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Now showing items 65 - 80 of 87

  • A Label-Free Silicon Quantum Dots-Based Photoluminescence Sensor for Ultrasensitive Detection of Pesticides

    Yi, Yinhui   Zhu, Gangbing   Liu, Chang   Huang, Yan   Zhang, Youyu   Li, Haitao   Zhao, Jiangna   Yao, Shouzhuo  

    Sensitive, rapid, and simple detection methods for the screening of extensively used organophosphorus pesticides and highly toxic nerve agents are in urgent demand. A novel label-free silicon quantum dots (SiQDs)-based sensor was designed for ultrasensitive detection of pesticides. This sensing strategy involves the reaction of acetylcholine chloride (ACh) with acetylcholinesterase (AChE) to form choline that is in turn catalytically oxidized by choline coddase (ChOx) to produce betaine and H2O2 which can quench the photoluminescence (PL) of SiQDs. Upon the addition of pesticides, the activity of AChE is inhibited, leading to the decrease of the generated H2O2, and hence the PL of SiQDs increases. By measuring the increase in SiQDs PL, the inhibition efficiency of pesticide to AChE activity was evaluated. It was found that the inhibition efficiency was linearly dependent on the logarithm of the pesticides concentration. Consequently, pesticides, such as carbaryl, parathion, diazinon, and phorate, were determined with the SiQDs PL sensing method. The lowest detectable concentrations for carbaryl, parathion, diazinon, and phorate reached 7.25 x 10(-9), 3.25 x 10(-8), 6.76 x 10(-8), and 1.9 x 10(-7) g/L, respectively, which were much lower than those previously reported. The detecting results of pesticide residues in food samples via this method agree well with those from high-performance liquid chromatography. The simple strategy reported here should be suitable for on-site pesticides detection, especially in combination with other portable platforms.
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  • Room-temperature ionic liquids/multi-walled carbon nanotubes/chitosan composite electrode for electrochemical analysis of NADH

    Wang, Qiong   Tang, Hao   Me, Qingji   Tan, Liang   Zhang, Youyu   Li, Biaomo   Yao, Shouzhuo  

    An electrochemical sensing platform was developed based on the integration of room-temperature ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate, BMIM.BF4) and multi-walled carbon nanotubes (MWNTs) with polymeric matrix (chitosan, CHIT). The resulting composite were investigated and characterized by FTIR, TEM, SEM, EDS and electrochemical methods. The BMIM.BF4/MWNTs/CHIT have good dispersibility in aqueous solution and can form a relative uniform film with unique structure. Electrochemical studies suggested that the BMIM.BF4/MWNTs/CHIT composite system provided a synergistic augmentation on the voltammetric and amperometric behaviors of electrochemical oxidation of NADH, which indicated by the decrease of the peak potential of NADH oxidation and the improvement of amperometric response. Additionally, the BMIM.BF4/MWNTs/CHIT/GC electrode shows good analytical performance such as low detection limit (0.06 mu M), good regeneration and antifouling properties for determination of NADH. This nanomaterials-based composite may be used as electrochemical transducers and have potential application for designing a variety of NAD(+)-dependent electrochemical biosensors. (c) 2007 Published by Elsevier Ltd.
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  • Monitoring of DNA oxidative damage with piezoelectric quartz crystal method

    Wu, Yaohui   Yi, Lin   Xie, Qingji   Zhang, Youyu   Yin, Fan   Yao, Shouzhuo  

    The piezoelectric quartz crystal (PQC) sensor was used to detect the whole process of DNA damage oxidized by H2O2 system containing Cu2+ or Zn2+ based on the density-viscosity change of the detected solution. The PQC impedance method has been applied to further investigate the damage process of DNA oxidized by H2O2 system containing Cu2+. It was found that the ratio of DELTAR1 to DELTAf0 or DELTAL1 coincided well with that calculated from Martin's equations reflecting the solution density-viscosity effect, suggesting that the continuing change in liquid loading on to the PQC surface caused the significant variation of DELTAf0, DELTAR1 and DELTAL1. It has also been found that the H2O2 system containing Cu2+ could oxidize DNA more completely than that containing Zn2+, and a trace Cu2+ in the system could cause DNA damage. However, no significant breakage in the DNA backbone was observed if the system contained only H2O2. The DNA concentration was linearly related to DELTAf0s, which is the different between the initial frequency and the frequency after a reaction time of 45 min, in the range of 50-1000 mug ml-1. The effect of H2O2 or Cu2+ concentration of was also investigated. The above-mentioned results that the H2O2 system containing Cu2+ or Zn2+ could break the DNA backbone were also supported by the agarose gel electrophoresis technique.
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  • Immobilization of enzymes through one-pot chemical preoxidation and electropolymerization of dithiols in enzyme-containing aqueous suspensions to develop biosensors with improved performance

    Fu, Yingchun   Chen, Chao   Xie, Qingji   Xu, Xiahong   Zou, Can   Zhou, Qingmei   Tan, Liang   Tang, Hao   Zhang, Youyu   Yao, Shouzhuo  

    A protocol of one-pot chemical preoxidation and electropolymerization of monomers (CPEM) in enzyme-containing aqueous suspensions (or solutions) was proposed as a universal strategy for high-activity and high-load immobilization of enzymes to construct amperometric biosensors, which was proven to be effective for the monomer of 1,4-benzenedithiol (BDT), 1,6-hexanedithiol, o-phenylenediamine, o-aminophenol or pyrrole, the preoxidant of K3Fe(CN)(6) or p-benzoquinone, and the enzyme of glucose oxidase (GOx) or alkaline phosphatase (AP) to develop GOx-based glucose biosensors or AP-based disodium phenyl phosphate biosensors. As a case examined in detail, a well-dispersed aqueous suspension of the poorly soluble BDT was obtained through its dispersion assisted by ultrasonication and coexisting GOx, which was then subject to chemical preoxidation through adding K3Fe(CN)(6), yielding many composites of insoluble BDT oligomers with lots of high-activity enzyme molecules entrapped. Some insoluble composites were then electrochemically codeposited with poly(1,4-benzenedithiol) on an Au electrode, yielding an enzyme film with high-load and high-activity enzyme immobilized. The glucose biosensor prepared here from the CPEM protocol showed much better performance than that from the preoxidant-free conventional electropolymerization (CEP) protocol, with a detection sensitivity increase by a factor of 32 in this case. The GOx-based and AP-based first-generation biosensors developed from the present CPEM protocol all exhibited notably improved performance compared with the analogues from the preoxidant-free CEP protocol. The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate various electrode modification processes. The values of quantity and enzymatic specific activity (ESA) of the immobilized enzymes were evaluated through the EQCM and the conventional UV-vis spectrophotometric method, given that the CPEM protocol notably improved the quantity and the ESA of immobilized enzymes as compared with the preoxidant-free CEP protocol. The proposed CPEM protocol may be interesting in a number of fields, including biosensing, biocatalysis, biofuel cells, bioaffinity chromatography, and biomaterials, and the successful electropolymerization of dithiols in aqueous suspensions (two-phase electropolymerization) may open a new avenue for many monomers that are poorly soluble in neutral aqueous solutions to in situ immobilize biomolecules for bioapplications.
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  • Voltammetric immunoassay for alpha-fetoprotein by using a gold nanoparticle/dendrimer conjugate and a ferrocene derived ionic liquid

    Shen, Youming   Shen, Guangyu   Zhang, Youyu  

    An immunosensor is described for the voltammetric determination of alpha-fetoprotein. It is making use of an AuNP-dendrimer conjugate and an ionic liquid. A gold electrode was first modified with chitosan. Then, the AuNP-dendrimer conjugate was covalently immobilized on the electrode. Following this, an ionic liquid was placed on the electrode via formation of a covalent bond between the amino groups of PAMAM and the aldehyde groups of an ionic liquid containing ferrocene. Thus, the redox probe ferrocene becomes immobilized on the electrode surface. PAMAM increases the amount of ferrocene immobilized on the electrode due to its globular shape and rich amino groups. The use of AuNPs improves the conductivity of the electrode. The modified electrode was applied to the determination of alpha-fetoprotein in human serum and has a linear response that covers the 0.05 to 30 ng mL(-1) alpha-fetoprotein concentration range, with a detection limit of 0.02 ng mL(-1). This assay is stable, selective and reproducible. It is perceived to provide a powerful tool for the early detection of cancer markers.
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  • Three-dimensional network polyamidoamine dendrimer-Au nanocomposite for the construction of a mediator-free horseradish peroxidase biosensor

    Luo, Jiao   Dong, Mingnan   Lin, Fanbo   Liu, Meiling   Tang, Hao   Li, Haitao   Zhang, Youyu   Yao, Shouzhuo  

    A three-dimensional network PAMAM-Au nanocomposite (3D-PAMAM-Au NC) was prepared by using the first generation polyamidoamine dendrimer (G1 PAMAM) as the dispersant agent. The resultant 3D-PAMAM-Au NC was successfully used as an immobilization matrix for the construction of a reagentless mediator-free horseradish peroxidase (HRP)-based H(2)O(2) biosensor on a multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode. With the advantages of the three-dimensional network, the organic-inorganic hybrid materials dramatically facilitate the direct electron transfer of HRP, and good bioelectrocatalytic activity towards H(2)O(2) was demonstrated. Under optimum conditions, the current response of the enzyme modified electrode at -0.30 V was detected. The current response is linearly correlated to H(2)O(2) concentration within the range of 18.00 mu M to 20.80 mM with a correlation coefficient of 0.9992 and a sensitivity of 377.78 mu A mM(-1) cm(-2). The detection limit was down to 6.72 mu M (S/N = 3). Furthermore, the biosensor exhibits some other excellent characteristics, such as high selectivity, short response time, and long-term stability. The 3D-PAMAM-Au NC has proved to be a promising biosensing platform for the construction of mediator-free biosensors, and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biofuel cells.
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  • A simple assay platform for sensitive detection of Sudan I-IV in chilli powder based on CsPbBr3 quantum dots

    Wu, Cuiyan   Lu, Qiujun   Miu, Xuran   Fang, Aijin   Li, Haitao   Zhang, Youyu  

    Sudan dyes are phenyl-azoic derivatives widely used in industry. Classified as carcinogenic and are strictly forbidden in foodstuffs; however, some unscrupulous businessmen adopted it for coloring foodstuffs. Here, a simple and effective fluorescence (FL) assay platform has been developed for the detection of Sudan I-IV based on CsPbBr3 perovskite quantum dots (QDs). It was found that the fluorescent emission of CsPbBr3 QDs can be effectively quenched by Sudan I-IV. Under the optimized conditions, the FL quenching efficiency of CsPbBr3 QDs was quantitatively correlated to the logarithmic concentrations of Sudan I-IV over the ranges of 100-10,000, 0.1-1000, 0.1-2000 and 0.4-1000 ng mL(-1) for Sudan I-IV, and the corresponding limits of detection were 3.33, 0.03, 0.03 and 0.04 ng mL(-1) (at 3 sigma/slope), respectively. CsPbX3 QDs (X =3D Cl, Br, and I or mixed halide systems Cl/Br and Br/I) was utilized as sensor in FL assay, which have unique optical properties of high FL quantum yields (up to 90%), narrow half peak width (26 nm) and tunable FL emissions spectra (410-700 nm). Meanwhile, the practical use of this assay platform for Sudan I-IV detection in chilli powder samples was also demonstrated, which indicated the potential in practical applications.
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  • Green synthesis of carbon dots with down- and up-conversion fluorescent properties for sensitive detection of hypochlorite with a dual-readout assay

    Yin, Bangda   Deng, Jianhui   Peng, Xue   Long, Qian   Zhao, Jiangna   Lu, Qiujun   Chen, Qiong   Li, Haitao   Tang, Hao   Zhang, Youyu   Yao, Shouzhuo  

    High quality carbon dots (C-dots) with down-and up-conversion fluorescence have been synthesized through low-temperature carbonization using sweet pepper as the carbon source. The C-dots with a quantum yield (QY) of 19.3% exhibit superior photophysical properties, for example, narrow and symmetric emission spectra, large stock shifts, resistance to photobleaching, and excitation-dependent fluorescence behavior. The excellent C-dots serve as useful fluorescent probes for hypochlorite (ClO-) detection by both down-and up-conversion fluorescence. Two consecutive linear ranges allow a wide determination of ClO- concentrations with a low detection limit of 0.05 mu mol L-1 and 0.06 mu mol L-1 (S/N = 3) for down-and up-conversion fluorescence measurements, respectively. The proposed detection method is advantageous because it is simple, sensitive, dual-signalling model and low-cost and has potential extensive applications in environmental and biological assays.
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  • A versatile matrix of an ionic liquid functionalized with aldehyde and ferrocene groups for label-free electrochemical immunosensors

    Shen, Youming   Shen, Guangyu   Zhang, Youyu  

    A novel ionic liquid functionalized with aldehyde and ferrocene groups was successfully synthesized. It was used to develop a label-free electrochemical immunosensor for the detection of human immunoglobulin G by casting this multifunctional ionic liquid entrapped in a Nafion matrix on a gold electrode. This multifunctional material was redox-active because of the introduction of ferrocene on the surface of the electrode through the covalent attachment of ferrocene to the ionic liquid, which avoided the use of other redox species in the electrolyte solution. In the meantime, the covalent attachment also avoided signal decrease resulting from the leakage of ferrocene into solution. In addition, the versatile ionic liquid can be used as a substrate for direct antibody immobilization due to the existence of the aldehyde group, which greatly simplified the process of sensor fabrication. The proposed sensor exhibited a good performance in a linear range from 0.05 to 35 ng mL(-1) with a detection limit of 0.03 ng mL(-1) based on 3s and provided a novel strategy for clinical detection due to its satisfactory stability, selectivity and reproducibility.
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  • A CeO2@MnO2 core–shell hollow heterojunction as glucose oxidase-like photoenzyme for photoelectrochemical sensing of glucose

    Wang, Haiyan   Yang, Weipeng   Wang, Xiaoxia   Huang, Linna   Zhang, Youyu   Yao, Shouzhuo  

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  • A novel fluorescent nanosensor based on small-sized conjugated polyelectrolyte dots for ultrasensitive detection of phytic acid

    Shi, Huizhen   Zhang, Anman   Du, Huifeng   Zhang, Min   Zhang, Yanran   Huang, Hongmei   Xiao, Yi   Zhang, Youyu   He, Xiaoxiao   Wang, Kemin  

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  • A specific AIE and ESIPT fluorescent probe for peroxynitrite detection and imaging in living cells

    Shen, Youming   Li, Mengyue   Yang, Ming   Zhang, Youyu   Li, Haitao   Zhang, Xiangyang  

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  • Recent Advances in the Development of Water Oxidation Electrocatalysts at Mild pH

    Li, Peipei   Zhao, Runbo   Chen, Hongyu   Wang, Huanbo   Wei, Peipei   Huang, Hong   Liu, Qian   Li, Tingshuai   Shi, Xifeng   Zhang, Youyu   Liu, Meiling   Sun, Xuping  

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  • Characterization of and biomolecule immobilization on the biocompatible multi-walled carbon nanotubes generated by functionalization with polyamidoamine dendrimers

    Zhang, Baoling   Chen, Qiong   Tang, Hao   Xie, Qingji   Ma, Ming   Tan, Liang   Zhang, Youyu   Yao, Shouzhuo  

    Polyamidoamine (PAMAM) dendrimers were covalently tethered onto the surface of multi-walled carbon nanotubes (MWCNTs). The morphology and dispersive properties of the MWCNT-PAMAM hybrids were characterized and the peripheral functional groups were identified. Cytotoxicity to human osteosarcoma MG-63 cells, and protein and DNA immobilization ability of the hybrids were evaluated in detail. The dendrimers were present on the surface of MWCNTs in high density. The MWCNT-PAMAM hybrids exhibited good dispersibility and stability in aqueous solution. We showed that the hybrids are biocompatible, with no obvious cytotoxicity at concentration <25 mu g mL(-1) over 24h. They possess excellent biomolecule-immobilization ability (bovine serum albumin and 5'-Fam-CAAggTCgTgTAAAggTCAg-3' were used as models). The functionalization of MWCNTs with PAMAM dendrimers improved the biomolecule-immobilization ability 70-fold and simultaneously decreased the cellular toxicity by about 30%. It is expected that the MWCNT-PAMAM hybrids will find promising applications in biosensors and biomolecule delivery systems in gene or protein therapy. (c) 2010 Elsevier B.V. All rights reserved.
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  • Ultrasensitive electrochemical aptasensor for thrombin based on the amplification of aptamer-AuNPs-HRP conjugates

    Zhao, Jie   Zhang, Youyu   Li, Haitao   Wen, Yanqing   Fan, Xiaoyu   Lin, Fanbo   Tan, Liang   Yao, Shouzhuo  

    Successful development of an ultrasensitive and highly specific electrochemical aptasensor for thrombin based on amplification of aptamer-gold nanoparticles-horseradish peroxidase (aptamer-AuNPs-HRP) conjugates was reported. In this electrochemical protocol, aptamer1 (Apt1) was immobilized on core/shell Fe(3)O(4)/Au magnetic nanoparticles (AuMNPs) and served as capture probe. Aptamer2 (Apt2) was dual labeled with AuNPs and HRP and used as detection probe. In the presence of thrombin, the sandwich format of AuMNPs-Apt1/thrombin/Apt2-AuNPs-HRP was fabricated. Remarkable signal amplification was realized by taking the advantage of AuNPs and catalytic reactions of HRP. Other proteins, such as human serum albumin, lysozyme, fibrinogen, and IgG did not show significant interference with the assay for thrombin. Linear response to thrombin concentration in the range of 0.1-60 pM and lower detection limit down to 30 fM (S/N = 3) was obtained with the proposed method. This electrochemical aptasensor is simple, rapid (the whole detection period for a thrombin sample is less than 35 min), sensitive and highly specific, it shows promising potential in protein detection and disease diagnosis. (C) 2010 Elsevier B.V. All rights reserved.
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  • A Dual-Response Near-Infrared Fluorescent Probe for Rapid Detecting Thiophenol and Its Application in Water Samples and Bio-imaging

    Li, Yaqian   Su, Wei   Zhou, Zile   Huang, Zhen   Wu, Cuiyan   Yin, Peng   Li, Haitao   Zhang, Youyu  

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