Co-reporter:Di Su, Xiaocai Hu, Chaoqing Dong, and Jicun Ren
Analytical Chemistry September 19, 2017 Volume 89(Issue 18) pp:9788-9788
Publication Date(Web):August 14, 2017
DOI:10.1021/acs.analchem.7b01735
Caspase-3 is a key enzyme executing apoptosis during ontogenesis and homeostasis of multicellular organisms, and is a very important and potential drug target in treatment of apoptosis disturbance. So far, no commercial drugs for caspase-3 are available, and it is urgently necessitated to develop an effective method for caspase-3 activity assay and its inhibitor screening. In this paper, we propose a new method for determination of caspase-3 activity and its inhibition constant by combining single molecule fluorescence correlation spectroscopy (FCS) with a microwell chip. Its principle is based on measurement of the enzyme reaction kinetics and homogeneous detection of the reaction product by FCS. This system can reduce the requirement sample volume to 1 μL level. The caspase-3 substrates are doubly labeled with fluorophore and biotin, the enzyme reaction can be quickly terminated in the presence of streptavidin, and the reaction products can be selectively detected by FCS. We established the model of caspase-3 inhibitor screening by combining the dynamics of enzyme reaction with FCS theory. This new method was successfully used for determination of inhibition constants of certain inhibitors and assay of drug-induced apoptosis. Compared to current methods, this method shows high sensitivity, small reagent dosage and short analysis time. We believe that this method will become an efficient platform for screening of caspase-3 inhibitors and detection of apoptosis.
Co-reporter:Bocheng Zhang, Heng Liu, Xiangyi Huang, Chaoqing Dong, and Jicun Ren
Analytical Chemistry November 21, 2017 Volume 89(Issue 22) pp:12609-12609
Publication Date(Web):October 27, 2017
DOI:10.1021/acs.analchem.7b04166
A single-nanoparticle detection method is reported for characterizing the size distribution of noble metal nanoparticles in solution by combining resonance light scattering correlation spectroscopy (RLSCS) with the maximum entropy method (MEM). The principle of RLSCS is based on the autocorrelation analysis of the resonance light scattering (RLS) fluctuations due to Brownian motion of a single nanoparticle in a highly focused detection volume (less than 1.0 fL), which resembles fluorescence correlation spectroscopy (FCS). However, RLS intensity of nanoparticles such as gold nanoparticles (GNPs) is proportional to the sixth power of sizes according to the Mie theory, which is different from the optical properties of fluorescent molecules. Herein the present FCS theoretical model cannot be directly applied in RLSCS to characterize GNPs. In this study, we used GNPs as model samples and first established an RLSCS theoretical model for the size distribution of GNPs by using the maximum entropy method (MEM), which is called MEM-RLSCS. This model covers the contribution of single-particle brightness of GNPs to the MEM fitting process based on the Mie theory. Then we preformed computer simulations of this model. The simulated results documented that the model proposed was able to well describe the diffusion behaviors and size distribution of nanoparticles. We investigated the effects of certain factors such as size difference, the relative concentration, and single-particle brightness on the size distribution. Finally, we used the MEM-RLSCS for characterization of GNPs in solution, and the results obtained were in agreement with the size distribution of GNPs from transmission electron microscopy (TEM). This method is also suitable for characterization of other metal nanoparticles (such as silver nanoparticles) in solution and in situ study diffusion dynamics of nanoparticles in living cells.
Co-reporter:Jinjie Wang, Xiangyi Huang, Heng Liu, Chaoqing Dong, and Jicun Ren
Analytical Chemistry May 16, 2017 Volume 89(Issue 10) pp:5230-5230
Publication Date(Web):April 24, 2017
DOI:10.1021/acs.analchem.6b04547
In this work, we propose fluorescence and scattering light cross-correlation spectroscopy (FSCCS) based on laser confocal configuration using silver nanoparticle (SNPs) and Alexa Fluor 488 (Alexa) as probe pairs. FSCCS is a single molecule (particle) method, and its principle is similar to that of fluorescence cross-correlation spectroscopy (FCCS). We established the setup of FSCCS using single wavelength laser and developed an immunoassay model of FSCCS. The reliability and adaptability of FSCCS method were evaluated by homogeneous sandwich immunoassay mode. In the study, liver cancer biomarker alpha-fetoprotein (AFP) was used as an assay model, two different antibodies were labeled with SNPs and fluorophore Alexa Fluor 488, respectively. In the optimal conditions, the linear range of AFP covers 5 pM to 580 pM and the detection limit is 3.1 pM. This method was successfully applied for direct determination of AFP levels in human serum samples, and the obtained results were in good agreement with data obtained via ELISAs. The advantage of this method lies in its simplicity, attractive SNPs probes, high sensitivity and selectivity and high efficiency. We believe that FSCCS method exhibits promising potential applications in homogeneous bioassays and study on the molecular interaction and nanoparticle-molecule interaction.
Co-reporter:Aidi Zhang, Yannan Bian, Jinjie Wang, Kuiyong Chen, Chaoqing Dong and Jicun Ren
Nanoscale 2016 vol. 8(Issue 9) pp:5006-5014
Publication Date(Web):28 Jan 2016
DOI:10.1039/C5NR08504G
Semiconductor quantum dots (QDs) are very important fluorescent nanocrystals with excellent optical properties. However, QDs, at the single-particle level, show severe fluorescence intermittency (or blinking) on a wide time scale from milliseconds to minutes, which limits certain optical and biological applications. Generally, blinking behavior of QDs strongly depends on their surface state and surrounding environment. Therefore, current blinking suppression approaches are mostly focused on the introduction of an inorganic shell and organic small molecule compounds. In this study, we described a “bottom up” approach for the synthesis of CdSe/CdS/polymer core/shell/shell QDs via the in situ one-pot polymerization approach in order to control the blinking behavior of QDs. Three monomers (dithiothreitol (DTT), phenylenediamine (PDA), and hexamethylenediamine (HDA)) were respectively used to polymerize with hexachlorocyclotriphosphazene (HCCP), and then the polyphosphazene polymers were obtained with cyclotriphosphazene as the basic macromolecular backbone. By regulating the molar ratios of the activated comonomers, we can control the blinking behavior of CdSe/CdS/polymer QDs. Under the optimal conditions, the percentage of “non-blinking” CdSe/CdS/polymer QDs (the “on time” fraction > 99% of the overall observation time) was up to 78%. The suppression mechanism was attributed to the efficient passivation of QD surface traps by the sulfhydryl or phenyl groups in the polyphosphazene polymers.
Co-reporter:Yannan Bian, Xiangyi Huang and Jicun Ren
Analytical Methods 2016 vol. 8(Issue 6) pp:1333-1338
Publication Date(Web):07 Jan 2016
DOI:10.1039/C5AY02844B
Fumonisin B1 (FB1) is considered to be the most prevalent mycotoxin in naturally contaminated cereals throughout the world and is potentially hazardous to humans and animals. Therefore, it is necessary to develop sensitive, fast and reliable methods for the detection of FB1. In this paper, we reported a homogeneous immunoassay for sensitive detection of FB1 in maize using single molecule fluorescence correlation spectroscopy (FCS). In this study, a competitive immunoassay model was used, and FB1 labeled with a fluorescent dye was used as a fluorescent tracer. The principle of competitive immunoassay is based on sensitively distinguishing the fluorescent tracer and tracer–antibody complex by FCS technique due to the significant difference in the characteristic diffusion times between the tracer and tracer–antibody complex. We firstly synthesized the fluorescent FB1 tracer using Alexa 488 as labeling probes, and then optimized the experimental conditions for competitive immunoassay. We observed a good linear relationship between the fraction of the Alexa 488-labeled FB1 immune complex in reaction solution and the FB1 concentration in samples. Under optimal conditions, the linear range is from 1.0 μg L−1 to 25.0 μg L−1, and the detection limit is 1.0 μg L−1 for FB1. This method was successfully used for the determination of FB1 in spiked and natural samples. The results obtained by FCS are in good agreement with those obtained by the ELISA method. Our results demonstrate that the quantitative FCS method is rapid, simple and highly sensitive, and it can easily be extended to detect other chemical contaminants for food safety.
Co-reporter:Hongyan Hu;Xiangyi Huang
Luminescence 2016 Volume 31( Issue 3) pp:830-836
Publication Date(Web):
DOI:10.1002/bio.3030
Abstract
Triplex DNA has become one of the most useful recognition motifs in the design of new molecular biology tools, therapeutic agents and sophisticated DNA-based nanomaterials because of its direct recognition of natural double-stranded DNA. In this paper, we developed a sensitive and microscale method to study the formation and stability characterization of triplex DNA using fluorescence correlation spectroscopy (FCS). The principle of this method is mainly based on the excellent capacity of FCS for sensitively distinguishing between free single-strand DNA (ssDNA) fluorescent probes and fluorescent probe–double-strand DNA (dsDNA) hybridized complexes. First, we systematically investigated the experimental conditions of triplex DNA formation. Then, we evaluated the equilibrium association constants (Ka) under different ssDNA probe lengths, composition and pH. Finally, we used FCS to measure the hybridization fraction of a 20-mer perfectly matched ssDNA probe and three single-base mismatched ssDNA probes with 146-mer dsDNA. Our data illustrated that FCS is a useful tool for the direct determination of the thermodynamic parameters of triplex DNA formation and discrimination of a single-base mismatch of triplex DNA without denaturation. Compared with current methods, our method is characterized by high sensitivity, good universality and small sample and reagent requirements. More importantly, our method has the potential to become a platform for triplex DNA research in vitro. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Xiaocai Hu;Di Su;Zhixue Du;Xiangyi Huang;Chaoqing Dong
Microchimica Acta 2016 Volume 183( Issue 8) pp:2457-2465
Publication Date(Web):2016 August
DOI:10.1007/s00604-016-1891-7
We report on a method for direct determination of the molar concentration of gold nanoparticles (GNP) in solution by using resonance light scattering correlation spectroscopy (RLSCS). RLSCS is based on the correlation analysis of the fluctuations of resonance light scattering due to Brownian motion of single nanoparticles in a highly-focused laser volume. Similar to single molecule fluorescence correlation spectroscopy, the number of particles in the detection volume is reciprocally related to the G(0) value in the RLSCS plot. A model is established for quantification of GNP concentration, and the effect of laser illumination intensity was studied. An excellent linear relationship exists between the concentration of GNP and the reciprocal G(0) value of the correlation plots at low laser illumination intensity. The method was applied to the determination of the molar concentrations of GNP in sizes of 15, 20, 30, and 40 nm to give detection limits of 300, 80, 10, and 40 pM, respectively. The results obtained by RLSCS were in good agreement with that of combined atomic emission spectroscopy and transmission electron microscopy (AES-TEM). A sensitive microscale method was reported for the determination of the activity of the enzyme caspase 3 by RLSCS by using GNP as labeling probes. The assay is based on the measurement of the change of the molar concentration of GNP when peptide-labeled GNP substrates were cleaved by caspase 3. The method is shown to enable the determination of caspase 3 (with a 0.1 nM detection limit) and to monitoring drug-induced cell apoptosis.
Co-reporter:Lingao Ruan, Di Su, Chang Shao, Jinjie Wang, Chaoqing Dong, Xiangyi Huang and Jicun Ren
Analyst 2015 vol. 140(Issue 4) pp:1207-1214
Publication Date(Web):05 Dec 2014
DOI:10.1039/C4AN01816H
In this paper, a sensitive and microscale method for drug screening is described using single molecule spectroscopy fluorescence correlation spectroscopy (FCS). The principle of this method is mainly based on the competition of candidate drugs to the fluorescent probe–target complexes and the excellent capacity of FCS for sensitively distinguishing the free fluorescent probes and the fluorescent probe–target complexes in solution. In this study, the screening of protein kinase inhibitors was used as a model, tyrosine-protein kinase ABL1 was used as a target and a known inhibitor dasatinib derivative labeled with a fluorescent dye was used as a fluorescent affinity probe. We firstly established the theoretical model of drug screening based on the binding process of fluorescent probes and targets, the competition of candidate drugs to the fluorescent probe–target complexes and FCS theory. Then, the dasatinib derivatives were synthesized and labeled with the fluorescent dye Alexa 488, and the binding and dissociation processes of Alexa 488-dasatinib and ABL1 were systematically investigated. The dissociation constant and the dissociation rate for the Alexa 488-dasatinib–ABL1 complex were determined. Finally, the established method was used to screen candidate drugs. The dissociation constants of ABL1 kinase to six known drugs for treating chronic myeloid leukemia (CML) were evaluated and the results obtained are well consistent with the reported values. Furthermore, a homemade chip with micro-wells was successfully utilized in FCS measurements as the carrier of samples, and the sample requirements were only 1–2 μL in this case. Our results demonstrated that the drug screening method described here is universal, sensitive and shows small sample and reagent quantity requirements. We believe that this method will become a high throughput platform for screening of small molecule drugs.
Co-reporter:Zhancheng Xu;Tao Lan;Xiangyi Huang;Chaoqing Dong
Luminescence 2015 Volume 30( Issue 5) pp:605-610
Publication Date(Web):
DOI:10.1002/bio.2793
Abstract
We described a new and sensitive method for the determination of mercury ions (Hg2+) on the basis of fluorescence correlation spectroscopy (FCS) and recognition of oligonucleotides. In this assay, 30-nm gold nanoparticles (GNPs) were modified with oligonucleotides containing thymine bases (T) as fluorescent probes, and the principle of this assay was based on the specific binding of Hg2+ by two DNA thymine bases. When two GNPs labelled with different oligonucleotides were mixed with a sample containing Hg2+, the T-Hg2+-T binding reaction should cause GNPs to form dimers (or oligomers), which would lead to a significant increase in the characteristic diffusion time of GNPs in the detection volume. The FCS method is a single molecule detection method and can sensitively detect the change in the characteristic diffusion time of GNPs before and after binding reactions. The quantitative analysis was performed according to the relation between the change in the characteristic diffusion time of GNPs and the concentration of Hg2+. Under optimal conditions, the linear range of this method was from 0.3 nM to 100 nM, and the detection limit was 0.14 nM for Hg2+. This new method was successfully applied for direct determination of Hg2+ levels in water and cosmetics samples. Copyright © 2014 John Wiley & Sons, Ltd.
Co-reporter:Tao Lan, Jinjie Wang, Chaoqing Dong, Xiangyi Huang, Jicun Ren
Talanta 2015 Volume 132() pp:698-704
Publication Date(Web):15 January 2015
DOI:10.1016/j.talanta.2014.10.004
•A novel photon burst counting technique based on a RLSCS is reported.•A homogeneous immunoassay was developed by using this technique.•In immunoassay, the sandwich mode was used, and proteins were labeled on GNPs.•The method can detect the photon burst count changes before and after immunoreaction.•The method is successfully used for detection of PSA levels in human sera.In this paper, we reported a sensitive single particle method by combining the photon burst counting technique with gold nanoparticles (GNPs) as labeling probes. The photon bursting of single GNPs will be generated in a highly focused laser beam (less than 1 fL) due to the plasmon resonance scattering and Brownian motion of GNPs. We observed an excellent linear relationship between the photon burst counts and the number of particles in GNPs solution. We investigated the statistical behaviors of background noise and photon burst signal of GNPs, and proposed the data processing method based on Gaussian distribution of the background noise. A new homogeneous sandwich immunoassay was developed by using this single particle method. We evaluated the performance of this method by using prostate-specific antigen (PSA) as a model. The linear range of PSA was 1–1000 pmol/L and the detection limit was 0.8 pmol/L. This novel method was successfully used for the direct detection of cancer biomarker PSA in human serum samples. Our results were in good agreement with conventional ELISA assays.
Co-reporter:Jinjin Yin, Aidi Zhang, Chaoqing Dong, Jicun Ren
Talanta 2015 Volume 144() pp:13-19
Publication Date(Web):1 November 2015
DOI:10.1016/j.talanta.2015.05.034
•A novel single nanoparticle detection method based on FCS was reported.•A homogeneous assay of thrombin was developed using this method.•Aptamer and QDs were used as recognition unit of thrombin and probes.•The method can detect the changes of diffusion times before and after reaction.•The method is used for detection of thrombin in human serum.In this study, an aptamer-based single particle method was developed for the thrombin detection in human serum samples using fluorescence correlation spectroscopy (FCS). In this method, quantum dots (QDs) were used as the fluorescent probes and thrombin-binding aptamer (TBA) was used as molecular recognition unit. When two QDs probes labeled with TBA (QD-TBA1 and QD-TBA2) are mixed in a sample containing thrombin targets, the binding of targets will cause QDs to form dimers (or oligomers) with bigger sizes, which leads to the nearly double increase in the characteristic diffusion time of QDs in the detection volume of FCS. FCS method can detect the change in the characteristic diffusion time of QDs. Firstly, the diffusion and blinking behaviors of QD-TBA probes in the presence of thrombin were investigated by FCS and total internal reflection fluorescence microscopy (TIRFM) imaging system, and the experimental results documented that QD-TBAs were bound together with “one-by-one” structure when thrombin were added into the solution. And then, the assay conditions were optimized in order to improve the sensitivity and specificity of this method. Under the optimized conditions, the linear range of the method is from 5.0 nM to 500 nM of thrombin, and the limit of detection is about 2.6 nM. Finally, this method was applied to homogeneous determination of thrombin in human serum samples.
Co-reporter:Heng Liu ; Chaoqing Dong
Journal of the American Chemical Society 2014 Volume 136(Issue 7) pp:2775-2785
Publication Date(Web):January 26, 2014
DOI:10.1021/ja410284j
In this study, a new tempo-spatially resolved fluctuation spectroscopy under dark-field illumination is described, named dark-field illumination-based scattering correlation spectroscopy (DFSCS). DFSCS is a single-particle method, whose principle is similar to that of fluorescence correlation spectroscopy (FCS). DFSCS correlates the fluctuations of the scattered light from single nanoparticle under dark-field illumination. We developed a theoretical model for translational diffusion of nanoparticles in DFSCS system. The results of computer simulations documented that this model was able to well describe the diffusion behaviors of nanoparticles in uniformly illuminated field. The experimental setup of DFSCS was achieved by introducing a dark-field condenser to the frequently used bright-field microscope and an electron multiplying charge-coupled device (EMCCD) as the array detector. In the optimal condition, a stack of 500 000 frames were collected simultaneously on 64 detection channels for a single measurement with acquisition rate of 0.5 ms per frame. We systematically investigated the effect of certain factors such as particle concentration, viscosity of the solution, and heterogeneity of gold nanoparticles (GNPs) samples on DFSCS measurements. The experiment data confirmed theoretical model proposed. Furthermore, this new method was successfully used for investigating dynamic behaviors of GNPs in live cells. Our preliminary results demonstrate that DFSCS is a practical and affordable tool for ordinary laboratories to investigate the dynamic information of nanoparticles in vitro as well as in vivo.
Co-reporter:Chaoqing Dong, Heng Liu, and Jicun Ren
Langmuir 2014 Volume 30(Issue 43) pp:12969-12976
Publication Date(Web):2017-2-22
DOI:10.1021/la503055v
The current method for investigating the blinking behavior is to immobilize quantum dots (QDs) in the matrix and then apply a fluorescent technique to monitor the fluorescent trajectories of individual QDs. So far, no method can be used to directly assess the blinking state of ensemble QDs in free solution. In this study, a new method was described to characterize the blinking state of the QDs in free solution by combining single molecule fluorescence correlation spectroscopy (FCS) with ensemble spectroscopic methods. Its principle is based on the observation that the apparent concentration of bright QDs obtained by FCS is less than its actual concentration measured by ensemble spectroscopic method due to the QDs blinking. We proposed a blinking index (Kblink) for characterizing the blinking state of QDs, and Kblink is defined as the ratio of the actual concentration (Cb,actual) measured by the ensemble spectroscopic method to the apparent concentration (Cb,app) of QDs obtained by FCS. The effects of certain factors such as laser intensity, growth process, and ligands on blinking of QDs were investigated. The Kblink data of QDs obtained were successfully used to characterize the blinking state of QDs and explain certain experimental results.
Co-reporter:Bocheng Zhang ; Tao Lan ; Xiangyi Huang ; Chaoqing Dong
The Journal of Physical Chemistry C 2014 Volume 118(Issue 26) pp:14495-14501
Publication Date(Web):June 11, 2014
DOI:10.1021/jp500843k
In this work, we reported an efficient method for eliminating the optical trapping effect on characterization of nanoparticle diffusion parameters by resonance light scattering correlation spectroscopy (RLSCS). The RLSCS represents a new single nanoparticle method and its principle was based on measuring the resonance light scattering fluctuations in a highly focused laser beam due to the Brownian motion of single nanoparticles such as gold nanoparticles (GNPs), which resembled fluorescence correlation spectroscopy (FCS). In RLSCS analysis, the polarizability of nanoparticles are much higher than fluorescent molecules in FCS, and the sizes of them are larger, therefore, the optical trapping force significantly affects the diffusion behaviors of nanoparticles under a highly focused laser beam. In this study, we used the 632.8 nm He—Ne laser as the light source, which was close to the resonance scattering band of GNPs, and chose GNPs (from 20 to 100 nm) as model samples. We theoretically and experimentally investigated the optical trapping effect of GNPs in RLSCS, and observed a good linear relation between the characteristic diffusion times of GNPs and laser intensity in the certain condition (below 100 μW). This result was in line with the theoretical deduction. By the extrapolation strategy, we effectively eliminated the optical trapping effect and accurately obtained the diameter of GNPs, which was in good agreement with that obtained by transmission electron microscopy. The method described here can extend to FCS analysis of fluorescent nanoparticles as well.
Co-reporter:Zhancheng Xu;Xiangyi Huang;Chaoqing Dong
Microchimica Acta 2014 Volume 181( Issue 7-8) pp:723-730
Publication Date(Web):2014 June
DOI:10.1007/s00604-013-1132-2
We have studied the fluorescence properties and diffusion behaviors of gold nanoparticles (GNPs) in solution by using fluorescence correlation spectroscopy (FCS) at single molecule level. The GNPs display a high photo-saturation feature. Under illumination with strong laser light, they display higher brightness per particle (BPP) despite their low quantum yields. Based on the unique fluorescence properties and diffusion behaviors of GNPs, we have developed a sensitive and homogenous thrombin assay. It is based on a sandwich strategy and is making use of GNPs to which two different aptamers are conjugated. When the differently aptamer-labeled GNPs are mixed with solutions containing thrombin, the affinity reaction causes the GNPs to form dimers or oligomers. This leads to an increase in the diffusion time of the GNPs in the detection volume that is seen in FCS. The FCS method enables sensitive detection of the change in the characteristic diffusion time of the GNPs before and after the affinity reaction. Quantitative analysis of thrombin is based on the measurement of the change in the diffusion time. Under optimal conditions, the calibration plot is linear in the 0.5 nM to 110 nM thrombin concentration range, and the detection limit is 0.5 nM. The method was successfully applied to the direct determination of thrombin in human plasma.
Co-reporter:Dr. Chaoqing Dong;Heng Liu;Aidi Zhang ;Dr. Jicun Ren
Chemistry - A European Journal 2014 Volume 20( Issue 7) pp:1940-1946
Publication Date(Web):
DOI:10.1002/chem.201303605
Abstract
Semiconductor quantum dots (QDs) are very important optical nanomaterials with a wide range of potential applications. However, the blinking of single QDs is an intrinsic drawback for some biological and photoelectric applications based on single-dot emission. In this work, we systematically investigated the effects of certain synthetic conditions on the blinking behavior of aqueous CdTeS alloyed QDs, and observed that blinking behaviors of QDs were able to be controlled by the structure and concentration of the thiol compounds that were used as surface ligands. In optimal conditions, completely nonblinking QDs were prepared using certain thiol ligands as stabilizers in aqueous phase. The suppressed blinking mechanism was mainly attributed to elimination of QDs surface traps by coordination of thiol ligands with vacant Cd atoms, formation of appropriate CdS coating on QDs, and controlling the growth dynamics of QDs. Nonblinking QDs show high quantum yield, small size, and good solubility, and will be applied to some fields that were previously limited by blinking of traditional QDs.
Co-reporter:Bocheng Zhang, Tao Lan, Xiangyi Huang, Chaoqing Dong, and Jicun Ren
Analytical Chemistry 2013 Volume 85(Issue 20) pp:9433
Publication Date(Web):September 23, 2013
DOI:10.1021/ac4023956
In this article, we reported a new and sensitive method for characterizing rapid rotational and translational diffusion of gold nanoparticles (GNPs) and gold nanorods (GNRs) by resonance light scattering correlation spectroscopy (RLSCS). The RLSCS is a new single nanoparticle method, and its principle is based on measuring the resonance light scattering fluctuations in a highly focused volume due to Brownian motion of single particles, which resembles fluorescence correlation spectroscopy (FCS). On the basis of the theory of FCS, we first developed a model for rotational and translational diffusion and aspect ratio of nanoparticles in the RLSCS system. Then, we investigated the effects of certain factors such as the wavelength of illumination light and viscosity of solution using GNPs and GNRs as model samples and discovered that the polarization anisotropy and the scattering light intensity of GNPs and GNRs were significantly dependent on the wavelengths of illumination light. Using the 632.8 nm He–Ne laser as a light source, which was close to the resonance scattering band, we successfully obtained the translational and rotational diffusion coefficients and aspect ratios of anisotropic nanoparticles by the RLSCS method. The results obtained by this new method were in good agreement with transmission electron microscopy and theoretical calculation. Furthermore, the homogeneous sandwich immunoreaction was investigated using the antibody-modified GNPs as the probes. The changes in translational diffusion behaviors and aspect ratios of GNPs in immunoreaction were observed by the RLSCS method. By these changes, we can develop a new homogeneous immunoassay. Our preliminary results illustrated that the RLSCS method was a powerful tool for characterizing rapid rotational and translational diffusion behaviors of anisotropic nanoparticles in solution. We believe that the RLSCS method exhibits the wide applications in biological science especially in vivo study on the interaction of nanoparticles and biomolecules.
Co-reporter:Aidi Zhang, Chaoqing Dong, Heng Liu, and Jicun Ren
The Journal of Physical Chemistry C 2013 Volume 117(Issue 46) pp:24592-24600
Publication Date(Web):October 26, 2013
DOI:10.1021/jp408544x
The blinking behavior of single quantum dots (QDs) is an intrinsic drawback for some biological and photoelectric applications that rely on single-dot emission. Some studies demonstrate that the blinking behavior of QDs is mainly attributed to nonradiative recombination processes associated with traps at the nanocrystal surface. In this study, we systematically investigated the effects of surface ligand alkylthiols on the blinking of CdSe/CdS QDs prepared in the organic phase and observed that the blinking of CdSe/CdS QDs was significantly dependent on the annealing time and structure and concentration of alkylthiol ligands. In the optimal conditions, we prepared thiol-modified CdSe/CdS QDs with a “nonblinking” fraction up to 83%. The mechanism of the blinking suppression was mainly attributed to modifying surface traps of QDs with alkylthiols. In this modification, the decomposition of alkylthiols can slowly release activated “S” under high temperature. Then the activated S can bind to surface traps of QDs, which induces a secondary growth of the core/shell QDs coupled with surface reconstruction and the efficient suppression of the blinking. The method described here can be used to suppress the blinking of other QDs.
Co-reporter:Yao Lu;Xiangyi Huang
Microchimica Acta 2013 Volume 180( Issue 7-8) pp:635-642
Publication Date(Web):2013 June
DOI:10.1007/s00604-013-0965-z
We describe a sensitive sandwich immunoassay for alpha-fetoprotein (AFP). It is making use of gold nanoparticles (GNPs) and magnetic beads (MBs) as labels, and of resonance Rayleigh scattering for detection. Two antibodies were labeled with GNPs and MBs, respectively, and MB-antigen-GNP complexes were formed in the presence of antigens. The MB labels also serve as solid phase carriers that can be used to magnetically separate the immuno complex. The GNP labels are used as optical probes, and Rayleigh scattering was used to determine the concentration of free GNPs-antibody after separation of the MB-antigen-GNP complexes. The concentration of AFP is related to the intensity of light scattered by free GNPs in the 13.6 pM to 436 pM concentration range, and the limit of detection is 13.6 pM. The method was applied to the determination of AFP in sera of cancer patients, and the results agree well with those obtained by conventional ELISA.
Co-reporter:Fengzhao Yang;Zhancheng Xu;Jinjie Wang;Feng Zan;Chaoqing Dong
Luminescence 2013 Volume 28( Issue 3) pp:392-400
Publication Date(Web):
DOI:10.1002/bio.2395
ABSTRACT
In this study, we report for the first time a one-pot approach for the synthesis of new CdSeTeS quaternary-alloyed quantum dots (QDs) in aqueous phase by microwave irradiation. CdCl2 was used as a Cd precursor during synthesis, NaHTe and NaHSe were used as Te and Se precursors and mercaptopropionic acid (MPA) was used as a stabilizer and source of sulfur. A series of quaternary-alloyed QDs of different sizes were prepared. CdSeTeS QDs exhibited a wide emission range from 549 to 709 nm and high quantum yield (QY) up to 57.7 %. Most importantly, the quaternary-alloyed QDs possessed significantly long fluorescence lifetimes > 100 ns as well as excellent photostability. Results of high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX) and powder X-ray diffraction (XRD) spectroscopy showed that the nanocrystals possessed a quaternary alloy structure with good crystallinity. Fluorescence correlation spectroscopy (FCS) showed that QDs possessed good water solubility and monodispersity in aqueous solution. Furthermore, CdSeTeS QDs were modified with alpha-thio-omega-carboxy poly(ethylene glycol) (HS-PEG-COOH) and the modified QDs were linked to anti-epidermal growth factor receptor (EGFR) antibodies. QDs with the EGFR antibodies as labeling probes were successfully applied to targeted imaging for EGFR on the surface of SiHa cervical cancer cells. We believe that CdSeTeS QDs can become useful probes for in vivo targeted imaging and clinical diagnosis. Copyright © 2012 John Wiley & Sons, Ltd.
Co-reporter:Tao Lan, Chaoqing Dong, Xiangyi Huang, Jicun Ren
Talanta 2013 Volume 116() pp:501-507
Publication Date(Web):15 November 2013
DOI:10.1016/j.talanta.2013.07.024
•A homogeneous immunoassay is developed for the detection of biomarkers using RLSCS.•In immunoassay, the competitive mode was used, and proteins were labeled with SNPs.•The diffusion time of SNPs will change before and after immunoreaction.•The RLSCS can sensitively detect the changes in the diffusion time of SNPs.•The method is successfully used for detection of E2 and AFP levels in real samples.In this paper, we reported a sensitive, universal and homogeneous method for assay of biomarkers by combining resonance light scattering correlation spectroscopy (RLSCS) with silver nanoparticles (SNPs) as labeling probes. In the homogeneous assay, the competitive immunoreaction mode was used, and antibody and antigen (or hapten) were labeled with SNPs with strong plasmonic scattering property, respectively. The antibody-labeled SNPs were firstly mixed with a sample containing antigens, and the part of antibody-labeled SNPs was bound to antigens of interest in the sample. And then, the antigen-labeled SNPs were added into the mixed solution above, and they were bound to free antibody-labeled SNPs (excess) to form dimers (or oligomers), which led to the significant increase in the characteristic diffusion time of SNPs in the tiny detection volume (about 0.5 fL). In the competitive mode, the characteristic diffusion time of SNPs decreased with an increase of antigen concentration. The RLSCS is a novel single particle method and can sensitively detect the changes in the characteristic diffusion time of SNPs before and after the immunoreactions. In order to demonstrate the universality of this new method, small biomolecules, 17-β estradiol (E2), and biomacromolecules, liver cancer antigen alpha-fetoprotein (AFP), were used as assay models. In the optimal conditions, the linear ranges of this method were from 10 pM to 10 nM for E2 and 100 pM to 10 nM for AFP, respectively, and the detection limits were 10 pM for E2 and 100 pM for AFP, respectively. The presented method was successfully used to the determination of E2 levels in human urine and AFP levels in human sera, and the results obtained were in good agreement with conventional ELISA assays.
Co-reporter:Xiangyi Huang, Jinjie Wang, Heng Liu, Tao Lan, Jicun Ren
Talanta 2013 Volume 106() pp:79-84
Publication Date(Web):15 March 2013
DOI:10.1016/j.talanta.2012.12.014
In this paper, we report a new strategy for detection of hydrogen peroxide and glucose using quantum dot (QD)-based fluorescence resonance energy transfer (FRET) and tyramide reaction. The principle of FRET is based on highly sensitive reaction of a carbocyanine dye (Cy5) labeled tyramide and hydrogen peroxide catalyzed by horseradish peroxidase (HRP), and the fluorescence spectrum of QDs (EXmax 605 nm) partially overlaps with the absorption bands of Cy5. We firstly conjugated HRP to QDs, and then demonstrated an efficient FRET between HRP conjugated QDs (as energy donors) and tyramide labeled Cy5 (as energy acceptors) due to the formation of Cy5-labeled HRP–QDs assemblies in the presence of H2O2. We observed that the fluorescence Cy5 depended linearly on the H2O2 concentration within a range of concentration from 10 to 100 nM and the detection limit of this assay was 10 nM. Based on the principle for determination of H2O2, we develop a new strategy for assay of glucose by coupling with glucose oxidase-mediated reaction. The established methods were successfully used for determination of glucose levels in human sera, and the results obtained were in good agreement with commercially available method. Our method is at least 1 order of magnitude more sensitive than in the commercially available method. More importantly, our method described here can be extended to other assay designs using different oxidase enzymes, energy donors and energy acceptors, such as near-infrared (NIR)-to-visible upconversion nanoparticles and silicon and carbon QDs.Highlights► A strategy is developed for detection of H2O2 and glucose using QD-based FRET. ► The principle of FRET is based on highly sensitive tyramide reaction. ► Emissions of energy donors and acceptors both appeared on the spectra. ► This method is successfully used for determination of glucose levels in human sera. ► This method is 1 order of magnitude more sensitive than in the commercially method.
Co-reporter:Feng Zan and Jicun Ren
Journal of Materials Chemistry A 2012 vol. 22(Issue 5) pp:1794-1799
Publication Date(Web):02 Dec 2011
DOI:10.1039/C1JM13982G
In this paper, we describe a simple and efficient approach for synthesis of highly luminescent InP/ZnS core/shell quantum dots (QDs) in gas-liquid phase reaction using zinc phosphide (Zn3P2) as a new phosphorus source and indium(III) myristate as indium precursor. The effects of experimental conditions, such as the ratios of reactants, reaction temperature and overcoating time of ZnS shell, were systematically investigated. We observed that the molar ratio of In:myristic acid (MA) and the overcoating time of ZnS had significant influences on the optical properties of the InP/ZnS core/shell QDs. Under the optimal conditions, we prepared highly photoluminescent InP/ZnS QDs with emission range of 540–660 nm and the quantum yields were about 30–60%. The characterization of high-resolution transmission electron microscopy and X-ray diffraction (XRD) showed that the InP/ZnS QDs had good monodispersity and a nice crystal structure. Furthermore, we observed that the luminescence efficiency of InP/ZnS QDs was significantly improved after UV irradiation in the presence of dithiothreitol. Compared with the commonly used expensive and extremely flammable tris(trimethylsilyl)phosphine (P(TMS)3) as phosphorus precursor, Zn3P2 is a low-cost and stable phosphorus source. Our method is an easy and fast way for large-scale synthesis of highly luminescent InP/ZnS QDs for wide applications in the future.
Co-reporter:Heng Liu, Chaoqing Dong, Xiangyi Huang, and Jicun Ren
Analytical Chemistry 2012 Volume 84(Issue 8) pp:3561
Publication Date(Web):March 13, 2012
DOI:10.1021/ac2031833
In the paper, we present a novel single particle method, named spatially resolved scattering correlation spectroscopy (SRSCS), based on a total internal reflection (TIR) configuration and strong resonance light scattering (RLS) of silver nanoparticles (AgNPs). The principle of SRSCS is similar to fluorescence correlation spectroscopy (FCS), and it is based on measuring the RLS fluctuations in a small volume due to Brownian motion of single nanoparticles. We first established a highly sensitive SRSCS system. In the SRSCS system, a millimeter-scale hole is employed to efficiently separate nanoparticle scattering light from the background reflected beam, and an electron multiplying charge-coupled device (EMCCD) is used as an array detector. The SRSCS system was successfully used for detection and imaging of single AgNPs in solution. Furthermore, we developed the model of SRSCS according to the FCS method and systematically investigated the effects of certain factors such as particle concentration, viscosity of the solution, hardware and software binning and accumulation time on SRSCS measurements using AgNPs as a model sample. A series of calibration experiments were conducted, and the experimental data obtained were in good agreement with the SRSCS model. This new method is multiplexing, spatially resolved, and free of photobleaching and may become a useful method for study on heterogeneous systems, such as the motion of proteins on the cell membrane.
Co-reporter:Lingao Ruan, Zhancheng Xu, Tao Lan, Jinjie Wang, Heng Liu, Chaodong Li, Chaoqing Dong, and Jicun Ren
Analytical Chemistry 2012 Volume 84(Issue 17) pp:7350
Publication Date(Web):August 2, 2012
DOI:10.1021/ac301654g
Apoptosis plays a crucial role in many biological processes and pathogenesis of various malignancies and diseases of the immune system. In this paper, we described a novel method for sensitive detection of drug-induced apoptosis by using fluorescence correlation spectroscopy (FCS). The principle of this method is based on the assay of DNA fragmentation in the process of the drug-induced apoptosis. FCS is a single molecule method, and it can be used for sensitive and selective assay of DNA fragmentation without separation. We first developed a highly sensitive method for characterization of DNA fragments using a home-built FCS system and SYBR Green I as fluorescent DNA-intercalating dye, and then established a model of drug-induced apoptosis using human pancreatic cancer cells and a drug lidamycin. Furthermore, FCS method established was used to directly detect the fragmentation of DNA extracted from apoptotic cells or in the apoptotic cell lysate. In FCS assay, the single-component model and the multiple-components model were used to fit raw FCS data. The characteristic diffusion time of DNA fragments was used as an important parameter to distinguish the apoptotic status of cells. The obtained data documented that the characteristic diffusion time of DNA fragments from apoptotic cells significantly decreased with an increase of lidamycin concentration, which implied that DNA fragmentation occurred in lidamycin-induced apoptosis. The FCS results are well in line with the data obtained from flow cytometer and gel electrophoresis. Compared to current methods, the method described here is sensitive and simple, and more importantly, our detection volume is less than 1 fL, and the sample requirement can easily be reduced to nL level using a droplets array technology. Therefore, our method probably becomes a high throughput detection platform for early detection of cell apoptosis and screening of apoptosis-based anticancer drugs.
Co-reporter:Xiangyi Huang, Tao Lan, Bocheng Zhang and Jicun Ren
Analyst 2012 vol. 137(Issue 16) pp:3659-3666
Publication Date(Web):17 May 2012
DOI:10.1039/C2AN35503E
In this paper, we report a new strategy for highly sensitive determination of hydrogen peroxide, glucose and uric acid based on fluorescence resonance energy transfer (FRET) using gold nanoparticles (AuNPs) as energy acceptors. The principle is based on highly sensitive reaction of tetramethyl rhodamine (TMR) labeled tyramide and hydrogen peroxide catalysed by horseradish peroxidase (HRP), and the fluorescence spectrum of TMR (EXmax 575 nm) partially overlaps with the visible absorption bands of AuNPs. We demonstrated an efficient FRET between tyramide labeled TMR (as energy donors) and HRP (BSA) conjugated AuNPs (as energy acceptors) due to the formation of TMR-labeled HRP–AuNPs or TMR-labeled BSA–AuNPs in the presence of H2O2. We observed that the quenching of the fluorescence signal depended linearly on the H2O2 concentration within a range of concentrations from 25 to 400 nM and the detection limit of this assay was 10 nM. Based on the principle for determination of H2O2, we developed a new strategy for assay of glucose and uric acid by coupling with glucose oxidase (GOx)-mediated and uricase-mediated reaction. The established methods were successfully used for determination of glucose and uric acid levels in human sera, and the results obtained are in good agreement with commercially available methods. Our methods are at least 1 order of magnitude more sensitive than the commercially available methods. More importantly, our method described here can be extended to other assay designs using different oxidase enzymes, energy donors and energy acceptors, such as fluorescent quantum dots, near-infrared (NIR)-to-visible upconversion nanoparticles and even other metallic nanoparticles.
Co-reporter:Hongqi Chen and Jicun Ren
Analyst 2012 vol. 137(Issue 8) pp:1899-1903
Publication Date(Web):08 Mar 2012
DOI:10.1039/C2AN16202D
A new method for quenching kinetic discrimination of Fe2+ and Fe3+, and sensitive detection of trace amount of Fe2+ was developed by using synchronous fluorescence scan technique. The principle of this assay is based on the quenching kinetic discrimination of Fe2+ and Fe3+ in CePO4:Tb3+ nanocrytals–H2O2 hybrid system and the Fenton reaction between Fe2+ and H2O2. Stable, water-soluble and well-dispersible CePO4:Tb3+ nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy (TEM) and electron diffraction spectroscopy (EDS). We found that both Fe2+ and Fe3+ could quench the synchronous fluorescence of CePO4:Tb3+ nanocrytals-H2O2 system, but their quenching kinetics velocities were quite different. In the presence of Fe3+, the synchronous fluorescent intensity was unchanged after only one minute, but in the presence of Fe2+, the synchronous fluorescent intensity decreased slowly until 28 min later. The Fenton reaction between Fe2+ and H2O2 resulted in hydroxyl radicals which effectively quenched the synchronous fluorescence of the CePO4:Tb3+ nanocrystals due to the oxidation of Ce3+ into Ce4+ by hydroxyl radicals. Under optimum conditions, the linear range for Fe2+ is 3 nM–2 μM, and the limit of detection is 2.0 nM. The method was used to analyze water samples.
Co-reporter:Chaoqing Dong
Luminescence 2012 Volume 27( Issue 3) pp:199-203
Publication Date(Web):
DOI:10.1002/bio.1330
ABSTRACT: In this study, a one-step approach for aqueous synthesis of highly luminescent semiconductors, CdTe quantum dots (QDs), using long-chain thiols-mercaptoundecanoic acid (MUA) as surface ligand, was developed in a microwave irradiation system. The synthetic conditions were systematically investigated. The as-prepared MUA-coated QDs were characterized by various spectroscopy techniques, transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The experimental results document that MUA-coated CdTe QDs have small diameter, good stability, high luminescence and long lifetime. Particularly, it was confirmed, using fluorescence correlation spectroscopy (FCS) that, compared with other ligand, MUA formed a thicker ligand layer on the QD surfaces, which will help their stability and conjugation with biomolecules. Furthermore, MUA-coated QDs were successfully used for HeLa cell imaging. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Hongqi Chen, Jicun Ren
Talanta 2012 Volume 99() pp:404-408
Publication Date(Web):15 September 2012
DOI:10.1016/j.talanta.2012.05.071
A new method was developed for selective and sensitive determination of trace chromium (VI) based on the inner filter effect (IFE) of upconversion luminescent nanoparticles (NaYF4:Yb3+, Er3+) as fluorescence probes. In this study, water-soluble and well dispersible upconversion luminescent nanoparticles (NaYF4:Yb3+, Er3+) were firstly synthesized by hydrothermal method, and characterized by transmission electron microscopy (TEM) and luminescence spectroscopy. And then, the IFE method was established for determination of chromium (VI). The principle of this assay is based on the complementary overlap of the green emission band of nanoparticles (NaYF4:Yb3+, Er3+) with the absorption spectrum of a pink chelate complex (Cr(III)-diphenylcarbazone), which was generated by the quantitative reaction between diphenylcarbazide (DPC) and Cr(VI) in mineral acid solution. Under the optimal condition, the decrease in the upconversion luminescent nanoparticles was proportional to the concentration of chromium (VI) due to IFE. The linear range is 0.070–10.0×10−6 mol L−1 Cr(VI), and the limit of detection (3σ) is 2.40×10−8 mol L−1 Cr(VI). The method described here is sensitive than the method of spectrophotometry. This assay was used in the determination of Cr(VI) in water samples.Highlights► Upconversion NaYF4:Yb3+, Er3+ (λem=551 nm, λex=980 nm) were synthesized. ► NaYF4:Yb3+, Er3+ nanoparticles were used as fluorescence probe. ► The chelate generated by the reaction between DPC and Cr(VI) was used as absorbent. ► A new inner filter effect method was developed for determination chromium (VI).
Co-reporter:Feng Zan ; Chaoqing Dong ; Heng Liu
The Journal of Physical Chemistry C 2012 Volume 116(Issue 6) pp:3944-3950
Publication Date(Web):January 19, 2012
DOI:10.1021/jp210371w
In this study, we first synthesized a series of highly fluorescent InP/ZnS core/shell QDs under varied reaction conditions and then systematically investigated the blinking behaviors of QDs by single molecule imaging technique. In the measurement of blinking processes, the PL intensity trajectories of single QDs with different emission peak were recorded by a total internal reflection fluorescence (TIRF) imaging system. We observed that particle size, molar ratio of myristic acid/indium (MA:In), and the overcoating of ZnS shell had significant influence on the blinking behaviors of InP/ZnS QDs. Statistical analysis documented that both the on and off events (mon and moff) followed the power-law distributions P(ton/off) = Bt–mon/off, and the values for mon and moff were in the ranges of 1.3–1.7 and 1.4–1.9, respectively. As the wavelength of emission peak increased from 565 to 646 nm, the on-time fraction changed from 30% to 70%. The QDs prepared under higher MA/In ratio possessed a longer on-time fraction. The optimal overcoating time of the ZnS shell was about 3 h for blinking suppression in this case. Furthermore, we found that UV irradiation of QDs certainly suppressed the off-time fraction by reducing surface traps. We were able to control the blinking behavior of QDs by varying the synthesis parameters, and prepared InP/ZnS QDs with the on-time fraction up to 80% for future biological and photoelectric applications.
Co-reporter:Jie Gao, Xiangyi Huang, Heng Liu, Feng Zan, and Jicun Ren
Langmuir 2012 Volume 28(Issue 9) pp:4464-4471
Publication Date(Web):January 25, 2012
DOI:10.1021/la204289k
Gold nanoparticles (GNPs) are attractive alternative optical probes and good biocompatible materials due to their special physical and chemical properties. However, GNPs have a tendency to aggregate particularly in the presence of high salts and certain biological molecules such as nucleic acids and proteins. How to improve the stability of GNPs and their bioconjugates in aqueous solution is a critical issue in bioapplications. In this study, we first synthesized 17 nm GNPs in aqueous solution and then modified them with six thiol compounds, including glutathione, mercaptopropionic acid (MPA), cysteine, cystamine, dihydrolipoic acid, and thiol-ending polyethylene glycol (PEG-SH), via a Au–S bond. We systematically investigated the effects of the thiol ligands, buffer pH, and salt concentrations of the solutions on the colloidal stability of GNPs using UV–vis absorption spectroscopy. We found that GNPs modified with PEG-SH were the most stable in aqueous solution compared to other thiol compounds. On the basis of the above results, we developed a simple and efficient approach for modification of GNPs using a mixture of PEG-SH and MPA as ligands. These biligand-modified GNPs were facilely conjugated to antibody using 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide and N-hydroxysulfosuccinimide as linkage reagents. We conjugated GNPs to epidermal growth factor receptor antibodies and successfully used the antibody–GNP conjugates as targeting probes for imaging of cancer cells using the illumination of a dark field. Compared to current methods for modification and conjugation of GNPs, our method described here is simple, has a low cost, and has potential applications in bioassays and cancer diagnostics and studies.
Co-reporter:Xiangyi Huang, Jicun Ren
Analytica Chimica Acta 2011 Volume 686(1–2) pp:115-120
Publication Date(Web):7 February 2011
DOI:10.1016/j.aca.2010.11.043
In this paper, we report a new strategy of chemiluminescence resonance energy transfer (CRET) by using gold nanoparticles (AuNPs) as efficient long-range energy acceptor in sandwich immunoassays. In the design of CRET system, we chose the highly sensitive chemiluminescence (CL) reaction of luminol and hydrogen peroxide catalysed by horseradish peroxidase (HRP) because the CL spectrum of luminol (λmax 425 nm) partially overlaps with the visible absorption bands of AuNPs. On the basis of CRET strategy, we developed a sandwich immunoassay of alpha fetoprotein (AFP) cancer marker. In immunoassay, two antibodies (anti-AFP-1 and anti-AFP-2) were conjugated to AuNPs and horseradish peroxidase (HRP), respectively. The sandwich-type immunoreactions between the AFP (antigen) and the two different antibodies bridged the donors (luminol) and acceptors (AuNPs), which led to the occurrence of CRET from luminol to AuNPs upon chemiluminescent reaction. We observed that the quenching of chemiluminescence signal depended linearly on the AFP concentration within a range of concentration from 5 to 70 ng mL−1 and the detection limit of AFP was 2.5 ng mL−1. Our method was successfully applied for determination of AFP levels in sera from cancer patients, and the results were in good agreement with ELISA assays. This approach is expected to be extended to other assay designs, that is, using other antibodies, analytes, chemiluminescent substance, and even other metallic nanoparticles.
Co-reporter:Tao Lan, Chaoqing Dong, Xiangyi Huang and Jicun Ren
Analyst 2011 vol. 136(Issue 20) pp:4247-4253
Publication Date(Web):30 Aug 2011
DOI:10.1039/C1AN15497D
In this paper, we reported a single particle technique for the one-step homogeneous immunoassay of a cancer marker by resonance light scattering correlation spectroscopy (RLSCS). The setup of RLSCS was similar to fluorescence correlation spectroscopy (FCS), and its principle was based on measuring the resonance light scattering fluctuations in a small volumes (less than 1 fL) due to Brownian motion of single particles. In homogeneous immunoassay, we used a sandwich strategy and conjugated two different antibodies (Ab) with gold nanoparticles (GNPs) respectively. When two different GNPs labeled with antibodies are mixed in a sample containing antigen (Ag) targets, the binding of targets will cause GNPs to form dimers (or oligomers), which leads to the significant increase in the characteristic diffusion time of GNPs in the detection volume. The RLSCS method can sensitively detect the change in the characteristic diffusion time of GNPs before and after immune reactions. We used this technology in homogeneous immunoassays for the liver cancer biomarker alpha-fetoprotein (AFP). The conditions of the immune reaction were investigated systematically. In the optimal conditions, the linear range of this assay is from 1 pM to 1 nM and the detection limit is 1 pM for AFP. This new method was successfully applied for the direct determination of AFP levels in sera from healthy subjects and cancer patients. Our results were in good agreement with ELISA assays.
Co-reporter:Zhong Li;Chaoqing Dong;Lichuan Tang;Xin Zhu;Hongjin Chen
Luminescence 2011 Volume 26( Issue 6) pp:439-448
Publication Date(Web):
DOI:10.1002/bio.1250
ABSTRACT
In this paper, we described a strategy for synthesis of thiol-coated CdTe/CdS/ZnS (core–shell–shell) quantum dots (QDs) via aqueous synthesis approach. The synthesis conditions were systematically optimized, which included the size of CdTe core, the refluxing time and the number of monolayers and the ligands, and then the chemical and optical properties of the as-prepared products were investigated. We found that the mercaptopropionic acid (MPA)-coated CdTe/CdS/ZnS QDs presented highly photoluminescent quantum yields (PL QYs), good photostability and chemical stability, good salt tolerance and pH tolerance and favorable biocompatibility. The characterization of high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and fluorescence correlation spectroscopy (FCS) showed that the CdTe/CdS/ZnS QDs had good monodispersity and crystal structure. The fluorescence life time spectra demonstrated that CdTe/CdS/ZnS QDs had a longer lifetime in contrast to fluorescent dyes and CdTe QDs. Furthermore, the MPA-stabilized CdTe/CdS/ZnS QDs were applied for the imaging of cells. Compared with current synthesis methods, our synthesis approach was reproducible and simple, and the reaction conditions were mild. More importantly, our method was cost-effective, and was very suitable for large-scale synthesis of CdTe/CdS/ZnS QDs for future applications. Copyright © 2010 John Wiley & Sons, Ltd.
Co-reporter:Chaoqing Dong and Jicun Ren
Analyst 2010 vol. 135(Issue 6) pp:1395-1399
Publication Date(Web):21 Apr 2010
DOI:10.1039/C0AN00063A
Quantum dots (QDs) have been widely used in biological and medical fields as labeling probes due to their unique and fascinating optical properties. However, few reports have been found on how to characterize molar concentrations of aqueous QDs and their bioconjugates, mainly due to the lack of suitable analytical tools. In this paper, we describe a simple and efficient method for characterizing molar extinction coefficients of different sized QDs using fluorescence correlation spectroscopy (FCS). Different from previous methods based on FCS, the molar extinction coefficients of QDs were determined by comparing the count rate per molecule or brightness per particle (BPP) of QDs and chosen reference dyes. The feasibility of the method was verified in principle and by experiments.
Co-reporter:Xin Qiu, Li Chuan Tang, Chao Qing Dong, Ji Cun Ren
Chinese Chemical Letters 2010 Volume 21(Issue 10) pp:1227-1230
Publication Date(Web):October 2010
DOI:10.1016/j.cclet.2010.05.007
Gold nanoparticles (GNPs) have been widely used as probes and nanomaterials in certain biological and biomedical fields thanks to its special physical and chemical properties. However, it is still difficult to characterize GNPs-bioconjugates in solution, which has greatly limited further bioapplications of GNPs. In this study, we reported a single particle method for characterizing GNPs-biomolecules in solution using resonance light scattering correlation spectroscopy (RLSCS). The interaction of GNPs with bovine serum albumin (BSA) and thiol-modified oligonucletides were investigated.
Co-reporter:Fagong Xu Dr.;Chaoqing Dong Dr.;Chao Xie Dr. Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 3) pp:1010-1016
Publication Date(Web):
DOI:10.1002/chem.200902555
Abstract
DNA and RNA analysis is of high importance for clinical diagnoses, forensic analysis, and basic studies in the biological and biomedical fields. In this paper, we report the ultrahighly sensitive homogeneous detection of DNA and microRNA by using a novel single-silver-nanoparticle counting (SSNPC) technique. The principle of SSNPC is based on the photon-burst counting of single silver nanoparticles (Ag NPs) in a highly focused laser beam (about 0.5 fL detection volume) due to Brownian motion and the strong resonance Rayleigh scattering of single Ag NPs. We first investigated the performance of the SSNPC system and then developed an ultrasensitive homogeneous detection method for DNA and microRNA based on this single-nanoparticle technique. Sandwich nucleic acid hybridization models were utilized in the assays. In the hybridization process, when two Ag-NP–oligonucleotide conjugates were mixed in a sample containing DNA (or microRNA) targets, the binding of the targets caused the Ag NPs to form dimers (or oligomers), which led to a reduction in the photon-burst counts. The SSNPC method was used to measure the change in the photon-burst counts. The relationship between the change of the photon-burst counts and the target concentration showed a good linearity. This method was used for the assay of sequence-specific DNA fragments and microRNAs. The detection limits were at about the 1 fM level, which is 2–5 orders of magnitude more sensitive than current homogeneous methods.
Co-reporter:Lichuan Tang, Chaoqing Dong, Jicun Ren
Talanta 2010 Volume 81(4–5) pp:1560-1567
Publication Date(Web):15 June 2010
DOI:10.1016/j.talanta.2010.03.002
In this paper, we developed a highly sensitive homogeneous immunoassay by combining fluorescence correlation spectroscopy (FCS) with silver nanoparticles (SNPs)–antibody conjugates as probes. We first synthesized 14 nm SNPs in aqueous solution and then modified SNPs with 11-mercaptoundecanoicacid (MUA) via SNP–S bond. Resonance light scattering correlation spectroscopy (RLSCS) was utilized to characterize SNPs and MUA–functionalized SNPs (MUA–SNPs). The immune reaction of alpha fetal protein (AFP) antigen and its antibody was used as a reaction model and AFP labeled with Alexa Fluor 647 was used as the tracer antigen in homogeneous competitive immunoassay. We observed that the antigen–antibody complexes showed the significant increase in the diffusion times and fluorescence intensity compared to free dye-labeled antigen. On the advantages of the effects of SNPs on fluorescence enhancement and diffusion time, the homogeneous competitive immunoassay was performed by the two-component model analysis of FCS. Under the optimal condition, the detection limit was 1.5 pM and the linear range was from 6 pM to 60 pM (R > 0.99). This assay was successfully applied for the determination of the AFP level in human serum samples, the relative standard deviation was about 5%, and the recoveries were over 90%.
Co-reporter:Feng Zan
Luminescence 2010 Volume 25( Issue 5) pp:378-383
Publication Date(Web):
DOI:10.1002/bio.1163
Abstract
In this paper, we described a simple approach for aqueous synthesis of highly luminescent ZnSe(S) alloyed quantum dots (QDs) in the presence of 3-mercaptopropionic acid as stabilizers using zinc chloride and NaHSe as precursors. The synthesis conditions were systematically investigated. We observed that the pH value of the Zn precursor solution had significant influence on the optical properties and the structure of the as-prepared ZnSe(S) QDs. The optimal pH value and molar ratio of Zn2+ to HSe− were 12.0 and 25 : 1 respectively. Under the optimal conditions, we prepared highly photoluminescent ZnSe(S) QDs at up to 31% quantum yield (compared with Rhodamine 6G). The characterization of HRTEM and XRD showed that the ZnSe(S) QDs had good monodispersity and nice crystal structure. The fluorescence life time spectra demonstrated that ZnSe(S) QDs had a long lifetime in contrast to fluorescent dyes. Compared with the currently used organometallic approach, our method was ‘green’, the reaction condition was mild and the as-prepared ZnSe(S) QDs were water-soluble. More importantly, our method was low cost, and was very suitable for large-scale synthesis of highly luminescent ZnSe(S) QDs for the future applications. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Chao Xie, Fagong Xu, Xiangyi Huang, Chaoqing Dong, and Jicun Ren
Journal of the American Chemical Society 2009 Volume 131(Issue 35) pp:12763-12770
Publication Date(Web):August 13, 2009
DOI:10.1021/ja903873n
In this paper, we present for the first time a single gold nanoparticle counter (SGNPC) in solution based on the photon bursting in a highly focused laser beam (less than 1 fL) due to the plasmon resonance scattering and Brownian motion of gold nanoparticles (GNPs). The photon burst intensity of single 36 nm GNPs is several tens to hundreds times stronger than that of quantum dots (QDs) and organic dyes. The relationship between the photon burst counts and GNPs concentration shows an excellent linearity. The linear range is over 4 orders of magnitude, and the detection limit of GNPs (36 nm) is 17 fM. On the basis of this single nanoparticle technique, we developed an ultrasensitive and highly selective detection platform for homogeneous immunoassay and DNA hybridization assays using GNPs as probes, which were 2−5 orders of magnitude more sensitive than current homogeneous methods. We used this technology to construct homogeneous sandwich immunoassays for cancer biomarkers, such as carcinoembryonic antigen (CEA) and alpha fetal protein (AFP), and aptamer recognition for thrombin. The detection limits are 130 fM for CEA, 714 fM for AFP and 2.72 pM for thrombin. Our method was successfully applied for direct determination of CEA, AFP and thrombin levels in sera from healthy subjects and cancer patients. In homogeneous DNA hybridization detection, we chose methylenetetrahydrofolate reductase (MTHFR) gene as a target. This assay successfully distinguished DNA sequences with single base mismatches, and the detection limits for the target were at 1 fM level.
Co-reporter:Chao Xie;Chaoqing Dong
Frontiers of Chemistry in China 2009 Volume 4( Issue 2) pp:191-195
Publication Date(Web):2009 June
DOI:10.1007/s11458-009-0036-5
In this paper, we first introduced the basic principle of fluorescence cross-correlation spectroscopy (FCCS) and then established an FCCS setup using a single wavelength laser. We systematically optimized the setup, and the detection volume reached about 0.7 fL. The homebuilt setup was successfully applied for the study of the binding reaction of human immunoglobulin G with goat antihuman immunoglobulin G. Using quantum dots (745 nm emission wavelength) and Rhodamine B (580 nm emission wavelength) as labeling probes and 532 nm laser beam as an excitation source, the cross-talk effect was almost completely suppressed. The molecule numbers in a highly focused volume, the concentration, and the diffusion time and hydrodynamic radii of the reaction products can be determined by FCCS system.
Co-reporter:Liwen Shao;Chaoqing Dong;Fuming Sang;Huifeng Qian
Journal of Fluorescence 2009 Volume 19( Issue 1) pp:
Publication Date(Web):2009 January
DOI:10.1007/s10895-008-0396-0
Luminescent quantum dots (QDs) have widely used in some biological and biomedical fields due to their unique and fascinating optical properties, meanwhile the interaction of QDs with biomolecules recently attract increasing attention. In this paper, we employed fluorescence correlation spectroscopy (FCS) to investigate the nonspecific interaction between CdTe QDs and bovine serum albumin (BSA) as a model, and evaluate their stoichiometric ratio and association constant. Our results documented that BSA was able to bind to CdTe QDs and form the QD–BSA complex by a 1:1 stoichiometric ratio. The association constant evaluated is 1.06 ± 0.14 × 107 M−1 in 0.01 M phosphate buffer (pH = 7.4). Furthermore, we found that QD–BSA complex dissociated with increase of ion strength, and we speculated that the interaction of CdTe QDs with BSA was mainly attributed to electrostatic attraction. Our preliminary results demonstrate that fluorescence correlation spectroscopy is an effective tool for investigation of the interaction between quantum dots (or nanoparticles) and biomolecules.
Co-reporter:Chao Xie, Chaoqing Dong, Jicun Ren
Talanta 2009 Volume 79(Issue 3) pp:971-974
Publication Date(Web):15 August 2009
DOI:10.1016/j.talanta.2009.05.013
In this paper, fluorescence correlation spectroscopy (FCS) is used for investigation of homogeneous immune reaction using synthetic peptide as antigen. The binding process of CA125 peptide antigen and its antibody was systematically investigated. The dissociation constant and dissociation rate for antigen–antibody complex were determined, which were kdiss = 0.94 ± 0.05 nM and koff = 0.00215 ± 0.0001 s−1, respectively. Under optimal conditions, the detection limit of the competitive immunoassay was 4 × 10−10 M (S/N = 3). The good recoveries were obtained with human serum samples. Our preliminary results demonstrated that the homogeneous competitive immunoassay based on FCS is simple, rapid, sensitive and small sample and reagent requirement, and this method maybe possess great potential applications in clinical diagnosis, food and environmental analyses and biological and biomedical studies.
Co-reporter:Hua He, Chao Xie and Jicun Ren
Analytical Chemistry 2008 Volume 80(Issue 15) pp:5951
Publication Date(Web):July 1, 2008
DOI:10.1021/ac8005796
In this paper, we investigated the fluorescent properties of gold nanoparticles (GNPs) with several tens of nanometers by ensemble fluorescence spectrometry, fluorescence correlation spectroscopy (FCS), and fluorescence microscopy. We observed that GNPs synthesized by the citrate reduction of chloroauric acid possessed certain fluorescence, narrow full width at half-maximum (17 nm), and with an increase of particle sizes, the emission intensity showed a gradual increase while the emission wavelength remained almost constant (at 610 nm). Especially, the fluorescence of GNPs possessed the excellent behavior of antiphotobleaching under strong light illumination. Despite their low quantum yields, GNPs exhibited strong native fluorescence under relatively high excitation power. The fluorescence of GNPs could be characterized by fluorescence imaging and FCS at the single particle level. On the basis of this excellent antiphotobleaching of GNPs and easy photobleaching of cellular autofluorescence, we developed a new method for imaging of cells using GNPs as fluorescent probes. The principle of this method is that after cells stained with GNPs or GNPs bioconjugates are illuminated by strong light, the cellular autofluorescence are photobleached and the fluorescence of GNPs on cell membrane or inside cells can be collected for cell imaging. On the basis of this principle, we imaged living HeLa cells using GNPs as fluorescent probes and obtained good cell images by photobleaching of cellular autofluorescence. Furthermore, anti-EGFR/GNPs were successfully used as targeted probes for fluorescence imaging of cancer cells. Our preliminary results demonstrated that GNPs possessed excellent behaviors of antiphotobleaching and were good fluorescent probes in cell imaging. Our cellular imaging method described has potential applications in cancer diagnostics, studies, and immunoassays.
Co-reporter:Chaoqing Dong;Liwen Shao;Jiacheng Guo Dr.
ChemPhysChem 2008 Volume 9( Issue 15) pp:2245-2251
Publication Date(Web):
DOI:10.1002/cphc.200800398
Abstract
Some nanoparticles, such as quantum dots (QDs), are widely used in the biological and biomedical fields due to their unique optical properties. However, little is currently known about the interaction between these nanoparticles and biomolecules. Herein, we systemically investigated the interaction between chaperonin GroEL and water-soluble CdTe QDs based on fluorescence correlation spectroscopy (FCS), capillary electrophoresis, and fluorescence spectrometry. We observed that some water-soluble CdTe QDs were able to enter the inner cavity of GroEL and formed an inclusion complex after the activation of chaperonin GroEL with ATP. The inclusion of GroEL was size-selective to QDs and only small QDs were able to enter the inner cavity. The inclusion could suppress the fluorescence quenching of the QDs. Meanwhile, we evaluated the association constant between chaperonin GroEL and CdTe QDs by FCS. Our results further demonstrated that FCS was a very useful tool for study of the interaction of QDs and biomolecules.
Co-reporter:Hua He, Jicun Ren
Talanta 2008 Volume 77(Issue 1) pp:166-171
Publication Date(Web):19 October 2008
DOI:10.1016/j.talanta.2008.05.059
We propose a novel evanescent wave scattering imaging method using an objective-type total internal reflection system to image and track single gold nanoparticles (GNPs) in solution. In this imaging system, only a millimeter-scale hole is employed to efficiently separate GNPs scattering light from the background reflected beam. The detailed experimental realization of the imaging system was discussed, and the effect of the hole size on imaging was investigated. We observed that the hole diameters from 2.5 to 4 mm are suitable to perform the scattering imaging by adjusting the incidence angle. The technology was successfully applied to track single gold nanoparticles in solution and on live cell membrane via the anti-epidermal growth factor receptor antibody. Compared to total internal fluorescence microscopy, the resonance light scattering detection has no photobleaching or blinking inherent to fluorescent dyes and quantum dots. Compared to conventional dark-field microscopy, the evanescent wave illumination can be conveniently applied to study membrane dynamics in living cells. Additionally, the objective-based configuration provides a free space above the coverslip, and allows imaging and concomitant manipulation of live cells in culture by microinjection, patch-clamping, AFM and other techniques.
Co-reporter:Qing Zhi, Chao Xie, Xiangyi Huang, Jicun Ren
Analytica Chimica Acta 2007 Volume 583(Issue 2) pp:217-222
Publication Date(Web):5 February 2007
DOI:10.1016/j.aca.2006.09.068
Co-reporter:Chaoqing Dong, Pudun Zhang, Rui Bi, Jicun Ren
Talanta 2007 Volume 71(Issue 3) pp:1192-1197
Publication Date(Web):28 February 2007
DOI:10.1016/j.talanta.2006.06.019
In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the hybridization fraction of the ssDNA probe with its perfectly matched 146 mer ssDNA and a base mismatched 146 mer ssDNA from human methylenetetrahydrofolate reductase (MTHFR) gene. The ssDNA fragments in this study were obtained by asymmetric PCR techniques. The measurements were performed on a laboratory-built FCS system based on the two components fitting procedure. The obtained results showed that FCS could discriminate the difference of thermal stability between perfectly matched and mismatched DNA duplex, and be used to characterize the genotype of C677T in MTHFR gene. Our data illustrated that FCS was a useful tool for rapid screening of single point genetic mutations/polymorphisms (SNP) combined with DNA hybridization.
Co-reporter:Kanglin Wang;Xin Qiu;Chaoqing Dong Dr.
ChemBioChem 2007 Volume 8(Issue 10) pp:
Publication Date(Web):15 MAY 2007
DOI:10.1002/cbic.200700174
All that scatters… A single-molecule detection technique, named resonance light-scattering correlation spectroscopy, has been developed based on the extremely strong resonance light scattering of gold nanoparticles. This technology was successfully used to determine the size of gold nanoparticles, and to rapidly detect solution-phase DNA hybridization. Complementary and single-base mismatch oligonucleotides could be distinguished within 5 min.
Co-reporter:Xiangyi Huang, Jifang Weng, Fuming Sang, Xingtao Song, Chengxi Cao, Jicun Ren
Journal of Chromatography A 2006 Volume 1113(1–2) pp:251-254
Publication Date(Web):28 April 2006
DOI:10.1016/j.chroma.2006.02.087
In this paper, we present a universal, highly efficient and sensitive method for the characterization of quantum dot (QD) bioconjugates based on capillary electrophoresis with laser-induced fluorescent (LIF) detection. We first prepared CdTe QDs in aqueous phase by a chemical route with mercaptopropionic acid as a ligand, and then were coupled to certain proteins using bifunctional linkage reagent or electrostatic attraction. The QD bioconjugates were characterized by capillary electrophoresis with LIF detection. We found that QD bioconjugates were efficiently separated with free QDs by the optimization of buffer pH. Furthermore, we found that ultrafiltration was an effective and simple approach to purify QD conjugates with bovine serum albumin (BSA). Due to their broad absorption spectra and size dependent emission wavelength tunability, QDs can be excited to emit different colour fluorescence using a single wavelength laser source, and therefore, we believe that CE with LIF detection will become a universal and efficient tool for the characterization of QD bioconjugates.
Co-reporter:Fuming Sang
Journal of Separation Science 2006 Volume 29(Issue 9) pp:1275-1280
Publication Date(Web):31 MAY 2006
DOI:10.1002/jssc.200600029
EvaGreen is a new DNA intercalating dye successfully used in quantitative real-time PCR. In the present work, we firstly apply EvaGreen to the analysis of dsDNA by CE with LIF detection. Comparisons of EvaGreen dye with the commonly used dyes SYBR Green I and SYBR Gold were preformed in dsDNA analysis by CE. The linear range of dsDNA using EvaGreen was slightly wider than that using SYBR Gold and SYBR Green I, and the detection limits of dsDNA were not significantly different for the three dyes. Good separations of dsDNA fragments were obtained using the three dyes. Reproducibility of migration time and the peak area of dsDNA fragments with EvaGreen were better than those for SYBR Green I and SYBR Gold. The RSD values were 0.24–0.27% for migration time and 3.45–7.59% for peak area within the same day, 1.35–1.63% for migration time and 6.72–12.05% for peak area for three days. Our data demonstrated that EvaGreen is well suited for the dsDNA analysis by CE with LIF detection.
Co-reporter:Fuming Sang;Xiaofeng Qu
Journal of Separation Science 2006 Volume 29(Issue 15) pp:2390-2394
Publication Date(Web):6 SEP 2006
DOI:10.1002/jssc.200600176
In this paper, we describe a simple method for fabrication of high quality poly(dimethylsiloxane) (PDMS)/glass microchip by twofold replica molding of PDMS. This technique first served to transfer the negative microchannels from the glass template to the PDMS substrate as a master, and then this PDMS master with positive microchannels was used to replicate the PDMS replica with negative microchannels. Finally, the PDMS replica was bound to a glass sheet by UV radiation. The fabricated microchips were successfully applied for the detection of C677T mutation from the human methylenetetrahydrofolate reductase gene.
Co-reporter:Liang Li, Jicun Ren
Journal of Solid State Chemistry 2006 Volume 179(Issue 6) pp:1814-1820
Publication Date(Web):June 2006
DOI:10.1016/j.jssc.2006.03.026
Two kinds of bi-functional nanomaterials, CdTe@FeOOH and CdTe@Ni(OH)2, were synthesized in water phase. In the synthesis, using the luminescent CdTe nanocrystals (NCs) as a core, Fe3+ (Ni2+) was added to CdTe NCs aqueous solution and slowly hydrolyzed to deposit a layer of hydroxide onto the luminescent CdTe NCs in the presence of stabilizer. TEM, XRD, XPS, UV, fluorescence spectrometer and physical property measurement system (PPMS) were used to characterize the final products, and the results showed that the as-prepared nanoparticles with core/shell structure exhibited certain magnetic properties and fluorescence.Fluorescent and magnetic bi-functional CdTe@FeOOH and CdTe@Ni(OH)2 nanoparticles were prepared by seed-mediated approach in water phase.
Co-reporter:Jifang Weng, Xingtao Song, Liang Li, Huifeng Qian, Keying Chen, Xuemin Xu, Chengxi Cao, Jicun Ren
Talanta 2006 Volume 70(Issue 2) pp:397-402
Publication Date(Web):15 September 2006
DOI:10.1016/j.talanta.2006.02.064
In this paper, our main aim is to explore the feasibility for application of luminescent CdTe quantum dots prepared in aqueous phase to live and fixed cell imaging. The highly luminescent CdTe quantum dots (QDs) were first prepared in aqueous phase using 3-mercaptopropionic acid (MPA) as a ligand, and then were covalently coupled to a plant lectin (UEA-1) and antibody anti-von Willebrand factors (anti-vWF) as fluorescent probes. Two probes QD-UEA-1 and QD-anti-vWF) were able to specifically bind the corresponding cell membrane receptor and cytoplasm immunogen, respectively. The good cell images were obtained in live cells and fixed cells using laser confocal scanning microscopy. Our preliminary results illustrated that CdTe QDs prepared in water phase were highly luminescent, water-soluble, stable, and easily conjugated with biomolecules since their surface were coated with MPA containing free carboxyl group. We predict that QDs prepared in water phase will probably become an attractive alternative probe in cellular imaging and bio-labeling.
Co-reporter:Hua He;Huifeng Qian;Chaoqing Dong;Kanglin Wang Dr.
Angewandte Chemie 2006 Volume 118(Issue 45) pp:
Publication Date(Web):20 OCT 2006
DOI:10.1002/ange.200602758
Schwankungsfrei: Anders als in organischen Lösungsmitteln hergestellte Quantenpunkte (QDs) zeigen CdTe-QDs aus wässriger Thiopropionsäure-Lösung eine gleichmäßige Fluoreszenz unter kontinuierlicher Laseranregung (siehe Abbildung; graue Linie: Hintergrundintensität). Die Gegenwart von Thiogruppen auf der QD-Oberfläche ist entscheidend für dieses Verhalten.
Co-reporter:Xiangyi Huang;Liang Li;Huifeng Qian;Chaoqing Dong Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 31) pp:
Publication Date(Web):7 JUL 2006
DOI:10.1002/anie.200601196
No need to FRET: An efficient chemiluminescence resonance energy transfer (CRET) between luminol and CdTe quantum dots (QDs) is demonstrated. The system is based on horseradish peroxidase (HRP)–QD conjugates and the luminol/hydrogen peroxide chemiluminescence reaction. Multiple QD acceptors with different emission wavelengths can also be used simultaneously. The CRET approach can offer an alternative to fluorescence energy transfer (FRET) investigations.
Co-reporter:Xiangyi Huang;Liang Li;Huifeng Qian;Chaoqing Dong Dr.
Angewandte Chemie 2006 Volume 118(Issue 31) pp:
Publication Date(Web):7 JUL 2006
DOI:10.1002/ange.200601196
Konkurrenz für FRET: Ein effizienter resonanter Chemilumineszenzenergietransfer (CRET) zwischen Luminol und CdTe-Quantenpunkten (QDs) tritt auf, wenn man Merrettichperoxidase(HRP)-QD-Konjugate mit der Luminol-Wasserstoffperoxid-Chemilumineszenzreaktion koppelt. Dabei können mehrere QD-Acceptoren mit unterschiedlichen Emissionswellenlängen gleichzeitig eingesetzt werden. Der CRET-Ansatz bietet eine Alternative zu Fluoreszenzenergietransfer(FRET)-Untersuchungen.
Co-reporter:Hua He;Huifeng Qian;Chaoqing Dong;Kanglin Wang Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 45) pp:
Publication Date(Web):20 OCT 2006
DOI:10.1002/anie.200602758
Blinking marvelous! In contrast to quantum dots (QDs) synthesized in organic solutions, CdTe QDs synthesized in aqueous solutions containing thiopropionic acid do not blink. The fluorescence of these QDs is steady under continuous laser excitation (see picture, the gray line is the background intensity). The presence of thio groups on the surface of the QDs is key to their antiblinking behavior.
Co-reporter:Liang Li, Huifeng Qian and Jicun Ren
Chemical Communications 2005 (Issue 32) pp:4083-4085
Publication Date(Web):13 Jul 2005
DOI:10.1039/B505791D
A seed-mediated growth approach for preparation of multifunctional CdTe@Co(OH)2
(core–shell) nanoparticles in the aqueous phase is reported.
Co-reporter:Liang Li, Huifeng Qian and Jicun Ren
Chemical Communications 2005 (Issue 4) pp:528-530
Publication Date(Web):02 Dec 2004
DOI:10.1039/B412686F
In this paper, we present a new method for rapid synthesis of high quantum yield CdTe nanocrystals in the aqueous phase by microwave irradiation with controllable temperature.
Co-reporter:Pudun Zhang, Liang Li, Chaoqing Dong, Huifeng Qian, Jicun Ren
Analytica Chimica Acta 2005 Volume 546(Issue 1) pp:46-51
Publication Date(Web):1 August 2005
DOI:10.1016/j.aca.2005.05.034
In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the size of water-soluble quantum dots (QDs). The measurements were performed on a home-built FCS system based on the Stokes–Einstein equation. The obtained results showed that for bare CdTe QDs the sizes from FCS were larger than the ones from transmission electron microscopy (TEM). The brightness of QDs was also evaluated using FCS technique. It was found that the stability of the surface chemistry of QDs would be significantly improved by capping it with hard-core shell. Our data demonstrated that FCS is a simple, fast, and effective method for characterizing the fluorescent quantum dots, and is especially suitable for determining the fluorescent nanoparticles less than 10 nm in water solution.
Co-reporter:Feng Zan and Jicun Ren
Journal of Materials Chemistry A 2012 - vol. 22(Issue 5) pp:NaN1799-1799
Publication Date(Web):2011/12/02
DOI:10.1039/C1JM13982G
In this paper, we describe a simple and efficient approach for synthesis of highly luminescent InP/ZnS core/shell quantum dots (QDs) in gas-liquid phase reaction using zinc phosphide (Zn3P2) as a new phosphorus source and indium(III) myristate as indium precursor. The effects of experimental conditions, such as the ratios of reactants, reaction temperature and overcoating time of ZnS shell, were systematically investigated. We observed that the molar ratio of In:myristic acid (MA) and the overcoating time of ZnS had significant influences on the optical properties of the InP/ZnS core/shell QDs. Under the optimal conditions, we prepared highly photoluminescent InP/ZnS QDs with emission range of 540–660 nm and the quantum yields were about 30–60%. The characterization of high-resolution transmission electron microscopy and X-ray diffraction (XRD) showed that the InP/ZnS QDs had good monodispersity and a nice crystal structure. Furthermore, we observed that the luminescence efficiency of InP/ZnS QDs was significantly improved after UV irradiation in the presence of dithiothreitol. Compared with the commonly used expensive and extremely flammable tris(trimethylsilyl)phosphine (P(TMS)3) as phosphorus precursor, Zn3P2 is a low-cost and stable phosphorus source. Our method is an easy and fast way for large-scale synthesis of highly luminescent InP/ZnS QDs for wide applications in the future.
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