:Ya Cao, Sha Zhu, Jiacui Yu, Xuejun Zhu, Yongmei Yin, and Genxi Li
Analytical Chemistry 2012 Volume 84(Issue 10) pp:4314
Publication Date(Web):April 12, 2012
DOI:10.1021/ac203401h
Based on small molecule-linked DNA and the nicking endonuclease-assisted amplification (NEA) strategy, a novel electrochemical method for protein detection is proposed in this work. Specifically, the small molecule-linked DNA (probe 1) can be protected from exonuclease-catalyzed digestion upon binding to the protein target of the small molecule, so the DNA strand may hybridize with another DNA strand (probe 2) that is previously immobilized onto an electrode surface. Consequently, the NEA process is triggered, resulting in continuous removal of the DNA strands from the electrode surface, and the blocking effect against the electrochemical species [Fe(CN)6]3–/4– becomes increasingly lower; thus, increased electrochemical waves can be achieved. Because the whole process is activated by the target protein, an electrochemical method for protein quantification is developed. Taking folate receptor (FR) as an example in this work, we can determine the protein in a linear range from 0.3 to 15 ng/mL with a detection limit of 0.19 ng/mL. Furthermore, because the method can be used for the assay of FR in serum samples and for the detection of other proteins such as streptavidin by simply changing the small molecule moiety of the DNA probes, this novel method is expected to have great potential applications in the future.
Co-reporter:Jing Zhao, Li Zhu, Xiaoxi Li, Bing Bo, Yongqian Shu, Genxi Li
Electrochemistry Communications 2012 Volume 23() pp:56-58
Publication Date(Web):September 2012
DOI:10.1016/j.elecom.2012.07.009
The occurrence of multi-drug resistance (MDR) has become a major obstacle to the successful performance of chemotherapy for cancer patients, so it is highly required to develop methods to assay the reversal effect on MDR in tumor cells. In this paper, we report a simple but efficient electrochemical method to assay the reversal effect on MDR by using limonin as reversal agent and multi-drug resistant leukemia cells K562/ADM as target cells. The strategy is based on the over-expression of P-glycoprotein (P-gp) in K562/ADM cells that may promote the efflux of the intracellular anticancer drug kaempferol. Consequently, kaempferol molecules accumulate outside the cells. They then adsorb onto the surface of the working electrode, which is modified by β-cyclodextrin/multi-walled carbon nanotubes (β-CD/MWCNTs), to give a well-defined electrochemical response. However, after K562/ADM cells have been incubated with the P-gp inhibitor limonin, efflux of the intracellular anticancer drug molecules will be prohibited, so the peak currents can be observed to decrease in a limonin concentration-dependent manner. Therefore, the proposed method in this work can efficiently characterize the reversal effect of limonin on MDR, which might have potential use in screening the reversal agents for cancer treatments in the future.Highlights► An electrochemical method is proposed to assay the reverse of multi-drug resistance. ► Limonin is used as the model P-glycoprotein inhibitor to reveal the reversal effect. ► Kaempferol is used as both the anticancer drug and the electrochemical probe. ► Reversal effect in K562/ADM cells is demonstrated by observing the current decrease.
Co-reporter:Peng Miao, Limin Ning, Xiaoxi Li, Pengfei Li, and Genxi Li
Bioconjugate Chemistry 2012 Volume 23(Issue 1) pp:141
Publication Date(Web):December 11, 2011
DOI:10.1021/bc200523p
We herein report a novel electrochemical method in this paper to monitor protein phosphorylation and to assay protein kinase activity based on Zr4+ mediated signal transition and rolling circle amplification (RCA). First, substrate peptide immobilized on a gold electrode can be phosphorylated by protein kinase A. Then, Zr4+ links phosphorylated peptide and DNA primer probe by interacting with the phosphate groups. After the introduction of the padlock probe and phi29 DNA polymerase, RCA is achieved on the surface of the electrode. As the RCA product, a very long DNA strand, may absorb a large number of electrochemical speices, [Ru(NH3)6]3+, via the electrostatic interaction, localizing them onto the electrode surface, initiated by protein kinase A, a sensitive electrochemical method to assay the enzyme activity is proposed. The detection limit of the method is as low as 0.5 unit/mL, which might promise this method as a good candidate for monitoring phosphorylation in the future.
Co-reporter:Yuanyuan Xu;Yangyang Chen;Nana Yang;Lizhou Sun
Chinese Journal of Chemistry 2012 Volume 30( Issue 9) pp:1962-1965
Publication Date(Web):
DOI:10.1002/cjoc.201200267
Abstract
In this work, we have prepared Ag nanoclusters (Ag NCs) at gold electrode surface by using thiol-modified oligodeoxynucleotide consisting of eighteen cytosine deoxyribonucleotides (polyC18) as template and NaBH4 as reducing agent. Experimental results show that Ag nanoclusters (Ag NCs) can be formed around the template polyC18, while the formation can be characterized with electrochemical method. Further studies reveal that the fabricated Ag NCs may display high catalytic activity for the reduction of hydrogen peroxide (H2O2), which can be further used for the detection of H2O2.
Co-reporter:Min Shen, Mei Yang, Hao Li, Zhiqiang Liang, Genxi Li
Electrochimica Acta 2012 60() pp: 309-313
Publication Date(Web):
DOI:10.1016/j.electacta.2011.11.047
Co-reporter:Jing Zhao, Xiaolin He, Bing Bo, Xinjian Liu, Yongmei Yin, Genxi Li
Biosensors and Bioelectronics 2012 Volume 34(Issue 1) pp:249-252
Publication Date(Web):15 April 2012
DOI:10.1016/j.bios.2012.02.016
In this paper, we report a “signal-on” electrochemical aptasensor for simultaneous determination of two tumor markers MUC1 and VEGF165, by using a ferrocene-labeled aptamer-complementary DNA (cDNA) as probe. Since the cDNA immobilized on an electrode surface can hybridize with both MUC1 aptamer and VEGF165 aptamer to form a long double strand with ferrocene far away from the electrode surface, the probe cannot give electrochemical signal. Nevertheless, the presence of the two tumor markers will inhibit the hybridization of cDNA with the aptamers, thus the distance between ferrocene and the electrode is changed, and a “signal-on” electrochemical method to detect two tumor markers is developed. Experimental results show that the electrochemical signal increases with the addition of either tumor markers, but the biggest electrochemical signal can only be obtained when both tumor markers are present. Therefore, the proposed electrochemical aptasensor can not only detect the two markers but also distinguish their co-existence. It may also display high selectivity and sensitivity towards the detection of the tumor markers, so it might have potential clinical application in the future.Highlights► A “signal-on” electrochemical aptasensor simultaneously detects MUC1 and VEGF165 ► Aptasensors not only detect the two markers but also distinguish their co-existence ► The well specificity and sensitivity of the detection are also demonstrated.
Co-reporter:Qi Fan, Jing Zhao, Hao Li, Li Zhu, Genxi Li
Biosensors and Bioelectronics 2012 Volume 33(Issue 1) pp:211-215
Publication Date(Web):15 March 2012
DOI:10.1016/j.bios.2012.01.003
Herein we report a sensitive electrochemical biosensor for DNA detection by making use of exonuclease III and probe DNA functionalized gold nanoparticles. While probe DNA P1 modified on a gold electrode surface can self-hybridize into a stem-loop structure with an exonuclease III-resistant 3′ overhang end, in the presence of target DNA, P1 may also hybridize with the target DNA to form a duplex region. Therefore, exonuclease III may selectively digest P1 from its 3′-hydroxyl termini until the duplex is fully consumed. Since a single target DNA can trigger exonuclease III digestion of numerous P1 strands, the first signal amplification is achieved. On the other hand, since the digested P1, exposing its complementary sequence to probe DNA P2, can further hybridize with P2 that has been previously modified on the surface of gold nanoparticles, many nanoparticles loaded with numerous DNA strands are immobilized onto the electrode surface. Consequently, large amount of electroactive molecules [Ru(NH3)6]3+ can bind with the DNA strands to produce an intense electrochemical response as the second signal amplification. Based on the studies with cyclic voltammetry (CV) and chronocoulometry (CC) techniques, the proposed biosensor can sensitively detect specific target DNA at a picomolar level with high specificity.Highlights► A dual signal amplification-assisted electrochemical DNA biosensor was developed. ► Dual signal amplification was based on the use of ExoIII and gold nanoparticles. ► The biosensor could sensitively detect target DNA at a picomolar level. ► The well specificity and reproduction of the detection were also demonstrated.
Co-reporter:Hao Li, Ya Cao, Xiaolan Wu, Zonghuang Ye, Genxi Li
Talanta 2012 Volume 93() pp:358-363
Publication Date(Web):15 May 2012
DOI:10.1016/j.talanta.2012.02.055
Based on oligopeptide, a novel strategy to fabricate electrochemical biosensor is proposed in this work by fine-tuning the scan pulse frequency of square wave voltammetry (SWV) to synchronize with the surface electron transfer (ET) of the oligopeptide modified on an electrode surface. By using this strategy, the surface ET dynamics of our peptide-based biosensor can show significant difference in the presence and absence of a detection target, thus the proposed strategy has been employed for the assay of amyloid β 1–42 (Aβ 1–42) soluble oligomer, which is among the most neurotoxic species of Aβ peptide. Experimental results reveal that our sensor might be an appropriate candidate for quantitative assay of Aβ 1–42 soluble oligomer. Moreover, the strategy proposed in this work may be extended for the fabrication of more peptide-based biosensors in the future.Highlights► Signal-on biosensing is achieved by synchronizing SWV frequency with probe dynamics. ► Simple peptide probe recognizes Aβ 1–42 soluble oligomer specifically. ► Sensor recognizes its target quantitatively and works well in biological matrix.
Co-reporter:GuiFang Chen;YangYang Chen;NaNa Yang;XueJun Zhu
Science China Life Sciences 2012 Volume 55( Issue 6) pp:527-532
Publication Date(Web):2012 June
DOI:10.1007/s11427-012-4317-8
Curcumin, a major bioactive compound in turmeric, has a broad spectrum of antioxidant, anticarcinogenic, antimutagenic and anti-inflammatory properties. At the molecular level, curcumin modulates many structurally unrelated membrane proteins through several signaling pathways. Curcumin has been suggested to change the properties of cell membranes and affect the membrane-bound proteins indirectly; however, the detailed mechanism has yet to be investigated. In this paper, self-assembled bilayer lipid membranes are artificially constructed on the surface of a gold electrode to mimic biomembranes, and interaction between the supported membranes and curcumin is studied electrochemically. Results show that curcumin interacts with the membranes strongly, in a concentration-dependent manner. At low concentrations, curcumin tends to insert into the outer monolayer only, while at high concentrations, it may also begin to penetrate the inner monolayer. The results obtained in this work may enhance our understanding of the effect of curcumin, and possibly flavonoids, on cell membranes and membrane proteins.
Co-reporter:Jing Zhao, Tao Liu, Qi Fan and Genxi Li
Chemical Communications 2011 vol. 47(Issue 18) pp:5262-5264
Publication Date(Web):29 Mar 2011
DOI:10.1039/C1CC10186B
An ultra-sensitive, fast, simple and easily operated method for sequence-specific detection of polynucleotides is proposed herein, which is based on a novel target-triggered isothermal exponential degradation reaction (TT-isoTexpDR) and the color change of probe-functionalized gold nanoparticles.
Co-reporter:Xiaoli Zhu, Jing Zhao, Yao Wu, Zhongming Shen, and Genxi Li
Analytical Chemistry 2011 Volume 83(Issue 11) pp:4085
Publication Date(Web):May 5, 2011
DOI:10.1021/ac200058r
A novel strategy to fabricate an aptasensor for potassium with high sensitivity and selectivity by using nicking endonuclease is proposed in this work. A nicking endonuclease (Nt.CviPII), which may recognize specific nucleotide sequences in double-stranded DNA formed by a potassium-binding aptamer and a linker DNA but cleave only the linker strand, may transfer and amplify the quantitative information of the potassium detection to that of the linker DNA through elaborate strand-scission cycles. Since the technique for gene assay is much more mature, the linker DNA can thereby be detected by a number of available methods. Here, taking advantage of a simple and fast gold nanoparticles-based sensing technique, we are able to assay the linker and consequently potassium ion simply by UV–vis spectroanalysis and even with the naked eye. Results show that a 2 μL sample containing 0.1 mM of potassium is enough to induce distinct color appearance of the nanoparticles, and the potassium ion can be easily distinguished from many other ions. The strategy proposed in this work shows some unique advantages over some traditional methods and may be further developed for the detection of some other chemicals in the future.
Co-reporter:Min Shen, Jing Wang, Mei Yang, Genxi Li
Electrochemistry Communications 2011 Volume 13(Issue 2) pp:114-116
Publication Date(Web):February 2011
DOI:10.1016/j.elecom.2010.11.027
Human serum transferrin (hTf) is a principal protein that binds to and transports Ti(IV) in blood, so the Ti(IV)–transferrin complex (Ti2–hTf) is studied in this work with an electrochemical method. While the direct electrochemistry of the complex is achieved after being embedded in a polyethyleneimine (PEI) film, thus a pair of stable, well-defined and quasi-reversible cyclic volammetric peaks can be observed with the formal potential at − 639 mV (vs. SCE), the role of reduction of Ti(IV) in trafficking of Ti(IV) by human serum transferrin is also discussed based on the experimental results that Ti2–hTf undergoes a proton-coupled one electron transfer reaction and Ti(IV)–transferrin is reduced to Ti(III)–transferrin under a mildly acidic condition. This work may provide more information about the transport of titanium in vivo.
Co-reporter:Jing Zhao, Guifang Chen, Li Zhu, Genxi Li
Electrochemistry Communications 2011 Volume 13(Issue 1) pp:31-33
Publication Date(Web):January 2011
DOI:10.1016/j.elecom.2010.11.005
Based on the strong interaction between single-stranded DNA (ssDNA) and graphene material, we have designed a simple but smart platform in this work to fabricate electrochemical biosensors by using graphene quantum dots modified pyrolytic graphite electrode coupled with specific sequence ssDNA molecules as probes. Due to the excellent conductivity of graphene material, the modified electrode can exhibit very fine electrochemical response. Nevertheless, the probe ssDNA will inhibit the electron transfer between the electrochemical active species [Fe(CN)6]3-/4- and the electrode after the probe molecules are strongly bound to the surface of the modified electrode via their interaction with graphene. However, when the target molecules such as target ssDNA or target protein also exist in the test solution, the probe ssDNA will bind with the target instead of graphene if the sequence of the probe ssDNA is designed as complementary to the target DNA or as the aptamer of the target protein. As a result, the obtained peak currents of [Fe(CN)6]3-/4- will increase with the target molecules, thus various electrochemical biosensors can be easily developed with this proposed platform. The fabricated electrochemical biosensors may also have high sensitivity and selectivity, which may have potential applications in the future.
Co-reporter:Yuanyuan Xu, Jing Wang, Ya Cao and Genxi Li
Analyst 2011 vol. 136(Issue 10) pp:2044-2046
Publication Date(Web):30 Mar 2011
DOI:10.1039/C0AN00806K
A new method to assay protein poly(ADP-ribosyl)ation was proposed based on the interaction between the substrate of poly(ADP-ribosyl)ation nicotinamide adenine dinucleotide and gold nanoparticles, which needed no coupled enzymes or other modified catalytic substrate.
Co-reporter:Jing Wang, Ya Cao, Yun Li, Zhiqiang Liang, Genxi Li
Journal of Electroanalytical Chemistry 2011 Volume 656(1–2) pp:274-278
Publication Date(Web):15 June 2011
DOI:10.1016/j.jelechem.2010.10.012
In this paper, we report an electrochemical strategy for the detection of phosphorylation based on enzyme-linked electrocatalysis. In this strategy, the substrate peptides modified on a gold electrode surface are firstly phosphorylated by protein kinase, and then biotinylated via the recognition and combination with the specific biotin-labeled antibody. After that, gold nanoparticles (Au-NPs) which are modified with horseradish peroxidase (HRP) loaded streptavidin are immobilized on the surface of the electrode through biotin–avidin interaction. As a result, HRP on the electrode surface may take catalytic reaction towards the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), and the generated electrochemical signals can be used to monitor phosphorylation. This proposed electrochemical strategy can be employed to detect kinase activity with a satisfactory detection limit of 1 × 10−3 unit/mL and linear range from 1 × 10−3 to 1 × 10−2 unit/mL. Furthermore, the inhibition of protein kinase has been also studied by using this strategy.
Co-reporter:Qianlu Yang, Jing Zhao, Nandi Zhou, Zonghuang Ye, Genxi Li
Biosensors and Bioelectronics 2011 Volume 26(Issue 5) pp:2228-2231
Publication Date(Web):15 January 2011
DOI:10.1016/j.bios.2010.09.039
It has been reported that human telomeric repeat binding factor 1 (hTRF1) may cause telomeric DNA bent; however there is no direct evidence, thus controversy still exists. In this work, the interaction between hTRF1 and a simulated telomeric DNA was investigated by using electrochemical method. While the telomeric DNA was immobilized on a gold electrode surface, a guanine-quadruplex–hemin complex was linked at the end of the DNA to serve as an electrochemical signal reporter. If hTRF1 made the telomeric tracts bent, electrochemical response from “off” to “on” could be observed. Therefore, this electrochemical method could give direct evidence whether hTRF1 binding to telomeric DNA would induce a shallow distortion of the DNA molecules, and a new way to explore the structural information of telomere was also proposed in this paper.
Co-reporter:Peng Miao, Limin Ning, Xiaoxi Li, Yongqian Shu, Genxi Li
Biosensors and Bioelectronics 2011 Volume 27(Issue 1) pp:178-182
Publication Date(Web):15 September 2011
DOI:10.1016/j.bios.2011.06.047
In this work we have developed a novel electrochemical biosensor for the detection of alkaline phosphatase (AP) by the use of two complementary DNA probes (DNA 1 and DNA 2) coupled with λ exonuclease (λ exo). Firstly, the 5′-phosphoryl end of DNA 1 is dephosphorylated by AP. Then DNA 1 hybridizes with DNA 2, previously modified on a gold electrode surface. In this double-strand DNA, DNA 2 strand will be promptly cleaved by λ exo with its phosphoryl at the 5′ end. After the DNA 2 strand is completely digested, DNA 1 will be released from the double strands and then hybridizes with another DNA 2 strand on the electrode surface, thus the cycle of the release of DNA 1 and the digestion of DNA 2 continues. Since the DNA probes may absorb hexaammineruthenium(III) chloride, the electrochemical species, and the removal of the DNA 2 strand from the electrode surface will result in the decrease of the detected electrochemical signal, which is initially activated by AP, an electrochemical biosensor to assay the activity of AP is proposed in this work. This method may have a linear detection range from 1 to 20 unit/mL with a detection limit of 0.1 unit/mL, and the detection of the enzymatic activity in complex biological fluids can also be realized.
Co-reporter:Zhaoyin Wang, Lei Liu, Yuanyuan Xu, Lizhou Sun, Genxi Li
Biosensors and Bioelectronics 2011 Volume 26(Issue 11) pp:4610-4613
Publication Date(Web):15 July 2011
DOI:10.1016/j.bios.2011.04.052
Protein biotinylation plays an important role in metabolism and transcription regulation, so study of protein biotinylation has received more and more interests. In this work, the bifunctional Escherichia coli biotin-inducible repressor protein A (BirA) and its substrate for protein biotinylation, a unique peptide with a specific sequence, are introduced as a model to electrochemically simulate the committed step in fatty acid biosynthesis. With the help of gold nanoparticles and peroxidase-labeled streptavidin involved in the electrochemical system, protein biotinylation is achieved on the surface of the working electrode, and the process of protein biotinylation can be electrochemically assayed by the obtained electrochemical response. Therefore, a new method to assay protein biotinylation is proposed and this work may provide a new perspective for understanding protein biotinylation in vitro.
Co-reporter:Kai Zhang, Xiaoli Zhu, Jing Wang, Langlai Xu and Genxi Li
Analytical Chemistry 2010 Volume 82(Issue 8) pp:3207
Publication Date(Web):March 26, 2010
DOI:10.1021/ac902771k
A novel strategy for the fabrication of electrochemical aptasensor is proposed in this work, and the strategy has been employed to develop an aptasensor for the assay of adenosine deaminase activity. While a well-designed oligonucleotide containing three functional regions (an adenosine aptamer region, a G-quadruplex halves region, and a linker region) is adopted in our strategy as the core element, the enzymatic reaction of adenosine catalyzed by adenosine deaminase plays a key role as well in the regulation of the binding of the G-quadruplex halves with hemin, the electroactive probe, which is to reflect the activity of the enzyme indirectly but accurately. The detection limit of the fabrication biosensor can be lowered to 0.2 U mL−1 of adenosine deaminase, and 1 nM of the inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride is enough to present distinguishable electrochemical response. Moreover, since the electroactive probe is not required to be bound with the oligonucleotide, this strategy may integrate the advantages of both the labeled and label-free strategies.
Co-reporter:Tao Liu, Jing Zhao, Dongmei Zhang and Genxi Li
Analytical Chemistry 2010 Volume 82(Issue 1) pp:229
Publication Date(Web):December 2, 2009
DOI:10.1021/ac902198v
DNA methylation, catalyzed by methylases, plays a critical role in many biological processes, and methylases have been regarded as promising targets for antimicrobial drugs. In this paper, we propose a simple and sensitive colorimetric assay method to detect the activity of methylases so as to monitor DNA methylation using DNA-modified gold nanoparticles (AuNPs) coupled with enzyme-linkage reactions. The duplex DNA molecules modified on the surface of AuNPs are first methylated by DNA adenine methylation (Dam) methyltransferase (MTase) and then cut by methylation-sensitive restriction endonuclease Dpn I. Removal of duplex from the AuNP surfaces by the methylation/cleavage process will destabilize the nanoparticles, resulting in aggregation of AuNPs and a red-to-blue color change. Consequently, the enzyme activity of Dam MTase can be assayed and DNA methylation can be detected. Furthermore, this study may provide a sensitive platform to screen inhibitors for Dam MTase.
Co-reporter:Ya Cao, Jing Wang, Yuanyuan Xu, Genxi Li
Biosensors and Bioelectronics 2010 Volume 25(Issue 5) pp:1032-1036
Publication Date(Web):15 January 2010
DOI:10.1016/j.bios.2009.09.021
In this paper, an electrochemical biosensor to assay purine nucleoside phosphorylase (PNP) activity is reported. Due to the facilitation of sliver nanoparticles, which are modified on an electrode surface, to the electron transfer reactivity of guanosine and guanine, the electrochemical response of these species can clearly reveal the activity of the enzyme PNP. This electrochemical biosensor for the assay of PNP activity may have a broad linear range of 4–20 unit/mL with a detection limit of 0.1 unit/mL, which is good enough for clinical applications. Meanwhile, on the basis of the finding that guanosine and guanine can induce silver nanoparticles to different agglomeration degrees, we have also developed a rapid UV–vis spectroscopy assay method for PNP activity. This work may show acceptable reliability and specificity for the assay of PNP activity, and may avoid the utilization of coupled enzymes or radiochemical reagents, which are required to the previous reports.
Co-reporter:Jing Wang, Min Shen, Ya Cao, Genxi Li
Biosensors and Bioelectronics 2010 Volume 26(Issue 2) pp:638-642
Publication Date(Web):15 October 2010
DOI:10.1016/j.bios.2010.07.006
In this paper, we report a simple but ultrasensitive electrochemical method for the detection of phosphorylation and the activity of protein kinase A (PKA). In this detection system, the substrate peptides form a compact and positively charged self-assembly monolayer (SAM) on an electrode surface. It will block the positively charged electrochemical probe [Ru(NH3)5Cl]2+ from getting access to the electrode, keeping the “Off” state of the detection system. After the phosphorylation by the enzyme, the SAM becomes loose due to the generation of phosphate groups. Meanwhile, due to the electrostatic interaction between the negative phosphate groups and positively charged SAM, [Ru(NH3)5Cl]2+ molecules can move and get close to the electrode surface. As a result, electrochemical signal is observed and the system is at “On” state. Furthermore, the switch between the “On” and “Off” states can be achieved by the catalysis of PKA and alkaline phosphatase, respectively. The electrochemical response can be used to assay the PKA activity with an extraordinarily low detection limit of 1 × 10−4 unit/mL and wide linear range from 1 × 10−4 to 1 × 10−2 unit/mL. This assay can also be performed by using serum samples with high specificity and reproducibility.
Co-reporter:Ting Li, Qi Fan, Tao Liu, Xiaoli Zhu, Jing Zhao, Genxi Li
Biosensors and Bioelectronics 2010 Volume 25(Issue 12) pp:2686-2689
Publication Date(Web):15 August 2010
DOI:10.1016/j.bios.2010.05.004
Breast cancer is one of the most common cancers to cause death in the world, and the accurate diagnosis is of great importance to determine the stage of the disease and then to design the suitable therapy. Compared with the traditional detection methods relying on the recognition of only one tumor marker, we herein propose a sensitive electrochemical immunoassay to detect breast cancer cells by simultaneously measuring two co-expressing tumor markers, human mucin-1 and carcinoembryonic antigen on the surface of the cancer cells, which may efficiently improve the accuracy of the detection as well as facilitate the classification of the cancer cells. The experimental results have revealed that well electrochemical response can be observed only under the condition that both of the tumor markers are identified on the surface of the tumor cells. With this method, breast cancer cell MCF-7 can be easily distinguished from other kinds of cells, such as acute leukemia cells CCRF-CEM and normal cells islet beta cells. Moreover, the prepared cytosensor can specially monitor breast cancer cell MCF-7 in a wide range from 104 to 107 cell mL−1 with well reproduction and low detection limit, which may have great potential in clinical applications.
Co-reporter:Xiaoli Zhu, Yuexing Liu, Jinghua Yang, Zhiqiang Liang, Genxi Li
Biosensors and Bioelectronics 2010 Volume 25(Issue 9) pp:2135-2139
Publication Date(Web):15 May 2010
DOI:10.1016/j.bios.2010.02.017
Triplex DNA technology has been considered as an attractive antigen strategy for the treatment of genetic-based diseases. Assay of the formation of triplex is an important part in the development of triplex technology. In this paper, we present a novel method to assay triplex DNA. The strategy is based on the unspecific interaction between single-stranded triplex-forming oligonucleotide (TFO) and negatively charged gold nanoparticles (AuNPs). While triplex is formed, gold nanoparticles will aggregate without the protection of triplex-forming oligonucleotide under a certain concentration of salt. Consequently, the color of the gold nanoparticles will change from red to blue. The formation of triplex DNA and the discrimination of triplex-forming oligonucleotide candidates are thereby easily monitored by the color changes of gold nanoparticles. Also by precisely controlling the working salt concentration, we are allowed to assay single-nucleotide polymorphism of triplex-forming oligonucleotides. Mismatched variants and length variants of triplex-forming oligonucleotides with single-nucleotide or double-nucleotides differences can be well discriminated. This method presented here is simple, fast, and with considerable selectivity, so we expect it will be a promising candidate for the assay of triplex DNA and the screening of appropriate triplex-forming oligonucleotide.
Co-reporter:Ya Cao, Jing Wang, Yuanyuan Xu, Genxi Li
Biosensors and Bioelectronics 2010 Volume 26(Issue 1) pp:87-91
Publication Date(Web):15 September 2010
DOI:10.1016/j.bios.2010.05.019
A new strategy to fabricate electrochemical biosensor is reported in this paper based on the selective combination of enzyme catalysis and electorcatalysis, thus an electrochemical method to assay the activity of indoleamine 2,3-dioxygensae (IDO) is proposed. Tryptophan, the substrate of IDO, is firstly covalently immobilized on a gold electrode surface. Oxidation of the tryptophan residue catalyzed by IDO and the subsequent hydrolyzation of the product by acetic acid may yield kynurenine, which may induce the immobilization of dithiobis [succinimidylpropionate] (DSP)-modified platinum nanoparticles (Pt NPs) onto the surface of the gold electrode. Since Pt NPs can electrochemically catalyze the reduction of H2O2 to produce electrochemical signals and the electrochemical wave can be correlated with the enzyme activity, electrochemical method to detect IDO activity is thus achieved. Under optimized conditions, IDO activity can be assayed in the range of 20–400 U/mL with a detection limit of 6.84 U/mL. The proposed biosensor shows high sensitivity, acceptable reliability, and can be used for the investigation of the enzymatic inhibition by inhibitors as well as the screen of the enzymatic activity in complex matrix such as serum samples.
Co-reporter:Xiaoli Zhu Dr.;Yuexing Liu;Junyi Huang Dr. Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 5) pp:1441-1444
Publication Date(Web):
DOI:10.1002/chem.200902783
Co-reporter:Lei Liu, Peng Miao, Yuanyuan Xu, Zhipeng Tian, Zhigang Zou, Genxi Li
Journal of Photochemistry and Photobiology B: Biology 2010 Volume 98(Issue 3) pp:207-210
Publication Date(Web):8 March 2010
DOI:10.1016/j.jphotobiol.2010.01.005
The increasing incidence of cancer all over the world demands new, effective and secure materials for treatment. In this paper, we propose Pt/TiO2 nanocomposite for cancer-cell treatment because noble metal nanoparticles are supposed to enhance the photocatalytic activity of TiO2 nanoparticles. To evaluate the cancer-cell killing effect of our Pt/TiO2 nanocomposite, TiO2 and Au/TiO2 nanoparticles are also introduced. The prepared Pt/TiO2 nanocomposite are characterized with transmission electron microscopy (TEM) and UV–vis adsorption spectra. Results of cell treatment indicate that Pt/TiO2 nanocomposite, as extremely stable metal–semiconductor nanomaterial, can exhibit a very high photodynamic efficiency under a mild ultraviolet radiation. And our Pt/TiO2 nanocomposite shows to be more effective in cancer-cell treatment than TiO2 and Au/TiO2 nanoparticles. As a result, Pt/TiO2 nanocomposite may be supposed to have a promising application for cancer-cell treatment.
Co-reporter:NanDi Zhou;Ya Cao
Science China Chemistry 2010 Volume 53( Issue 4) pp:720-736
Publication Date(Web):2010 April
DOI:10.1007/s11426-010-0134-8
This paper reviews the recent progress in the electron transfer and interfacial behavior of redox proteins. Significant achievements in the relevant fields are summarized including the direct electron transfer between proteins and electrodes, the thermodynamic and kinetic properties, catalytic activities and activity regulation of the redox proteins. It has been demonstrated that the electrochemical technique is an effective tool for protein studies, especially for probing into the electron transfer and interfacial behavior of redox proteins.
Co-reporter:Xiaoli Zhu;Ya Cao;Zhiqiang Liang
Protein & Cell 2010 Volume 1( Issue 9) pp:842-846
Publication Date(Web):2010 September
DOI:10.1007/s13238-010-0110-2
This paper reports a novel method to detect human leukemic lymphoblasts (CCRF-CEM cells). While the aptamer of the cancer cells was employed as the recognition element to target cancer cells, peroxidaseactive DNAzyme was used as the sensing element to produce catalysis-induced colorimetric signals. The elegant architecture integrating the aptamer and DNAzyme made it feasible to detect cancer cells easily and rapidly by the color change of the substrate for DNAzyme. Experimental results showed that 500 cells can well indicate the cancer, while as control, 250,000 Islet Island Beta cells only show tiny signals, suggesting that the method proposed in this paper has considerable sensitivity and selectivity. Furthermore, since it does not require expensive apparatus, or modification or label of DNA chains, the method we present here is also cost-effective and conveniently operated, implying potential applications in future cancer diagnosis.
Co-reporter:Ting Liu, Wei Zhu, Xiang Yang, Lin Chen, Rongwu Yang, Zichun Hua and Genxi Li
Analytical Chemistry 2009 Volume 81(Issue 6) pp:2410
Publication Date(Web):February 16, 2009
DOI:10.1021/ac801267s
The detection of apoptosis based on the interaction between annexin V and phosphatidylserine is presented in this paper. The in vitro experimental results demonstrate that annexin V in polyethylenimine film can maintain its high affinity with phosphatidylserine translocated from the inner to the outer plasma membrane of the apoptotic cells, which may consequently inhibit the redox reaction of [Ru(NH3)5Cl]2+/+ at the annexin V and polyethylenimine comodified pyrolytic graphite electrode. Therefore, if Ca2+, the required ion for the function of annexin V, is added into the test solution, the redox wave of [Ru(NH3)5Cl]2+/+ can be clearly changed to indicate apoptosis and a simple and convenient method to detect apoptosis is developed.
Co-reporter:Zhiqiang Zhu, Yuanyuan Su, Jiang Li, Di Li, Jiong Zhang, Shiping Song, Yun Zhao, Genxi Li and Chunhai Fan
Analytical Chemistry 2009 Volume 81(Issue 18) pp:7660
Publication Date(Web):August 19, 2009
DOI:10.1021/ac9010809
We report a highly sensitive electrochemical sensor for the detection of Hg2+ ions in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles (Au NPs)-based signal amplification. The MSO probe contains seven thymine bases at both ends and a “mute” spacer in the middle, which, in the presence of Hg2+, forms a hairpin structure via the Hg2+-mediated coordination of T−Hg2+−T base pairs. The thiolated MSO probe is immobilized on Au electrodes to capture free Hg2+ in aqueous media, and the MSO-bound Hg2+ can be electrochemically reduced to Hg+, which provides a readout signal for quantitative detection of Hg2+. This direct immobilization strategy leads to a detection limit of 1 μM. In order to improve the sensitivity, MSO probe-modified Au NPs are employed to amplify the electrochemical signals. Au NPs are comodified with the MSO probe and a linking probe that is complementary to a capture DNA probe immobilized on gold electrodes. We demonstrated that this Au NPs-based sensing strategy brings about an amplification factor of more than 3 orders of magnitude, leading to a limit of detection of 0.5 nM (100 ppt), which satisfactorily meets the sensitivity requirement of U.S. Environmental Protection Agency (EPA). This Au NPs-based Hg2+ sensor also exhibits excellent selectivity over a spectrum of interference metal ions. Considering the high sensitivity and selectivity of this sensor, as well as the cost-effective and portable features of electrochemical techniques, we expect this Au NPs amplified electrochemical sensor will be a promising candidate for field detection of environmentally toxic mercury.
Co-reporter:Fanben Meng, Jinghua Yang, Tao Liu, Xiaoli Zhu and Genxi Li
Analytical Chemistry 2009 Volume 81(Issue 21) pp:9168
Publication Date(Web):October 1, 2009
DOI:10.1021/ac901455n
A strategy to assemble cells on a solid support surface, here the surface of a gold electrode, is developed by transfecting cells with thiolated DNA molecules which have been immobilized on the gold electrode surface in advance. This strategy to assemble cells can present a general and convenient method for cell assembly on a solid support surface. What is more interesting, since efficient electric communication via the thiolated DNA between the electroactive species inside the cells and the substrate electrode can be achieved, an approach to “look” into the inner part of the cells is proposed. For the test in this work, one drug, kaempferol, and one dye molecule, methylene blue, inside the cells have been detected by the commonly used electrochemical method linear scan voltammetry, and satisfactory results have been obtained.
Co-reporter:Qianlu Yang, Yongjun Nie, Xiaoli Zhu, Xinjian Liu, Genxi Li
Electrochimica Acta 2009 Volume 55(Issue 1) pp:276-280
Publication Date(Web):15 December 2009
DOI:10.1016/j.electacta.2009.08.050
Here we report that human telomere guanine-rich sequence AGGG(TTAGGG)3 (G4) and hemin can form a G-quadruplex–hemin complex (GHC) which exhibits good electrochemical characteristics. The redox signals of the complex and the electrocatalytic activities toward the reduction of hydrogen peroxide have been investigated. Based on this, two small molecular ligands of G-quadruplex, also known as candidates of anticancer drug, 5,10,15,20-tetra-(N-methyl-4-pyridyl) porphyrin (TMPyP4) and N,N′-bis[2-(1-piperidino)-ethyl]-3,4,9,10-perylenetetracarboxylic diimide (PIPER), were used as model molecules to interrogate their binding activities and their effects on electrochemical behavior of GHC. Besides, spectrometric methods were simultaneously used to verify the interactions and binding stoichiometry between these molecules and GHC. These studies may provide a new way to characterize the structure and properties of human telomere and may have further applications.
Co-reporter:Kun Han, Lin Chen, Zhaosheng Lin, Genxi Li
Electrochemistry Communications 2009 Volume 11(Issue 1) pp:157-160
Publication Date(Web):January 2009
DOI:10.1016/j.elecom.2008.10.054
In this paper, we report a novel and more general signal-on strategy for the fabrication of electrochemical aptamer-based (E-AB) biosensor. The principle is that the interaction between the target and the aptamer strand may induce the formation and subsequent dissociation of target–aptamer complex from an electrode surface, and consequently, the remaining DNA strand on the electrode surface can hybridize again with a ssDNA containing an electrochemical probe. Differential pulse voltammetric studies have revealed that this target induced disassociation (TID) strategy is an effective signal-on method for the detection of ATP molecules with good selectivity. The TID strategy may also have several advantages, such as independence on the specific structure of either the aptamers or their complementary sequences and promotion of the generalization of E-AB sensors, the more convincible results due to the signal-on model, and the unnecessity to label the aptamers, which provides the optimized status for the reaction with the targets, etc.
Co-reporter:Peng Miao, Lei Liu, Yun Li, Genxi Li
Electrochemistry Communications 2009 Volume 11(Issue 10) pp:1904-1907
Publication Date(Web):October 2009
DOI:10.1016/j.elecom.2009.08.013
A novel and sensitive electrochemical method for determination of mercury (II) ions (Hg2+) based on the formation of thymine–Hg2+–thymine complexes and gold nanoparticle-mediated signal amplification is reported. Two 5′ end thiolated complementary oligonucleotides containing six strategically placed thymine–thymine mistakes were introduced in this work. One of the two oligonucleotides was immobilized on a gold electrode and the other one on gold nanoparticles (AuNPs). Due to six thymine–thymine mistakes the two oligonucleotides were not able to be hybridized, so AuNPs could not be immobilized onto the electrode surface after the electrode was immersed in the DNA–AuNPs solution. However, if Hg2+ existed, T–Hg2+–T complexes could be formed and AuNPs could be immobilized onto the electrode surface. Meanwhile, large numbers of [Ru(NH3)6]3+ molecules as electrochemical species could be localized onto the electrode surface. The Hg2+ detection limit of this assay could be as low as 10 nM, which is the US Environmental Protection Agency (EPA) limit of Hg2+ for drinkable water. This method is proven to be simple, convenient, high sensitive and selective.
Co-reporter:Han Xiao;Deli Hong;Tongyang Zhu;Shanli Liu
Journal of Applied Electrochemistry 2009 Volume 39( Issue 8) pp:1163-1167
Publication Date(Web):2009 August
DOI:10.1007/s10800-009-9778-5
The ion-channel formation of outer membrane protein F (OmpF) can be achieved in phosphatidylcholine bilayer membrane modified on a pyrolytic graphite electrode, which makes it possible to sense the porin functionality conveniently with an electrochemical technique through the change in the redox peaks currents of an electroactive marker. The effect of ionic strength, pH on the ion permeability of OmpF and the effect of the protein concentration on the ion-channel formation have been thus examined. This study may provide a simple and rapid way to probe other similar biological processes within natural cellular membranes.
Co-reporter:Jing Wang, Wenying Meng, Xiaofeng Zheng, Shanli Liu, Genxi Li
Biosensors and Bioelectronics 2009 Volume 24(Issue 6) pp:1598-1602
Publication Date(Web):15 February 2009
DOI:10.1016/j.bios.2008.08.030
In this paper, we report a novel electrochemical detection approach for platelet-derived growth factor (PDGF) via “sandwich” structure and gold nanoparticles (Au-NPs) mediated amplification technique. The “sandwich” structure is fabricated based on the fact that PDGF has two aptamer-binding sites, which makes it possible for one PDGF molecule to connect with two aptamers simultaneously. It is found that this electrochemical system with “sandwich” structure and Au-NPs can significantly amplify the signal of electrochemical probe [Ru(NH3)5Cl]2+ for PDGF detection, and thus increase the detection sensitivity significantly. As a result, this PDGF detection approach obtains an extraordinarily low detection limit of 1 × 10−14 M for purified samples, 1 × 10−12 M for contaminated-ridden samples or undiluted blood serum. This detection approach can also exhibit good stability and excellent specificity.
Co-reporter:Shiping Song ;Zhiqiang Liang Dr.;Juan Zhang;Lihua Wang Dr. ;Chunhai Fan
Angewandte Chemie 2009 Volume 121( Issue 46) pp:8826-8830
Publication Date(Web):
DOI:10.1002/ange.200901887
Co-reporter:Jing Wang;Ya Cao;Guifang Chen
ChemBioChem 2009 Volume 10( Issue 13) pp:2171-2176
Publication Date(Web):
DOI:10.1002/cbic.200900408
Co-reporter:Shiping Song ;Zhiqiang Liang Dr.;Juan Zhang;Lihua Wang Dr. ;Chunhai Fan
Angewandte Chemie International Edition 2009 Volume 48( Issue 46) pp:8670-8674
Publication Date(Web):
DOI:10.1002/anie.200901887
Co-reporter:Peng Miao, Lei Liu, Yongjun Nie, Genxi Li
Biosensors and Bioelectronics 2009 Volume 24(Issue 11) pp:3347-3351
Publication Date(Web):15 July 2009
DOI:10.1016/j.bios.2009.04.041
We herein report an ultrasensitive electrochemical sensing strategy for picomole determination of glutathione by using two gold electrodes and two complementary thiolated oligonucleotides. When one gold electrode whose surface has been immobilized with one of the two oligonucleotides is immersed in a glutathione solution for detection, due to the ligand release effect, the oligonucleotides will be replaced by glutathione. Consequently, the released oligonucleotide molecules will exist in the solution, and therefore, if the other gold electrode is immersed in this solution, the released oligonucleotide molecules will be immobilized onto this electrode surface. Meanwhile, since the complementary oligonucleotide molecules have been previously modified on the surface of gold nanoparticles, the nanoparticles can be thus immobilized onto this electrode surface through hybridization, and large numbers of [Ru(NH3)6]3+ molecules as electrochemical species can be localized onto the electrode surface via the electrostatic interaction between the electrochemical species and oligonucleotide molecules. And, since the nanoparticles can amplify the detection signal, ultrasensitive detection of glutathione can be achieved in the range of 1 × 10−12 to 1 × 10−10 M, with a detection limit as low as 4 × 10−13 M. Moreover, this method has shown fairly good utility in the detection of glutathione in fetal calf serum.
Co-reporter:Jing Wang, Ya Cao, Yuanyuan Xu, Genxi Li
Biosensors and Bioelectronics 2009 Volume 25(Issue 2) pp:532-536
Publication Date(Web):15 October 2009
DOI:10.1016/j.bios.2009.08.010
In this paper, a very simple and easily-operated colorimetric multiplexed immunoassay method for sequential detection of tumor markers has been presented. Magnetic microparticles which are conjugated with biotinylated antibodies are firstly added into the test solution. After fast magnetic collection, these complexes are separated from non-specific proteins. Through different enzymatic reactions of 3,3′,5,5′-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) catalyzed by horseradish peroxidase molecules which are loaded on the surfaces of gold nanoparticles, two antigens carcinoembryonic antigen and α-fetoprotein can be detected even with naked eyes. The detection limit obtained from the spectrophotometric measurements is as low as 0.02 ng/mL. This proposed method also has high specificity and reproducibility, as well as excellent efficiency of 94 min for the detection of serum samples. So, this new multiplexed immunoassay method might be a promising approach for the diagnosis of cancer and some other diseases in clinical applications.
Co-reporter:Fanben Meng, Yuexing Liu, Lei Liu and Genxi Li
The Journal of Physical Chemistry B 2009 Volume 113(Issue 4) pp:894-896
Publication Date(Web):January 7, 2009
DOI:10.1021/jp806268z
A pH-driven DNA sway rod is prepared by immobilizing thiolated DNA, mercaptohexanol, and cysteine on a gold electrode surface. As pH changes around the pI of cysteine, contrary electrostatic effect is produced between the negative DNA and amphoteric cysteine, which actuates reversible conformational transitions, such as sway of the DNA molecules, rodlike chain-to-globule, and so forth. The nanoscale motion can be detected by commonly used electrochemical technique and reversible electrochemical signal may be observed.
Co-reporter:Han Xiao, Lei Liu, Fanben Meng, Junyi Huang and Genxi Li
Analytical Chemistry 2008 Volume 80(Issue 13) pp:5272
Publication Date(Web):June 5, 2008
DOI:10.1021/ac8005268
This paper reports an electrochemical approach for detection of apoptosis. Here we prepare a gold electrode modified with a helix peptide ferrocene (Fc)−GDGDEVDGC. Fc is used as an electroactive reporter and the peptide as a recognition and cleavage site of caspase-3, which is a special proteinase to apoptosis. Results show that this method may sensitively and specifically detect apoptotic cells with signal decline of 85%. This approach is different from the previous methods for apoptosis detection, because it does not need any fluorescent materials, expensive biological instruments, or complicated procedures.
Co-reporter:Xiaoli Zhu, Wenjun Zhang, Han Xiao, Junyi Huang, Genxi Li
Electrochimica Acta 2008 Volume 53(Issue 13) pp:4407-4413
Publication Date(Web):20 May 2008
DOI:10.1016/j.electacta.2008.01.042
In this work, we have studied a hemin–DNA complex in relation to ribozymes/deoxyribozymes by using electrochemical techniques. We have also studied the gaseous ligand binding property of the complex, where oxygen and nitric oxide are chosen as the ligands. It is found that the complex can accept nitric oxide and form a relatively stable ligand binding complex, but it is not ready to accept oxygen due to a DNA barrier. A better understanding of this complex may contribute to the knowledge of primitive lives.
Co-reporter:Zhenyu Shao, Yuexing Liu, Han Xiao, Genxi Li
Electrochemistry Communications 2008 Volume 10(Issue 10) pp:1502-1504
Publication Date(Web):October 2008
DOI:10.1016/j.elecom.2008.07.051
In this paper, we report a non-PCR-based electrochemical assay that can detect telomerase activity. Telomerase from HeLa cells may induce telomerization of thiolated primers immobilized on a gold electrode surface. With the telomerization reaction, more and more guanine-rich telomeric repeats are formed, so the electrochemical oxidation signal of guanine at about 1.00 V, which is utilized to indicate the elongated guanine-rich telomeric repeats tethered to the primers, will be increased. This assay method can detect the telomerase activity originated from 3000 HeLa cells and thus holds promise as a simple and sensitive approach in clinical diagnosis of cancer.
Co-reporter:Junyi Huang, Lin Chen, Xin Zhang, Shanli Liu, Genxi Li
Electrochemistry Communications 2008 Volume 10(Issue 3) pp:451-454
Publication Date(Web):March 2008
DOI:10.1016/j.elecom.2008.01.007
The ion-channel behavior of annexin V in phosphatidylcholine bilayer membranes (BLM) is studied from the peaks currents of Fe(CN)63-/4- and Ru(bpy)32+ which are used as electrochemical probes. It is demonstrated that annexin V can form pores in the lipid membrane that allow both Fe(CN)63-/4- and Ru(bpy)32+ probes to reach the surface of the substrate electrode. The influence of Ca2+, pH and protein concentration on the ion-channel formation is also examined. This may provide a simple and general way to study this important biological process.
Co-reporter:Jing Zhao, Xiaoli Zhu, Ting Li and Genxi Li
Analyst 2008 vol. 133(Issue 9) pp:1242-1245
Publication Date(Web):25 Jul 2008
DOI:10.1039/B806588H
Although different kinds of film materials and some modification techniques are applied for the development of protein-film electrochemistry, the design of a more ordered adsorption platform with improved sensitivity is still required. Here we employ single-strand DNA (ssDNA)-functionalized gold nanoparticles as scaffolds for the construction of a multilayered uniform self-assembled structure via the hybridization of complementary ssDNA. After adsorbing with native conformation onto the uniformly built electrode, cytochrome c responded very well in voltammetry experiments. The peak currents increase with the addition of the number of gold nanoparticle layers, which indicates that the multilayer gold nanoparticles not only provide a compatible microenvironment for the protein to undergo direct electron transfer reactions but also amplify the electrochemical signals by increasing the binding sites for the protein immobilization. Furthermore, ultra-sensitive detection of cytochrome c by using this multilayer gold nanoparticle-modified electrode is carried out. The linear range is from 2 × 10−9 to 1 × 10−7 M with a detection limit of 6.7 × 10−10 M.
Co-reporter:Junyi Huang, Dongmei Zhang, Wei Xing, Xiang Ma, Yanxia Yin, Qun Wei, Genxi Li
Analytical Biochemistry 2008 Volume 375(Issue 2) pp:385-387
Publication Date(Web):15 April 2008
DOI:10.1016/j.ab.2007.12.016
In this study, an electrochemical method to assay calcineurin activity is proposed. Although the enzyme could not exhibit electron transfer reactivity and the catalytic reaction of the substrate could not give any electrochemical wave, p-nitrophenol as the catalytic reaction production could be oxidized at the calcineurin/Triton X-100 film modified electrode to exhibit useful wave that might be employed to assay the enzyme activity. The effect of Ni2+ and Zn2+ on calcineurin was also investigated. Whereas Ni2+ was confirmed to be able to enhance the enzymatic activity, Zn2+ was found to be an inhibitor to calcineurin.
Co-reporter:Guifang Chen, Xiang Ma, Fanben Meng, Genxi Li
Bioelectrochemistry 2008 Volume 72(Issue 2) pp:169-173
Publication Date(Web):April 2008
DOI:10.1016/j.bioelechem.2008.02.001
In this work, the electron transfer reactivity of kaempferol was studied and the interaction in vivo between kaempferol and protein was simulated. Dimethylsulfoxide (DMSO) as an aprotic solvent was employed to simulate the specific environment. Various residues of amino acids were used to study the effect of the amino acids in the active site of protein on the electron transfer reactivity of kaempferol. Experimental results revealed that the redox activity of kaempferol was different in aprotic medium DMSO from that in water, and a new redox process was further found. Of all the residues tested, nitrogenous nucleophile, for example, imidazole, was observed to be able to facilitate the electron transfer of kaempferol, and the mechanism was also proposed. This work might provide a simple model to study the electron transfer reactivity of some small active organic molecules, especially medicines, in specific environment, which might approach a more accurate understanding of the activity of some medicines in vivo.
Co-reporter:Guifang Chen, Xiaoli Zhu, Fanben Meng, Zhiguo Yu, Genxi Li
Bioelectrochemistry 2008 Volume 72(Issue 1) pp:77-80
Publication Date(Web):February 2008
DOI:10.1016/j.bioelechem.2007.11.005
In this report, apoferritin as a stable bionanomaterial was modified with hemoglobin on pyrolytic graphite electrode. Rapid electron transfer reactions of hemoglobin were achieved with the help of apoferritin in a large pH range. Moreover, hemoglobin as an enzyme exhibits fine electrocatalytic activity towards the reaction of hydrogen peroxide, and a wide concentration range of linear relationship between the reduction peak current and the concentration of hydrogen peroxide has been obtained with a higher upper detection limit, which may be further developed for a hydrogen peroxide biosensor. Therefore, a new property of apoferritin is explored, in which apoferritin works as a bionanomaterial to be an accelerant of the electron transfer of Hb and a stabilizer to retain the catalytic ability of the protein under mal-condition.
Co-reporter:Xiaoqiang Liang, Guifang Chen, Xin Zhang, Shanli Liu, Genxi Li
Journal of Photochemistry and Photobiology B: Biology 2008 Volume 90(Issue 1) pp:53-56
Publication Date(Web):30 January 2008
DOI:10.1016/j.jphotobiol.2007.11.001
Reduction of ferric methemoglobin (metHb) to its ferrous form is observed by short-time ultraviolet A (UVA) irradiation of metHb together with nicotinamide adenine dinucleotide (NADH). And, severely structural destruction of metHb occurs when long-time UVA irradiation is exerted. However, neither reduction nor destruction can be observed in the absence of NADH under otherwise the same experimental conditions. Accordingly, the O2-binding ability of the protein increases by short-time UVA irradiation of metHb together with NADH, which corresponds with the reduction of metHb, while it decreases by long-time UVA irradiation, which corresponds with the structural destruction. Besides, it is found that the reduction reaction and the conformational destruction proceed more rapidly with higher concentrations of NADH.
Co-reporter:Lei Liu, Xiaoli Zhu, Dongmei Zhang, Junyi Huang, Genxi Li
Electrochemistry Communications 2007 Volume 9(Issue 10) pp:2547-2550
Publication Date(Web):October 2007
DOI:10.1016/j.elecom.2007.07.032
This paper reports an electrochemical method to detect folate receptor positive tumor cells by making use of the interaction between folic acid immobilized on gold nanoparticles and its receptor over-expressed on tumor cell membrane. Experimental results have shown that a gold electrode modified with folic acid functionalized gold nanoparticles can clearly denote folate receptor positive tumor cells, such as ovarian tumor cells and human cervical cancer cells. So, electrochemical technique has been introduced for cancer cells detection and a simple method to detect folate receptor positive tumor cells has been developed.
Co-reporter:Rongwu Yang, Ge Gao, Ting Liu, Shanli Liu, Genxi Li
Electrochemistry Communications 2007 Volume 9(Issue 1) pp:94-96
Publication Date(Web):January 2007
DOI:10.1016/j.elecom.2006.08.042
The amount of oxygen carried by hemoglobin is studied with a polyethyleneimine modified pyrolytic graphite electrode. The medicinal herb, salidroside, is shown to enhance the ability of hemoglobin to carry oxygen in vitro. When salidroside is added to the test solution, the reduction current in the presence of oxygen increases according to the amount of the herb added. No such increase is seen in the absence of oxygen. Furthermore, the percent increase is larger for lower concentrations of oxygen in the solution. UV–Vis spectrometry indicates that the salidroside does not greatly change the conformation of the hemoglobin.
Co-reporter:Hai-Bin Zhu;Da-Hua Hu;Hua-Ze Dong;Gen-Xi Li;Shao-Hua Gou
Chinese Journal of Chemistry 2007 Volume 25(Issue 3) pp:
Publication Date(Web):5 MAR 2007
DOI:10.1002/cjoc.200790066
[2+2] macrocyclic Schiff bases of three kinds have been synthesized from chiral 1,4-diamines by use of different methods. Macrocyclic Schiff bases 1a–1c have been selectively obtained based on a non-templated dilution method from chiral 1,4-diamines a–c and dialdehyde DA1, whereas macrocycles 2a–2c have been selectively produced from reaction of diamines a–c and dialdehyde DA2 in the presence of boric acid as templates. Macrocyclic Schiff bases 3a–3c have been afforded in high selectivity from diamines a–c and dialdehyde DA3 by means of sodium-template. All the titled compounds have been confirmed by 1H NMR and ESI-MS analyses.
Co-reporter:Xiaoli Zhu, Ishida Yuri, Xin Gan, Iwao Suzuki, Genxi Li
Biosensors and Bioelectronics 2007 Volume 22(Issue 8) pp:1600-1604
Publication Date(Web):15 March 2007
DOI:10.1016/j.bios.2006.07.007
Direct electron transfer reactions of microperoxidase were achieved with the help of semiconductive zinc oxide nanoparticles on a pyrolytic graphite electrode. The enzyme could also exhibit fine electrocatalytic activity towards the reduction of hydrogen peroxide. Thereby, a hydrogen peroxide biosensor was constructed based on the electrocatalysis of microperoxidase. Further studies revealed that after irradiating the microperoxidase/zinc oxide nanoparticles co-modified electrode with UV light for 4 h, the catalytic ability of microperoxidase could be greatly promoted, which could be beneficial to developing more sensitive hydrogen peroxide biosensors. As comparison, it was found that the catalytic activity of the enzyme would be depressed if microperoxidase/agarose co-modified electrode was irradiated. We supposed it was the photovoltaic effect of the zinc oxide nanoparticles that improved the catalytic ability of microperoxidase.
Co-reporter:Hui Zhou, Lei Liu, Kun Yin, Shanli Liu, Genxi Li
Electrochemistry Communications 2006 Volume 8(Issue 7) pp:1168-1172
Publication Date(Web):July 2006
DOI:10.1016/j.elecom.2006.05.016
Tyrosinase, which is also named poly-phenol oxidase, has the ability to oxidize several kinds of phenolic compounds to homologous o-quinones. In this work, nano titanium dioxide particles (TiO2 NPs) and tyrosinase are co-immobilized onto the surface of glassy carbon electrode to electrochemically study the effect of TiO2 NPs on the catalytic activity of tyrosinase. And, the influence of the photovoltaic effect of this nanomaterial on the catalytic ability of this enzyme is especially investigated. It is found that TiO2 NPs can greatly enhance the catalytic ability of tyrosinase. Moreover, the photovoltaic effect of this nanomaterial can further make tyrosinase to exhibit a higher enzymatic activity. This phenomenon may be due to the increasing amount of oxytyrosinase generated by the photovoltaic effect under ultraviolet (UV) light irradiation, which is an important intermediate in the process of the catalytic reactions.
Co-reporter:Hui Zhou;Zhong Chen;Libin Shang;Rongwu Yang
Journal of Chemical Technology and Biotechnology 2006 Volume 81(Issue 1) pp:58-61
Publication Date(Web):16 AUG 2005
DOI:10.1002/jctb.1357
Hemoglobin (Hb) embedded in lactobionic acid (LA) film can give a pair of stable, well-defined, and quasi-reversible cyclic voltammetric peaks, located at the potential characteristic of the heme Fe(III)/Fe(II) redox couple. The formal potential of the protein in LA film was −209 mV. The apparent heterogeneous electron transfer rate constant and the number of protons concomitant per electron during the electron transfer process have been calculated. Hydrogen peroxide could also be catalytically reduced by the protein in LA film. Copyright © 2005 Society of Chemical Industry
Co-reporter:Xinjian Liu, Ting Chen, Lifang Liu, Genxi Li
Sensors and Actuators B: Chemical 2006 Volume 113(Issue 1) pp:106-111
Publication Date(Web):17 January 2006
DOI:10.1016/j.snb.2005.02.029
A stable film made from hydroxyethylcellulose (HEC) on pyrolytic graphite (PG) electrode was employed for incorporating hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP), and the electrochemical characteristics of the proteins were studied correspondingly. Experimental results revealed that HEC film could greatly accelerate electron transfer between the proteins and electrode, and the proteins showed a thin layer electrochemical behavior in the film. Moreover, all the proteins in the film exhibited good catalytic activity towards the reduction of hydrogen peroxide (H2O2) in the low H2O2 concentration range. In the high concentration range, H2O2 would exhibit toxicity effect on the proteins. The electrochemical properties and electrocatalytic abilities of the three heme proteins in HEC film have been compared, and the optimal conditions for H2O2 biosensor fabrication have been obtained.
Co-reporter:Hui Zhou, Ziyi Sun, Tomonori Hoshi, Yoshitomo Kashiwagi, Jun-ichi Anzai, Genxi Li
Biophysical Chemistry 2005 Volume 114(Issue 1) pp:21-26
Publication Date(Web):1 April 2005
DOI:10.1016/j.bpc.2004.11.001
Danthron is an important natural occurring component in laxative drugs. In this paper, electrochemical investigation of danthron and its interaction with DNA is reported. Via the electrochemical approach assisted by ultraviolet–visible (UV–Vis) spectroscopy, we have proved that danthron intercalates into DNA strands forming some nonelectroactive complexes, which results in the decrease of redox peak currents of danthron. In addition, the decrease of the peak currents is proportional to the concentration of DNA. The difference between the interaction of danthron with double-stranded DNA (dsDNA) and with single-stranded DNA (ssDNA) has also been studied. This character implies the potential of danthron to discriminate dsDNA and ssDNA.
Co-reporter:Xinjian Liu, Yi Xu, Xiang Ma, Genxi Li
Sensors and Actuators B: Chemical 2005 Volume 106(Issue 1) pp:284-288
Publication Date(Web):29 April 2005
DOI:10.1016/j.snb.2004.08.010
A new film of Triton X-100 to incorporate hemoglobin for biosensor fabrication is presented in this paper. In this film, hemoglobin displays a pair of redox peaks in pH 6.0 NaAc–HAc buffer solution with a formal potential of −0.257 V (versus SCE) and shows a thin-layer behavior. Without electron mediator or promoter, the modified electrode has an electrocatalytic activity to the reduction of hydrogen peroxide (H2O2), which shows a linear dependence on the H2O2 concentration ranging from 1.0 × 10−6 to 1.0 × 10−4 mol/L. The detection limit of 3.0 × 10−7 mol/L is estimated when the signal-to-noise ratio is 3. The KMapp value of hemoglobin in Triton X-100 film has been determined to be 4.27 mmol/L. Ascorbate, uric acid, dopamine, catechol, cystine and epinephrine will not interfere with the sensitive determination of H2O2.
Co-reporter:Chunhai Fan, Xinjian Liu, Jiantao Pang, Genxi Li, Hugo Scheer
Analytica Chimica Acta 2004 Volume 523(Issue 2) pp:225-228
Publication Date(Web):11 October 2004
DOI:10.1016/j.aca.2004.07.038
Although heme protein-based, amperometric nitric oxide (NO) biosensors have been well documented in previous studies, most have been conducted in anaerobic conditions. Herein we report a novel hemoglobin-based NO biosensor that is not only very sensitive but also usable in air. The heme protein was entrapped in a sodium montmorillonite film, which was immobilized at a pyrolytic graphite electrode surface. Film-entrapped hemoglobin can directly exchange electrons with the electrode, and this process has proven to favor the catalytic reduction of oxygen. In addition, NO induced a cathodic potential shift of the catalytic reduction peak of oxygen. This potential shift was proportional to the logarithm of NO concentration ranging from 4.0 × 10−11 to 5.0 × 10−6 mol/L. The detection limit has been estimated to be 20 pM, approximately four orders lower than previously reported amperometric detectors.
Co-reporter:Wenjun Zhang, Hui Zhou, Genxi Li, Hugo Scheer
Biophysical Chemistry 2004 Volume 111(Issue 3) pp:229-233
Publication Date(Web):1 November 2004
DOI:10.1016/j.bpc.2004.06.004
The effect the composition of a water–glycerol mixture has on the electrochemical properties of hemoglobin (Hb) is studied. With the increased glycerol concentrations, the peak-to-peak separation of hemoglobin is found to increase from ∼40 to 200 mV, with the apparent standard potential of hemoglobin negatively shifted, which demonstrate that the electron-transfer activity of hemoglobin will decrease at relatively high glycerol concentrations and the oxidized state of hemoglobin will be more stable with the increasing glycerol concentrations. Meanwhile, the electrocatalytic activity of hemoglobin to hydrogen peroxide, as well as the binding of ligands or effectors to hemoglobin in the presence of glycerol, are also been investigated. Our studies indicate that glycerol will decrease the electrocatalytic activity of hemoglobin, while have little effect on the microenvironment around the heme site.
Co-reporter:Libin Shang;Xinjian Liu;Chunhai Fan
Annali di Chimica 2004 Volume 94(Issue 5-6) pp:
Publication Date(Web):27 MAY 2004
DOI:10.1002/adic.200490055
A reagentless nitric oxide (NO) biosensor was prepared using a pyrolytic graphite (PG) electrode modified with a composite film containing horseradish peroxidase (HRP) and kieselguhr. Noticeably, the electron-transfer reactivity of HRP was significantly enhanced when incorporated in the inorganic kieselguhr material. Consequently, we observed the direct electrochemical response of HRP in this composite film, which would be otherwise electrochemically silent (in the absence of kieselguhr). Importantly, this modified electrode demonstrated nice catalytic activity, as well as high stability, towards the reduction of NO. The peak current related to NO was linearly proportional to its concentration from 2.0×10-7 to 2.0×10-5 mol/L, and the relative standard deviation was 4 % for five successive determinations at a NO concentration of 1.0×10-5 mol/L. The critical level in concentration was estimated to be (4.0±0.3)×10-8 mol/L.
Co-reporter:Xin Gan;Tao Liu;Jun Zhong;Xinjian Liu Dr.
ChemBioChem 2004 Volume 5(Issue 12) pp:
Publication Date(Web):3 NOV 2004
DOI:10.1002/cbic.200400080
Silver nanoparticles (11±1.5 nm) could greatly enhance the electron-transfer reactivity of myoglobin (Mb) and its catalytic ability toward hydrogen peroxide (H2O2). Direct fast electron transfer between Mb and a pyrolytic graphite (PG) electrode was achieved, and a pair of well-defined, quasireversible redox peaks was obtained. The cathodic and anodic peaks were located at −329 and −281 mV, respectively. Meanwhile, the catalytic ability of the protein toward the reduction of H2O2 was also studied, and a H2O2 biosensor was subsequently fabricated. Its detection limit was 1.0×10−6 M with a sensitivity of 0.0205 μA per μM of H2O2. The apparent Michaelis–Menten constant was calculated to be 1303 μM. Flocculation assay showed that the protein maintained plasmon layers surrounding the surface of silver nanoparticles and avoided silver-nanoparticle aggregation. On the other hand, UV-visible spectroscopy studies revealed that silver nanoparticles could induce a small change of the heme-group environment of the protein; this contributed to the enhancement of the electron-transfer reactivity and the catalytic activity.
Co-reporter:Haiyan Wang, Rong Guan, Chunhai Fan, Dexu Zhu, Genxi Li
Sensors and Actuators B: Chemical 2002 Volume 84(2–3) pp:214-218
Publication Date(Web):15 May 2002
DOI:10.1016/S0925-4005(02)00027-8
An unmediated hydrogen peroxide biosensor was prepared by co-immobilizing hemoglobin (Hb) with kieselgubr at a pyrolytic graphite electrode surface. Hb exhibited direct electrochemistry in the film, as well as peroxidase-like activity. This modified electrode showed high stability, catalytic activity towards the reduction of hydrogen peroxide. A linear dependence of the catalytic current on the concentration of hydrogen peroxide was observed in the concentration range of 5.0×10−6 to 3.0×10−4 mol/l with a detection limit of 2.1×10−6 mol/l. The apparent Michaelis-Menten constant (KMapp) was estimated to be 975 μmol/l.
Co-reporter:Chunhai Fan, Qiuxia Gao, Dexu Zhu, Gerhard Wagner and Genxi Li
Analyst 2001 vol. 126(Issue 7) pp:1086-1089
Publication Date(Web):11 Jun 2001
DOI:10.1039/B102873C
Hemoglobin was incorporated in a montmorillonite membrane.
Electrochemical and spectroscopic studies revealed that the electron
transfer reactivity and peroxidase activity of the protein were both
enhanced. Nevertheless, its structure was still maintained native-like in
the membrane. An unmediated hydrogen peroxide biosensor was accordingly
prepared. The calibration plot of this H2O2 sensor
was linear in the range of 1.0 × 10−6–6.0
× 10−4 mol L−1. The relative
standard deviation was 3.1% for six successive determinations at a
concentration of 1.0 × 10−4 mol
L−1. The detection limit was 6.0 ×
10−7 mol L−1. Possible interferences in
real sample analyses are discussed.
Co-reporter:Chunhai Fan, Gerhard Wagner, Genxi Li
Bioelectrochemistry 2001 Volume 54(Issue 1) pp:49-51
Publication Date(Web):August 2001
DOI:10.1016/S0302-4598(01)00107-6
Hemoglobin, after being treated with dimethyl sulfoxide, exhibits a direct electrochemical response at a pyrolytic graphite electrode. The apparent standard potential (E°′) of hemoglobin is −0.119 V (vs. NHE). Meanwhile, since no electrochemical mediator is required for its direct electrochemistry, this work provides a convenient way to perform electrochemical research on this protein.
Co-reporter:Chunhai Fan, Genxi Li, Jianqin Zhu, Dexu Zhu
Analytica Chimica Acta 2000 Volume 423(Issue 1) pp:95-100
Publication Date(Web):20 September 2000
DOI:10.1016/S0003-2670(00)01093-X
Nitric oxide (NO) is an important bioregulatory molecule in vivo. A reagentless, hemoglobin (Hb) based nitric oxide biosensor is prepared, based on the direct electrochemistry of Hb. Spectroscopic studies show that Hb maintains most of its 3-dimensional structure in the film, and keeps its reactivity with NO. The electrochemical reduction of NO is catalyzed employing the Hb modified electrode. Experimental results reveal that the peak current related to NO is linearly proportional to its concentration. It can detect traces of NO as low as 2.9 μM. This biosensor is also shown to be simply constructed, biocompatible and stable.
Co-reporter:Chunhai Fan, Xiaocheng Chen, Genxi Li, Jianqin Zhu, Dexu Zhu and Hugo Scheer
Physical Chemistry Chemical Physics 2000 vol. 2(Issue 19) pp:4409-4413
Publication Date(Web):07 Sep 2000
DOI:10.1039/B005527L
Direct
electrochemistry was carried out to investigate the interaction between haemoglobin (Hb) and nitric oxide (NO), employing a Hb–DNA film modified electrode. DNA was used as an electrochemical “promoter” for the
direct electron transfer of Hb at the electrode surface. Aside from a pair of peaks corresponding to the redox reaction of Hb, two additional peaks were observed in a solution containing NO. The pre-peak, located at −0.070 V s. SCE, was proposed to come from the chemical redox reaction, i.e., NO-induced oxidation of Hb in
the film, coupled electron transfer process of Hb. The other peak, at −0.684 V s. SCE, was assigned to the
reduction of heme-ligated NO. These
phenomena
were proposed
to be related to the
electron transfer and binding process between Hb and NO.
Co-reporter:Guifang Chen, Jing Zhao, Xinjian Liu, Ge Gao, Junyi Huang, Genxi Li
Journal of Biotechnology (20 January 2007) Volume 127(Issue 4) pp:653-656
Publication Date(Web):20 January 2007
DOI:10.1016/j.jbiotec.2006.07.029
We have developed a simple electrochemical method to detect DNA damage caused by the photovoltaic effect of nano-TiO2. Meanwhile, we have found that resveratrol, a Chinese Traditional Medicinal Herb species, can have a repairing effect to the oxidized DNA, which can also be detected with the proposed technique in this paper.
Co-reporter:Xiaolu Hu, Chao Li, Chang Feng, Xiaoxia Mao, Yang Xiang and Genxi Li
Chemical Communications 2017 - vol. 53(Issue 34) pp:NaN4694-4694
Publication Date(Web):2017/03/29
DOI:10.1039/C7CC00687J
A simple colorimetric assay is developed for the sensitive and selective detection of an antibody, which combines a protein binding-induced signaling approach with a novel DNAzyme-based conformational switching strategy.
Co-reporter:Chao Li, Xiaoxi Li, Luming Wei, Muyun Liu, Yangyang Chen and Genxi Li
Chemical Science (2010-Present) 2015 - vol. 6(Issue 7) pp:NaN4317-4317
Publication Date(Web):2015/05/05
DOI:10.1039/C5SC00891C
Various strategies have been proposed for the detection of disease protein biomarkers; however, most methods are too expensive, cumbersome or limited in sensitivity for clinical use. Here, we report that a fabricated complex can be used as a powerful tool to detect trace proteins in complex samples. In this strategy, a DNA–protein complex that comprises of one target molecule and two or more deoxyribozyme-containing probes can exhibit autonomous cleavage behavior on the surface of the substrate DNA modified electrode. In the meantime, the complex can remove the cleaved DNA fragment from the electrode surface by taking advantage of the proximity effect. The proposed approach allows one-step and highly sensitive detection of a variety of targets based on the changes of the direct electrochemical readout. Moreover, this method may also have considerable advantages over the commonly reported DNA amplification-assisted immunoassays, particularly in terms of assay simplicity and cost, which may hold great potential for application in resource-constrained regions.
Co-reporter:Hao Li, Haona Xie, Nana Yang, Yue Huang, Lizhou Sun and Genxi Li
Chemical Communications 2013 - vol. 49(Issue 47) pp:NaN5389-5389
Publication Date(Web):2013/05/09
DOI:10.1039/C3CC42353K
A bi-functional peptide is designed to incorporate protein recognition and signal amplification functions into a single short peptide sequence.
Co-reporter:Yue Huang, Hao Li, Yuanyuan Zhang, Weiwei Li, Lizhou Sun and Genxi Li
Chemical Communications 2015 - vol. 51(Issue 55) pp:NaN11007-11007
Publication Date(Web):2015/05/26
DOI:10.1039/C5CC03700J
This communication reports a novel strategy for the detection of proteins based on the integration of three signal amplification reactions via sharing a specially designed DNA sequence. This strategy has been demonstrated by the assay of human TNF-α in the serum of ovarian cancer patients, showing potential clinical applications.
Co-reporter:Luming Wei, Xiaoying Wang, Dan Wu, Chao Li, Yongmei Yin and Genxi Li
Chemical Communications 2016 - vol. 52(Issue 32) pp:NaN5636-5636
Publication Date(Web):2016/03/18
DOI:10.1039/C6CC00205F
A novel colourimetric method for protein assays is proposed based on proximity ligation induced assembly of Mg2+-dependent DNAzymes, which may offer simple, cost-effective, sensitive and selective detection of the target protein.
Co-reporter:Xiaoli Zhu, Bin Zhang, Zonghuang Ye, Hai Shi, Yalan Shen and Genxi Li
Chemical Communications 2015 - vol. 51(Issue 4) pp:NaN643-643
Publication Date(Web):2014/11/05
DOI:10.1039/C4CC07990F
Here, we report a graphene oxide–aptamer–nanochannel architecture for the fabrication of a novel stimuli-responsive gate. The gate is switched OFF in the absence of ATP, and is switched ON when ATP is present. The concept we proposed may contribute to a versatile platform for the development of stimuli-responsive gates.
Co-reporter:Chao Li, Jiehua Ma, Qiongxuan Fan, Yaqin Tao and Genxi Li
Chemical Communications 2016 - vol. 52(Issue 50) pp:NaN7853-7853
Publication Date(Web):2016/05/24
DOI:10.1039/C6CC02633H
A novel dynamic light scattering (DLS)-based immunoassay that utilizes manganese dioxide nanosheet-modified gold nanoparticles (MnO2–GNPs) as an activatable nanoprobe has been developed to detect tumor markers down to femtomolar levels.
Co-reporter:Jing Zhao, Tao Liu, Qi Fan and Genxi Li
Chemical Communications 2011 - vol. 47(Issue 18) pp:NaN5264-5264
Publication Date(Web):2011/03/29
DOI:10.1039/C1CC10186B
An ultra-sensitive, fast, simple and easily operated method for sequence-specific detection of polynucleotides is proposed herein, which is based on a novel target-triggered isothermal exponential degradation reaction (TT-isoTexpDR) and the color change of probe-functionalized gold nanoparticles.
Co-reporter:Zhaoyin Wang, Limin Ning, Aiping Duan, Xiaoli Zhu, Haiyan Wang and Genxi Li
Chemical Communications 2012 - vol. 48(Issue 60) pp:NaN7509-7509
Publication Date(Web):2012/06/08
DOI:10.1039/C2CC33088A
A G-quadruplex–hemin complex assembled at an electrode surface may exhibit “smart” behaviors under benign conditions, which can be further used in fabricating a set of logic gates. Desirably, these logic gates can be integrated into a logic network with the advantages of integrity, unification and reversibility.
Co-reporter:Chao Li, Zhaoyin Wang, Tao Gao, Aiping Duan and Genxi Li
Chemical Communications 2013 - vol. 49(Issue 36) pp:NaN3762-3762
Publication Date(Web):2013/03/19
DOI:10.1039/C3CC40543E
A new strategy to fabricate an aptamer-protein nanowire at an electrode surface is reported in this paper, and a simple electrochemical method to determine the concentration of a protein is proposed with high sensitivity and selectivity.
Co-reporter:Chao Li, Yucai Yang, Dan Wu, Tianqi Li, Yongmei Yin and Genxi Li
Chemical Science (2010-Present) 2016 - vol. 7(Issue 5) pp:NaN3016-3016
Publication Date(Web):2016/02/03
DOI:10.1039/C5SC04256A
An enzyme-linked immunosorbent assay that is dependent on enzyme amplification has dominated the current field of protein detection; however, limited multiple detection ability and susceptible enzymatic reactions, and low sensitivity may severely hinder its application. Here, we report a new signal amplification scheme based on allochroic molecule modified carboxyl graphene oxide (cGO), which can be used to develop a multicolor immunoassay named as allochroic-cGO linked immunosorbent assay (ALISA). Thanks to high adsorption levels and a wide selection of allochroic molecules, the simultaneous colorimetric detection of diagnostic biomarkers at a picogram level can be successfully achieved for the first time. In addition, the color change triggered by acidic or basic water can provide a simple, rapid, stable and economical signal output, further meeting the growing biodetection requirements. Moreover, with the help of ALISA, we demonstrate that the combined detection of three tumor biomarkers, including carcino-embryonic antigen, neuron-specific enolase, and cytokeratin-19 fragment, is more valuable for differentiating lung cancer patients than the detection of a single biomarker, further manifesting the superiority of ALISA. All in all, this straightforward approach not only opens up new prospects for multicolor immunoassays, but also has great potential for applications in resource-constrained settings.
Co-reporter:Hao Li, Haona Xie, Yue Huang, Bing Bo, Xiaoli Zhu, Yongqian Shu and Genxi Li
Chemical Communications 2013 - vol. 49(Issue 84) pp:NaN9850-9850
Publication Date(Web):2013/09/02
DOI:10.1039/C3CC45529G
A novel probe with catalytic activity is used for highly sensitive MDM2 detection.
Co-reporter:
Analytical Methods (2009-Present) 2014 - vol. 6(Issue 8) pp:NaN2585-2585
Publication Date(Web):2014/01/27
DOI:10.1039/C3AY42211A
Detection of heavy metal ions has attracted great attention, and the colorimetric assay has remarkable advantages, such as convenient, efficient, free-equipment and always visible. Herein, we report a highly sensitive and selective colorimetric sensor for the determination of copper(II) ions based on the conformational change of Cu2+-binding peptides immobilized onto the surface of gold nanoparticles. In the presence of copper(II) ions, the peptides modified gold nanoparticles (p-AuNPs) will cooperatively bind together, resulting in aggregation and precipitation of the p-AuNPs, thus color change can be observed from wine red to colorless. Nevertheless, other cations like Mg2+, Ca2+, Zn2+, Fe3+, Pb2+, Mn2+, Ba2+, Ni2+, Co2+, K+ and Ag+ cannot have such an effect, so no obvious disturbance occurs in the same concentration to Cu2+. With this well-designed sensing platform, the detection range of copper(II) ions is found to be 10–150 μM, which falls into the maximum accepted level of 1.3 ppm (∼20 μM) as set by the US Environmental Protection Agency. Moreover, modification of AuNPs with differential binding peptides may provide new and simple platforms for the detection of other heavy metal ions, so the strategy proposed for the detection of Cu2+ in this work can be extended for more applications in the future.
Co-reporter:Xiaoli Zhu, Yalan Shen, Jiepei Cao, Li Yin, Fangfang Ban, Yongqian Shu and Genxi Li
Chemical Communications 2015 - vol. 51(Issue 49) pp:NaN10005-10005
Publication Date(Web):2015/05/01
DOI:10.1039/C5CC02039E
Here we report a reduced graphene oxide-assisted rolling circle amplification for the detection of miRNA SNPs. The difference of the signal of a miRNA SNP reaches 100 fold, a value over 10 times larger than some current methodologies, which allows the discrimination of a SNP even with the naked eye.
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