Ling-bo Qu

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Organization: Zhengzhou University

Department: Department of Chemistry

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TOPICS

Material Chemistry

Carbon Nanotubes

Analytical Chemistry

capillary electrophoresis

Chemicals
References

Synthesis of glycine-functionalized graphene quantum dots as highly sensitive and selective fluorescent sensor of ascorbic acid in human serum

Co-reporter:Rui Liu, Ran Yang, Chaojie Qu, Haichen Mao, Yue Hu, Jianjun Li, Lingbo Qu

Sensors and Actuators B: Chemical 2017 Volume 241() pp:644-651

Publication Date(Web):31 March 2017

DOI:10.1016/j.snb.2016.10.096

•Highly photoluminescence GLY-GQDs were synthesized and characterized.•The obtained GLY-GQDs were noted as a fluorescence probe for the determination of AA.•Relative to the reported methods, the proposed method is more sensitive and selective for the determination of AA.•The proposed method is much simpler and faster, a whole detection just needs 8 min.In this work, highly photoluminescent glycine (GLY) functionalized graphene quantum dots (GQDs) (GLY-GQDs) were synthesized by a simple and green pyrolysis method employing ethylene glycol as carbon source, GLY as functional molecule. The as-synthesized GLY-GQDs exhibited excellent water solubility with a fluorescence quantum yield of 21.7%. The fluorescence of GLY-GQDs was intensively quenched by Ce4+ via forming non luminescent complexes of GLY-GQDs-Ce4+. When ascorbic acid (AA) was in presence, Ce4+ was reduced to Ce3+ and the fluorescence of GLY-GQDs regained. In the light of this theory, a simple AA sensor was fabricated without complicated, costly and time-consuming operations. Under the optimal conditions, the fluorescence recovery ratio and the concentration of AA has a linear relationship in the range of 0.03–17.0 μM and with a detection limit of 25 nM which was one order higher sensitive than the reported methods Furthermore, this established sensor system also shows a high selectivity toward AA over a wide range of common biological molecules such as uric acid, dopamine and glutathione and so on. The proposed method was successfully applied for the AA detection in serum samples. All these suggested the potential of this GLY-GQDs based sensor in the clinical analysis.

A Direct C2-Selective Phenoxylation and Alkoxylation of Quinoline N-Oxides with Various Phenols and Alcohols in the Presence of H-Phosphonate

Co-reporter:Wen-Zhu Bi;Chen Qu;Xiao-Lan Chen;Zhi-Dong Liu;Kai Sun;Xu Li;Yu-Fen Zhao

European Journal of Organic Chemistry 2017 Volume 2017(Issue 34) pp:5125-5130

Publication Date(Web):2017/09/15

DOI:10.1002/ejoc.201701080

A practical and efficient method for the synthesis of 2-aroxy(alkoxy)quinolines has been developed by direct cross-dehydrogenative coupling reaction between quinoline N-oxides and readily available phenols and alcohols in the presence of H-phosphonate and CCl4 under mild conditions.

Reduced graphene oxide nanosheets functionalized with poly(styrene sulfonate) as a peroxidase mimetic in a colorimetric assay for ascorbic acid

Co-reporter:Jing Chen;Jia Ge;Lin Zhang;Zhaohui Li;Jianjun Li;Yanjun Sun

Microchimica Acta 2016 Volume 183( Issue 6) pp:1847-1853

Publication Date(Web):2016/06/01

DOI:10.1007/s00604-016-1826-3

The authors describe a highly sensitive colorimetric method for the determination of ascorbic acid. It is based on the finding that nanosheets of reduced graphene oxide that were functionalized with poly(styrene sulfonate) (PSS-rGO) possess peroxidase-like activity that catalyzes the oxidization of the substrate 3,3’,5,5’-tetramethylbenzidine (TMB) by H2O2 to form a blue product (oxidized TMB; oxTMB) that can be quantified by photometry or visually. If ascorbic acid is present, a fraction of H2O2 will be consumed and hence less oxTMB (with an absorption peak at 652 nm) will be formed. Ascorbic acid can be quantified by photometry in the 0.8 to 60 μM concentration range with a 0.15 μM detection limit. The method was successfully applied to the determination of ascorbic acid in vitamin C tablets and orange juice.

Amperometric L-cysteine sensor based on a carbon paste electrode modified with Y2O3 nanoparticles supported on nitrogen-doped reduced graphene oxide

Co-reporter:Suling Yang;Gang Li;Yuanyuan Wang;Guifang Wang;Lingbo Qu

Microchimica Acta 2016 Volume 183( Issue 4) pp:1351-1357

Publication Date(Web):2016 April

DOI:10.1007/s00604-015-1737-8

We describe an electrochemical sensor for L-cysteine that is based on the use of Y2O3 nanoparticles (Y2O3-NPs) supported on nitrogen-doped reduced graphene oxide (N-rGO). The material was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. Deposited on a carbon paste electrode, the material displays a strongly oxidation peak for L-cysteine at pH 7.0 (compared to an unmodified electrode). The current, measured at a potential 0.7 V (vs. Ag/AgCl), increases linearly in the 1.3 to 720 μM L-cysteine concentration range, and the detection limit is 0.8 μM. The sensor was successfully applied to the determination L-cysteine in spiked syrup.

Poly(styrene sulfonate) and Pt bifunctionalized graphene nanosheets as an artificial enzyme to construct a colorimetric chemosensor for highly sensitive glucose detection

Co-reporter:Jing Chen, Jia Ge, Lin Zhang, Zhaohui Li, Lingbo Qu

Sensors and Actuators B: Chemical 2016 Volume 233() pp:438-444

Publication Date(Web):5 October 2016

DOI:10.1016/j.snb.2016.04.118

•PSS-GN-Pt was firstly proposed as a novel peroxidase-like mimic successfully.•PSS-GN-Pt had high peroxidase-like activities that can quickly catalyze the oxidation of TMB at room temperature.•A novel colorimetric and visual method for glucose detection has been developed using PSS-GN-Pt.•The detection limit for glucose has reached to 9.28 × 10−8 M and the method could be applied in injection and serum samples.In this work, we developed a highly sensitive and simple colorimetric method for glucose detection using poly(styrene sulfonate)/Pt-modified graphene nanosheets (PSS-GN-Pt) as peroxidase mimetics. First, in the presence of glucose, H2O2 was generated as the main by-product of glucose oxidase (GOx)-catalyzed reaction. Then, the obtained H2O2 triggered the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to generate blue color with the aid of PSS-GN-Pt nanocomposites as peroxidase mimetics. Via this method, as low as 9.28 × 10−8 M glucose could be detected with a linear range from 2 × 10−7 M to 1 × 10−3 M. Besides absorbency measuring, the visual detection of glucose by naked eyes could also be realized very easily through the observable color changing from colorless to blue. In addition, this strategy was further used to determine the concentrations of glucose both in injection and serum samples with satisfying results. This proposed nanosystem holds great potential for diabetes mellitus research and can be easily expanded to the detection of various H2O2-involved analytes.

PSS-GN nanocomposites as highly-efficient peroxidase mimics and their applications in colorimetric detection of glucose in serum

Co-reporter:Jing Chen, Jia Ge, Lin Zhang, Zhaohui Li, Saisai Zhou and Lingbo Qu

RSC Advances 2015 vol. 5(Issue 110) pp:90400-90407

Publication Date(Web):16 Oct 2015

DOI:10.1039/C5RA15837K

In this report, poly(sodium styrene sulfonate)-functionalized graphene nanosheets (PSS-GN) with good water dispersibility were prepared and for the first time proposed as a peroxidase-like mimic. The intrinsic catalytic activity of PSS-GN nanocomposites was investigated and the results showed that PSS-GN nanocomposites had higher mimetic enzyme catalytic activity compared with horseradish peroxidase (HRP), which might be due to the stronger binding affinity between negatively charged PSS and the positively charged peroxide substrate (3,3,5,5-tetramethylbenzidine, TMB). On the basis of the high catalyze activity, these PSS-GN nanocomposites were utilized for sensitive and selective colorimetric detection of H2O2 as well as glucose. The linearity between analyte concentration and system absorption ranged from 0.005 to 1 mM for H2O2 and 0.006 to 0.4 mM for glucose with a detection limit of 0.15 μM and 0.28 μM, respectively. Moreover, this strategy was further utilized to determine the concentrations of glucose in serum samples with satisfying results. This assay exhibits good analytical performance, acceptable stability and good selectivity. We envision that this sensing system could be used as a tool for a wide range of potential applications in enzyme-based chemical and biological analysis.

A rapid fluorescence “switch-on” assay for glutathione detection by using carbon dots–MnO2 nanocomposites

Co-reporter:Qi-Yong Cai, Jie Li, Jia Ge, Lin Zhang, Ya-Lei Hu, Zhao-Hui Li, Ling-Bo Qu

Biosensors and Bioelectronics 2015 Volume 72() pp:31-36

Publication Date(Web):15 October 2015

DOI:10.1016/j.bios.2015.04.077

•A novel fluorescence “switch-on” biosensor is designed for glutathione detection by using carbon dots–MnO2 nanocomposites.•This sensing system displays remarkable properties including simplicity, very short assay time, low-cost as well as nontoxicity.•Results for human serum samples demonstrated that this biosensor is highly applicable for the detection of GSH in biological environments.Glutathione (GSH) serves many cellular functions and plays crucial roles in human pathologies. Simple and sensitive sensors capable of detecting GSH would be useful tools to understand the mechanism of diseases. In this work, a rapid fluorescence “switch-on” assay was developed to detect trace amount of GSH based on carbon dots–MnO2 nanocomposites, which was fabricated through in situ synthesis of MnO2 nanosheets in carbon dots colloid solution. Due to the formation of carbon dots–MnO2 nanocomposites, fluorescence of carbon dots could be quenched efficiently by MnO2 nanosheeets through fluorescence resonance energy transfer (FRET). However, the presence of GSH would reduce MnO2 nanosheets to Mn2+ ions and subsequently release carbon dots, which resulted in sufficient recovery of fluorescent signal. This proposed assay demonstrated highly selectivity toward GSH with a detection limit of 300 nM. Moreover, this method has also shown sensitive responses to GSH in human serum samples, which indicated its great potential to be used in disease diagnosis. As no requirement of any further functionalization of these as-prepared nanomaterials, this sensing system shows remarkable advantages including very fast and simple, cost-effective as well as environmental-friendly, which suggest that this new strategy could serve as an efficient tool for analyzing GSH level in biosamples.

Capillary electrophoresis coupled with electrochemiluminescence for determination of atomoxetine hydrochloride and the study on its interactions with three proteins

Co-reporter:Hua-jin Zeng;Ran Yang;Ying Zhang;Jian-jun Li

Luminescence 2015 Volume 30( Issue 2) pp:124-130

Publication Date(Web):

DOI:10.1002/bio.2700

ABSTRACT

A simple, rapid and sensitive method for the determination of atomoxetine hydrochloride (AH) by capillary electrophoresis with electrochemiluminescence detection (CE-ECL) using tris(2,2′-bipyridyl) ruthenium (II) was developed. Under optimized conditions, the determinations of AH in capsules and rat plasmas and the study on its interactions with three plasma proteins, including bovine serum albumin, cytochrome c and myoglobin were performed successfully. Relative to some previous studies, in this paper the methodologies for the determination of AH in aqueous solution and spiked plasma systems were established, respectively. By comparing the difference between the two work curves of two systems, the matrix effect in plasma samples on the determination of AH by the CE-ECL method was discussed in detail. The results indicated that the effect of the matrix in plasma samples should not be ignored even if no obvious interference was found in the electropherograms and the establishment of method validation in complex samples by the CE-ECL method was necessary. Copyright © 2014 John Wiley & Sons, Ltd.

High-selective and sensitive voltammetric sensor for butylated hydroxyanisole based on AuNPs–PVP–graphene nanocomposites

Co-reporter:Ling Wang, Ran Yang, Huan Wang, Jianjun Li, Lingbo Qu, Peter de B. Harrington

Talanta 2015 Volume 138() pp:169-175

Publication Date(Web):1 June 2015

DOI:10.1016/j.talanta.2015.01.016

•The Au–PVP–graphene (GR) nanocomposite was synthesized via a simple approach.•The enlarged surface area and the enhanced electron rate of composite were discussed.•A sensitive electrochemical sensor of butylated hydroxyanisole (BHA) was built.•The electrochemical reaction mechanism of BHA was proposed.•The saturating absorption capacity at Au–PVP–graphene/GCE was calculated.Gold nanoparticles (AuNPs) and reduced graphene oxide (graphene) composites were synthesized via a simple one-pot approach in the presence of polyvinylpyrrolidone (PVP). Further, the Au–PVP–graphene nanocomposite was used as a new sensing material for the electrochemical detection of butylated hydroxyanisole (BHA). Because of the greatly enlarged surface area, the enhanced electron transfer rate, and a stronger enrichment of BHA, the sensor based on Au–PVP–graphene modified glassy carbon electrode (GCE) displayed highly sensitive electrochemical responses to BHA. Applying linear sweep voltammetry, a good linear relationship of the oxidation peak current with respect to concentrations of BHA across the range of 0.2–100.0 µM and a detection limit of 0.04 µM was achieved. The practical analytical performance of the Au–PVP–graphene/GCE was examined by evaluating detection of BHA in soybean oil and the flour samples. Satisfactory results revealed that this work offered a new way for the sensitive and simple determination of BHA in complex samples.A sensitive and selective electrochemical sensor for the fast determination of butylated hydroxyanisole (BHA) based on Au–PVP–graphene nanocomposite was fabricated. The sensor has superior electrocatalytic activity for the redox of BHA due to its large surface, fast electron transfer character and strong enrichment effect on BHA.

An aptamer-based signal-on bio-assay for sensitive and selective detection of Kanamycin A by using gold nanoparticles

Co-reporter:Jing Chen, Zhaohui Li, Jia Ge, Ran Yang, Lin Zhang, Ling-bo Qu, Hong-qi Wang, Ling Zhang

Talanta 2015 Volume 139() pp:226-232

Publication Date(Web):1 July 2015

DOI:10.1016/j.talanta.2015.02.036

•A fluorescence switch on assay for Kanamycin A detection was developed.•Aptamer and gold nanoparticles were used to realize this assay.•This assay exhibited high sensitivity and selectivity.•This assay could be used in milk samples for Kanamycin A detection.•Binding affinity between aptamer and Kanamycin A was studied by using MST.In this study, a simple and sensitive aptamer-based fluorescence method for the detection of Kanamycin A by using gold nanoparticles (AuNPs) has been developed. In this assay, AuNPs were utilized as DNA nanocarrier as well as efficient fluorescence quencher. In the absence of Kanamycin A, dye-labeled aptamer could be adsorbed onto the surface of AuNPs and the fluorescence signal was quenched. In the presence of Kanamycin A, the specific binding between dye-labeled aptamer and its target induced the formation of rigid structure, which led to dye-labeled aptamer releasing from the surface of AuNPs and the fluorescence intensity was recovered consequently. Under optimum conditions, calibration modeling showed that the analytical linear range covered from 0.8 nM to 350 nM and the detection limit of 0.3 nM was realized successfully. This proposed bio-assay also showed high selectivity over other antibiotics. Meanwhile, this strategy was further used to determine the concentrations of Kanamycin A in milk sample with satisfying results.A novel biosensing strategy for Kanamycin A detection based on FRET assay using gold nanoparticles as aptamer nanocarrier as well as efficient fluorescence quencher.

High-sensitive electrochemical sensor of Sudan I based on template-directed self-assembly of graphene-ZnSe quantum dots hybrid structure

Co-reporter:Ling Wang, Ran Yang, Jianjun Li, Lingbo Qu, Peter de B. Harrington

Sensors and Actuators B: Chemical 2015 215() pp: 181-187

Publication Date(Web):

DOI:10.1016/j.snb.2015.03.034

Sensitive electrochemical sensor for the determination of pentachlorophenol in fish meat based on ZnSe quantum dots decorated multiwall carbon nanotubes nanocomposite

Co-reporter:Suxiang Feng;Ran Yang;Xiaojie Ding;Jianjun Li;Cheng Guo;Lingbo Qu

Ionics 2015 Volume 21( Issue 12) pp:3257-3266

Publication Date(Web):2015 December

DOI:10.1007/s11581-015-1512-1

In this work, a very sensitive electrochemical sensor for the determination of pentachlorophenol (PCP) was constructed based on the electrocatalytic activity of the composite of ZnSe quantum dots (ZnSe QDs) decorated multiwall carbon nanotubes (MWCNTs) (ZnSe QDs-MWCNTs). The behaviors of PCP on the surface of ZnSe QDs-MWCNT modified electrode showed that the composite of ZnSe QDs-MWCNTs introduced a favorable access for the electron transfer and make an obvious electrocatalytic activity toward the oxidation of PCP. Differential pulse voltammetry (DPV) was used for the quantitative determination of PCP. Under the optimum conditions, the peak current of PCP was proportional to its concentration at the range of 8.0 × 10−8 to 4.0 × 10−6 mol L−1 with a detection limit 2.0 × 10−9 mol L−1 (S/N = 3). Compared with the reported papers, the proposed method was more sensitive and simple. The developed method was successfully applied for the determination of PCP in fish meat with satisfactory recoveries.

Sensitive voltammetric sensor based on Isopropanol–Nafion–PSS–GR nanocomposite modified glassy carbon electrode for determination of Clenbuterol in pork

Co-reporter:Ling Wang, Ran Yang, Jing Chen, Jianjun Li, Lingbo Qu, Peter de B. Harrington

Food Chemistry 2014 Volume 164() pp:113-118

Publication Date(Web):1 December 2014

DOI:10.1016/j.foodchem.2014.04.052

•PSS functionalized graphene (GR) was synthesized via one-step chemical reduction.•PSS–GR exhibited high electrocatalytic activity towards the oxidation of clenbuterol.•A novel sensitive electrochemical sensor of clenbuterol was established.In the present study, poly(sodium 4-styrenesulfonate) (PSS) functionalized graphene (GR) was synthesised via a simple one-step chemical reduction of exfoliated graphite oxides in the presence of PSS. Characterisation of as-made nanocomposite using Fourier transform infrared spectroscopy (FT-IR) and ultraviolet and visible spectroscopy (UV–vis) clearly demonstrate the successful attachment of PSS to graphene sheets. A novel clenbuterol (CLB) electrochemical sensor was fabricated based on isopropanol–Nafion–PSS–GR composite film modified glassy carbon electrode. In the Britton–Robinson buffer (pH 1.2), the sensor exhibited superior electrocatalytic activity towards the oxidation of CLB. Applying linear sweep voltammetry, a good linear relationship of the oxidation peak current with respect to concentrations of CLB cross the range of 7.5 × 10−8–2.5 × 10−5 mol L−1 and a detection limit of 2.2 × 10−8 mol L−1 were achieved. The proposed method was successfully applied for the determination of CLB in pork.

Supersensitive electrochemical sensor for the fast determination of rutin in pharmaceuticals and biological samples based on poly(diallyldimethylammonium chloride)-functionalized graphene

Co-reporter:Dandan Miao, Jianjun Li, Ran Yang, Jiajia Qu, Lingbo Qu, Peter de B. Harrington

Journal of Electroanalytical Chemistry 2014 Volume 732() pp:17-24

Publication Date(Web):15 October 2014

DOI:10.1016/j.jelechem.2014.08.018

•PDDA-Gr was prepared via in situ reduction of exfoliated graphite oxides in the presence of PDDA.•PDDA-Gr is used to build a supersensitive sensor for determination of rutin.•The electrochemical reaction mechanism of rutin was discussed in detail.•The method was applied to the determination of rutin in complex biological samples.In this work, poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (PDDA-Gr) was prepared via in situ reduction of exfoliated graphite oxides in the presence of PDDA. The obtained nanostructure was used as a novel immobilization platform for the electrochemical sensor of rutin. PDDA-Gr has superior electrocatalytic activity for the redox of rutin due to its large surface, fast electron transfer character and strong adsorption effect on rutin. The electron transfer rate constant (ks) and the electroactive surface area were calculated as 1.59 s−1 and 0.3324 cm2 respectively. The saturating absorption capacity (Γ) value of rutin on modified electrode was calculated to be 2.23 × 10−9 mol cm−2. Applying differential pulse voltammetry (DPV), a good linear relationship of the reduction peak current and the concentrations of rutin in the range of 0.0004–1.0 μM was achieved. The detection limit was 0.04 nM (S/N of 3). Under the optimum conditions, the metabolite of rutin, quercetin can be effectively separated from rutin, which suggested the great potential of the proposed method for the practical application in pharmacokinetic and clinical analyses. The method was successfully applied to the fast determination of rutin in medicine tablets and human plasma with satisfactory recoveries.

Assembly of multi-walled carbon nanotubes–ZnSe quantum dot hybrids for a paeonol electrochemical sensor

Co-reporter:Ling Wang, Ran Yang, Jianjun Li and Lingbo Qu

Analytical Methods 2014 vol. 6(Issue 10) pp:3449-3455

Publication Date(Web):26 Mar 2014

DOI:10.1039/C4AY00684D

Hybrid materials formed from acid functionalized multi-walled carbon nanotubes (MWCNTs) and glutathione (GSH)-capped ZnSe quantum dots (ZnSe QDs) were prepared by a non-covalent self-assembly method. Black spots decorated on the surface of MWCNTs under transmission electron microscopy (TEM) demonstrate successful attachment of ZnSe QDs on the surface of MWCNTs. The obtained ZnSe QD–MWCNTs can accelerate greatly the transfer rate of electrons and showed an obvious synergistic electrocatalytic effect for the oxidation of paeonol (PN). Based on this electrocatalytic activity, a novel electrochemical sensor was established. Under the optimum conditions, the peak currents had a good linear relationship with the concentration of PN in the ranges of 0.06 to 10.0 μM and 10.0 to 50.0 μM. The detection limit was reduced at 0.04 μM. The established sensing platform was applied to the determination of PN in pharmaceutical and clinical analyses with satisfactory recoveries.

Spectroscopy and Molecular Docking Study on the Interaction Behavior Between Nobiletin and Pepsin

Co-reporter:Hua-jin Zeng;Tingting Qi;Ran Yang;Jing You

Journal of Fluorescence 2014 Volume 24( Issue 4) pp:1031-1040

Publication Date(Web):2014 July

DOI:10.1007/s10895-014-1379-y

In this study, the binding mode of nobiletin (NOB) with pepsin was investigated by spectroscopic and molecular docking methods. NOB can interact with pepsin to form a NOB-pepsin complex. The binding constant, number of binding sites and thermodynamic parameters were measured, which indicated that NOB could spontaneously bind with pepsin through hydrophobic and electrostatic forces with one binding site. Molecular docking results revealed that NOB bound into the pepsin cavity. Synchronous and three-dimensional fluorescence spectra results provide data concerning conformational and some micro-environmental changes of pepsin. Furthermore, the binding of NOB can inhibit pepsin activity in vitro. The present study provides direct evidence at a molecular level to show that NOB could induce changes in the enzyme pepsin structure and function.

Sensitive and Simple Voltammetric Detection of Sudan I by Using Platinum Nanoparticle-Modified Glassy Carbon Electrode in Food Samples

Co-reporter:Lanlan Yu;Yexuan Mao;Yue Gao

Food Analytical Methods 2014 Volume 7( Issue 6) pp:1179-1185

Publication Date(Web):2014 July

DOI:10.1007/s12161-013-9731-4

A highly sensitive and simple voltammetric method is developed for determination of Sudan I by using platinum nanoparticles modified the glassy carbon electrode. With the optimized experimental conditions, the anodic peak currents of Sudan I are proportional to its concentration in the range of 0.002–0.3 μmol L−1 and 0.3–7.0 μmol L−1, and the limit of detection of 0.7 nmol L−1 is obtained. Some dynamic parameters are also investigated in this research. This proposed method is successfully applied to the detection of Sudan I in food, such as ketchup, chili powder, duck egg yolk, and chafing dish foodstuffs, which indicates its applicability and reliability.

Electrochemical preparation of Ag nanoparticles/poly(methylene blue) functionalized graphene nanocomposite film modified electrode for sensitive determination of rutin

Co-reporter:Suling Yang, Gang Li, Junhong Zhao, Huimin Zhu, Lingbo Qu

Journal of Electroanalytical Chemistry 2014 s 717–718() pp: 225-230

Publication Date(Web):

DOI:10.1016/j.jelechem.2014.01.004

Study on the binding of chlorogenic acid to pepsin by spectral and molecular docking

Co-reporter:Hua-jin Zeng;Hui-li Liang;Jing You

Luminescence 2014 Volume 29( Issue 7) pp:715-721

Publication Date(Web):

DOI:10.1002/bio.2610

ABSTRACT

The interaction of pepsin with chlorogenic acid (CHA) was investigated using fluorescence, UV/vis spectroscopy and molecular modeling methods. Stern–Volmer analysis indicated that the fluorescence quenching of pepsin by CHA resulted from a static mechanism, and the binding constant was 1.1846 × 10⁵ and 1.1587 × 10⁵ L/mol at 288 and 310 K, respectively. The distance between donor (pepsin) and acceptor (CHA) was calculated to be 2.39 nm and the number of binding sites for CHA binding on pepsin was ~ 1. The results of synchronous fluorescence and three-dimensional fluorescence showed that binding of CHA to pepsin could induce conformational changes in pepsin. Molecular docking experiments found that CHA bonded with pepsin in the area of the hydrophobic cavity with Van der Waals' forces or hydrogen bonding interaction, which were consistent with the results obtained from the thermodynamic parameter analysis. Furthermore, the binding of CHA can inhibit pepsin activity in vitro. Copyright © 2013 John Wiley & Sons, Ltd.

Peroxides as “Switches” of Dialkyl H-Phosphonate: Two Mild and Metal-Free Methods for Preparation of 2-Acylbenzothiazoles and Dialkyl Benzothiazol-2-ylphosphonates

Co-reporter:Xiao-Lan Chen, Xu Li, Ling-Bo Qu, Yu-Chun Tang, Wen-Peng Mai, Dong-Hui Wei, Wen-Zhu Bi, Li-Kun Duan, Kai Sun, Jian-Yu Chen, Dian-Dian Ke, and Yu-Fen Zhao

The Journal of Organic Chemistry 2014 Volume 79(Issue 17) pp:8407-8416

Publication Date(Web):August 18, 2014

DOI:10.1021/jo501791n

Two mild and metal-free methods for the preparation of two kinds of important benzothiazole derivatives, 2-acylbenzothiazoles and dialkyl benzothiazol-2-ylphosphonates, respectively, were developed. The dialkyl H-phosphonate (RO)2P(O)H exists in equilibrium with its tautomer dialkyl phosphite (RO)2POH. TBHP triggered α-carbon-centered phosphite radical formation, whereas DTBP triggered phosphorus-centered phosphonate radical formation. The two types of radicals led respectively to two different reaction processes, the direct C2-acylation of benzothiazoles and C2-phosphonation of benzothiazoles.

Preparation of electrochemically reduced graphene oxide/multi-wall carbon nanotubes hybrid film modified electrode, and its application to amperometric sensing of rutin

Co-reporter:SULING YANG;GANG LI;MEIFANG HU;LINGBO QU

Journal of Chemical Sciences 2014 Volume 126( Issue 4) pp:1021-1029

Publication Date(Web):2014 July

DOI:10.1007/s12039-014-0654-4

Through a facile electrochemical method, we prepared an electrochemically reduced graphene oxide (ERGO)/multi-wall carbon nanotubes (MWNTs) hybrid film modified glassy carbon electrode (GCE), and characterized it by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and x-ray diffraction (XRD) The experimental results demonstrated that ERGO-MWNTs/GCE exhibited excellent electrocatalytic activity toward rutin as evidenced by the significant enhancement of redox peak currents in comparison with a bare GCE, ERGO/GCE and MWNTs/GCE. This method has been applied for the direct determination of rutin in real samples with satisfactory results.

A sensitive electrochemical chlorophenols sensor based on nanocomposite of ZnSe quantum dots and cetyltrimethylammonium bromide

Co-reporter:Jianjun Li, Xiao Li, Ran Yang, Lingbo Qu, Peter de B. Harrington

Analytica Chimica Acta 2013 Volume 804() pp:76-83

Publication Date(Web):4 December 2013

DOI:10.1016/j.aca.2013.09.049

•Nanocomposite based ZnSe QDs and CTAB was prepared and characterized.•A novel electrochemical sensor for the determination of CPs was built.•The proposed sensor was more sensitive, simple and environment-friendly.In this work, a very sensitive and simple electrochemical sensor for chlorophenols (CPs) based on a nanocomposite of cetyltrimethylammonium bromide (CTAB) and ZnSe quantum dots (ZnSe–CTAB) through electrostatic self-assembly technology was built for the first time. The composite of ZnSe–CTAB introduced a favorable access for the electron transfer and gave superior electrocatalytic activity for the oxidation of CPs than ZnSe QDs and CTAB alone. Differential pulse voltammetry (DPV) was used for the quantitative determination of the CPs including 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP). Under the optimum conditions, the peak currents of the CPs were proportional to their concentrations in the range from 0.02 to 10.0 μM for 2-CP, 0.006 to 9.0 μM for 2,4-DCP, and 0.06 to 8.0 for PCP. The detection limits were 0.008 μM for 2-CP, 0.002 μM for 2,4-DCP, and 0.01 μM for PCP, respectively. The method was successfully applied for the determination of CPs in waste water with satisfactory recoveries. This ZnSe–CTAB electrode system provides operational access to design environment-friendly CPs sensors.A very sensitive and simple electrochemical sensor for chlorophenols (CPs) based on nanocomposite of cetyltrimethylammonium bromide (CTAB) and ZnSe quantum dots (ZnSe–CTAB) through electrostatic self-assembly technology was built for the first time. The nanocomposite of ZnSe–CTAB introduced a favorable access for the electron transfer and showed excellent electrocatalytic activity for the oxidation of CPs.

Nano-sized copper oxide/multi-wall carbon nanotube/Nafion modified electrode for sensitive detection of dopamine

Co-reporter:Suling Yang, Gang Li, Yelin Yin, Ran Yang, Jianjun Li, Lingbo Qu

Journal of Electroanalytical Chemistry 2013 Volume 703() pp:45-51

Publication Date(Web):15 August 2013

DOI:10.1016/j.jelechem.2013.04.020

•Nano-sized CuO/MWNTs/Nafion modified electrode was fabricated.•The morphology of CuO/MWNTs were characterized by SEM, EDS, XRD and XPS.•Dopamine can effectively accumulate at CuO/MWNTs/Nafion.•This newly exploited electrochemical sensor was successfully used to determine dopamine in real sample.A novel nano-sized copper oxide/multi-wall carbon nanotubes/Nafion (CuO/MWNTs/Nafion) composite film–modified electrode was fabricated, and applied for a sensitive and selective determination of dopamine. The morphology and structure of the as-prepared CuO/MWNTs nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS). The excellent electrocatalytic activity of the CuO/MWNTs/Nafion nanocomposite for the oxidation of dopamine was studied by voltammetry. Dopamine can effectively accumulate at CuO/MWNTs/Nafion composite film-modified electrode and produce a pair of sensitive redox peaks in 0.1 mol L–1 phosphate buffer solution (PBS) (pH 6.0). This newly exploited electrochemical sensor was successfully used to determine dopamine in real sample.

Immobilization of gold nanoparticles on multi-wall carbon nanotubes as an enhanced material for selective voltammetric determination of dopamine

Co-reporter:Suling Yang, Yelin Yin, Gang Li, Ran Yang, Jianjun Li, Lingbo Qu

Sensors and Actuators B: Chemical 2013 178() pp: 217-221

Publication Date(Web):

DOI:10.1016/j.snb.2012.12.068

Interaction between baicalein and amyloid-β fibrils studied by fluorescence spectroscopy

Co-reporter:Sheng-mei Song;Yong-xiang Wang;Li-min Xiong

Chemical Research in Chinese Universities 2013 Volume 29( Issue 1) pp:20-25

Publication Date(Web):2013 February

DOI:10.1007/s40242-013-2180-1

The interaction between baicalein and amyloid-β(Aβ) polypeptide was investigated by fluorescence and UV-Vis absorbance spectroscopy. The absence of the characteristic peak of tyrosinate(Tyr) in the absorption spectra of Aβ-baicalein complexes provided evidence that the sole Tyr residue in Aβ is not bound to baicalein, but remains close to it. The intrinsic fluorescence of Tyr residues in Aβ1–42 aggregates was quenched strongly by the excited-state ionization of baicalein. In this complex the hydroxyl group was not ionized, but to ionize immediately upon excitation. Absorbance, fluorescence and synchronous spectroscopies show that the formation of Schiff base between the quinone of baicalein and the lysine(Lys) side chains of Aβ1–42 is another major reason in the depolymerization of Aβ1–42 aggregates by baicalein. It is desirable that our research would offer some valuable reference for the application of flavonoid derivants in Alzheimer’s disease(AD) treatment.

High sensitive determination of theophylline based on gold nanoparticles/l-cysteine/Graphene/Nafion modified electrode

Co-reporter:Lijuan Zi, Jianjun Li, Yexuan Mao, Ran Yang, Lingbo Qu

Electrochimica Acta 2012 Volume 78() pp:434-439

Publication Date(Web):1 September 2012

DOI:10.1016/j.electacta.2012.06.018

In the work described on this paper, a gold nanoparticles (GNP)/l-cysteine (l-cys)/Graphene (Gr)/Nafion composite film modified glass carbon electrode (GCE) was fabricated and characterized. The modified electrode showed excellent electrocatalytic activity towards the oxidation of theophylline (TP) in 0.1 mol L−1 H2SO4 medium. Differential pulse voltammetry (DPV) was used for the determination of TP. Under the optimum conditions, the peak current of TP was proportional to its concentration at the range of 4.0 × 10−9 to 6.0 × 10−5 mol L−1 with a detection limit 4.0 × 10−10 mol L−1. The newly developed method was successfully applied for the determination of TP in tea samples and pharmaceutical tablets with good percentage of recoveries.

AFM and fluorescence spectrascopy investigation for disaggregation of existing Aβ fibrils by baicalein

Co-reporter:Sheng Mei Song, Yong Xiang Wang, Li Min Xiong, Ling Bo Qu, Mao Tian Xu

Chinese Chemical Letters 2012 Volume 23(Issue 5) pp:595-598

Publication Date(Web):May 2012

DOI:10.1016/j.cclet.2012.03.001

The wavelength for the peak of fluorescence emission of thioflavin T (ThT) was changed from 445 nm to 481 nm when ThT was added in Aβ solution which indicating the β-sheet structure of Aβ fibril. The significant decrease in the intensity of fluorescence at 481 nm was observed when the baicalein was added in mixed solution of Aβ and ThT, suggesting that the depolymerization of Aβ fibrils happened and there were Aβ fibrils left to react with ThT to keep the initial fluorescence intensity. And the existing Aβ fibrils are disaggregated by baicalein in a time- and dose-dependent manner. AFM images of the morphologies of the Aβ1–42 fibrils obviously changed smaller and more dispersive when baicalein added indicating also the depolymerization of Aβ. The results demonstrate a basis for development of a potential herb drug candidate for the treatment of Alzheimer's disease (AD).

The Interaction of Flavonoid-Lysozyme and the Relationship Between Molecular Structure of Flavonoids and Their Binding Activity to Lysozyme

Co-reporter:Ran Yang;Lanlan Yu;Huajin Zeng;Ruiling Liang;Xiaolan Chen

Journal of Fluorescence 2012 Volume 22( Issue 6) pp:1449-1459

Publication Date(Web):2012 November

DOI:10.1007/s10895-012-1082-9

In this work, the interactions of twelve structurally different flavonoids with Lysozyme (Lys) were studied by fluorescence quenching method. The interaction mechanism and binding properties were investigated. It was found that the binding capacities of flavonoids to Lys were highly depend on the number and position of hydrogen, the kind and position of glycosyl. To explore the selectivity of the bindings of flavonoids with Lys, the structure descriptors of the flavonoids were calculated under QSAR software package of Cerius2, the quantitative relationship between the structures of flavonoids and their binding activities to Lys (QSAR) was performed through genetic function approximation (GFA) regression analysis. The QSAR regression equation was KA = 37850.460 + 1630.01Dipole +3038.330HD-171.795MR. (r = 0.858, \( r_{\text{CV}}^2 = 0.444 \), F(11,3) = 7.48), where KA is binding constants, Dipole, HD and MR was dipole moment, number of hydrogen-bond donor and molecular refractivity, respectively. The obtained results make us understand better how the molecular structures influencing their binding to protein which may open up new avenues for the design of the most suitable flavonoids derivatives with structure variants.

Preparation of yttrium hexacyanoferrate/carbon nanotube/Nafion nanocomposite film-modified electrode: Application to the electrocatalytic oxidation of l-cysteine

Co-reporter:Lingbo Qu, Suling Yang, Gang Li, Ran Yang, Jianjun Li, Lanlan Yu

Electrochimica Acta 2011 Volume 56(Issue 7) pp:2934-2940

Publication Date(Web):28 February 2011

DOI:10.1016/j.electacta.2010.12.090

An yttrium hexacyanoferrate nanoparticle/multi-walled carbon nanotube/Nafion (YHCFNP/MWNT/Nafion)-modified glassy carbon electrode (GCE) was constructed. Several techniques, including infrared spectroscopy, energy dispersive spectrometry, scanning electron microscopy and electrochemistry, were performed to characterize the yttrium hexacyanoferrate nanoparticles. The electrochemical behavior of the YHCFNP/MWNT/Nafion-modified GCE in response to l-cysteine oxidation was studied. The response current of l-cysteine oxidation at the YHCFNP/MWNT/Nafion-modified GCE was obviously higher than that at the bare GCE or other modified GCE. The effects of pH, scan rate and interference on the response to l-cysteine oxidation were investigated. In addition, on the basis of these findings, a determination of l-cysteine at the YHCFNP/MWNT/Nafion-modified GCE was carried out. Under the optimum experimental conditions, the electrochemical response to l-cysteine at the YHCFNP/MWNT/Nafion-modified GCE was fast (within 4 s). Linear calibration plots were obtained over the range of 0.20–11.4 μmol L−1 with a low detection limit of 0.16 μmol L−1. The YHCFNP/MWNT/Nafion-modified GCE exhibited several advantages, such as high stability and good resistance against interference by ascorbic acid and other oxidizable amino acids.

Determination of melamine by flow injection analysis based on chemiluminescence system

Co-reporter:Hua-jin Zeng, Ran Yang, Qing-wen Wang, Jian-jun Li, Ling-bo Qu

Food Chemistry 2011 Volume 127(Issue 2) pp:842-846

Publication Date(Web):15 July 2011

DOI:10.1016/j.foodchem.2011.01.021

In this paper, based upon the phenomenon that melamine can obviously enhance the CL signal of the luminol–H2O2 system in basic medium, a simple, rapid and sensitive flow injection chemiluminescence (FI-CL) method for the determination of melamine has been developed. Under the optimum conditions, the linear range for the determination of melamine was 0.2–80 μg mL−1 with a detection limit of 0.12 μg mL−1 calculated as proposed by IUPAC and a relative standard deviation of 3.26% for 11 solutions of 10 μg mL−1 melamine on the same day. The proposed method was satisfactorily applied to determine melamine in milk-based products and satisfactory results were obtained without interferences from the sample matrix. Moreover, one assay produce takes only 25 s and the minimum sampling rate is about 120 samples h−1, which indicated that the FI-CL method was suitable for high throughput and real-time melamine analysis.Research highlights► A novel FI-CL method was developed for determination of melamine in milk products. ► Parameters affecting reproducibility and CL detection were optimized systematically. ► A assay produce takes only 25 s and the sampling rate is about 120 samples h−1.

Capillary electrophoresis coupled with end-column electrochemiluminescence for the determination of ephedrine in human urine, and a study of its interactions with three proteins

Co-reporter:Ran Yang;Hua-Jin Zeng;Jian-Jun Li;Ying Zhang;Shi-Jun Li

Luminescence 2011 Volume 26( Issue 5) pp:374-379

Publication Date(Web):

DOI:10.1002/bio.1336

ABSTRACT

A tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺)-based electrochemiluminescence (ECL) detection coupled with capillary electrophoresis (CE) method has been established for the sensitive determination of ephedrine for the first time. Under the optimized conditions [ECL detection at 1.15 V, 25 mmol/L phosphate buffer solution (PBS), pH 8.0, as running buffer, separation voltage 12.5 kV, 5 mmol/L Ru(bpy)₃²⁺ with 60 mmol/L PBS, pH 8.5, in the detection cell] linear correlation (r = 0.9987) between ECL intensity and ephedrine concentration was obtained in the range 6.0 × 10^–8–6.0 × 10^–6 g/mL. The detection limit was 4.5 × 10^–9 g/mL (S:N = 3). The developed method was successfully applied to the analysis of ephedrine in human urine and the investigation of its interactions with three proteins, including bovine serum albumin (BSA), cytochrome C (Cyt-C) and myoglobin (Mb). The number of binding sites and the binding constants between ephedrine and BSA, Cyt-C and Mb were 8.52, 12.60, 10.66 and 1.55 × 10⁴ mol/L, 6.58 × 10³ mol/L and 1.59 × 10⁴ mol/L, respectively. Copyright © 2011 John Wiley & Sons, Ltd.

Determination of puerarin in biological samples and its application to a pharmacokinetic study by flow-injection chemiluminescence

Co-reporter:Ran Yang;Qingwen Wang;Huajin Zeng;Zao Qin;Jianjun Li;Lingbo Qu

Luminescence 2011 Volume 26( Issue 5) pp:368-373

Publication Date(Web):

DOI:10.1002/bio.1281

ABSTRACT

A simple and sensitive flow injection–chemiluminescence (FI–CL) method has been developed for the determination of puerarin, based on the fact that puerarin can greatly inhibit CL of the luminol–H₂O₂–haemoglobin system. The inhibition of CL intensity was linear to the logarithm of the concentration of puerarin in the range 0.08–10.0 μg/mL (r² = 0.9912). The limit of detection was 0.05 μg/mL (3σ) and the relative standard deviation (RSD) for 1.0 μg/mL (n = 11) of puerarin solution was 1.4%. Coupled with solid-phase extraction (SPE) as the sample pretreatment, the determination of puerarin in biological samples and a preliminary pharmocokinetic study of puerarin in rats were performed. The recoveries for plasma and urine at three different concentrations were 89.2–110.0% and 91.4–104.8%, respectively. The pharmacokinetics of puerarin in plasma of rat coincides with the two-compartment open model. The T_1/2α, T_1/2β, CL/F, V_Z/F, AUC_{(0 – t)}, MRT_{(0 – ∞)}, T_max and C_max were 0.77 ± 0.21 h, 7.55 ± 2.64 h, 2.43 ± 1.02 L/kg/h, 11.40 ± 3.45 L/kg, 56.67 ± 10.65 mg/h/L, 5.04 ± 2.78 h, 1.00 ± 0.35 h and 19.70 ± 4.67 μg/mL, respectively. Copyright © 2011 John Wiley & Sons, Ltd.

Simultaneous voltammetric determination of ascorbic acid and uric acid using a Nafion/multi-wall carbon nanotubes composite film-modified electrode

Co-reporter:Gang Li;Suling Yang;Lingbo Qu;Ran Yang

Journal of Solid State Electrochemistry 2011 Volume 15( Issue 1) pp:161-166

Publication Date(Web):2011 January

DOI:10.1007/s10008-010-1088-7

A Nafion/multi-wall carbon nanotubes (MWNT) composite film-modified electrode was fabricated. The modified electrode showed excellent electrocatalytic activity toward ascorbic acid (AA) and uric acid (UA) in 0.1-mol L−1 NaCl medium (pH 6.5). Compared to the bare electrode that only displayed a broad and overlapped oxidation peak, the Nafion/MWNT film-modified electrode not only remarkably enhanced the anodic peak currents of AA and UA but also avoided the overlapping of the anodic peaks of AA and UA with a 320-mV separation of both peaks. Under the optimized conditions, the peak currents of AA and UA were proportional to their concentration at the ranges of 8.0 × 10−5 to 6.0 × 10−3 mol L−1 and 6.0 × 10−7 to 8.0 × 10−5 mol L−1, respectively. The proposed method was used for the detection of AA and UA in real samples with satisfactory results.

Pharmacokinetic study of six flavones in rat plasma and tissues after oral administration of ‘JiangYaBiFeng’ using SPE-HPLC–DAD

Co-reporter:Hua-jin Zeng, Ran Yang, Cheng Guo, Qing-wen Wang, Ling-bo Qu, Jian-jun Li

Journal of Pharmaceutical and Biomedical Analysis 2011 56(4) pp: 815-819

Publication Date(Web):

DOI:10.1016/j.jpba.2011.07.015

Simultaneous determination of eight active components in Chinese medicine ‘JiangYaBiFeng’ tablet by HPLC coupled with diode array detection

Co-reporter:Ran Yang, Hua-jin Zeng, Qing-wen Wang, Cheng Guo, Jian-jun Li, Ling-Bo Qu

Journal of Pharmaceutical and Biomedical Analysis 2011 55(3) pp: 552-556

Publication Date(Web):

DOI:10.1016/j.jpba.2011.01.021

Nafion/multi-wall carbon nanotubes composite film coated glassy carbon electrode for sensitive determination of caffeine

Co-reporter:Suling Yang, Ran Yang, Gang Li, Lingbo Qu, Jianjun Li, Lanlan Yu

Journal of Electroanalytical Chemistry 2010 Volume 639(1–2) pp:77-82

Publication Date(Web):15 February 2010

DOI:10.1016/j.jelechem.2009.11.025

A Nafion/multi-wall carbon nanotubes (MWNTs) composite film-modified electrode was fabricated and applied for the sensitive and selective determination of caffeine. Multi-wall carbon nanotubes (MWNTs) were easily dispersed homogeneously into methanol by ultrasonication in the presence of 0.1% Nafion. After evaporating the methanol, a Nafion/MWNTs composite film-modified electrode was achieved. Caffeine can be effectively accumulated at Nafion/MWNTs composite film-modified electrode and produce a sensitive anodic peak at around 1330 mV (vs. SCE) in a 0.01 mol L−1 H2SO4 medium (pH 2.0). Compared to the bare electrode and Nafion film-modified electrode, the Nafion/MWNTs film-modified electrode can remarkably increase the anodic peak current of caffeine. Under the suitable conditions, the anodic peak current was linear to caffeine concentration in the range of 6.0 × 10−7−4.0 × 10−4 mol L−1, and the limit of detection was 2.3 × 10−7 mol L−1. The Nafion/MWNTs composite film-modified electrode can be renewed by repetitiously cycling in a blank solution for about three cycles. This newly exploited method was successfully used to determine caffeine in beverage samples.

Gold nanoparticles/ethylenediamine/carbon nanotube modified glassy carbon electrode as the voltammetric sensor for selective determination of rutin in the presence of ascorbic acid

Co-reporter:Suling Yang, Lingbo Qu, Gang Li, Ran Yang, Cuicui Liu

Journal of Electroanalytical Chemistry 2010 Volume 645(Issue 2) pp:115-122

Publication Date(Web):1 July 2010

DOI:10.1016/j.jelechem.2010.04.019

In this paper, the electrochemical behavior of rutin on a gold nanoparticles/ethylenediamine/multi-wall carbon nanotubes modified glassy carbon electrode (AuNPs/en/MWNTs/GCE) was investigated and the electrochemical parameters of rutin were calculated. Rutin effectively accumulated on the AuNPs/en/MWNTs/GCE and caused a pair of redox peaks at around 487 mV and 432 mV (vs. SCE) in 0.1 M phosphate buffer solution (pH 3.5). Under optimized conditions, the anodic peak current was linear to the rutin concentration in the range of 4.8 × 10−8 M−9.6 × 10−7 M. The regression equation was: ipa = 2.3728Crutin−0.1782 (ipa: 10−5 A, Crutin: μM, r = 0.9973). The detection limit of 3.2 × 10−8 M was obtained. The proposed method was successfully used to the determination of rutin content in tablet samples with satisfactory results.

Modified glassy carbon electrode with Nafion/MWNTs as a sensitive voltammetric sensor for the determination of paeonol in pharmaceutical and biological samples

Co-reporter:Suling Yang;Lingbo Qu;Ran Yang;Jianjun Li

Journal of Applied Electrochemistry 2010 Volume 40( Issue 7) pp:1371-1378

Publication Date(Web):2010 July

DOI:10.1007/s10800-010-0104-z

A simple, highly sensitive method was reported for directly voltammetric determination of paeonol in drug samples and human biological samples. Nafion/multi-wall carbon nanotubes’ (MWNTs) composite film was coated on the glassy carbon electrode. The adsorptive voltammetric behavior of paeonol on the Nafion/MWNTs-modified electrode was investigated using cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). The results indicated that the Nafion/MWNTs-modified electrode could remarkably enhance electrocatalytic activity toward the oxidation of paeonol, and showed an excellent resistance capability toward the electrode passivation. A highly sensitive voltammetric sensor was developed for the detection of paeonol in pharmaceutical and biological samples. Under the optimum conditions, the anodic peak current was proportional to paeonol concentration in the range of 6.0 × 10−7–6.0 × 10−5 M with a detection limit of 4.0 × 10−7 M. Some kinetic parameters were determined, and multi-step mechanism for oxidation of paeonol was proposed.

Voltammetric determination of theophylline at a Nafion/multi-wall carbon nanotubes composite film-modified glassy carbon electrode

Co-reporter:Suling Yang;Ran Yang;Gang Li;Jianjun Li;Lingbo Qu

Journal of Chemical Sciences 2010 Volume 122( Issue 6) pp:919-926

Publication Date(Web):2010 November

DOI:10.1007/s12039-010-0080-1

A Nafion/multi-wall carbon nanotubes (MWNTs) composite film-modified electrode was fabricated and applied to the sensitive and convenient determination of theophylline (TP). Multi-wall carbon nanotubes (MWNTs) were easily dispersed homogeneously into 0.1% Nafion methanol solution by sonication. Appropriate amount of Nafion/MWNTs suspension was coated on a glassy carbon electrode. After evaporating methanol, a Nafion/MWNTs composite film-modified electrode was achieved. TP could effectively accumulate at Nafion/MWNTs composite film-modified electrode and cause a sensitive anodic peak at around 1180 mV (vs SCE) in 0.01 mol/L H2SO4 medium (pH 1.8). In contrast with the bare glassy carbon electrode, Nafion film-modified electrode, Nafion/MWNTs film-modified electrode could remarkably increase the anodic peak current and decreased the overpotential of TP oxidation. Under the optimized conditions, the anodic peak current was proportional to TP concentration in the range of 8.0 × 10−8–6.0×10−5 mol/L, with a detection limit of 2.0 × 10−8 mol/L. This newly developed method was used to determine TP in drug samples with good percentage of recoveries.

Development of ELISA and immunochromatographic assay for ofloxacin

Co-reporter:Wu Yong Sun, Wen Ying Liu, Ling Bo Qu

Chinese Chemical Letters 2007 Volume 18(Issue 9) pp:1107-1110

Publication Date(Web):September 2007

DOI:10.1016/j.cclet.2007.07.008

Two rapid, sensitive and reliable immunoassay methods, namely competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) and colloidal gold-based immunochromatographic assay (CGIA), were developed to detect ofloxacin (OFL). The linear range of the CI-ELISA was from 0.5 to 128 ng/mL with a limit of detection (LOD) of 0.35 ng/mL. Good recoveries were obtained in analyzing simulated swine urine samples. The CGIA could accurately estimate OFL at concentrations as low as 10 ng/mL in less than 10 min, and test results were read visually without any instrument.

Investigation of the Interaction between Isoflavonoids and Bovine Serum Albumin by Fluorescence Spectroscopy

Co-reporter:Ling-Bo Qu;Xiao-Lan Chen;Ran Yang;Ling Wang;Hua-Jin Zeng

Chinese Journal of Chemistry 2007 Volume 25(Issue 8) pp:

Publication Date(Web):15 AUG 2007

DOI:10.1002/cjoc.200790215

The interactions of bovine serum albumin (BSA) with three structurally related isoflavonoids, genistein, puerarin and daidzein, were studied under physiological conditions by fluorescence spectroscopic technique. The quenching mechanism of these compounds with BSA was suggested as static quenching and the binding constants were determined at different temperatures based on the fluorescence quenching results. The transfer efficiency of energy and distance between the acceptor and BSA were investigated on the basis of the mechanism of the Förster energy transference. According to the thermodynamic parameters it has been suggested that the acting force be mainly hydrophobic force. The comparison of binding potency of the three isoflavonoids to BSA showed that the substitution by 5-OH and 8-Glc could enhance the binding affinity. All these obtained in the work can make us better understand the mode of the action and pharmacological activities of the isoflavonoids.

Chrysin and its phosphate ester inhibit cell proliferation and induce apoptosis in Hela cells

Co-reporter:Ting Zhang, Xiaolan Chen, Lingbo Qu, Jinglan Wu, Ran Cui, Yufen Zhao

Bioorganic & Medicinal Chemistry 2004 Volume 12(Issue 23) pp:6097-6105

Publication Date(Web):1 December 2004

DOI:10.1016/j.bmc.2004.09.013

To improve the biological activities of chrysin (CR), we synthesize Diethyl Chysin-7-yl phosphate (CPE: C19H19O7P) and tetraethyl bis-phosphoric ester of chrysin (CP: C23H28O10P2) through a simplified Atheron–Todd reaction. The interactions of the CR and CPE with lysozyme were explored by electrospray ionization mass spectrometry (ESI) and fluorescence spectrometry method. Experimental results indicate that CPE could form the noncovalent compound with lysozyme, while the interaction of the CR with lysozyme was not detected. In addition, whether and how the compounds CPE and CP affect proliferation and apoptosis in human cervical cancer Hela cells were investigated. Moreover, the effects of CPE and CP in Hela cells were compared with that of the nonmodified CR compound. The Hela cells were co-cultured with CR, CP, and CPE as experimental groups, respectively, and corresponding control groups treated without CR, CP, and CPE. The proliferation and apoptosis were detected using MTT assay, HCl denatured-methyl green-pyronin staining, PCNA immunohistochemistry and TUNEL techniques. The cell growth IC50, relative absorbance (RA), proliferating index (PI), PCNA-IR (immunoreactivity IR) integration value (IV), and apoptosis index (AI) were calculated and their correlation was analyzed in each group. The results show that all CR, CP, and CPE could inhibit proliferation and induce apoptosis in Hela cells. Moreover, the effects of CP and CPE were more potent than that of CR. The CP and CPE were proved to be a kind of stronger apoptosis inducers than nonphosphated CR. There was a negative correlation between proliferation and apoptosis. In conclusion, the CR, CP, and CPE could effectively inhibit growth by down-regulated expression of PCNA, and induce apoptosis in Hela cells. The efficiency of the modified CP and CPE preceded nonmodified CR compounds. The CP and CPE may be a new potential anti-cancer drug for therapy of human cervical carcinoma.The MTT relative absorbance of all test compounds with different concentrations in Hela cells following treatment for 72 h was shown.

Simple and sensitive determination of sparfloxacin in pharmaceuticals and biological samples by immunoassay

Co-reporter:Hua-Jin Zeng, Ran Yang, Bing Liu, Li-Fang Lei, ... Ling-Bo Qu

Journal of Pharmaceutical Analysis (June 2012) Volume 2(Issue 3) pp:214-219

Publication Date(Web):1 June 2012

DOI:10.1016/j.jpha.2012.02.001

Plasma quinolone concentrations are not routinely measured in clinical practice. However, in order to optimize quinolone treatment, monitoring of plasma concentrations could sometimes be useful particularly in critically ill patients. In this study, anti-sparfloxacin antibody was obtained by immunizing rabbits with sparfloxacin conjugated with bovine serum albumin using isobutyl chloroformate method. After the assay procedure was optimized, the standard curve of sparfloxacin was established. The practical measuring range of the competitive ELISA extended from 5 ng/mL to 2 μg/mL. The recovery rates and coefficients of variation for rat plasma, urine and tissues were 87.7–106.2% and 4.8–15.3%, respectively. To demonstrate the potential of the ELISA, a preliminary pharmacokinetics and tissue distribution study of sparfloxacin in rats and quantitative analysis of sparfloxacin in several pharmaceuticals were performed and compared with high-performance liquid chromatography (HPLC). The experimental data indicated that the proposed method would be a valuable tool in therapeutic drug monitoring (TDM) for sparfloxacin.

New peptide inhibitors modulate the self-assembly of islet amyloid polypeptide residues 11–20 in vitro

Co-reporter:Yexuan Mao, Lanlan Yu, Ran Yang, Chuanguo Ma, Lingbo Qu, Peter de B. Harrington

European Journal of Pharmacology (5 June 2017) Volume 804() pp:102-110

Publication Date(Web):5 June 2017

DOI:10.1016/j.ejphar.2017.03.015

The structural transition and misfolding of human islet amyloid polypeptide may cause a common metabolic disease Type 2 diabetes mellitus. Seventeen peptides have been synthesized, possessing different lengths, compositions, and peptide conformation. In this study, the mechanism of these peptides on inhibiting the formation of hIAPP11–20 amyloid fibrils was investigated using a conventional ThT fluorescence assay and microscale thermophoresis. The results showed that short peptides AT, SA, RF, KS, KT and KN, and cyclic peptides cyclic-KS, cyclic-KT and cyclic-KN displayed considerable inhibitory effect on hIAPP11–20 fibril formation and a strong affinity for hIAPP11–20. The detailed investigation indicated that the phenylalanine residue and some special peptide composition significantly inhibit amyloid formation. The peptide conformation of the designed peptide inhibitors may also play an important role. Microscale thermophoresis quantified the binding affinities between hIAPP11–20 and the peptides; and revealed that high affinity binding more likely leads to inhibiting fibril formation of hIAPP11–20 and vice versa, which is in accordance with the results from the ThT assays. These findings suggest a feasible model of peptide inhibitor design for inhibiting amyloid formation. In addition, microscale thermophoresis was proven as a promising rapid method for preliminarily screening inhibitors of hIAPP11–20.

Assembly of multi-walled carbon nanotubes–ZnSe quantum dot hybrids for a paeonol electrochemical sensor

Co-reporter:

Analytical Methods (2009-Present) 2014 - vol. 6(Issue 10) pp:

Publication Date(Web):

DOI:10.1039/C4AY00684D