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ABSTRACT: Enzyme-linked immunosorbent assay (ELISA) methods based on natural enzyme-labeled probes have been applied in the immunoassays, but most have some inevitable limitations (e.g. harsh preparation, purification and storage) and are unsuitable for routine use. Herein we synthesized a new class of irregular-shaped platinum nanoparticles (ISPtNP) with a mean length of 7.0nm and a narrowing width from 2.0 to 5.0nm along the longitudinal axes, which were utilized as peroxidase-like mimics for the development of colorimetric immunoassays. Compared with bioactive horseradish peroxidase (HRP), the synthesized ISPtNP exhibited a low Km value (~0.12mM) and a high Kcat value (~2.27×10(4)s(-1)) for 3,3',5,5'-tetramethylbenzidine (TMB) with strong thermal stability and pH tolerance. The catalytic mechanism of the ISPtNP toward TMB/H2O2 was for the first time discussed and deliberated in this work. Based on a sandwich-type assay format, two types of colorimetric immunoassay protocols were designed and developed for the detection of rabbit IgG (RIgG, as a model) by using the synthesized ISPtNP and conventional HRP as the labeling of detection antibodies, respectively. Similar detection limits (LODs) of 2.5ngmL(-1) vs. 1.0ngmL(-1) were obtained toward RIgG with the ISPtNP labeling compared to HRP format. Intra- and inter-assay coefficients of variation were less than 13%. Importantly, the ISPtNP-based assay system could be suitable for use in a mass production of miniaturized lab-on-a-chip devices and open new opportunities for protein diagnostics and biosecurity.
Analytica chimica acta 05/2013; 776:79-86. · 4.31 Impact Factor
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ABSTRACT: Squaric acid, a 2-dimensional planar structure of squarate C4O4 units linked by protons in a layered sheet, was utilized for the first time as a catalytic substrate for ultrasensitive electronic determination of low-abundance proteins by coupling a target-induced electrocatalytic reaction with the in situ cycling signal amplification strategy.
Chemical Communications 04/2013; · 6.17 Impact Factor
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ABSTRACT: This paper describes the use of QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) for the extraction, cleanup and detection of 10 paralytic shellfish toxins (PSP) in sea food by HILIC-MS/MS with positive ESI. Matrix matched calibration standards were used to compensate for matrix effects. The toxins were extracted with acetonitrile/water (90:10, v/v) containing 0.1% formic acid and cleaned by HLB and GCB sorbents. Qualitative and quantitative detection for the analytes were carried out under the multiple reaction monitoring (MRM) in positive ionization mode after chromatography separation on a TSK-gel Amide-80® column (150mm×2.0mm×3μm). Studies at three fortification levels for the toxins in the range of 8.1-225.5μg/kg gave mean recoveries from 71.3% to 104.6% with relative standard deviation (RSD)⩽15.8%. The limit of detection (LOD) was below the recommended regulatory limit of 170μgSTX(equ.)/kg and the proposed method fully meets the needs of daily monitoring.
Food Chemistry 04/2013; 137(1-4):115-21. · 3.65 Impact Factor
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ABSTRACT: This works reports a new signal-on amplification strategy for sensitive electronic detection of nucleic acid based on the isothermal circular strand-displacement polymerization (ICSDP) reaction. The assay mainly involves a hybridization of ferrocene-labeled hairpin DNA with blocker DNA, a strand-displacement process with target DNA, and an ICSDP-based polymerization reaction. The signal is amplified by the labeled ferrocene on the hairpin probe with target recycling. Upon addition of target analyte, the blocker DNA is initially displaced by target DNA from the hairpin/blocker DNA duplex owing to the difference of the folding free energy, then the newly formed target/blocker DNA duplex causes the ICSDP reaction with the aid of the primer and polymerase, and then the released target DNA retriggers the strand-displacement for target recycling. Numerous ferrocene molecules are close to the electrode surface due to the reformation of hairpin DNA, each of which produces an electronic signal within the applied potentials, thereby resulting in the amplification of electrochemical signal. Under the optimal conditions, the ICSDP-based amplification method displays good electrochemical responses for detection of target DNA at a concentration as low as 0.03pM.
Biosensors & bioelectronics 03/2013; 47C:106-112. · 5.43 Impact Factor
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ABSTRACT: Chiral recognition based on enantioselective sensors is superior to conventional chromatographic enantioseparation techniques in terms of simplicity and rapidity. Normally, highly specific enantioselective receptors are used for the fabrication of enantioselective sensors. However, to date there only limited number of highly specific chiral selectors are reported, which greatly confines the development of enantioselective sensors. Herein, we demonstrate the feasibility of using relatively weak chiral selectors to construct an enantioselective biosensor for accurate chiral discrimination of enantiomers. The detection of racemic mixture of (R)- and (S)-1,2,3,4-Tetrahydro-1-naphthylamine (TNA) was demonstrated as an example. The sensor was made up of a dual-channel microfluidic chip. One channel of the chip was modified with human serum albumin (HSA), which was reported to be a weak chiral selector for TNA; while the other channel was modified with a monoclonal anti-TNA antibody, which was a non-enantioselective TNA receptor. A portable localized surface plasmon resonance (LSPR) detection system was integrated with the microfluidic chip to accomplish the signal collection. Our investigation revealed that the combination of LSPR responses obtained from the two channels can be used for quantitative discrimination of the (R)- and (S)-TNA. The limit of detection was found to be 150nM for (R)-TNA and 100nM for (S)-TNA. The feasibility of use relatively weak chiral selectors could potentially promote the development of various enantioselective sensors.
Biosensors & bioelectronics 03/2013; 47C:199-205. · 5.43 Impact Factor
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ABSTRACT: Surface imprinting over nanostructured matrices is an effective solution to overcome template removal and achieve high binding capacity. In this work, a facile method was developed for synthesis of polydopamine-coated molecularly imprinted silica nanoparticles (PDA-coated MIP silica NPs) based on self-polymerization of dopamine (DA) on the surface of silica NPs in the presence of template protein. Transmission electronic microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) showed that PDA layers were successfully attached on the surface of silica NPs and the corresponding thickness was about 5nm, which enabled the MIP silica NPs to have fast binding kinetics and high binding capacity. Under the aqueous media, the imprinted silica NPs showed much higher binding affinity toward template than non-imprinted (NIP) silica NPs. The protein recognition properties were examined by single-protein or competitive batch rebinding experiments and rebinding kinetics study, validating that the imprinted silica NPs have high selectivity for the template. The resultant BHb-MIP silica NPs could not only selectively separate BHb from the protein mixture, but also specifically deplete high-abundance BHb from cattle whole blood. In addition, the stability and regeneration were also investigated, which indicated that the imprinted silica NPs had excellent reusability.
Biosensors & bioelectronics 03/2013; 47C:120-126. · 5.43 Impact Factor
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ABSTRACT: Dynamic coating of the surface in capillary electrophoresis with chemiluminescence detection (CE-CL) using an off-column coaxial flow interface for the determination of four hemeproteins was developed. This method is based on the luminol-hydrogen peroxide reaction catalyzed by metalloproteins in alkaline medium. The experimental setup of the CE-CL system with the proposed off-column coaxial interface was evaluated by separation and detection of dopamine and catechol based on inhibition of the luminol-potassium ferricyanide reaction. Highly efficient separation of the two model compounds with symmetrical peak shape and satisfactory reproducibility was achieved by using this interface. In addition, in order to obtain a good resolution for hemeproteins, polyvinylpyrrolidone (PVP) combined with sodium dodecyl sulfate (SDS) were introduced as dynamic modifiers to reduce the unwanted adsorption of non-specific protein. Several parameters affecting the CE separation and CL detection were investigated in detail. Under the optimized conditions, a mixture of the four hemeproteins (horseradish peroxidase (HRP), catalase (Cat), myoglobin (Mb) and cytochrome C (Cyt C)) could be well separated within 20 min. The linear ranges of the four proteins were 5.7 × 10(-8) to 1.1 × 10(-6) mol L(-1) for HRP, 4.0 × 10(-8) to 2.0 × 10(-6) mol L(-1) for Cat, 1.1 × 10(-10) to 5.6 × 10(-8) mol L(-1) for Mb, and 3.8 × 10(-7) to 7.7 × 10(-6) mol L(-1) for Cyt C. The limits of detection (LODs) (S/N = 3) for HRP, Cat, Mb and Cyt C were 2.2 × 10(-8) mol L(-1) (104.5 amol), 1.6 × 10(-8) mol L(-1) (74 amol), 5.6 × 10(-11) mol L(-1) (0.26 amol), and 1.95 × 10(-7) mol L(-1) (0.89 fmol), respectively. The proposed method has been successfully applied to the analysis of low-level Mb in a spiked human urine sample and the recoveries were above 97%. Our primary result demonstrated that the proposed CE-CL method has great potential for Mb determination in clinical diagnosis.
The Analyst 02/2013; · 4.23 Impact Factor
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ABSTRACT: A molecularly imprinted inorganic-organic hybrid monolithic capillary column (MIP hybrid monolith) was synthesized by one-pot process and its application in selective recognition and capture of lysozyme (Lyz) from complex biological samples was described for the first time. Due to a combination of rigid silica matrices and flexible organic hydrogels in one-pot process, stable and accessible recognition sites in the as-prepared MIP hybrid monolith could be obtained after the removal of template protein, which facilitated the rebinding of template and provided good reproducibility and lifetime of use. The morphology, permeability, and pore properties of the as-prepared MIP hybrid monolith were characterized and a uniform monolithic matrix with high surface area and large through-pores was observed. The recognition behavior of MIP and non-imprinted (NIP) hybrid monolith was evaluated by separating template protein from unfractionated protein mixture and the result indicated that the MIP hybrid monolith has much higher affinity toward the template protein than NIP hybrid monolith. High imprinted factor (IF) and separation efficiency could be obtained. In addition, the practicality of the Lyz-MIP hybrid monolith was further evaluated by selective separation of Lyz from egg white and capture of Lyz from human serum by adopting it as an in-tube solid phase microextraction (in-tube SPME), and the good results demonstrated its potential in proteome analysis.
Journal of chromatography. A 02/2013; · 4.19 Impact Factor
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ABSTRACT: A simple and rapid capillary electrophoresis (CE) with an acidic potassium permanganate chemiluminescence (CL) detection method was developed to determine three alkaloids (curine, sinomenine and magnoflorine) simultaneously. A laboratory-built CE-CL detection interface was used. The field-amplified sample stacking technique was applied to the online concentration of alkaloids. Experimental conditions for CE separation and CL detection were investigated in detail to acquire optimum conditions. Under optimal conditions, the three alkaloids were baseline separated within 6 min, and the detection limits (S/N = 3) ranged from 0.03 µg/mL to 0.49 µg/mL. This method was successfully applied to determine the above three alkaloids in Sinomenium acutum, and the result of the determination of sinomenine was in good agreement with those given by high-performance liquid chromatography and CE methods. In addition, a possible CL reaction mechanism of sinomenine-KMnO(4) -H(2) SO(4) was proposed. Copyright © 2013 John Wiley & Sons, Ltd.
Luminescence 02/2013; · 1.73 Impact Factor
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ABSTRACT: A novel magneto-controlled electrochemical DNA biosensor is designed for the ultrasensitive detection of lead coupling a lead-specific DNAzyme with DNA-based hybridization chain reaction (HCR). To construct such a magnetic lead sensor, DNAzyme-based molecular beacons, selective to cleavage in the presence of Pb2+, are initially immobilized onto magnetic beads, which were used as the recognition elements. Upon addition of target lead, catalytic cleavage of substrate DNA segments in the double-stranded DNAzymes results in the capture of the initiator strands via the conjugated catalytic strands on magnetic beads. The captured DNA initiator strands trigger the hybridization chain reaction between two alternating hairpin DNA structures labeled with ferrocene to form a nicked double-helix on the magnetic beads. Numerous ferrocene molecules are formed on the neighboring probes, each of which produces an electrochemical signal within the applied potential. Under optimal conditions, the electrochemical signal of the magnetic lead sensor increases with the increasing lead level in the sample, and exhibits a linear response over a Pb2+ concentration range of 0.1-75nM with a detection limit of 37pM. Quantitative measurement of Pb2+ in the complex sample demonstrates the selectivity of the sensor scheme and points favorably to the application of such technologies to the analysis of environmental samples. The unique combination of a DNAzyme with hybridization chain reaction makes it possible to change the DNAzyme to select for other compounds of interest. This work represents the initial steps toward the creation of a robust field sensor for lead in groundwater or drinking water.
Biosensors & bioelectronics 01/2013; 45C:52-57. · 5.43 Impact Factor
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ABSTRACT: Field amplified sample stacking (FASS) was combined with a simple, rapid, sensitive CE-ESI-MS method to achieve the on-line enrichment and simultaneous determination of Clenbuterol (CLE), Salbutamol (SAL), Terbutaline (TER) and Formoterol (FOR). Samples were diluted in deionized water, and electrokinetic injection (10kV×50s) was employed to carry out FASS. With FASS, the four β2-agonists had simultaneously baseline enhancement as much as 319, 332, 297 and 115 fold, respectively. Consequently, satisfactory LODs (S/N=3) of 0.08, 0.1, 0.1 and 0.5ng/mL for CLE, SAL, TER and FOR were obtained. The separation of the four analytes was performed at 22kV in ammonium acetate/ammonia (20mmol/L, pH 9.0), using 7.5mmol/L acetic acid in isopropanol/water 50/50% (v/v) as sheath liquid. In addition, an excellent linear response was obtained with RSD less than 1.3% for migration times and less than 6.7% for peak areas (n=5). The recoveries of spiked urine samples were in the range of 82.7-101% with RSD lower than 9.8%. The proposed method has been applied to analyze human urine samples successfully.
Talanta 01/2013; 104C:97-102. · 3.79 Impact Factor
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ABSTRACT: A novel and nonenzyme immunosensing protocol is proposed for ultrahighly sensitive detection of low-abundance-proteins (carcinoembryonic antigen as a model) using dual nanogold-linked complementary bio-barcodes with superstructures for in situ amplified electronic signals.
Molecular BioSystems 01/2013; · 3.53 Impact Factor
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ABSTRACT: The picture shows an approach to real-time monitoring of single molecular binding events by the construction of a reconfigurable colorimetric DNA switch, described on page 234. A significant spectral shift of over 60 nm is achievable from on-off switching. The switching is based on changing the interparticle distance between gold nanoparticles in dimers, actuated by targeted DNA binding. The extraordinary spectral shift allows the unaided eye to observe single-target biomolecular binding events in real time under a darkfield microscope.
Small 01/2013; 9(2):233. · 8.35 Impact Factor
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ABSTRACT: An HPLC system combining a chemiluminescence detector was applied to estimate the singlet oxygen ((1) O(2) ) generation ability of di-sulfonic phthalocyanine zinc (ZnPcS(2) ) isomers. As photosensitizers, ZnPcS(2) produces (1) O(2) in air-saturated solutions under photoirradiation. The latter reacts with methyl Cypridina luciferin analogue (MCLA) to initiate chemiluminescence. This photoinduced chemiluminescence (PCL) of MCLA provides an easy method for evaluating the isomers' (1) O(2) generation ability during a simultaneous HPLC separation procedure. The cis-isomers and trans-isomers of ZnPcS(2) show different (1) O(2) generation abilities, which are in accordance with differences in their absorption spectra. Copyright © 2013 John Wiley & Sons, Ltd.
Luminescence 01/2013; · 1.73 Impact Factor
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ABSTRACT: A new electrochemical immunosensing protocol was designed for detection of carcinoembryonic antigen (CEA, as a model protein) by using graphene-carried poly(o-phenylenediamine)/gold hybrid nanosheets (GNPGs) as signal tags on the hierarchical dendritic gold microstructures (HDGMs)-modified glassy carbon electrode. To prepare the signal tags, poly(o-phenylenediamine) molecules were initially immobilized on the surface of graphene nanosheets via the π-stacking interaction. Then gold nanoparticles were assembled onto the poly(o-phenylenediamine)-modified graphene nanosheets, which were used for the labeling of anti-CEA detection antibodies and horseradish peroxidase (HRP). The as-prepared GNPGs were characterized by using atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. The assay was carried out with a sandwich-type immunoassay format in pH 5.5acetic acid-buffered saline solutions containing 2.5mmolL(-1) H(2)O(2). Under optimal conditions, the electrochemical immunoassay exhibited a wide dynamic range of 0.005-80ngmL(-1) toward CEA standards with a low detection limit of 5.0pgmL(-1). Intra- and inter-assay coefficients of variation were less than 11.5%. No significant difference at the 0.05 significance level was encountered in the analysis of 6clinical serum specimens and 6spiked blank new born cattle serum specimens between the developed immunoassay and commercially available electrochemiluminescent (ECL) method for the detection ofCEA.
Biosensors & bioelectronics 01/2013; 44C:108-114. · 5.43 Impact Factor
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ABSTRACT: Platinum-cerium oxide hybrid nanocatalysts (CeO(2)-Pt) were for the first time designed as bionanolabels for highly efficient electrochemical immunosensing of low-abundance proteins coupling nanocatalyst-based redox cycling with in situ signal amplification strategy.
Chemical Communications 01/2013; · 6.17 Impact Factor
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ABSTRACT: In this study, an electrochemical impedance biosensor for cyanobacterial toxin microcystin-LR (MC-LR) detection has been developed. MC-LR aptamers were immobilized on the gold electrode through Au-S interaction, in the presence of target (MC-LR); the binding of MC-LR and aptamers probe led to a complex formation change on the electrode surface and resulted in the impedance decreasing. The decrease rate had a linear relationship with logarithm of the MC-LR concentration in the range of 1.0×10(-7)-5.0×10(-11)mol/L, with a detection limit of 1.8×10(-11)mol/L. The sensor has good selectivity and stability, it has been applied to detect MC-LR in three kinds of real water samples with satisfying results.
Talanta 01/2013; 103:371-4. · 3.79 Impact Factor
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ABSTRACT: Recent research has looked to develop innovative, powerful and novel biofunctionalized nanoparticles, controlling and tailoring their properties in a very predictable manner to meet the needs of clinic immunoassays in the biomedical field. This minireview briefly summarizes recent advances covering the last 3 years, exploiting nanoparticle-based electrochemical, optical, mass-sensitive, colorimetric and immunodipstick assays. The enormous signal enhancement associated with the use of nanoparticles and formation of nanoparticle-antibody-antigen assemblies provide the basis for sensitive detection of disease-related proteins or biomarkers. Rather than being exhaustive, this minireview focuses on selected examples to illustrate novel concepts and promising applications. Finally, a small amount of speculation of possible future developments in nanoparticle-based immunoassays is provided.
The Analyst 01/2013; · 4.23 Impact Factor
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ABSTRACT: The metal-organic framework (MOF) was first utilized as the sensing platform for assaying biomolecules. It has also been demonstrated that this novel strategy is effective and reliable for detection of HIV DNA and thrombin with high sensitivity and selectivity.
Chemical Communications 01/2013; · 6.17 Impact Factor
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Xiaojing Li,
Wenming Xiong,
Hua Lin,
Liyang Zhuo,
Shuiyuan Lv,
Xi Tang,
Minshi Chen,
Zhexiang Zou,
Zhenyu Lin,
Bin Qiu, Guonan Chen
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ABSTRACT: An RP LC-ESI-MS/MS method for the determination of the migration of 16 primary phthalic acid esters from plastic samples has been developed using distilled water, 3% acetic acid, 10% alcohol, and olive oil as food simulants. Detection limits were 1.6-18.5 μg/kg in distilled water, 1.4-17.3 μg/kg in 3% acetic acid, 1.4-19.2 μg/kg in 10% alcohol, and 31.9-390.8 μg/kg in olive oil. The RSDs were in the range of 0.07-11.28%. The real plastic products inspection showed that only few analyzed samples were phthalates contaminated. Bis-2-ethylhexyl ester and dibutyl phthalate were the common items migrated from the plastic products into food and feeds, but the migration concentrations were far below the limits set by European Union (1.5 mg/kg for bis-2-ethylhexyl ester and 0.3 mg/kg for dibutyl phthalate).
Journal of Separation Science 01/2013; · 2.73 Impact Factor
