Co-reporter:Peipei Liang, Huimin Bao, Jifang Yang, Luyan Zhang, Gang Chen
Carbon 2016 Volume 97() pp:25-34
Publication Date(Web):February 2016
DOI:10.1016/j.carbon.2015.04.024
Porous graphene oxide–poly(urea–formaldehyde) (GO–PUF) hybrid monolith was prepared by the in situ polycondensation of the urea–formaldehyde prepolymer solution in the presence of GO sheets and ammonium chloride. The amide groups in the residues of asparagine and glutamine in trypsin was allowed to condense with the residual N-hydroxymethyl groups of PUF in the monolith at low pH to fabricate bioreactors for proteolysis. The morphologies and structures of the prepared materials were investigated by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The results indicate that both GO–PUF hybrid and trypsin-immobilized GO–PUF hybrid mainly consist of irregular micrometer size flakes and pores that are interconnected to form 3D porous architectures. In addition, the feasibility and performance of the novel capillary bioreactors were demonstrated by the digestion and identification of bovine serum albumin, lysozyme, ovalbumin, and cytochrome c. The digestion time was significantly reduced to less than 10 s. The digests were identified by mass spectrometry with results that were comparable to those obtained by 12-h conventional in-solution tryptic digestion.
Co-reporter:Fenfen Ma;Wei Zhang;Joseph Wang;Luyan Zhang
Microchimica Acta 2016 Volume 183( Issue 9) pp:2579-2587
Publication Date(Web):2016 September
DOI:10.1007/s00604-016-1900-x
The article describes the preparation of an electrode for amperometric detection in capillary electrophoresis (CE). It consists of a copper wire that was coated with a composite consisting of carbon nanotubes and polyurethane that was fabricated by in-situ polyaddition from a mixture of polyurethane prepolymer, curing agent, and carbon nanotubes (CNTs) inside a fused silica capillary. The structure of the composite was characterized by scanning electron microscopy, X-ray diffraction, thermogravimetry and FT-IR. The results indicated that CNTs were well dispersed and embedded throughout the composite to form an interconnected conducting network. The performance and advantages of the detection electrode are demonstrated by the separation and detection of standard mixtures of the hesperidin, hesperetin, naringenin and naringin by CE. The four flavanones are well separated within 12 min in a 40 cm long capillary at a separation voltage of 12 kV using a 50 mM sodium borate buffer (pH 9.2). The CNT-based electrode offers lower detection potential (0.8 V), enhanced detection limits (0.22–0.31 μM), lower costs of operation, high resistance to surface fouling, and improved stability. It shows long-term stability and repeatability, and relative standard deviations are <5 % for the peak current (for n = 15). The method was applied to the determination of flavanone in the peels of citrus fruits.
Co-reporter:Huimin Ge, Huimin Bao, Luyan Zhang, Gang Chen
Carbon 2015 Volume 82() pp:579-589
Publication Date(Web):February 2015
DOI:10.1016/j.carbon.2014.11.011
Porous graphene was prepared by dissolving the sacrificial templates of cuprous oxide microsphere (Cu2OMS) in the composite of graphene and Cu2OMSs with diluted nitric acid. The composite was synthesized by the chemical reduction of a mixture containing graphene oxide, copper(II) sulfate in the presence of glucose and sodium hydroxide. The morphologies and structures of the prepared materials were investigated by scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The average size of the pores in the prepared porous graphene was measured to be ∼1.37 μm. The prepared graphene with a three-dimensional architecture was successfully employed in the enrichment and determination of low-abundance proteins and peptides based on its large surface area, unique structure, and high hydrophobicity, indicating great promise for a wide range of applications.
Co-reporter:Luyan Zhang, Wei Zhang, Gang Chen
Journal of Pharmaceutical and Biomedical Analysis 2015 Volume 115() pp:323-329
Publication Date(Web):10 November 2015
DOI:10.1016/j.jpba.2015.07.044
•A carbon nanotube/epoxy composite electrode was fabricated by polycondensation.•The electrode was applied in the detection of capillary electrophoresis.•The electrode exhibited high electrocatalytic activity toward phenols.•Bergeniae Rhizoma was analyzed by capillary electrophoresis with the electrode.This report describes the fabrication and the application of a novel carbon nanotube (CNT)-epoxy composite electrode as a sensitive amperometric detector for the capillary electrophoresis (CE). The composite electrode was fabricated on the basis of the in situ polycondensation of a mixture of CNTs and 1,2-ethanediamine-containing bisphenol A epoxy resin in the inner bore of a piece of fused silica capillary under heat. It was coupled with CE for the separation and detection of arbutin and bergenin in Bergeniae Rhizoma, a traditional Chinese medicine, to demonstrate its feasibility and performance. The two phenolic constituents were well separated within 10 min in a 45 cm capillary length at a separation voltage of 12 kV using a 50 mM borate buffer (pH 9.2). The CNT-based detector offered higher sensitivity, significantly lower operating potential, satisfactory resistance to surface fouling, and lower expense of operation, indicating great promise for a wide range of analytical applications. It showed long-term stability and reproducibility with relative standard deviations of less than 5% for the peak current (n = 15).
Co-reporter:Huimin Ge, Huimin Bao, Luyan Zhang and Gang Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 32) pp:5220-5228
Publication Date(Web):16 Jun 2014
DOI:10.1039/C4TB00302K
A graphene–cobalt microsphere hybrid was prepared by the chemical reduction of a mixture containing graphene oxide and cobalt chloride. It was found that a little amount of potassium borohydride or sodium borohydride could initiate the hydrazine-reduction of the mixture at a low temperature of 80 °C. The structure of the material was investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, vibrating sample magnetometery, Fourier transform infrared spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller (BET) techniques. The average size of the cobalt microspheres on graphene sheets was measured to be ∼590 nm. Magnetic investigations indicated that the graphene–cobalt microsphere hybrid exhibited ferromagnetic behavior at room temperature. In addition, the magnetic hybrid was successfully employed in the enrichment and identification of low-abundance proteins and peptides in combination with mass spectrometry.
Co-reporter:Huimin Ge, Huimin Bao, Luyan Zhang, Gang Chen
Analytica Chimica Acta 2014 Volume 845() pp:77-84
Publication Date(Web):3 October 2014
DOI:10.1016/j.aca.2014.07.044
•Trypsin was immobilized on miniature incandescent bulbs via chitosan coating.•The bulbs acted as enzymatic reactors and the generators of infrared radiation.•The bulb bioreactors were successfully employed in infrared-assisted proteolysis.•The proteolysis could accomplish within 5 min with high sequence coverages.A novel efficient proteolysis approach was developed based on trypsin-immobilized miniature incandescent bulbs and infrared (IR) radiation. Trypsin was covalently immobilized in the chitosan coating on the outer surface of miniature incandescent bulbs with the aid of glutaraldehyde. When an illuminated enzyme-immobilized bulb was immersed in protein solution, the emitted IR radiation could trigger and accelerate heterogeneous protein digestion. The feasibility and performance of the novel proteolysis approach were demonstrated by the digestion of hemoglobin (HEM), cytochrome c (Cyt-c), lysozyme (LYS), and ovalbumin (OVA) and the digestion time was significantly reduced to 5 min. The obtained digests were identified by MALDI-TOF-MS with the sequence coverages of 91%, 77%, 80%, and 52% for HEM, Cyt-c, LYS, and OVA (200 ng μL−1 each), respectively. The suitability of the prepared bulb bioreactors to complex proteins was demonstrated by digesting human serum.
Co-reporter:Ren Zhang, Sijie Lu, Luyan Zhang, Gang Chen
Journal of Chromatography A 2014 Volume 1374() pp:261-267
Publication Date(Web):29 December 2014
DOI:10.1016/j.chroma.2014.11.038
•Graphene and nickel nanoparticles were coated on anion exchange resin microspheres.•The prepared microspheres were embedded in pipette tips to form electrodes.•The electrodes exhibited high electrocatalytic activity toward carbohydrates.•The electrodes were applied in the detection of capillary electrophoresis.Graphene and nickel nanoparticles (NiNPs) were assembled on anion exchange resin (AER) microspheres based on the electrostatic interaction between graphene oxide sheets and AER and the subsequent chemical reduction. The prepared AER@graphene–NiNP composite core–shell microspheres were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Moreover, they were embedded in the bores of pipette tips to fabricate electrodes. The performance of the novel electrodes was demonstrated by measuring sucrose, glucose and fructose in combination with capillary electrophoresis. The three analytes were well separated within 8 min in a 40 cm long capillary at a separation voltage of 12 kV. The graphene–NiNP composite microsphere electrodes exhibited higher sensitivity (213.578–317.064 nA mM−1), lower detection limits (0.75–1.05 μM) and enhanced separation efficiency in the detection of these carbohydrates. The advantages of the electrodes include ease of fabrication, low cost and pronounced electrocatalytic activity toward carbohydrates, indicating great promise for a wide range of applications.
Co-reporter:Qiwen Chen, Luyan Zhang and Gang Chen
RSC Advances 2014 vol. 4(Issue 99) pp:56440-56444
Publication Date(Web):27 Oct 2014
DOI:10.1039/C4RA09909E
Far infrared (IR) radiation was employed in the embossing and bonding of poly(methyl methacrylate) (PMMA) microfluidic chips owing to its high penetration ability and heating efficiency. To emboss a channel plate, a piece of PMMA plate was sandwiched between a template and a glass plate. They were exposed to IR radiation for 5 min at 130 °C under pressure in a far IR-assisted embossing/bonding system. Subsequently, the embossed channel PMMA plate was bonded with a PMMA cover plate with the aid of far IR radiation and pressure. Satisfactory bonding could be achieved within 3 min at 100 °C. The fabricated microchips were successfully employed in the electrophoretic separation of four nitroaromatic compounds. Far IR-assisted embossing and bonding approaches indicate great promise for the mass production of PMMA microchips at low cost and should find a wide range of applications.
Co-reporter:Wei Zhang, Xia Zhang, Luyan Zhang, Gang Chen
Sensors and Actuators B: Chemical 2014 192() pp: 459-466
Publication Date(Web):
DOI:10.1016/j.snb.2013.11.016
Co-reporter:Shuang Liu, Huimin Bao, Luyan Zhang, Gang Chen
Journal of Proteomics 2013 Volume 82() pp:1-13
Publication Date(Web):26 April 2013
DOI:10.1016/j.jprot.2013.02.012
► This review focuses on the advances of microchip bioreactors in proteolysis. ► Various strategies have been developed to immobilize proteases in microchips. ► Proteolysis in microchip bioreactors can accomplish within 4 s to several minutes. ► The consumption of samples and reagents has been significant reduced. ► Microchip bioreactors will find wide applications in proteomics research.In proteome research, proteolysis is an important procedure prior to the mass spectrometric identification of proteins. The typical time of conventional in-solution proteolysis is as long as several hours to half a day. To enhance proteolysis efficiency, a variety of microchip bioreactors have been developed for the rapid digestion and identification of proteins in the past decade. This review mainly focuses on the recent advances and the key strategies of microchip bioreactors in protein digestion. The subjects covered include microchip proteolysis systems, the immobilization of proteases in microchannels, the applications of microchip bioreactors in highly efficient proteolysis, and future prospects. It is expected that microchip bioreactors will become powerful tools in protein analysis and will find a wide range of applications in high-throughput protein identification.
Co-reporter:Dengfeng Tang, Guo Ma, Luyan Zhang, Gang Chen
Journal of Chromatography A 2013 Volume 1316() pp:127-134
Publication Date(Web):5 November 2013
DOI:10.1016/j.chroma.2013.09.077
•A graphene–epoxy composite electrode was fabricated by in situ polycondensation.•The electrode was applied in the detection of capillary electrophoresis.•The electrode exhibited high electrocatalytic activity toward phenols.•Phenols in rosemary were measured by capillary electrophoresis with the electrode.This report describes the development and application of a novel graphene–epoxy composite electrode as a sensitive amperometric detector of capillary electrophoresis. The composite electrode was fabricated on the basis of the in situ polycondensation of a mixture of graphene and 1,2-ethanediamine-containing bisphenol A epoxy resin in the inner bore of a piece of fused silica capillary under heat. The structure of the material was investigated by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that graphene sheets were well dispersed and interconnected throughout the composite to form an electrically conductive network. The performance of this unique electrode was demonstrated by separating and detecting two naturally occurring phenolic compounds in rosemary in combination with capillary electrophoresis. The graphene-based detector offered significantly lower operating potentials, higher sensitivity, satisfactory resistance to surface fouling, and lower expense of operation, indicating great promise for a wide range of applications.
Co-reporter:Shijun Sheng;Shuang Liu;Luyan Zhang
Journal of Separation Science 2013 Volume 36( Issue 4) pp:721-728
Publication Date(Web):
DOI:10.1002/jssc.201200856
In this report, a graphene/poly(ethylene-co-vinyl acetate) composite electrode was fabricated by melt compounding for the amperometric detection of capillary electrophoresis. The composite electrode was fabricated by packing a mixture of graphene and melted poly(ethylene-co-vinyl acetate) in a piece of fused silica capillary under heat. The structure of the composite was investigated by scanning electron microscopy and Fourier transform infrared spectroscopy. The results indicated that graphene sheets were well dispersed in the composite to form an interconnected conducting network. The performance of this unique graphene-based detector has been demonstrated by separating and detecting rutin, quercitrin, kaempferol, and quercetin in Cacumen platycladi in combination with capillary electrophoresis. The four flavones have been well separated within 9 min in a 50-cm-long capillary at a separation voltage of 12 kV using a 50 mM sodium borate buffer (pH 9.2). The graphene-based detector offered significantly lower operating potentials, substantially enhanced signal-to-noise characteristics, lower expense of operation, high resistance to surface fouling, and enhanced stability. It showed long-term stability and repeatability with relative standard deviations of <5% for the peak current (n = 15).
Co-reporter:Taomin Huang;Nianzu Chen;Luyan Zhang
Chromatographia 2013 Volume 76( Issue 23-24) pp:1739-1745
Publication Date(Web):2013 December
DOI:10.1007/s10337-013-2535-2
A method based on capillary electrophoresis with amperometric detection (CE–AD) was developed for the determination of amifostine (a cytoprotective agent, WR2721) and 2-(3-aminopropylamino)ethanethiol) (WR1065, the active metabolite of WR2721) in rat plasma. The contents of WR1065 and amifostine were determined by measuring WR1065 in deproteinized rat plasma using CE–AD before and after it was incubated at 37 °C for 4 h in acidic solution, respectively. During the incubation, amifostine was quantitatively converted to WR1065. In addition, cysteine and uric acid in rat plasma were also determined simultaneously. The detection electrode was a 500 μm diameter platinum disc electrode at a detection potential of +1.0 V (vs. saturated calomel electrode). The analytes can be well separated within 9 min in a 50-cm-long fused-silica capillary at a separation voltage of 18 kV in a 100 mM phosphate buffer (pH 7.5). The relation between peak current and analyte concentration was linear over about 3 orders of magnitude with the limits of quantification (S/N = 3) ranging from 0.60 to 1.40 μM. The method has been validated. Satisfactory within-day and between-day precisions were obtained with relative standard deviations of ≤4.9 and ≤5.1 % for WR1065 and ≤5.0 and ≤5.3 % for amifostine, respectively. The within-day and between-day accuracy was in the range of 98.6–102.3 % and 95.7–97.2 % for WR1065 and 97.5–98.6 and 95.3–97.1 % for amifostine, respectively.
Co-reporter:Junchao Xu, Luyan Zhang, Gang Chen
Sensors and Actuators B: Chemical 2013 Volume 182() pp:689-695
Publication Date(Web):June 2013
DOI:10.1016/j.snb.2013.03.109
This report describes the development and application of a novel graphene/poly(ethyl 2-cyanoacrylate) composite electrode as a sensitive amperometric detector of capillary electrophoresis. The composite electrode was fabricated on the basis of the in situ polymerization of a mixture of graphene and ethyl 2-cyanoacrylate in the microchannel of a piece of fused silica capillary under heat. The structure of the material was investigated by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and infrared spectroscopy. The results indicated that graphene sheets were well dispersed and interconnected throughout the composite to form a conductive network. The performance of this unique detector was demonstrated by separating and detecting five naturally occurring phenolic compounds in combination with capillary electrophoresis. The graphene-based detector offered significantly lower operating potentials, substantially enhanced signal-to-noise characteristics, and lower expense of operation, indicate great promise for microchip capillary electrophoresis, flowing injection analysis, and other microfluidic analysis systems.
Co-reporter:Shijun Sheng;Dr. Shuang Liu;Dr. Luyan Zhang; Gang Chen
Chemistry – An Asian Journal 2013 Volume 8( Issue 1) pp:191-197
Publication Date(Web):
DOI:10.1002/asia.201200745
Abstract
Graphene sheets were assembled on anion exchange resin (AER) microspheres based on the electrostatic interactions between graphene oxide and AER and subsequent chemical reduction. The prepared graphene-coated AER microspheres were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. They were then embedded in the bores of pipette tips to fabricate disposable electrodes for electrochemical sensing. The workability and performance of the novel electrodes were examined by analyzing the electrochemical behavior of the electrodes for the sensing of ascorbic acid, dopamine, uric acid, acetaminophen, aniline, and glucose by cyclic voltammetry and amperometry. The advantages of the electrodes include ease of fabrication, low cost, pronounced electrocatalytic activity, and rapid response. Thus, they hold great promise for a wide range of applications.
Co-reporter:Huizhi Fan, Feina Yao, Shuyuan Xu, Gang Chen
Talanta 2013 Volume 117() pp:119-126
Publication Date(Web):15 December 2013
DOI:10.1016/j.talanta.2013.08.052
•Microchannel was coated with graphene oxide-poly(urea-formaldehyde) composite.•Trypsin was covalently linked to the carboxyl groups of graphene oxide.•The microchip bioreactors were successfully employed in efficient proteolysis.•The bioreactors indicate promise for high-throughput protein identification.Trypsin was covalently immobilized to graphene oxide (GO)-poly(urea-formaldehyde) (PUF) composite coated on the channel wall of poly(methyl methacrylate) microchips to fabricate microfluidic bioreactors for highly efficient proteolysis. A mixture solution containing urea-formaldehyde prepolymer and GO nanosheets was allowed to flow through the channels. The modification layer on the channel wall could further polycondense to form GO-PUF composite coating in the presence of ammonium chloride. The primary amino groups of trypsin could react with the carboxyl groups of the GO sheets in the coating with the aid of carboxyl activating agents to realize covalent immobilization. The feasibility and performance of the novel GO-based microchip bioreactors were demonstrated by the digestion of bovine serum albumin, lysozyme, ovalbumin, and myoglobin. The digestion time was significantly reduced to less than 5 s. The obtained digests were identified by MALDI-TOF MS with satisfactory sequence coverages that were comparable to those obtained by using 12-h in-solution digestion. The present proteolysis strategy is simple and efficient, offering great promise for high-throughput protein identification.
Co-reporter:Huimin Bao, Luyan Zhang, Gang Chen
Journal of Chromatography A 2013 1310() pp: 74-81
Publication Date(Web):
DOI:10.1016/j.chroma.2013.08.040
Co-reporter:Qiwen Chen, Luyan Zhang, and Gang Chen
Analytical Chemistry 2012 Volume 84(Issue 1) pp:171
Publication Date(Web):November 19, 2011
DOI:10.1021/ac2022772
A novel graphene-copper nanoparticle composite was prepared by the in situ chemical reduction of a mixture containing graphene oxide and copper(II) ions using potassium borohydride as a reductant. It was mixed with paraffin oil and packed into one end of a fused capillary to fabricate microdisc electrodes for sensing carbohydrates. The morphology and structure of the graphene-copper nanoparticle composite were investigated by scanning electron microscopy, X-ray diffraction, and Fourier transform-infrared spectroscopy. The results indicated that copper nanoparticles with an average diameter of 20.8 nm were successfully deposited on graphene nanosheets to form a well interconnected hybrid network. The analytical performance of these unique graphene-copper nanoparticle composite paste electrodes was demonstrated by sensing five carbohydrates in combination with cyclic voltammetry and capillary electrophoresis (CE). The advantages of the composite detectors include higher sensitivity, satisfactory stability, surface renewability, bulk modification, and low expense of fabrication. They should find applications in microchip CE, flowing-injection analysis, and other microfluidic analysis systems.
Co-reporter:Yuejiao Fu, Luyan Zhang, Gang Chen
Carbon 2012 Volume 50(Issue 7) pp:2563-2570
Publication Date(Web):June 2012
DOI:10.1016/j.carbon.2012.02.014
Carbon nanotube (CNT)-copper nanoparticle (CuNP) hybrid was prepared by the chemical reduction of a mixture containing cupric sulfate and CNTs. The structure of the material was investigated by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that CuNPs with an average diameter of about 15 nm were deposited on CNTs to form a well interconnected hybrid network. The material was mixed with paraffin oil and packed into the ends of fused capillaries to fabricate microdisc electrodes for sensing carbohydrates. Its analytical performance was demonstrated by sensing four carbohydrates in combination with capillary electrophoresis. The relation between peak current and analyte concentration was linear over about 3 orders of magnitude with detection limits ranging from 0.18 to 0.62 μM for all analytes.
Co-reporter:Shijun Sheng, Luyan Zhang, Gang Chen
Electrochemistry Communications 2012 Volume 24() pp:13-16
Publication Date(Web):October 2012
DOI:10.1016/j.elecom.2012.08.001
Graphene-coated anion exchange resin (AER) spheres were facilely prepared based on the electrostatic interaction between graphene oxide and AER and subsequent chemical reduction. They were embedded in the bores of polypropylene pipette tips to fabricate graphene ball electrodes for the amperometric detection of capillary electrophoresis. The feasibility and performance of the novel electrodes were demonstrated by measuring parabens in combination with micellar electrokinetic chromatography. The advantages of the electrodes include higher sensitivity, favorable signal-to-background characteristics, low expense of fabrication, ease of operation, and satisfactory reproducibility, indicating great promise for a wide range of applications.Highlights► Graphene-coated anion exchange resin microspheres were prepared. ► The coating exhibited a compact layer-by-layer stacking of graphene sheets. ► The graphene-wrapped microspheres were embedded in pipette tips to form electrodes. ► The electrodes were applied in the detection of capillary electrophoresis.
Co-reporter:Yuejiao Fu;Luyan Zhang
Journal of Separation Science 2012 Volume 35( Issue 3) pp:468-475
Publication Date(Web):
DOI:10.1002/jssc.201100816
Abstract
A method based on micellar electrokinetic chromatography with amperometric detection and far infrared-assisted extraction has been developed for the simultaneous determination of two flavones (rutin and farrerol) and three phenolic acids (syringic acid, vanillic acid, and 4-hydroxybenzoic acid) in the dried leaves of Rhododendron mucronulatum Turcz., a commonly used traditional Chinese medicine. The effects of some important factors such as the voltage applied on the infrared generator, irradiation time, the concentration of borate and sodium dodecylsulfate (SDS), separation voltage, and detection potential were investigated to acquire the optimum conditions. The detection electrode was a 300-μm diameter carbon disc electrode. The five analytes could be well separated within 8 min in a 40 cm-long capillary at a separation voltage of 12 kV in a 50 mM borate buffer (pH 9.2) containing 50 mM SDS. The relationship between peak current and analyte concentration was linear over about three orders of magnitude with the detection limits (S/N=3) ranging from 0.20 to 0.46 μM. The results indicated that far infrared irradiations significantly enhanced the extraction efficiency. The extraction time was substantially reduced to 6 min compared with 3 h for conventional hot solvent extraction.
Co-reporter:Dr. Weidong Qu;Dr. Huimin Bao;Dr. Luyan Zhang; Gang Chen
Chemistry - A European Journal 2012 Volume 18( Issue 49) pp:15746-15752
Publication Date(Web):
DOI:10.1002/chem.201202913
Abstract
A new approach based on far infrared-assisted in situ reduction was developed for the facile one-step preparation of graphene–nickel nanoparticle hybrid by refluxing a mixture solution containing graphene oxide, nickel(II) sulfate, and hydrazine over an far-infrared heater. The reduction time was as short as 20 min. The structure of the material was investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy, vibrating sample magnetometery, and Fourier transform infrared spectroscopy. Magnetic investigations indicate that the grapheme–nickel nanoparticle hybrid exhibits ferromagnetic behavior at room temperature. Meanwhile, the hybrid was successfully employed in the enrichment and identification of proteins and peptides in combination with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry based on its excellent magnetic responsibility, high dispersibility, large surface area, and hydrophobicity, indicating great promise for a wide range of applications.
Co-reporter:Huimin Bao;Shuang Liu;Luyan Zhang
Microchimica Acta 2012 Volume 179( Issue 3-4) pp:291-297
Publication Date(Web):2012 November
DOI:10.1007/s00604-012-0896-0
Trypsin was immobilized on cellulose-coated glass fibers via a condensation reaction between the aldehyde groups of the oxidized cellulose and the primary amino groups of trypsin. A piece of the modified fiber was inserted into the main channel of a poly(methyl methacrylate) microchip to form a microfluidic proteolytic bioreactor. Scanning electron microscopy of the cross section of the fiber revealed a rough film on the surface of the fiber glass. The performance of the bioreactor was demonstrated by the tryptic digestion of hemoglobin and cytochrome c, where the time for digestion was reduced to <10 s. The digests were identified by MALDI-TOF-MS to obtain peptide mass fingerprint spectra. The results indicated that the digestion in the microfluidic bioreactor is comparable to that of a 12-h solution tryptic digest and thus provides a promising platform for the high throughput identification of proteins.
Co-reporter:Zhibin Gan, Qiwen Chen, Yuejiao Fu, Gang Chen
Food Chemistry 2012 130(4) pp: 1122-1126
Publication Date(Web):
DOI:10.1016/j.foodchem.2011.08.018
Co-reporter:Huimin Bao, Qiwen Chen, Luyan Zhang and Gang Chen
Analyst 2011 vol. 136(Issue 24) pp:5190-5196
Publication Date(Web):19 Oct 2011
DOI:10.1039/C1AN15690J
In this report, trypsin was immobilized in the layer-by-layer (LBL) coating of graphene oxide (GO) and chitosan on a piece of glass fiber to fabricate microchip bioreactor for efficient proteolysis. LBL deposition driven by electrostatic forces easily took place on the surface of the glass fiber, providing mild environmental conditions so that the denaturation and autolysis of the immobilized trypsin was minimized. Prior to use, a piece of the prepared trypsin-immobilized glass fiber was inserted into the channel of a microchip to form a core-changeable bioreactor. The novel GO-based bioreactor can be regenerated by changing its fiber core. The feasibility and performance of the unique bioreactor were demonstrated by the tryptic digestion of bovine serum albumin, myoglobin, cytochrome c, and hemoglobin and the digestion time was significantly reduced to less than 10 s. The obtained digests were identified by MALDI-TOF MS. The digestion performance of the core-changeable GO-based microchip bioreactor was comparable to that of 12-h in-solution tryptic digestion. The novel microchip bioreactor is simple and efficient, offering great promise for high-throughput protein identification.
Co-reporter:Xia Wang, Jiyang Li, Weidong Qu, Gang Chen
Journal of Chromatography A 2011 Volume 1218(Issue 32) pp:5542-5548
Publication Date(Web):12 August 2011
DOI:10.1016/j.chroma.2011.06.034
This report describes the development and application of a novel graphene/poly(methyl methacrylate) composite electrode as a sensitive amperometric detector of capillary electrophoresis. The composite electrode was fabricated on the basis of the in situ polymerization of a mixture of graphene and prepolymerized methyl methacrylate in the microchannel of a piece of fused silica capillary under heat. SEM, XRD and FT-IR offered insights into the nature of the composite. The results indicated that graphenes were well dispersed in the composite to form an interconnected conducting network. The performance of this unique graphene-based detector has been demonstrated by separating and detecting seven naturally occurring phenolic compounds in Herba Geranii in combination with capillary electrophoresis. The graphene-based detector offered significantly lower operating potentials, substantially enhanced signal-to-noise characteristics, and lower expense of operation. The simplicity and significant performance exhibited by the graphene/poly(methyl methacrylate) composite electrode also indicate great promise for microchip CE, flowing injection analysis, and other microfluidic analysis systems.
Co-reporter:Yuejiao Fu;Luyan Zhang
Journal of Separation Science 2011 Volume 34( Issue 22) pp:3272-3278
Publication Date(Web):
DOI:10.1002/jssc.201100649
Abstract
In this work, a method based on capillary electrophoresis with amperometric detection and far-infrared-assisted extraction has been developed for the determination of mannitol, sucrose, glucose and fructose in Folium Lysium Chinensis, a commonly used traditional Chinese medicine. The water-soluble constituents in the herbal drug were extracted with double distilled water with the assistance of far-infrared radiations. The effects of detection potential, irradiation time, and the voltage applied on the infrared generator were investigated to acquire the optimum analysis conditions. The detection electrode was a 300-μm-diameter copper disk electrode at a detection potential of +0.65 V. The four carbohydrates could be well separated within 18 min in a 50-cm length fused-silica capillary at a separation voltage of 9 kV in a 50-mM NaOH aqueous solution. The relation between peak current and analyte concentration was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 0.66 to 1.15 μM for all analytes. The results indicated that far infrared significantly enhanced the extraction efficiency of the carbohydrates in Folium Lysium Chinensis. The extraction time was significantly reduced to 7 min compared with several hours for conventional hot solvent extraction.
Co-reporter:Qiwen Chen;Zhibin Gan; Joseph Wang; Gang Chen
Chemistry - A European Journal 2011 Volume 17( Issue 44) pp:12458-12464
Publication Date(Web):
DOI:10.1002/chem.201101758
Abstract
A carbon nanotube/poly(ethyl 2-cyanoacrylate) (CNT/PECA) composite electrode was developed for enhanced amperometric detection. The composite electrode was fabricated on the basis of water-vapor-initiated polymerization of a mixture of CNTs and ethyl 2-cyanoacrylate in the bore of a piece of fused silica capillary. The morphology and structure of the composite were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. The results indicate that the CNTs were well dispersed and embedded throughout the PECA matrix to form an interconnected CNT network. The analytical performance of this unique CNT-based detector has been demonstrated by separating and detecting six flavones in combination with capillary electrophoresis. The advantages of the CNT/PECA composite detector include lower operating potential, higher sensitivity, low expense of fabrication, satisfactory resistance to surface fouling, and enhanced stability; these properties indicate great promise for a wide range of applications.
Co-reporter:Haotian Duan, Yi Chen, Gang Chen
Journal of Chromatography A 2010 Volume 1217(Issue 27) pp:4511-4516
Publication Date(Web):2 July 2010
DOI:10.1016/j.chroma.2010.04.069
In this work, a method based on capillary electrophoresis with amperometric detection and far infrared-assisted extraction has been developed for the determination of rutin, gentisic acid, and quercetin in the leaves of Lycium barbarum Linn. The effects of detection potential, irradiation time, and the voltage applied on the infrared generator were investigated to acquire the optimum analysis conditions. The detection electrode was a 300-μm-diameter carbon disc electrode at a detection potential of +0.90 V. The three analytes could be well separated within 12 min in a 40 cm length fused-silica capillary at a separation voltage of 12 kV in a 50 mM borate buffer (pH 9.2). The relation between peak current and analyte concentration was linear over about 3 orders of magnitude with the detection limits (S/N = 3) of 0.31, 0.48, and 0.78 μM for rutin, gentisic acid, and quercetin, respectively. The proposed method has been applied to determine the three bioactive constituents in real plant samples.
Co-reporter:Haotian Duan, Luyan Zhang, Gang Chen
Journal of Chromatography A 2010 Volume 1217(Issue 1) pp:160-166
Publication Date(Web):1 January 2010
DOI:10.1016/j.chroma.2009.11.018
As an important phthalate plasticizer, dibutyl phthalate (DBP) was employed to decrease the bonding temperature of poly(methyl methacrylate) (PMMA) microfluidic chips in this work based on the fact that it can lower the glass transition temperature of PMMA. The channel plates of the PMMA microchips were fabricated by the UV-initiated polymerization of prepolymerized methyl methacrylate between a silicon template and a PMMA plate. Prior to bonding, DBP solution in isopropanol was coated on PMMA covers. When isopropanol in the coating was allowed to evaporate in air, DBP was left on the PMMA covers. Subsequently, the DBP-coated covers were bonded to the PMMA channel plates at 90 °C for 10 min under pressure. The channels in the complete microchips had been examined by optical microscope and scanning electron microscope. The results indicated that high quality bonding was achieved below the glass transition temperature of PMMA (∼105 °C). The performance of the PMMA microfluidic chips sealed by plasticizer-assisted bonding has been demonstrated by separating and detecting ionic species by capillary electrophoresis in connection with contactless conductivity detection.
Co-reporter:Bangguo Wei, Luyan Zhang and Gang Chen
New Journal of Chemistry 2010 vol. 34(Issue 3) pp:453-457
Publication Date(Web):15 Jan 2010
DOI:10.1039/B9NJ00670B
A novel multi-walled carbon nanotube/poly(urea-formaldehyde) (CNT/PUF) composite was prepared for enhanced electrochemical sensing. The composite electrodes were fabricated by the in situ polycondensation of a mixture containing CNTs, and the urea and formaldehyde prepolymer, in electrode tubes with the aid of a curing catalyst. The morphology and structure of the novel composite were investigated by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The results indicate that the CNTs were well dispersed and embedded throughout the PUF matrix to form an interconnected CNT network. The electrocatalytic performance of the CNT/PUF composite electrodes was demonstrated by measuring phenols using cyclic voltammetry and microchip capillary electrophoresis.
Co-reporter:Zhi Chen, Zhengyin Yu, Gang Chen
Talanta 2010 Volume 81(4–5) pp:1325-1330
Publication Date(Web):15 June 2010
DOI:10.1016/j.talanta.2010.02.028
A simple method based on disposable gelatin gel templates has been developed for the low-cost fabrication of poly(methyl methacrylate) (PMMA) microfluidic chips. Gelatin was dissolved in glycerol aqueous solution under heat to prepare a thermally reversible impression material. The molten gel was then sandwiched between a glass plate and a SU-8 template bearing negative relief of microstructure. After cooling, the negative SU-8 template could be easily separated from the solidified gelatin gel and a layer of gelatin template bearing positive relief of the microstructure was left on the glass plate. Subsequently, prepolymerized methyl methacrylate molding solution containing a UV-initiator was sandwiched between the gel template and a PMMA plate and was allowed to polymerize under UV light to fabricate PMMA channel plate at room temperature. Complete microchips could be obtained by bonding the channel plates with covers using plasticizer-assisted thermal bonding at 90 °C. Gelatin gel template can be mass-produced and will find application in the mass production of PMMA microchips at low cost. The prepared microfluidic microchips have been successfully employed in the capillary electrophoresis analysis of several ions in connection with contactless conductivity detection.
Co-reporter:Sheng Wang, Ting Liu, Luyan Zhang, Gang Chen, Pengyuan Yang
Journal of Proteomics 2009 Volume 72(Issue 4) pp:640-647
Publication Date(Web):2 May 2009
DOI:10.1016/j.jprot.2009.01.004
Alternating current (AC) has been employed to enhance the efficiency of chymotryptic proteolysis for peptide mapping. It was allowed to flow through the mixture solution of proteins and chymotrypsin via a pair of platinum wire electrodes. Bovine serum albumin (BSA) and cytochrome c (Cyt-c) were digested by the novel proteolysis approach to demonstrate its feasibility and performance. The results indicated that AC significantly accelerated in-solution chymotryptic proteolysis and the digestion time was substantially reduced to 5 min. The digests were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with sequence coverages of 46% (BSA) and 90% (Cyt-c) that were much better than those obtained by using 12-h conventional in-solution chymotryptic proteolysis. In addition, AC-assisted chymotryptic proteolysis was employed to digest human serum to demonstrate its suitability to complex protein sample. The present proteolysis strategy is simple and efficient and will find a wide range of applications in proteomic research.
Co-reporter:Joseph Wang, Gang Chen, Alexander Muck
Talanta 2009 Volume 78(Issue 1) pp:207-211
Publication Date(Web):15 April 2009
DOI:10.1016/j.talanta.2008.10.055
A new end-column ‘hybrid’ contactless conductivity detector for microchip capillary electrophoresis (CE) was developed. It is based on a “hybrid” arrangement where the receiving electrode is insulated by a thin layer of insulator and placed in the bulk solution of the detection reservoir of the chip, whereas the emitting electrode is in contact with the solution eluted from the channel outlet in a wall-jet arrangement. The favorable features of the new detector including the high sensitivity and low noise, can be attributed to both the direct contact of the ‘emitting’ electrode with the analyte solution as well as to the insulation of the detection electrode from the high DC currents in the electrophoretic circuit. Such arrangement provides a 10-fold sensitivity enhancement compared to currently used on-column contactless conductivity CE microchip detector as well as low values of noise and easy operation. The new design of the wall-jet conductivity detector was tested for separation of explosive-related methylammonium, ammonium, and sodium cations. The new detector design reconsiders the wall-jet arrangement for microchip conductivity detection in scope of improved peak symmetry, simplified study of inter-electrode distance, isolation of the electrodes, position of the wall-jet electrode to the separation channel, baseline stability and low limits of detection.
Co-reporter:Ting Liu, Sheng Wang, Gang Chen
Talanta 2009 Volume 77(Issue 5) pp:1767-1773
Publication Date(Web):15 March 2009
DOI:10.1016/j.talanta.2008.10.009
In this report, trypsin was immobilized on silica-coated fiberglass core in microchip to form a core-changeable bioreactor for highly efficient proteolysis. To prepare the fiber core, a layer of organic–inorganic hybrid silica coating was prepared on the surface of a piece of glass fiber by a sol–gel method with tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as precursors. Subsequently, trypsin was immobilized on the coating with the aid of glutaraldehyde. Prior to use, the enzyme-immobilized fiber was inserted into the channel of a microchip to form an in-channel fiber bioreactor. The novel bioreactor can be regenerated by changing its fiber core. The scanning electron microscopy images of the cross-section of a trypsin-immobilized fiber indicated that a layer of ∼1 μm thick film formed on the glass substrate. The feasibility and performance of the unique bioreactor were demonstrated by the tryptic digestion of bovine serum albumin (BSA) and cytochrome c (Cyt-c) and the digestion time was significantly reduced to less than 10 s. The digests were identified by MALDI-TOF MS with sequence coverages of 45% (BSA) and 77% (Cyt-c) that were comparable to those obtained by 12-h conventional in-solution tryptic digestion. The fiber-based microchip bioreactor provides a promising platform for the high-throughput protein identification.
Co-reporter:Sheng Wang, Huimin Bao, Luyan Zhang, Pengyuan Yang and Gang Chen
Analytical Chemistry 2008 Volume 80(Issue 14) pp:5640
Publication Date(Web):June 14, 2008
DOI:10.1021/ac800349u
In this report, infrared (IR)-assisted on-plate proteolysis has been developed for rapid peptide mapping. Protein solutions containing trypsin were allowed to digest directly on the spots of matrix-assisted laser desorption/ionization (MALDI) plates under IR radiation. The feasibility and performance of the novel proteolysis approach were investigated by the digestion of bovine serum albumin (BSA) and cytochrome c (Cyt-c). It was demonstrated that IR radiation substantially enhanced the efficiency of proteolysis and the digestion time was significantly reduced to 5 min. The digests were identified by MALDI time-of-flight mass spectrometry with sequence coverages of 55 (BSA) and 75% (Cyt-c) that were comparable to those obtained by using conventional in-solution tryptic digestion. The suitability of IR-assisted on-plate proteolysis to complex proteins was demonstrated by digesting human serum and casein extracted from commercially available milk sample. The present proteolysis strategy is simple and efficient, offering great promise for high-throughput protein identification.
Co-reporter:Sheng Wang, Huimin Bao, Pengyuan Yang, Gang Chen
Analytica Chimica Acta 2008 Volume 612(Issue 2) pp:182-189
Publication Date(Web):7 April 2008
DOI:10.1016/j.aca.2008.02.035
In this report, a four-component nanocomposite, trypsin-immobilized polyaniline-coated Fe3O4/carbon nanotube composite, was synthesized for highly efficient protein digestion. Fe3O4 was deposited by the chemical coprecipitation of Fe2+ and Fe3+ in an alkaline solution containing carbon nanotubes (CNTs) to prepare nano-Fe3O4/CNT composite. Subsequently, polyaniline (PA) was assembled on the Fe3O4/CNT composite by the in situ polymerization of aniline in the presence of trypsin to obtain trypsin-immobilized PA/Fe3O4/CNT nanocomposite. The novel 1D superparamagnetic biomaterial has been characterized by TEM, SEM, XRD, and magnetometric analysis. The feasibility and performance of the unique magnetic biomaterial have been demonstrated by the tryptic digestion of bovine serum albumin, myoglobin, and lysozyme within 5 min. The digests were identified by MALDI-TOF MS with sequence coverages that were comparable to those obtained from the conventional in-solution tryptic digestion. The present biocomposite offers considerable promise for protein analysis due to its high magnetic responsivity and excellent dispersibility. It can be easily isolated from the digests with the aid of an external magnetic field. Because the enzyme-immobilized nanocomposite can be prepared by a simple two-step deposition approach at low cost, it may find a wide range of biological applications including proteome research.
Co-reporter:Sheng Wang, Ting Liu, Luyan Zhang and Gang Chen
Journal of Proteome Research 2008 Volume 7(Issue 11) pp:5049-5054
Publication Date(Web):2017-2-22
DOI:10.1021/pr800476s
Infrared (IR) radiation was employed to enhance the efficiency of chymotryptic proteolysis for peptide mapping in this work. Protein solutions containing chymotrypsin in sealed transparent Eppendorf tubes were allowed to digest under an IR lamp at 37 °C. BSA and cytochrome c (Cyt-c) were digested by IR-assisted chymotryptic proteolysis to demonstrate the feasibility and performance of the novel digestion approach and the digestion time was significantly reduced to 5 min. The obtained digests were further identified by MALDI-TOF MS with the sequence coverages that were comparable to those obtained by using conventional in-solution digestion. The suitability of IR-assisted chymotryptic proteolysis to complex proteins was demonstrated by digesting human serum. The present proteolysis strategy is simple and efficient, offering great promise for high-throughput protein identification.
Co-reporter:Huimin Bao, Ting Liu, Xian Chen and Gang Chen
Journal of Proteome Research 2008 Volume 7(Issue 12) pp:5339-5344
Publication Date(Web):2017-2-22
DOI:10.1021/pr800572e
In this report, infrared (IR) radiation was employed to enhance the efficiency of in-gel proteolysis for MS-based protein identification. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the target protein bands excised from polyacrylamide gel were cut into small pieces that were further treated in trypsin solution. Subsequently, the wet gel pieces sealed in transparent Eppendorf tubes were exposed to an IR lamp to perform IR-assisted in-gel digestion. To demonstrate the feasibility and performance of the novel digestion approach, it was employed to digest BSA and cytochrome c (Cyt-c) in polyacrylamide gels after SDS-PAGE separations. The results indicated that IR radiation substantially enhanced the efficiency of in-gel proteolysis and the digestion time was significantly reduced to 5 min compared to 16 h for conventional in-gel digestion. The obtained digests were further identified by MALDI-TOF MS with improved sequence coverages. The suitability of IR-assisted in-gel proteolysis to real protein samples was demonstrated by digesting and identifying human serum albumin in gel separated from human serum by SDS-PAGE. The present proteolysis strategy is simple and efficient, offering great promise for the high-throughput protein identification in proteomics research.
Co-reporter:Bangguo Wei Dr.;Joseph Wang ;Zhi Chen Dr. Dr.
Chemistry - A European Journal 2008 Volume 14( Issue 31) pp:9779-9785
Publication Date(Web):
DOI:10.1002/chem.200801124
Abstract
This report describes the development and the application of a novel carbon-nanotube (CNT)–alginate composite modified electrode as a sensitive amperometric detector for capillary electrophoresis (CE). The composite electrode was fabricated on the basis of in situ gelation of a mixture of CNTs and sodium alginate on the surface of a carbon disc electrode in aqueous calcium chloride solution. SEM, energy-dispersive spectroscopy, XRD, and FTIR spectroscopy offered insights into the nature of the novel composite. The results indicated that the CNTs were well dispersed and embedded throughout the alginate matrix to form an interconnected carbon-nanotube network on the base electrode. The performance of this unique CNT-based detector has been demonstrated, in conjunction with CE, by separating and detecting five caffeic acid derivatives. The new CNT-based CE detector offered significantly lower operating potentials, substantially enhanced signal-to-noise characteristics, and a lower expense of operation. The simplicity and significant performance exhibited by the CNT–alginate composite modified electrode also indicate great promise for the use of this electrode in microchip CE, flowing-injection analysis, and other microfluidic analysis systems.
Co-reporter:Gang Chen
Talanta 2007 Volume 74(Issue 3) pp:326-332
Publication Date(Web):15 December 2007
DOI:10.1016/j.talanta.2007.05.046
As two important polymorphs of carbon, carbon nanotube (CNT) and diamond have been widely employed as electrode materials for electrochemical sensing. This review focuses on recent advances and the key strategies in the fabrication and application of electrochemical detectors in microchip and conventional capillary electrophoresis (CE) using CNT and boron-doped diamond. The subjects covered include CNT-based electrochemical detectors in microchip CE, CNT-based electrochemical detectors in conventional CE, boron-doped diamond electrochemical detectors in microchip CE, and boron-doped diamond electrochemical detectors in conventional CE. The attractive properties of CNT and boron-doped diamond make them very promising materials for the electrochemical detection in microchip and conventional CE systems and other microfluidic analysis systems.
Co-reporter:Jingjing Xu, Haiying Zhang, Gang Chen
Talanta 2007 Volume 73(Issue 5) pp:932-937
Publication Date(Web):31 October 2007
DOI:10.1016/j.talanta.2007.05.019
In this report, carbon nanotube/polystyrene (CNT/PS) composite electrodes have been fabricated as sensitive amperometric detectors of microchip capillary electrophoresis (CE) for the determination of rutin and quercetin in Flos Sophorae Immaturus. The composite electrode was fabricated on the basis of the in situ polymerization of a mixture of CNT and styrene in the microchannel of a piece of fused silica capillary under heat. The surface morphologies of the composite in the electrodes were observed by using a scanning electron microscope. The performance of this unique system has been demonstrated by separating and detecting rutin and quercetin. The new CNT-based CE detector offered significantly lower detection potentials, yielded substantially enhanced signal-to-noise characteristics, and exhibited resistance to surface fouling and hence enhanced stability. It demonstrated long-term stability and reproducibility with a relative standard deviation of less than 5% for the peak current (n = 20) and should also find a wide range of applications in conventional CE, flowing injection analysis, and other microfluidic analysis systems.
Co-reporter:Xiao Yao;Huixia Wu Dr.;Joseph Wang ;Song Qu Dr.
Chemistry - A European Journal 2007 Volume 13(Issue 3) pp:
Publication Date(Web):18 OCT 2006
DOI:10.1002/chem.200600469
We describe the development and application of a novel carbon nanotube/poly(methyl methacrylate) (CNT/PMMA) composite electrode as a sensitive amperometric detector of microchip capillary electrophoresis (CE). The composite electrode was fabricated by the in situ polymerization of a mixture of CNTs and prepolymerized methyl methacrylate in the microchannel of a piece of fused silica capillary under heat. The performance of this unique system was demonstrated by the separation and detection of phenolic pollutants and purines. The new CNT-based CE detector offered significantly lower operating potentials, yielded substantially enhanced signal-to-noise characteristics, and exhibited resistance to surface fouling and, hence, enhanced stability. Long-term stability and reproducibility with relative standard deviations of less than 5 % for the peak current (n=20) were also demonstrated. The simplicity and significant performance exhibited by the CNT/PMMA composite electrode indicate great promise for conventional CE, flowing-injection analysis, and other microfluidic analysis systems.
Co-reporter:Gang Chen ;Xuejiao Xu Dr.;Yuehe Lin ;Joseph Wang
Chemistry - A European Journal 2007 Volume 13(Issue 22) pp:
Publication Date(Web):16 MAY 2007
DOI:10.1002/chem.200700242
A sol–gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol–gel-modified PMMA microchip. The water contact angle for the sol–gel-modified PMMA was ≈27.4° compared with ≈66.3° for the pure PMMA. In addition, the electro-osmotic flow increased from 2.13×10−4 cm2 V−1 s−1 for the native-PMMA channel to 4.86×10−4 cm2 V−1 s−1 for the modified one. The analytical performance of the sol–gel-modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m−1 compared with 14 730.5 m−1 for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.
Co-reporter:Song Qu, Joseph Wang, Jilie Kong, Pengyuan Yang, Gang Chen
Talanta 2007 Volume 71(Issue 3) pp:1096-1102
Publication Date(Web):28 February 2007
DOI:10.1016/j.talanta.2006.06.003
An electrochemical sensing platform was developed based on the magnetic loading of carbon nanotube (CNT)/nano-Fe3O4 composite on electrodes. To demonstrate the concept, nano-Fe3O4 was deposited by the chemical coprecipitation of Fe2+ and Fe3+ in the presence of CNTs in an alkaline solution. The resulting magnetic nanocomposite brings new capabilities for electrochemical devices by combining the advantages of CNT and nano-Fe3O4 and provides an alternative way for loading CNT on electrodes. The fabrication and the performances of the magnetic nanocomposite modified electrodes have been described. Cyclic voltammetry (CV) and constant potential measurement indicated that the incorporated CNT exhibited higher electrocatalytic activity toward the redox processes of hydrogen peroxide. In addition, chitosan (CTS) has also been introduced into the bulk of the CNT/nano-Fe3O4 composite by coprecipitation to immobilize glucose oxidase (GOx) for sensing glucose. The marked electrocatalytic activity toward hydrogen peroxide permits effective low-potential amperometric biosensing of glucose, in connection with the incorporation of GOx into CNT/Fe3O4/CTS composite. The accelerated electron transfer is coupled with surface renewability. TEM images and XRDs offer insights into the nature of the magnetic composites. The concept of the magnetic loading of CNT nanocomposites indicates great promise for creating CNT-based biosensing devices and expands the scope of CNT-based electrochemical devices.
Co-reporter:Xiao Yao
Analytical and Bioanalytical Chemistry 2007 Volume 388( Issue 2) pp:475-481
Publication Date(Web):2007 May
DOI:10.1007/s00216-007-1198-y
Capillary electrophoresis with electrochemical detection has been employed for the determination of p-hydroxyacetophenone, chlorogenic acid, and caffeic acid in Herba Artemisiae Scopariae (the dried sprout of Artemisia scoparia Waldst. et Kit.). The effects of several important factors, such as the concentration and the acidity of the running buffer, separation voltage, injection time, and detection potential, were investigated to acquire the optimum conditions. The detection electrode was a 300-μm-diameter carbon disc electrode at a working potential of +0.90 V (relative to the saturated calomel electrode). The three analytes can be well separated within 11 min in a 40-cm-long fused-silica capillary at a separation voltage of 15 kV in 50 mM borate buffer (pH 9.2). The relation between peak current and analyte concentration was linear over about 3 orders of magnitude, with detection limits (signal-to-noise ratio of 3) of 0.31, 0.39, and 0.50 μM for p-hydroxyacetophenone, chlorogenic acid, and caffeic acid, respectively. The proposed method has been successfully applied to monitor the three bioactive constituents in real plant samples and to differentiate between different herbal drugs with satisfactory assay results.
Co-reporter:Guoxi Xu, Joseph Wang, Yi Chen, Luyan Zhang, Derong Wang and Gang Chen
Lab on a Chip 2006 vol. 6(Issue 1) pp:145-148
Publication Date(Web):30 Nov 2005
DOI:10.1039/B515842G
A novel method based on in situ surface polymerization of methyl methacrylate (MMA) has been developed for the rapid fabrication of poly(methyl methacrylate) (PMMA) capillary electrophoresis (CE) microchips. MMA containing both thermal and ultraviolet (UV) initiators was allowed to prepolymerize in a water bath to form a fast curing molding solution that was subsequently sandwiched between a nickel template and a PMMA plate. The images of the raised microchannels on the nickel template were precisely replicated into the synthesized PMMA substrates during the UV-initiated polymerization of the molding solution within 30 min under ambient temperature. The attractive performances of the novel PMMA microchips have been demonstrated in connection with amperometric detection for the separation and detection of several model analytes. The new approach significantly simplifies the process for fabricating PMMA devices and could be applied to other materials that undergo light-initiated polymerization.
Co-reporter:Gang Chen, Yuehe Lin, Joseph Wang
Talanta 2006 Volume 68(Issue 3) pp:497-503
Publication Date(Web):15 January 2006
DOI:10.1016/j.talanta.2005.07.004
During the past decade, significant progress in the development of miniaturized microfluidic systems has occurred due to the numerous advantages of microchip analysis. This review focuses on recent advances and the key strategies in microchip capillary electrophoresis (CE) with electrochemical detection (ECD) for separating and detecting a variety of environmental pollutants. The subjects covered include the fabrication of microfluidic chips, ECD, typical applications of microchip CE with ECD in environmental analysis, and future prospects. It is expected that microchip CE–ECD will become a powerful tool in the environmental field and will lead to the creation of truly portable devices.
Co-reporter:Xiao Yao, Joseph Wang, Luyan Zhang, Pengyuan Yang, Gang Chen
Talanta 2006 Volume 69(Issue 5) pp:1285-1291
Publication Date(Web):15 July 2006
DOI:10.1016/j.talanta.2006.01.003
A microchip capillary electrophoresis (CE)–amperometric detection (AD) system has been fabricated by integrating a two-dimensionally adjustable CE microchip and an amperometric detection cell containing a one-dimensionally adjustable disc detection electrode in a Plexiglas holder. It facilitates the precise three-dimensional alignment between the channel outlet and the detection electrode without a complicated three-dimensional manipulator. The performance of this unique system was demonstrated by separating four nitroaromatic pollutants (nitrobenzene, 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, and p-nitrobenzene). Factors influencing their separation and detection processes were examined and optimised. The four analytes have been well-separated within 120 s in a 75 cm long separation channel at a separation voltage of +2000 V using an electrophoretic separation medium containing 15 mM borax and 15 mM sodium dodecyl sulfate (pH 9.2). Highly linear response is obtained for the four analytes over the range of 0–5 ppm with the detection limits ranging from 12 to 52 ppb. The present system demonstrated long-term stability and reproducibility with relative standard deviations of less than 5% for the peak current (n = 9). The new approach for the microchannel–electrode alignment should find a wide range of applications in other microfluidic analysis systems.
Co-reporter:Gang Chen, Luyan Zhang, Xingliang Wu, Jiannong Ye
Analytica Chimica Acta 2005 Volume 530(Issue 1) pp:15-21
Publication Date(Web):7 February 2005
DOI:10.1016/j.aca.2004.08.053
A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of mannitol, sucrose, glucose, and fructose in Ligustrum lucidum Ait. for the first time. Effects of several important factors such as the concentration of NaOH, separation voltage, injection time, and detection potential were investigated to acquire the optimum conditions. The detection electrode was a 300 μm diameter copper disc electrode at a working potential of +0.65 V (versus saturated calomel electrode (SCE)). The four analytes can be well separated within 13 min in a 40 cm length fused-silica capillary at a separation voltage of 12 kV in a 75 mM NaOH aqueous solution. The relation between peak current and analyte concentration was linear over about three orders of magnitude with detection limits (S/N = 3) ranging from 1 to 2 μM for all analytes. The proposed method has been successfully applied to monitor the mannitol and sugar contents in the plant samples at different growth stages with satisfactory assay results.
Co-reporter:Gang Chen, Jianhua Li, Song Qu, Di Chen, Penyuan Yang
Journal of Chromatography A 2005 Volume 1094(1–2) pp:138-147
Publication Date(Web):11 November 2005
DOI:10.1016/j.chroma.2005.07.093
A novel method for bonding poly(methyl methacrylate) (PMMA) electrophoresis microchips at the temperature below the glass transition temperature of PMMA based on in situ polymerization has been demonstrated. Methyl methacrylate (MMA) containing initiators was allowed to prepolymerize in an 85 °C water bath for 8 min and 15 min to produce a bonding solution and a dense molding solution, respectively. The channel plate of the PMMA microchip was fabricated by the UV-initiated polymerization of the molding solution between a nickel template and a PMMA plate at room temperature. Prior to bonding, the blank cover was coated with a thin layer of the bonding solution and was bonded to the channel plate at 95 °C for 20 min under the pressure of binder clips. The attractive performance of the PMMA chips bonded by the new approach has been demonstrated by separating and detecting dopamine, catechol, three cations, and three organic acids in connection with end-column amperometric detection and contactless conductivity detection.
Co-reporter:Gang Chen, Luyan Zhang, Joseph Wang
Talanta 2004 Volume 64(Issue 4) pp:1018-1023
Publication Date(Web):15 November 2004
DOI:10.1016/j.talanta.2004.04.022
Multi-walled carbon nanotube (CNT) was mixed with epoxy to fabricate microdisc electrode used as a detector for a specially designed miniaturized capillary electrophoresis (CE)–amperometric detection system for the separation and detection of several bioactive thiols. The end-channel CNT amperometric detector offers favourable signal-to-noise characteristics at a relatively low potential (0.8 V) for detecting thiol compounds. Factors influencing the separation and detection processes were examined and optimized. Four thiols (homocysteine, cysteine, glutathione, and N-acetylcysteine) have been separated within 130 s at a separation voltage of 2000 V using a 20 mM phosphate running buffer (pH 7.8). Highly linear response is obtained for homocysteine, cysteine, glutathione, and N-acetylcysteine over the range of 5–50 μM with detection limits of 0.75, 0.8, 2.9, and 3.3 μM, respectively. Good stability and reproducibility (R.S.D. < 5%) are obtained reflecting the minimal adsorption of thiols at the CNT electrode surface. The new microchip protocol should find a wide range of bioanalytical applications involving assays of thiol compounds.
Co-reporter:Huimin Ge, Huimin Bao, Luyan Zhang and Gang Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 32) pp:NaN5228-5228
Publication Date(Web):2014/06/16
DOI:10.1039/C4TB00302K
A graphene–cobalt microsphere hybrid was prepared by the chemical reduction of a mixture containing graphene oxide and cobalt chloride. It was found that a little amount of potassium borohydride or sodium borohydride could initiate the hydrazine-reduction of the mixture at a low temperature of 80 °C. The structure of the material was investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, vibrating sample magnetometery, Fourier transform infrared spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller (BET) techniques. The average size of the cobalt microspheres on graphene sheets was measured to be ∼590 nm. Magnetic investigations indicated that the graphene–cobalt microsphere hybrid exhibited ferromagnetic behavior at room temperature. In addition, the magnetic hybrid was successfully employed in the enrichment and identification of low-abundance proteins and peptides in combination with mass spectrometry.
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