Co-reporter:Xiangyan Wang;Duanping Sun;Yanli Tong;Yongsheng Zhong
Microchimica Acta 2017 Volume 184( Issue 6) pp:1791-1799
Publication Date(Web):23 March 2017
DOI:10.1007/s00604-017-2160-0
A regenerable and ultrasensitive voltammetric biosensor is described for the determination of thrombin. It relies on a combination of (a) enzymatic catalysis, (b) a G-quadruplex/hemin DNAzyme system, and (c) AuPd nanoparticles for signal amplification. Poly(o-phenylenediamine) was decorated with AuPd nanoparticles and loaded with horseradish peroxidase (HRP) and thrombin aptamer (TBA), and the mixture was allowed to interact with hemin to form the G-quadruplex/hemin/HRP/AuPd/poly(o-phenylenediamine) bioconjugates. In the presence of thrombin, the bioconjugates remain immobilized on the surface of the modified glassy carbon electrode through a sandwich reaction. Poly(o-phenylenediamine) also acts as a redox mediator, and the electrochemical reaction of poly(o-phenylenediamine) in the presence of H2O2 is efficiently catalyzed by HRP, AuPd nanoparticles and G-quadruplex/hemin as the peroxidase mimics. Thus, a remarkably amplified electrochemical signal is obtained by the triple catalytic amplification. The biosensor has a dynamic range that spans the 100 f. to 20 nM thrombin concentration range, and the detection limit is 20 fM. The biosensor can be regenerated by applying an electrochemical desorption technique that breaks the gold-thiol bond and releases the components from the surface. In our perception, the mediator-free and signal-amplified biosensor demonstrated here has a large potential with respect to the quantitation of thrombin in clinical samples.
Co-reporter:Duanping Sun;Jing Lu;Xiangyan Wang;Yuanqing Zhang
Microchimica Acta 2017 Volume 184( Issue 9) pp:3487-3496
Publication Date(Web):22 June 2017
DOI:10.1007/s00604-017-2376-z
The authors describe a method for the detection and determination of human liver cancer cells in blood. The cytosensing system consists of a microfabricated chip-based electrochemical aptasensor that contains multifunctional hybrid electrochemical nanoprobes and an indium tin oxide (ITO) electrode array interface functionalized with cell-targeting aptamer and gold nanoparticles (AuNPs). The thiolated cell targeting aptamer (referred to as TLS11a) was immobilized on the ITO electrode/AuNPs for specific adhesion of hepatocellular carcinoma cells (HepG2). The hybrid nanoprobe system consists of hydroquinone (HQ) as an electrochemical probe, horseradish peroxidase (HRP), and an aptamer/hemin/G-quadruplex aggregate that was immobilized on gold/palladium-functionalized ZnO nanorods (ZnO@Au-Pd). The nanoprobes are capable of amplifying the voltammetric signal and capturing the target cells. Best operated at around −90 mV (vs Ag/AgCl), the electrode has a linear response that covers the 10^2 to 10^7 HepG2 cells per mL concentration range, with a 10 cell per mL detection limit. Captured cells may be released from the electrode via electrochemical desorption to break the Au-S bonds.
Co-reporter:Qi-Di HE, Dan-Ping HUANG, Guan HUANG, Zuan-Guang CHEN
Chinese Journal of Analytical Chemistry 2016 Volume 44(Issue 4) pp:542-550
Publication Date(Web):April 2016
DOI:10.1016/S1872-2040(16)60921-0
Gene is the genetic code of human beings, and only 0.1‰ difference among individuals but creates a wealthy diversity. Thus it is significant in practicality to explore the difference. Polymerase chain reaction (PCR) is one of the technologies mostly used in genetic research. But traditional thermal cyclers are not only time- and energy-consuming but also difficult to be integrated and portable. The combination of microfluidics and PCR can lessen the reaction volume significantly and increase the reaction efficiency with easy integration and miniaturization. In this review, we briefly introduced microchamber PCR chip and continuous-flow PCR chip according to their structures, as well the detection methods including capillary electrophoresis, fluorescence, electrochemistry and DNA hybridization array. Finally, we summarized the recent advance and pointed out the future development of microfluidic PCR chip.Microfluidic technologies have advanced considerably in fractionation of selective DNA fragments. It is now a perfect tool to replace gel electrophoresis in the laboratory except cost. But to deal with the next generation sequencing, microfluidic devices still have to challenge some options and demands in the future.
Co-reporter:Duanping Sun, Jing Lu, Yuwen Zhong, Yanyan Yu, Yu Wang, Beibei Zhang, Zuanguang Chen
Biosensors and Bioelectronics 2016 Volume 75() pp:301-307
Publication Date(Web):15 January 2016
DOI:10.1016/j.bios.2015.08.056
•A sandwich-type electrochemical aptasensor was developed for the HepG2 cells.•Fe3O4/MnO2/Au@Pd nanoelectrocatalysts were used as nanocarriers.•G-quadruplex/hemin/aptamer and HRP were immobilized on the nanocarriers.•The electrochemical cytosensor exhibits high sensitivity and selectivity.•AuNPs/GCE can be reusable based on electrochemical desorption.Human cancer is becoming a leading cause of death in the world and the development of a straightforward strategy for early detection of cancer is urgently required. Herein, a sandwich-type electrochemical aptamer cytosensor was developed for detection of human liver hepatocellular carcinoma cells (HepG2) based on the hybrid nanoelectrocatalysts and enzyme for signal amplification. The thiolated TLS11a aptamers were used as a selective bio-recognition element, attached to the gold nanoparticles (AuNPs) modified the glassy carbon electrode (GCE) surface. Meanwhile, the electrochemical nanoprobes were fabricated through the G-quadruplex/hemin/aptamer complexes and horseradish peroxidase (HRP) immobilized on the surfaces of Au@Pd core–shell nanoparticle-modified magnetic Fe3O4/MnO2 beads (Fe3O4/MnO2/Au@Pd). After the target cells were captured, the hybrid nanoprobes were further assembled to form an aptamer-cell-nanoprobes sandwich-like system on the electrode surface. Then, hybrid Fe3O4/MnO2/Au@Pd nanoelectrocatalysts, G-quadruplex/hemin HRP-mimicking DNAzymes and the natural HRP enzyme efficiently catalyzed the oxidation of hydroquinone (HQ) with H2O2, amplifying the electrochemical signals and improving the detection sensitivity. This electrochemical cytosensor delivered a wide detection range of 1×102–1×107 cells mL−1, high sensitivity with a low detection limit of 15 cells mL−1, good selectivity and repeatability. Finally, an electrochemical reductive desorption method was performed to break gold–thiol bond and desorb the components on the AuNPs/GCE for regenerating the cytosensor. These results have demonstrated that the electrochemical cytosensor has the potential to be a feasible tool for cost-effective cancer cell detection in early cancer diagnosis.
Co-reporter:Duanping Sun, Jing Lu, Zuanguang Chen, Yanyan Yu, Manni Mo
Analytica Chimica Acta 2015 Volume 885() pp:166-173
Publication Date(Web):23 July 2015
DOI:10.1016/j.aca.2015.05.027
•An electrochemical aptasensor was developed for the detection of HepG2 cells.•Dual recognition and enzymatic signal amplification were well designed.•The cytosensor performed well in sensitivity and selectivity.•A repeatable assembling and disassembling cytosensor can be achieved.In this work, a repeatable assembling and disassembling electrochemical aptamer cytosensor was proposed for the sensitive detection of human liver hepatocellular carcinoma cells (HepG2) based on a dual recognition and signal amplification strategy. A high-affinity thiolated TLS11a aptamer, covalently attached to a gold electrode through Au–thiol interactions, was adopted to recognize and capture the target HepG2 cells. Meanwhile, the G-quadruplex/hemin/aptamer and horseradish peroxidase (HRP) modified gold nanoparticles (G-quadruplex/hemin/aptamer–AuNPs–HRP) nanoprobe was designed. It could be used for electrochemical cytosensing with specific recognition and enzymatic signal amplification of HRP and G-quadruplex/hemin HRP-mimicking DNAzyme. With the nanoprobes as recognizing probes, the HepG2 cancer cells were captured to fabricate an aptamer-cell-nanoprobes sandwich-like superstructure on a gold electrode surface. The proposed electrochemical cytosensor delivered a wide detection range from 1 × 102 to 1 × 107 cells mL−1 and high sensitivity with a low detection limit of 30 cells mL−1. Furthermore, after the electrochemical detection, the activation potential of −0.9 to −1.7 V was performed to break Au–thiol bond and regenerate a bare gold electrode surface, while maintaining the good characteristic of being used repeatedly. The changes of gold electrode behavior after assembling and desorption processes were investigated by electrochemical impedance spectroscopy and cyclic voltammetry techniques. These results indicate that the cytosensor has great potential in disease diagnostic of cancers and opens new insight into the reusable gold electrode with repeatable assembling and disassembling in the electrochemical sensing.
Co-reporter:Haiyun Zhai, Zihao Su, Zuanguang Chen, Zhenping Liu, Kaisong Yuan, Lu Huang
Analytica Chimica Acta 2015 Volume 865() pp:16-21
Publication Date(Web):20 March 2015
DOI:10.1016/j.aca.2015.01.028
•A new GO-MISPE monolithic capillary column was prepared.•The column showed ability of impurities removal and excellent selectivity.•Phloxine B existed in real sample was enriched more than 90 times.•The GO-MISPE column presented good recovery and high stability.•The method was prospered to analyze phloxine B and LOD achieved 0.3 ng g−1.A method was developed to sensitively determine phloxine B in coffee bean by molecularly imprinted polymers (MIPs) coated graphene oxide (GO) solid-phase extraction (GO-MISPE) coupled with high-performance liquid chromatography and laser-induced fluorescence detection (HPLC–LIF). The GO-MISPE capillary monolithic column was prepared by water-bath in situ polymerization, using GO as supporting material, phloxine B, methacrylic acid (MAA), and ethylene dimethacrylate (EDMA) as template, functional monomer, and cross-linker, respectively. The properties of the homemade GO-MISPE capillary monolithic column, including capacity and specificity, were investigated under optimized conditions. The GO-MIPs were characterized by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy (FT-IR). The mean recoveries of phloxine B in coffee bean ranged from 89.5% to 91.4% and the intra-day and inter-day relative standard deviation (RSD) values all ranged from 3.6% to 4.7%. Good linearity was obtained over 0.001–2.0 μg mL−1 (r = 0.9995) with the detection limit (S/N = 3) of 0.075 ng mL−1. Under the selected conditions, enrichment factors of over 90-fold were obtained and extraction on the monolithic column effectively cleaned up the coffee bean matrix. The results demonstrated that the proposed GO-MISPE HPLC–LIF method can be applied to sensitively determine phloxine B in coffee bean.
Co-reporter:Duanping Sun, Jing Lu and Zuanguang Chen
RSC Advances 2015 vol. 5(Issue 73) pp:59306-59313
Publication Date(Web):02 Jul 2015
DOI:10.1039/C5RA08371K
The microfluidic cytometer has recently attracted increasing attention in cell sensing and counting due to its advantages of high-speed measurement, small sampling size and being cost effective. Up to now, the conventional microfluidic cytometer has usually used expensive microelectrodes directly in contact with a cell suspension to measure the changes in electrical signals. In this paper, we introduce a novel approach to construct an integrated microfluidic contactless conductivity cytometer for non-invasive analysis of samples with a small number of cells. The microfluidic chip is composed of a polydimethylsiloxane (PDMS) plate with a narrow microchannel on the top, a 100 μm thick glass plate in the middle and a glass substrate containing indium tin oxide (ITO) detecting electrodes on the bottom. This contactless measurement approach avoids direct contact between the detection buffer and the ITO electrodes, allowing the electrodes to be easily reused and lowering the cost of the device. When cells flow through a narrow microfluidic channel which is a little larger than the tested cell size, electrical signals are detected by a capacitively coupled contactless conductivity detection (C4D) system. Furthermore, human breast cancer (MCF-7) cells and hypertrophic cardiomyocytes (HCM) were used to successfully demonstrate the feasibility of the microfluidic contactless conductivity sensor for counting and detecting cells. Consequently, the designed microfluidic cytometer is cost-effective, easy-to-use and label-free. It is reasonable to expect that this microfluidic cytometer can become a promising tool for label-free cell counting and point-of-care clinical diagnosis in the developing world.
Co-reporter:Kaisong Yuan, Jianzhuang Wang, Haiyun Zhai, Zuanguang Chen, Lu Huang and Zihao Su
Analytical Methods 2015 vol. 7(Issue 19) pp:8297-8303
Publication Date(Web):13 Aug 2015
DOI:10.1039/C5AY01838B
A method employing molecularly imprinted solid-phase extraction (MISPE) coupled with capillary electrophoresis laser-induced fluorescence detection (CE-LIF) was developed for the determination of rose bengal in brown sugar. The rose bengal imprinted monolithic column was prepared by in situ polymerization, utilizing rose bengal as a template, methacrylic acid as a functional monomer and ethylene dimethacrylate as a cross-linker. The capacity and specificity of this column were evaluated by CE-LIF, and the morphology was characterized by scanning electron microscopy. The recoveries ranged from 89.7% to 90.3% (relative standard deviation 3.6–4.5%, n = 5). The capacities of the molecularly imprinted polymer and non-imprinted polymer columns were 1.314 μg mg−1 and 0.531 μg mg−1, respectively. The detection limit (S/N = 3) was 3 ng mL−1. The enrichment factor was higher than 63-fold and the MISPE column managed to remove rose bengal from the matrix of brown sugar effectively. This method can be applied to sensitively and effectively determine rose bengal in brown sugar.
Co-reporter:Sijing He, Qiyou Wang, Yanyan Yu, Qiujia Shi, Lin Zhang, Zuanguang Chen
Biosensors and Bioelectronics 2015 Volume 68() pp:462-467
Publication Date(Web):15 June 2015
DOI:10.1016/j.bios.2015.01.018
•Potassium ferricyanide-doped polyaniline (FC-PANI) nanoparticles were synthesized by one-step for the first time.•FC-PANI acting as the signal indicator was first introduced to the construction of label-free immunosensor.•This developed immunosensor displayed facile preparation procedure, wide linear range, a low detection limit, long-term stability, satisfying reproducibility and anti-interference ability.•This immunosensor was also successfully applied for the determination of CEA in human serum sample.A novel, label-free and inherent electroactive redox immunosensor for ultrasensitive detection of carcinoembryonic antigen (CEA) was proposed based on gold nanoparticles (AuNPs) and potassium ferricyanide-doped polyaniline (FC-PANI) nanoparticles. FC-PANI composite was synthesized via oxidative polymerization of aniline, using potassium ferricyanide (K3[Fe(CN)6]) as both oxidant and dopant. FC-PANI acting as the signal indicator was first fixed on a gold electrode (GE) to be the signal layer. Subsequently, the negatively charged AuNPs could be adsorbed on the positively charged FC-PANI modified GE surface by electrostatic adsorption, and then to immobilize CEA antibody (anti-CEA) for the assay of CEA. The CEA concentration was measured through the decrease of amperometric signals in the corresponding specific binding of antigen and antibody. The wide linear range of the immunosensor was from 1.0 pg mL−1 to 500.0 ng mL−1 with a low detection limit of 0.1 pg mL−1(S/N=3). The proposed method would have a potential application in clinical immunoassays with the properties of facile procedure, stability, high sensitivity and selectivity.
Co-reporter:Yanyan Yu, Zuanguang Chen, Wensi Jian, Duanping Sun, Beibei Zhang, Xinchun Li, Meicun Yao
Biosensors and Bioelectronics 2015 Volume 64() pp:566-571
Publication Date(Web):15 February 2015
DOI:10.1016/j.bios.2014.09.080
•An electrochemical biosensor based on EXPAR coupled with HCR was developed.•Avian influenza A (H7N9) virus DNA was detected with ultrasensitivity.•A detection range of 4 orders of magnitude was obtained.•The biosensor performed well in SNP and spiked cell lysates analysis.In this work, a simple and label-free electrochemical biosensor with duel amplification strategy was developed for DNA detection based on isothermal exponential amplification (EXPAR) coupled with hybridization chain reaction (HCR) of DNAzymes nanowires. Through rational design, neither the primer nor the DNAzymes containing molecular beacons (MBs) could react with the duplex probe which were fixed on the electrode surface. Once challenged with target, the duplex probe cleaved and triggered the EXPAR mediated target recycle and regeneration circles as well as the HCR process. As a result, a greater amount of targets were generated to cleave the duplex probes. Subsequently, the nanowires consisting of the G-quadruplex units were self-assembled through hybridization with the strand fixed on the electrode surface. In the presence of hemin, the resulting catalytic G-quadruplex–hemin HRP-mimicking DNAzymes were formed. Electrochemical signals can be obtained by measuring the increase in reduction current of oxidized 3.3′,5.5′-tetramethylbenzidine sulfate (TMB), which was generated by DNAzyme in the presence of H2O2. This method exhibited ultrahigh sensitivity towards avian influenza A (H7N9) virus DNA sequence with detection limits of 9.4 fM and a detection range of 4 orders of magnitude. The biosensor was also capable of discriminating single-nucleotide difference among concomitant DNA sequences and performed well in spiked cell lysates.
Co-reporter:Xiujuan Yang;Cui Liu
Chromatographia 2015 Volume 78( Issue 1-2) pp:119-123
Publication Date(Web):2015 January
DOI:10.1007/s10337-014-2807-5
A novel and rapid method was developed for the determination of uric acid in human urine by capillary electrophoresis with an improved electromagnetic induction detector. Electrophoretic parameters affecting the separation efficiency, such as buffer composition, buffer pH, buffer concentration, and electroosmotic flow modifier, were systematically investigated. An electrolyte solution consisting of 8.5 mmol L−1 tris(hydroxymethyl)aminomethane (Tris), 1.5 mmol L−1 citric acid, and 0.2 mmol L−1 cetyltrimethylammonium bromide, pH 8.0, was found to be suitable for sample determination. Uric acid was separated and detected within 2.3 min, with a linear response range from 5 to 400 µg mL−1 and a correlation coefficient of 0.9998. Intraday and interday precision were 1.6 and 2.5 % (n = 6), respectively. The recoveries were between 98.3 and 100.5 %. This simple, effective, and stable method is a good alternative to existing methods for uric acid determination. Also, the improved electromagnetic induction detector holds great promise in clinical analysis.
Co-reporter:Yanyan Yu, Zuanguang Chen, Lijuan Shi, Fan Yang, Jianbin Pan, Beibei Zhang, and Duanping Sun
Analytical Chemistry 2014 Volume 86(Issue 16) pp:8200
Publication Date(Web):July 23, 2014
DOI:10.1021/ac501505a
In this work, a simple and label-free electrochemical biosensor is developed for microRNA (miRNA) detection on the basis of an arched probe mediated isothermal exponential amplification reaction (EXPAR). The arched probe assembled on the electrode surface consists of two strands that are partially complementary to each other at both ends. The target can hybridize with the complementary sequence of the arched structure, leading to the cleavage of the probe. The strand fixed on the surface of the electrode self-assembles, in the presence of hemin, to G-quadruplex unit, yielding electrochemical signals. The other strand liberated into the solution triggers the EXPAR to recycle and regenerate targets. This method exhibits ultrahigh sensitivity toward miRNA with detection limits of 5.36 fM and a detection range of 3 orders of magnitude. The biosensor is capable of discriminating a single-nucleotide difference between concomitant miRNA and performs well in analyzing crude extractions from cancer cell lines.
Co-reporter:Zhenping Liu, Haiyun Zhai, Zuanguang Chen, Qing Zhou, Zhixian Liang, Zihao Su
Electrochimica Acta 2014 Volume 136() pp:370-376
Publication Date(Web):1 August 2014
DOI:10.1016/j.electacta.2014.05.090
•A novel Fe2O3/MWCNTs-COOH/OP modified carbon paste electrode was fabricated and characterized.•The electrode was useful for simultaneous determination of orange G and orange II in industrial wastewater.•Under optimized conditions, common ions and dyes did not interfered in the electrode activity.•The modified electrode exhibited good sensitivity, reproducibility and stability.•This proposed electrode displayed better electrocatalytic activity than other unmodified electrodes towards orange G and orange II.A novel Fe2O3 nano-materials/oxygen functionalized multi-walled carbon nanotubes/triton X-100 modified carbon paste electrode (Fe2O3/MWCNTs-COOH/OP/CPE) was prepared to simultaneously detect orange G (Or G) and orange II (Or II) by electrochemical methods. Compared with the bare carbon paste electrode (CPE), Fe2O3/MWCNTs-COOH/OP/CPE exhibited obvious electrocatalytic activities towards Or G and Or II. Furthermore, the two azo dyes were identified and separated successfully, and were simultaneously determined by the redox peaks in cyclic voltammograms (CVs) and differential pulse voltammogram (DPV) under optimum conditions. In DPV, anodic peak current (Ipa) and concentrations were linearly related well for 0.1-20.0 μM Or G and 0.2-50.0 μM Or II. The limits of detection (S/N = 3) of Or G and Or II were 0.05 μM and 0.1 μM, respectively. Therefore, the electrode is suitable for the determination of Or G and Or II in industrial wastewater due to high sensitivity and selectivity, low detection limit, good reproducibility, as well as easy preparation and regeneration.
Co-reporter:Sijing He, Zuanguang Chen, Yanyan Yu and Lijuan Shi
RSC Advances 2014 vol. 4(Issue 85) pp:45185-45190
Publication Date(Web):22 Sep 2014
DOI:10.1039/C4RA06925K
A novel hydrogen peroxide (H2O2) sensor was fabricated using electrodepositing platinum nanoparticles (PtNPs) on a glassy carbon electrode (GCE) modified with a highly stable poly-melamine film. Since the formation of the poly-melamine layer significantly increased the surface area, high-density PtNPs were homogeneously loaded onto the nanostructured matrix of poly-melamine. The PtNPs/poly-melamine heterostructure-based H2O2 sensor synergized the advantages of both the conducting film and the nanoparticle catalyst. This non-enzymatic sensor exhibited high electrocatalytic activity toward the reduction of H2O2, and provided a linear response for H2O2 in the concentration range from 5 μmol L−1 to 1650 μmol L−1 with a limit of detection (LOD, S/N = 3) of 0.65 μmol L−1. In addition, this proposed H2O2 sensor displayed high sensitivity, good anti-interference ability, excellent reproducibility and long-term stability. The excellent analytical performances and facile preparation process made this novel hybrid electrode promising for the development of H2O2 sensors.
Co-reporter:Haiyun Zhai, Jiangmei Li, Zuanguang Chen, Zihao Su, Zhenping Liu, Xiao Yu
Microchemical Journal 2014 Volume 114() pp:223-228
Publication Date(Web):May 2014
DOI:10.1016/j.microc.2014.01.006
•A simple glass/PDMS chip for sample pretreatment and contactless conductivity detection (CCD) was fabricated.•The chip was embedded with a home-made molecularly imprinted SPE (MISPE) monolithic column.•The MISPE monolithic column was convenient to be integrated in or replaced from the chip.•Two modes of on-line and off-line SPE were executed with CCD to analyze auramine O.A simple glass/PDMS microfluidic chip for on-line sample pretreatment and contactless conductivity detection, which consisted of a 0.17 mm-thick glass cover and a PDMS substrate embedded with an SPE monolithic column, was presented in this paper. Using this integrated microchip system, sample extraction, injection, separation and detection were automatically performed in sequence. A sample of auramine O was concentrated by molecularly imprinted SPE (MISPE), eluted to sample reservoir, and injected by electromigration into separation channel for electrophoresis separation and contactless conductivity detection, with the calculated detection limit (S/N = 3) being 2.5 μg mL− 1. The monolithic column was utilized to quantitatively extract auramine O, yielding an on-line enrichment factor of about 12. The microchip system is reliable and applicable to the analysis of auramine O in food sample.
Co-reporter:Jianbin Pan;Meicun Yao;Xinchun Li;Yinbao Li;Duanping Sun;Yanyan Yu
Luminescence 2014 Volume 29( Issue 5) pp:427-432
Publication Date(Web):
DOI:10.1002/bio.2565
ABSTRACT
A two-electrode configuration powered by batteries was designed for a microchip capillary electrophoresis–electrochemiluminescence system. A home-made working electrode for end-column mode detection and wall-jet configuration was made up of a platinum wire (0.3 mm diameter) and a quartz capillary (320 µm internal diameter). The platinum wire served as a pseudoreference electrode. The configuration of the detection power supply comprised two D-size batteries (connected in series), a switch, and an adjustable resistor. The microchip consisted of two layers: the bottom layer was a glass sheet containing injection and separation channels; the upper layer was polydimethylsiloxane block. In order to reduce the loss of electrochemiluminescence signal, a coverslip (0.17 mm thickness) was used as the floor of the detection reservoir. The performance of the system was demonstrated by separation and detection of atropine, anisodamine and proline. The linear response for proline ranged from 5 µm to 100 µm (r = 0.9968), and the limit of detection was 1.0 µm (S/N = 3). The system was further applied to the measurement of atropine in atropine sulfate injection solutions with the limit of detection 2.3 µm. This new system is a potential tool in pharmaceutical analysis. Copyright © 2013 John Wiley & Sons, Ltd.
Co-reporter:Duanping Sun;Jing Lu;Yanyan Yu
Microfluidics and Nanofluidics 2014 Volume 17( Issue 5) pp:831-842
Publication Date(Web):2014 November
DOI:10.1007/s10404-014-1373-3
The formation of three-dimensional (3D) multicellular cell spheroids such as microspheres and embryoid bodies has recently gained much attention as a useful cell culture technique, but few studies have investigated the suitability of glass for spheroids formation and culture. In this work, we present a novel three-dimensional microfluidic device made of poly(dimethylsiloxane) (PDMS) and glass for the easy and rapid synthesis and culture of tumor spheroid. The cell culture unit is composed of an array of microwells on the bottom of a glass plate, bigger microwells and elastomeric microchannels on the top of a PDMS plate. Cell suspension can be easily introduced into the cell culture unit and exchange with the external liquid environment by the microfluidic channels. A single tumor spheroid can be formed and cultured in each glass cell culture chamber, the surface of which was modified with poly(vinyl alcohol) to render it to be resistant to cell adhesion. As the cell culture medium could be replaced, spheroids of the human breast cancer (MCF-7) cells were cultured on the chip for 3 days, reaching the diameters of about 150 μm. Furthermore, the MCF-7 cells were successfully cultured on the chip in 2D and 3D culture modes. Results have shown that glass is well suitable for multicellular tumor spheroids culture. The established platform provides a convenient and rapid method for tumor spheroid culture, which is also adaptable for anticancer drug screening and fundamental biomedical research in cell biology.
Co-reporter:Yanyan Yu, Zuanguang Chen, Sijing He, Beibei Zhang, Xinchun Li, Meicun Yao
Biosensors and Bioelectronics 2014 Volume 52() pp:147-152
Publication Date(Web):15 February 2014
DOI:10.1016/j.bios.2013.08.043
•AuNPs/G/MWCNTs nanostructure was prepared.•Glucose oxidase was immobilized onto the structure via electrostatic attraction.•The direct electron transfer was achieved between the enzyme and the electrode.•The glucose biosensor fabricated exhibited satisfactory analytical performance.In this work, poly (diallyldimethylammonium chloride) (PDDA)-capped gold nanoparticles (AuNPs) functionalized graphene (G)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were fabricated. Based on the electrostatic attraction, the G/MWCNTs hybrid material can be decorated with AuNPs uniformly and densely. The new hierarchical nanostructure can provide a larger surface area and a more favorable microenvironment for electron transfer. The AuNPs/G/MWCNTs nanocomposite was used as a novel immobilization platform for glucose oxidase (GOD). Direct electron transfer (DET) was achieved between GOD and the electrode. Field emission scanning electron microscopy (FESEM), UV–vis spectroscopy and cyclic voltammetry (CV) were used to characterize the electrochemical biosensor. The glucose biosensor fabricated based on GOD electrode modified with AuNPs/G/MWCNTs demonstrated satisfactory analytical performance with high sensitivity (29.72 mA M−1 cm−2) and low limit of detection (4.8 µM). The heterogeneous electron transfer rate constant (ΚS) and the apparent Michaelis–Menten constant (Km) of GOD were calculated to be 11.18 s−1 and 2.09 mM, respectively. With satisfactory selectivity, reproducibility, and stability, the nanostructure we proposed offered an alternative for electrode fabricating and glucose biosensing.
Co-reporter:Jianping Yang, Zuanguang Chen, Poying Ching, Qiujia Shi and Xinchun Li
Lab on a Chip 2013 vol. 13(Issue 17) pp:3373-3382
Publication Date(Web):31 May 2013
DOI:10.1039/C3LC50264C
The nematode Caenorhabditis elegans is a useful model host for pathogenesis research that can be infected by a large number of human pathogens. Conventionally, nematode–pathogen infection assays are mainly performed on agar medium which are labor-intensive and time-consuming. To overcome these challenges, we develop for the first time an integrated microfluidic device for evaluating in vivo antimicrobial activity of natural compounds, which allows infection and anti-infection assays to be sequentially and automatically carried out in liquid medium. The device consists of a worm dispenser with 32 trap-construction chambers and concentration gradient generators, in which the processes of introduction, dispensation, confinement of worms in the chamber and drug delivery to the chamber can be integrated into a single device. In addition, the operation of the device is simple and does not require any expensive robotic fluid handling systems to dispense samples. To demonstrate the ability of this device, we devise an on-line screening experiment using a Caenorhabditis elegans–Staphylococcus aureus infection model and characterize the survival rate of the infected worms treated with antibiotics. Then, we applied the system to evaluate the antibacterial activity of several components of rhubarb: aloe-emodin, rhein and emodin at various concentrations. The device is able to load uniform worms into each chamber within 10 min and then generate various chemical concentrations automatically and simultaneously. Furthermore, the on-chip method only requires 6 h to establish the infection model and 48 h to perform the subsequent treatments. Based on the excellent advantages and scalable properties of microfluidics, the microfluidic platform holds a great potential in high-throughput screening for antimicrobials.
Co-reporter:Xinchun Li, Zuanguang Chen, Jianbin Pan, Fan Yang, Yinbao Li, Meicun Yao
Journal of Chromatography A 2013 Volume 1291() pp:174-178
Publication Date(Web):24 May 2013
DOI:10.1016/j.chroma.2013.03.064
•Differential pulsed amperometry on microchip is reported for the first time.•The nature of the novel pulse electrochemical technique is discussed.•Comparable detection sensitivity to triple pulsed amperometry is demonstrated.•The present detection strategy broadens electroanalytical community.•This electrochemical protocol has potential for other fluid analysis methods.In this work, we describe a novel electrochemical detection method, differential pulsed amperometry (DPA) on microchip capillary electrophoresis (MCE). In a pulse period, a sequential two-step sampling is executed at two different potentials (E1 and E2). Differential current signal of the duplex sampling events is recorded that functions as time domain. The performance of this detection scheme was evaluated by separating and detecting three model analytes including tyramine (Tym), tryptophan (Trp), and p-aminobenzoic acid (PABA). Multiple parameters that would affect electrochemical response and peak shape, such as sampling potential, sampling time, and electrode cleaning time, were investigated. This pulse technique exhibits better sensitivity over constant potential amperometry (CPA), nearly equal to triple pulsed amperometry (TPA). More importantly, DPA can generate more stable baseline than TPA, primarily due to the background subtraction through the two-step sampling, which is beneficial to further improve analytical sensitivity. In the optimal condition, the limits of detection for Tym, Trp and PABA, were down to 0.27 μM, 0.32 μM and 1.1 μM, respectively. DPA detection opens up a new avenue for microchip electrochemistry, and can be virtually extended to other fluid analysis techniques.
Co-reporter:Sifeng Wang;Xiuwen Tang;Lijuan Shi;Lin Zhang ;Meicun Yao
Journal of Separation Science 2013 Volume 36( Issue 21-22) pp:3615-3622
Publication Date(Web):
DOI:10.1002/jssc.201300720
A simple microchip CE method integrated with contactless conductivity detection was developed for the direct determination of partition coefficients of selected pharmaceuticals after phase distribution equilibrium. The equilibrium of distribution between two phases for four pharmaceuticals was performed using a 1-octanol/water system and 1-octanol/buffer system. During the concentration determination, several major factors affecting detection were investigated in detail for each pharmaceutical to optimize the detection sensitivity. In the optimal conditions, sufficient electrophoretic separation and sensitive detection for each target analyte can be achieved within 40 s. The two systems showed a pH-dependent partition behavior. Moreover, the measured values showed excellent agreement with those obtained by the traditional shake-flask method with HPLC–UV detection and literature reports, respectively. The developed method can be successfully applied to measure partition coefficient values of pharmaceuticals and requires much shorter analytical time compared to traditional methods.
Co-reporter:Xinchun Li;Fan Yang;Jianbin Pan;Yinbao Li
Journal of Separation Science 2013 Volume 36( Issue 9-10) pp:1590-1596
Publication Date(Web):
DOI:10.1002/jssc.201300041
L-3,4-dihydroxyphenylalanine (L-DOPA) is a well-recognized therapeutic compound to Parkinson's disease. Tyrosine is a precursor for the biosynthesis of L-DOPA, both of which are widely found in traditional medicinal material, Mucuna pruriens. In this paper, we described a validated novel analytical method based on microchip capillary electrophoresis with pulsed electrochemical detection for the simultaneous measurement of L-DOPA and tyrosine in M. pruriens. This protocol adopted end-channel amperometric detection using platinum disk electrode on a homemade glass/polydimethylsiloxane electrophoresis microchip. The background buffer consisted of 10 mM borate (pH 9.5) and 0.02 mM cetyltrimethylammonium bromide, which can produce an effective resolution for the two analytes. In the optimal condition, sufficient electrophoretic separation and sensitive detection for the target analytes can be realized within 60 s. Both tyrosine and L-DOPA yielded linear response in the concentration range of 5.0–400 μM (R2 > 0.99), and the LOD were 0.79 and 1.1 μM, respectively. The accuracy and precision of the established method were favorable. The present method shows several merits such as facile apparatus, high speed, low cost and minimal pollution, and provides a means for the pharmacologically active ingredients assay in M. pruriens.
Co-reporter:Jiangmei Li;Haiyun Zhai;Qing Zhou;Zhenping Liu;Zihao Su
Journal of Separation Science 2013 Volume 36( Issue 21-22) pp:3608-3614
Publication Date(Web):
DOI:10.1002/jssc.201300681
A novel method combining molecular imprinting and SPE was developed in a capillary column for the determination of auramine O in shrimp. The capillary monolithic column was prepared by UV-initiated in situ polymerization, using auramine O as template and methacrylic acid and ethylene dimethacrylate as functional monomer and cross-linker, respectively. The properties of the prepared capillary monolithic column were investigated under the optimized conditions coupled with HPLC, and then the morphologies of the inner polymers were characterized by SEM. The calibration curve was expressed as A = 103C + 19.8 (r = 0.9992) with a linear range of 0.25–25.0 μg/mL, and the recoveries of auramine O at different concentrations in shrimp ranged from 90.5 to 92.4% with RSDs ranging from 2.1 to 4.4%. The capacities of the molecularly imprinted polymer and nonimprinted polymer columns were 0.722 and 0.147 μg/mg, respectively, and the LOD (S/N = 3) of auramine O in shrimp was 17.85 μg/kg. Under the selected conditions, the enrichment factors obtained were higher than 70-fold. The results indicate that the prepared molecularly imprinted capillary monolithic column was reliable and applicable to the analysis of auramine O in shrimp.
Co-reporter:Zhirui Song, Yue Xu, Zuanguang Chen, Jianping Yang, Xinchun Li, Zhiguang Zhang
Analytical Biochemistry 2013 Volume 434(Issue 1) pp:73-77
Publication Date(Web):1 March 2013
DOI:10.1016/j.ab.2012.11.006
This article describes the determination of lactate in synovia by microchip capillary electrophoresis (MCE) integrated with contactless conductivity detection (CCD). The optimal running buffer consists of 10 mM tris(hydroxymethyl)aminomethane, 1 mM HCl, and 0.1 mM hexadecyltrimethylammonium bromide (pH 9.1). The quantitative measurement of lactate in dilute synovia samples can be finished in less than 40 s. The results indicated that the peak area had a good linear relationship with lactate concentration in the range of 20 to 1000 μM, and the correlation coefficient was 0.9984. The average recovery was from 96.6% to 106.1%, and the interday relative standard deviation was less than 4.0% (n = 6). The limit of detection (signal/noise = 3) reached 6.5 μM. To validate the assay results, we compared the current method with the high-performance liquid chromatography method by measuring lactate in synovia samples. The data analysis verified that there was no significant difference between the two methods. Due to significant features such as low cost, integration, and miniaturization, the MCE–CCD method may have great potential in clinical diagnosis.
Co-reporter:Jianbin Pan, Xinchun Li, Zuanguang Chen, Fan Yang, Xiaohang Wu, Yinbao Li, Duanping Sun, Yanyan Yu
Electrochimica Acta 2013 90() pp: 101-107
Publication Date(Web):
DOI:10.1016/j.electacta.2012.11.118
Co-reporter:Beibei Zhang;Yanyan Yu;Jianping Yang;Jianbin Pan
Chromatographia 2013 Volume 76( Issue 13-14) pp:821-829
Publication Date(Web):2013 July
DOI:10.1007/s10337-013-2479-6
In this paper, we describe a compact and low-cost light-emitting diode-induced fluorescence (LED-IF) detection coupled to microchip electrophoresis for the determination of sulfonamides in pharmaceutical formulations and rabbit plasma. Three fluorescein isothiocyanate-labeled sulfonamides in rabbit plasma were separated in the running buffer of 40 mM phosphate buffer (pH 7.0) at the separation voltage of 2.0 kV, and detected by LED-IF detector in which the high-power blue LED was driven at the constant current of 150 mA and the emitted fluorescence over 510 nm was collected by a planar photodiode. The linear concentration ranged from 2.0 to 125.0 μg mL−1, both for sulfadiazine and sulfamethazine with the correlation coefficients (r2) of 0.995 and 0.997, respectively, and from 2.0 to 100.0 μg mL−1 with the correlation coefficients (r2) of 0.997 for sulfaguanidine. The limits of detection for the three sulfonamides were 0.36–0.50 μg mL−1 (S/N = 3). Intra-day and inter-day precision of migration time and peak area for the determination of sulfonamides were <4.5 %. This method has been successfully applied to the analysis of sulfonamides in pharmaceuticals, and could be used to study the pharmacokinetics of sulfonamides in rabbit.
Co-reporter:Yanyan Yu, Zuanguang Chen, Beibei Zhang, Xinchun Li, Jianbin Pan
Talanta 2013 Volume 112() pp:31-36
Publication Date(Web):15 August 2013
DOI:10.1016/j.talanta.2013.03.057
•A facile UA sensor based on PDDA-G and graphite was fabricated.•The electrode showed excellent sensitivity and selectivity towards UA detection.•The sensor can eliminate the interferences from excess AA and DA.•UA in human urine samples were detected directly without pretreatment.In this work, a facile electrochemical sensor based on poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene (PDDA-G) and graphite was fabricated. The composite electrode exhibited excellent selectivity and sensitivity towards uric acid (UA), owing to the electrocatalytic effect of graphene nanosheets and the electrostatic attractions between PDDA-G and UA. The anodic peak current of UA obtained by cyclic voltammetry (CV) increased over 10-fold compared with bare carbon paste electrode (CPE). And the reversibility of the oxidation process was improved significantly. Differential pulse voltammetry (DPV) was used to determine UA in the presence of ascorbic acid (AA) and dopamine (DA). It was found that all of oxidation peaks of three species could be well resolved, and the peak current of UA was much stronger than the other two components. More importantly, considerable-amount of AA and DA showed negligible interference to UA assay. The calibration curve for UA ranged from 0.5 to 20 μmol L−1 with a correlation coefficient of 0.9934. The constructed sensor has been employed to quantitatively determine UA in urine samples.
Co-reporter:Jianping Yang;Fan Yang;Shuping Wang
Biomedical Microdevices 2013 Volume 15( Issue 2) pp:211-220
Publication Date(Web):2013 April
DOI:10.1007/s10544-012-9719-7
Behavioral Caenorhabditis elegans mutants are sought for the purposes of neurobiological research. Until now, large numbers of worms with neuronal defects have been obtained through mutagenesis techniques. However, the existing screening procedures are not only time-consuming and low-throughput, but also tedious and labor-intensive. Therefore, developing a rapid and convenient method to overcome these difficulties is necessary. The present study demonstrates for the first time a microdevice for the rapid screening of chemotaxis-defective mutants based on their chemotactic response. The microchip is capable of automatic introduction, local immobilization, and controllable generation of concentration gradients during the screening assays. With this device, six C. elegans behavioral assays can be performed using various attractants without requiring anesthetics for local capture, and ten mutants are effectively isolated from 104 mutagenized worms in 100 min. The microfluidics-based method is robust enough to sort the chemotaxis-defective worms with 91 % accuracy from a large population of wild type animals during a mutagenesis screen.
Co-reporter:Junshan Liu, Fei Xu, Sifeng Wang, Zuanguang Chen, Jianbin Pan, Xinran Ma, Xiaokai Jia, Zheng Xu, Chong Liu, Liding Wang
Electrochemistry Communications 2012 Volume 25() pp:147-150
Publication Date(Web):November 2012
DOI:10.1016/j.elecom.2012.10.012
A polydimethylsiloxane (PDMS) electrophoresis microchip with a thickness-controllable insulating layer for capacitatively coupled contactless conductivity detection is presented. A PDMS film is spin-coated on a glass slide with Pt microelectrodes to be the insulating layer, and then permanently bonded with a PDMS channel plate to make the whole microchip. The thickness of PDMS films can be precisely controlled down to submicrometers. With a microchip with a 0.6 μm-thick PDMS insulating layer, a superior limit of detection (LOD) of 0.07 μM for Na+ was obtained. For comparison, another two microchips with the same design but different insulating layer thicknesses (15 μm and 50 μm) were tested, and LODs were 1 μM and 3 μM respectively, which are almost two orders of magnitude higher. Moreover, the microchip detector also exhibited excellent linearity, reproducibilities and separation efficiencies.Highlights► The thickness of the insulating layer on the microchip can be precisely controlled down to submicrometers. ► With the new contactless conductivity microchip detector, a superior limit of detection (< 100 nM for inorganic ions) was obtained. ► The microchip detector exhibited excellent linearity, reproducibilities and separation efficiencies. ► The microchip detector holds great promise for a wide range of analytical applications.
Co-reporter:Jin Xiong Qian, Zuan Guang Chen
Chinese Chemical Letters 2012 Volume 23(Issue 2) pp:201-204
Publication Date(Web):February 2012
DOI:10.1016/j.cclet.2011.10.012
A novel electromagnetic induction detector with two inductors for CE was described here. The two inductors were used as signal detection and reference, respectively. The parameters affecting the detector performance (including coil turns, detection distance, excitation frequency, voltage, etc.) were optimized. Under the optimum condition, the feasibility of the detector was examined by analyzing inorganic ions. The fabricated detector showed good linear relationship between the response and the analytes concentrations, with a detection limit of 13 μmol/L for Na+ (S/N = 3). A variety of advantages, such as simple construction, ease of operation, and considerably universal response, suggested this novel detector a promising application prospect in analytical area.
Co-reporter:Xinchun Li, Zuanguang Chen, Yuwen Zhong, Fan Yang, Jianbin Pan, Yajing Liang
Analytica Chimica Acta 2012 710() pp: 118-124
Publication Date(Web):13 January 2012
DOI:10.1016/j.aca.2011.10.035
Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 μM (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.Graphical abstractHighlights► CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. ► Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. ► An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. ► Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip.
Co-reporter:Xiujuan Yang;Jun Feng;Rifang Liao;Xinchun Li
Chromatographia 2012 Volume 75( Issue 1-2) pp:71-76
Publication Date(Web):2012 January
DOI:10.1007/s10337-011-2151-y
A novel, rapid and validated capillary electrophoretic method with an improved electromagnetic induction detector has been developed for the determination of ibuprofen, acetaminophen, amantadine hydrochloride, aminopyrine, diclofenac sodium and codeine phosphate in three kinds of analgesic pharmaceutical preparations. Fabrication of the electromagnetic inductor was the same as previously described, but a brand new electric circuit was designed for the detector to lower the background noise and improve the detection sensitivity. Important factors which might influence the response of the detector, including the value of the adjustable inductor and resistor, excitation frequency and voltage, were examined. Electrophoretic parameters affecting separation efficiency, such as variety of buffer, buffer pH, buffer concentration and electroosmotic flow modifier, were also deliberately investigated. Under the optimal conditions, highly linear response was obtained for these six compounds over three orders of magnitude with detection limits ranging from 0.1 to 1.0 μg mL−1 (S/N = 3). The average recovery and RSD were within the range of 97.5–101.5 and 1.1–2.3%, respectively. This simple, convenient, effective and stable method held great promise in quality control of pharmaceutical preparations.
Co-reporter:Shuping Wang;Xinchun Li;Jianping Yang;Xiujuan Yang;Fenghua Hou
Chromatographia 2012 Volume 75( Issue 21-22) pp:1287-1293
Publication Date(Web):2012 November
DOI:10.1007/s10337-012-2324-3
In clinical medicine, urine creatinine concentration is an important marker in the evaluation of renal function and muscular dysfunctions. Herein, we reported a novel method for rapid determination of creatinine in urine by microchip electrophoresis with light-emitting diode induced fluorescence detection. Creatinine was derivatized by fluorescein isothiocyanate, and then quantitatively detected by the developed microchip LED induced fluorescence detection system. The excitation and emission wavelengths were 490 and 523 nm, respectively. The urine samples were analyzed after centrifuge and filtration. A baseline separation was obtained in <30 s using 10 mM borate buffer (pH 9.0, containing 45 mM sodium dodecylsulfate), with separation voltage of 1.5 kV. Good linearity was obtained (r2 = 0.9978) in the concentration range of 10.0–2.00 × 103 μM, and the limit of detection was 2.87 μM (S/N = 3). The recovery was 96.0–107 %, and the interday precision was <4.5 % (n = 6). To validate assay results, we compared the present method with the Jaffe’s colorimetric assay by measuring real urine samples. The method was reliable, sensitive, high-speed, low-cost and suitable for the routine analysis of creatinine in biofluids.
Co-reporter:Jing Zhao, Zuanguang Chen, Xinchun Li, Jianbin Pan
Talanta 2011 Volume 85(Issue 5) pp:2614-2619
Publication Date(Web):15 October 2011
DOI:10.1016/j.talanta.2011.08.029
A microfluidic chip manufactured from glass substrate and indium tin oxide (ITO) coated glass use for contactless conductivity detection was developed. The detecting electrodes were fabricated by screen-printing and chemical etching methods using an ITO-coated glass wafer. Then, the glass substrate containing separation channels was bonded with the bare side of the processed ITO-coated glass, thus producing an electrophoresis chip integrated with contactless conductivity detector. The prepared microchip displayed considerable stability and reproducibility. Sensitive response was obtained at optimal conditions (including the gap between electrodes, excitation frequency, and excitation voltage). The feasibility of this microfluidic device was examined by detection of inorganic ions, and further demonstrated by the quantification of aminopyrine and caffeine in a compound pharmaceutical. The two ingredients can be completely separated within 1 min. The detection limits were 8 μg mL−1 and 3 μg mL−1, respectively; with the correlation coefficient of 0.996–0.998 in the linear range from 10 μg mL−1 to 800 μg mL−1. The results have showed that the present method is sensitive, reliable and fast.Highlights► The proposed analytical system suffers less to environmental factors. ► Thick cover layer can be used for microchip without obvious loss of sensitivity. ► This novel microchip-CCD system is simple to fabricate and convenient to use.
Co-reporter:Hui Yang;Xin-chun Li;Fan Yang;Jun Feng;Miao-yin Lin
Microchimica Acta 2011 Volume 175( Issue 1-2) pp:
Publication Date(Web):2011 October
DOI:10.1007/s00604-011-0670-8
We describe an efficient and easily fabricated electrochemiluminescence detection system for microchip capillary electrophoresis. A 300-μm-diameter platinum disc working electrode was embedded in a titanium tube which provides an adequate holding for working electrode and acts as counter electrode. We also have designed a simplified detection cell with a guide channel for the electrode. The integrated working-counter electrode can be easily aligned to the outlet of the separation channel through the guide channel. The functionality of the system was demonstrated by separation and detection of proline and tripropylamine. The response to proline is linear in the range from 5 μM to 5,000 μM, and the detection limit is 1.0 μM (S/N = 3). The system was further applied to the determination of chlorpromazine hydrochloride in pharmaceutical formulations. The system is believed to have potential applications in pharmaceutical analysis.
Co-reporter:Xinchun Li;Jianbin Pan;Fan Yang;Jun Feng;Jinyuan Mo
Microchimica Acta 2011 Volume 174( Issue 1-2) pp:
Publication Date(Web):2011 July
DOI:10.1007/s00604-011-0592-5
We report on a simple amperometric detector for use in microchip capillary electrophoresis. A disposable syringe serves as the electrode holder that is fixed at the outlet of the separation channel. A carbon paste electrode is used to detect dopamine (DA) and catechol (CA) after electrophoretic separation. The two model analytes were well separated within 60 s. The response is linear in the concentration range from 4 to 500 μM, and the detection limit is 1.2 μM for DA (S/N = 3:1). The relative standard deviations of the inter-run and inter-electrode peak currents, respectively, are 2.8% and 5.7% for DA, and 3.9% and 6.5% for CA. Favorable column efficiency (expressed by the theoretical plate number which is 5.3 × 104 m-1 for DA) is achieved. The method was successfully applied to the separation and detection of 3-aminophenol (3-AP) in an injection powder containing sodium 4-aminosalicylate. The detection limit of 3-AP is as low as 1.7 μM, which meets the demand of the impurity test. The facile assembly allows convenient replacement of working electrodes and improves the longevity of the microanalytical system.
Co-reporter:Fan Yang, Xin-chun Li, Wen Zhang, Jian-bin Pan, Zuan-guang Chen
Talanta 2011 Volume 84(Issue 4) pp:1099-1106
Publication Date(Web):30 May 2011
DOI:10.1016/j.talanta.2011.03.020
In this paper, a compact and inexpensive light emitting diode induced fluorescence (LED-IF) detector with simplified optical configuration was developed and assembled in an integrated microfluidic device for microscale electrophoresis. The facile detector mainly consisted of an LED, a focusing pinhole, an emission filter and a photodiode, and was encapsulated in the upper layer of an aluminum alloy device with two layers. At the bottom layer, integrated circuit (IC) was assembled to manipulate the voltage for sample injection and separation, LED emission and signal amplifying. A high-power LED with fan-shaped heat sink was used as excitation source. The excitation light was focused by a 1.1 mm diameter pinhole fabricated in a thin piece of silver foil, and the obtained sensitivity was about 3 times as high as that using electrode plate. Other important parameters including LED driven current, fluorescence collection angle and detection distance have also been investigated. Under optimal conditions, considerable high-response of 0.09 fmol and 0.18 fmol mass detection limits at 0.37 nL injection volume for sodium fluorescein (SF) and FITC was achieved, respectively. This device has been successfully employed to separate penicillamine (PA) enantiomers. Due to such significant features as low-cost, integration, miniaturization, and ease of commercialization, the presented microfluidic device may hold great promise for clinical diagnostics and bioanalytical applications.
Co-reporter:Xiu-juan Yang, Zuan-guang Chen, Cui Liu, Ou-lian Li
Talanta 2010 Volume 82(Issue 5) pp:1935-1942
Publication Date(Web):15 October 2010
DOI:10.1016/j.talanta.2010.08.013
A new electromagnetic induction detector for capillary electrophoresis and its application are described. The detector is consisted of an inductor, a resistor, a high-frequency signal generator and a high-frequency millivoltmeter. The conditions affecting the response of the detector, including dimension of the magnetic ring, position of the capillary, number of coil turns, frequency, excitation voltage and value of the resistor were examined and optimized. The feasibility of the proposed detector was evaluated by detection of inorganic ions and separation of amino aids. Its quantification applicability was investigated by determination of aspirin and paracetamol in pharmaceutical preparation (Akafen powder). The primary factors affecting separation efficiency, which include variety of buffer, buffer concentration, injection time and injection height and separation voltage, were researched. Experimental results demonstrated that this new detector showed a well-defined correlation between sample concentrations and responses (r = 0.997–0.999), with detection limits of 30 μmol L−1 for aspirin and 10 μmol L−1 for paracetamol, as well as good reproducibility and stability. Compared with currently available detection techniques, this new detector has several advantages, such as simple construction, no complicated elements, ease of assembly and operation, and potential for universal applications. It can be an alternative to the traditional methods in the quality control of the pharmaceutical preparations.
Co-reporter:Xiang LI, Yan-Li TONG, Cui LIU, Ou-Lian LI, Xiu-Juan YANG, Zuan-Guang CHEN
Chinese Journal of Analytical Chemistry 2009 Volume 37(Issue 10) pp:1547-1554
Publication Date(Web):October 2009
DOI:10.1016/S1872-2040(08)60138-3
Co-reporter:Zuan-guang Chen, Ou-lian Li, Cui Liu, Xiu-juan Yang
Sensors and Actuators B: Chemical 2009 Volume 141(Issue 1) pp:130-133
Publication Date(Web):18 August 2009
DOI:10.1016/j.snb.2009.05.042
Co-reporter:Cui Liu, Yun-yan Mo, Zuan-guang Chen, Xiang Li, Ou-lian Li, Xie Zhou
Analytica Chimica Acta 2008 Volume 621(Issue 2) pp:171-177
Publication Date(Web):28 July 2008
DOI:10.1016/j.aca.2008.05.040
A new dual detection system for microchip is reported. Both fluorescence detector (FD) and contactless conductivity detector (CCD) were combined together and integrated on a microfluidic chip. They shared a common detection position and responded simultaneously. A blue light-emitting diode was used as excitation source and a small planar photodiode was used to collect the emitted fluorescence in fluorescence detection, which made the device more compact and portable. The coupling of the fluorescence and contactless conductivity modes at the same position of a single separation channel enhanced the detection characterization of sample and offered simultaneous detection information of both fluorescent and charged specimen. The detection conditions of the system were optimized. K+, Na+, fluorescein sodium, fluorescein isothiocyanate (FITC) and FITC-labeled amino acids were used to evaluate the performance of the dual detection system. The limits of detection (LOD) of FD for fluorescein Na+, FITC, FITC-labeled arginine (Arg), glycine (Gly) and phenylalanine (Phe) were 0.02 μmol L−1, 0.05 μmol L−1, 0.16 μmol L−1, 0.15 μmol L−1, 0.12 μmol L−1 respectively, and the limits of detection (LOD) of CCD achieved 0.58 μmol L−1 and 0.39 μmol L−1 for K+ and Na+ respectively.
Co-reporter:Zuanguang Chen, Quanwen Li, Oulian Li, Xie Zhou, You Lan, Yuanfang Wei, Jinyuan Mo
Talanta 2007 Volume 71(Issue 5) pp:1944-1950
Publication Date(Web):30 March 2007
DOI:10.1016/j.talanta.2006.08.040
A microfabricated thin glass chip for contactless conductivity detection in chip capillary electrophoresis is presented in this contribution. Injection and separation channels were photolithographed and chemically etched on the surface of substrate glass, which was bonded with a thin cover glass (100 μm) to construct a new microchip. The chip was placed over an independent contactless electrode plate. Owing to the thinness between channel and electrodes, comparatively low excitation voltage (20–110 V in Vp–p) and frequency (40–65 kHz) were suitable, and favorable signal could be obtained. This microchip capillary electrophoresis device was used in separation and detection of inorganic ions, amino acids and alkaloids in amoorcorn tree bark and golden thread in different buffer solutions. The detection limit of potassium ion was down to 10 μmol/L. The advantages of this microchip system exist in the relative independence between the microchip and the detection electrodes. It is convenient to the replacement of chip and other operations. Detection in different position of the channel would also be available.
Co-reporter:Zi-You Cai, Yong-Chong Li, Li-Hua Li, Zuan-Guang Chen
Journal of Pharmaceutical Analysis (October 2012) Volume 2(Issue 5) pp:356-360
Publication Date(Web):1 October 2012
DOI:10.1016/j.jpha.2012.07.003
A new method for the determination of arecoline in Semen Arecae decoction pieces by microchip capillary electrophoresis with contactless conductivity detection (MCE-CCD) was proposed. The effects of various electrophoretic operating parameters on the analysis of arecoline were studied. Under the optimal conditions, arecoline was rapidly separated and detected in 1 min with good linearity over the concentration range of 20–1500 μM (r2=0.9991) and the detection limit of 5 μM (S/N=3). The method was used for the analysis of arecoline satisfactorily with a recovery of 96.8–104%.
Co-reporter:
Analytical Methods (2009-Present) 2015 - vol. 7(Issue 19) pp:NaN8303-8303
Publication Date(Web):2015/08/13
DOI:10.1039/C5AY01838B
A method employing molecularly imprinted solid-phase extraction (MISPE) coupled with capillary electrophoresis laser-induced fluorescence detection (CE-LIF) was developed for the determination of rose bengal in brown sugar. The rose bengal imprinted monolithic column was prepared by in situ polymerization, utilizing rose bengal as a template, methacrylic acid as a functional monomer and ethylene dimethacrylate as a cross-linker. The capacity and specificity of this column were evaluated by CE-LIF, and the morphology was characterized by scanning electron microscopy. The recoveries ranged from 89.7% to 90.3% (relative standard deviation 3.6–4.5%, n = 5). The capacities of the molecularly imprinted polymer and non-imprinted polymer columns were 1.314 μg mg−1 and 0.531 μg mg−1, respectively. The detection limit (S/N = 3) was 3 ng mL−1. The enrichment factor was higher than 63-fold and the MISPE column managed to remove rose bengal from the matrix of brown sugar effectively. This method can be applied to sensitively and effectively determine rose bengal in brown sugar.
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![(S)-(1R,3S,5R,6S)-6-Hydroxy-8-methyl-8-azabicyclo[3.2.1]octan-3-yl 3-hydroxy-2-phenylpropanoate](http://img.cochemist.com/ccimg/55900/55869-99-3_b.png)
