Bingqian Liu

Fuzhou University, Min-hou, Fujian, China

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Publications (34)143.44 Total impact

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    ABSTRACT: Prostate-specific antigen (PSA), as a glycoprotein enzyme encoded in humans by the KLK3 gene, is one of the most important biomarkers for the diagnosis and prognosis of prostate cancer. Herein, a new electrochemical immunosensor for sensitive determination of PSA was designed by using redox and catalysis 'all-in-one' infinite coordination polymer (PtNP@ICP) as signal tag on the polyamidoamine dendrimers modified electrode interface. To construct such 'all-in-one' PtNP@ICP nanostructures, the coordination polymerization was fully carried between metal ions and polydentate bridging ligands, and the PtNP was encapsulated into the ICP in the process of polymerization. The prepared PtNP@ICP nanocatalyst was characterized by transmission electron microscope (TEM), energy dispersive X-ray spectrometry (EDX), ultraviolet and visible (UV-vis) spectrophotometry and Fourier transform infrared spectroscope (FTIR). And the synthesized PtNP@ICP was utilized as signal tag for the label of PSA. With a sandwich-type immunoassay format, the conjugated signal tag on the transducer increased with the increasing PSA concentration in the sample thus enhancing the signal of the electrochemical immunosensor due to the catalytic reduction toward H2O2 of the enveloped PtNP. Under optimal conditions, the current was proportional to the logarithm of PSA concentration ranging from 0.001 to 60ng/mL. The detection limit (LOD) was 0.3pg/mL at 3sB. The immunosensor displayed an acceptable reproducibility, stability and selectivity. In addition, the methodology was evaluated with human serum specimens receiving good correlation with results from commercialized enzyme-linked immunosorbent assay (ELISA) method.
    Biosensors & bioelectronics. 08/2014; 64C:6-12.
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    ABSTRACT: A new signal amplification strategy based on target-induced proximity ligation assay accompanying three-way junction-based rolling chain amplification was designed for ultrasensitive detection of concanavalin A (Con A) by coupling with a sequential injection mode. To construct such a proximity ligation assay system, two types of magnetic sensing probes including glucosamine/DNA1-conjugated magnetic bead (GA-MB-DNA1) and GA-MB-DNA2 were first synthesized and prepared through a typical carbodiimide coupling. In the presence of target Con A, GA-MB-DNA1 and GA-MB-DNA2 were ligated together based on the interaction between Con A and the conjugated glucosamine on the MB, thereby resulting in the formation of three-way DNA junction because of partial base pairing on the DNA1/DNA2. With the aid of ligase and polymerase, the formed three-way DNA junction could be used as the primer to produce numerous repeated oligonucleotide sequences through rolling circle amplification (RCA) reaction. The formed long oligonucleotide strand could cause the intercalation of numerous positively charged methylene blue molecules with negatively charged DNA backbone. During the electrochemical measurement, each of the intercalated indicators could produce an electrochemical signal within the applied potentials, resulting in the amplification of detectable electronic signal. By monitoring the change in the signal, we could indirectly determine the concentration of target Con A in the sample. Under the optimal conditions, the developed sensing platform exhibited high sensitivity for detection of Con A with a wide dynamic range of 1.96 pM - 98 nM and a low detection limit (LOD) of 1.5 pM at the 3sB level. Intra-assay and inter-assay coefficients of variation were less than 8.9% and 9.7%, respectively. In addition, the methodology was validated by assaying Con A spiked samples including newborn cattle serum and peanut, and the recovery in all cases was 88.8 - 134.7%.
    Analytical chemistry. 07/2014;
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    ABSTRACT: An omega (Ω)-like DNA nanostructure was for the first time utilized for homogenous electrochemical monitoring of small molecules (ATP used in this case) based on target-induced formation of DNAzyme-aptamer conjugates without the need for sample separation and washing.
    Chemical Communications 01/2014; · 6.38 Impact Factor
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    ABSTRACT: A new digital multimeter (DMM)-based immunosensing system was designed for quantitative monitoring of biomarker (prostate-specific antigen, PSA used in this case) by coupling with an external capacitor and an enzymatic catalytic reaction. The system consisted of a salt bridge-linked reaction cell and a capacitor/DMM-joined electronic circuit. A sandwich-type immunoreaction with target PSA between the immobilized primary antibody and glucose oxidase (GOx)-labeled detection antibody was initially carried out in one of the two half-cells. Accompanying the sandwiched immunocomplex, the conjugated GOx could catalyze the oxidation of glucose, simultaneously resulting in the conversion of [Fe(CN)6]3− to [Fe(CN)6]4−. The difference in the concentrations of [Fe(CN)6]3−/[Fe(CN)6]4− in two half-cells automatically produced a voltage that was utilized to charge an external capacitor. With the closing circuit switch, the capacitor discharged through the DMM, which could provide a high instantaneous current. Under the optimal conditions, the resulting currents was indirectly proportional to the concentration of target PSA in the dynamic range of 0.05–7 ng mL−1 with a detection limit (LOD) of 6 pg mL−1. The reproducibility, precision, and selectivity were acceptable. In addition, the methodology was validated by analyzing 12 clinical serum specimens, receiving a good accordance with the referenced values for the detection of PSA.
    Biosensors & bioelectronics 01/2014; 55:255–258. · 5.43 Impact Factor
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    ABSTRACT: We report on a protocol for a simultaneous competitive immunoassay for tetracycline (TC) and chloramphenicol (CAP) on the same sensing interface. Conjugates of TC and of CAP with bovine serum albumin were first co-immobilized on a glassy carbon electrode modified with gold nanoparticles. In parallel, monoclonal anti-TC and anti-CAP antibodies were conjugated onto CdS and PbS nanoclusters, respectively. In a typical assay, the immobilized haptens and the added target analytes competed for binding to the corresponding antibodies on the nanoclusters. Subsequently, Cd(II) and Pb(II) ions are released from the surface of the corresponding nanoclusters by treatment with acid and then were detected by square wave anodic stripping voltammetry. The currents at the peak potentials for Cd(II) and Pb(II) were used as the sensor signal for TC and CAP, respectively. This multiplex immunoassay enables the simultaneous determination of TC and CAP in a single run with dynamic ranges from 0.01 to 50 ng mL−1 for both analytes. The detection limits for TC and for CAP are 7.5 pg mL−1 and 5.4 pg mL−1, respectively. No obvious nonspecific adsorption and cross-reactivity was observed in a series of analyses. Intra-assay and inter-assay coefficients of variation were less than 10 %. The method was evaluated by analyzing TC and CAP in spiked samples of milk and honey. The recoveries range from 88 % to 107 % for TC, and from 91 % to 119 % for CAP. Figure We developed a new multiplexed electrochemical immunoassay for simultaneous determination of tetracycline and chloramphenicol, using metal sulfide nanoclusters as recognition elements.
    Microchimica Acta 01/2014; 181(1-2). · 3.43 Impact Factor
  • Bing Zhang, Yu He, Bingqian Liu, Dianping Tang
    Analytica Chimica Acta. 01/2014;
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    ABSTRACT: A new flow-through electrochemical aptasensor was designed for ultrasensitive monitoring of adenosine triphosphate (ATP) by coupling microvalve-programmable capillary column with CdS-functionalized DNA concatamer for signal amplification. Initially, a layer of primary DNA-conjugated polyacrylamide hydrogel was covalently linked onto the internal surface of capillary column, and then an automated sequenctial injection format with a syringe pump was employed for development of the programmable capillary-based aptasensor. In the presence of target DNA aptamer, the immobilized primary DNA hybridized with partial bases of the aptamer. The excess aptamer fregment could trigger the formation of DNA concatamer between auxiliary DNA1 and CdS-labeled auxiliary DNA2. Upon target ATP introduction, a specific ATP-aptamer reaction was excuated, thereby resulting in the release of CdS-functionalized DNA concatamer from the capillary. Subsenquent anodic stripping voltammetric detection of cadmium released under acidic conditions from the released CdS nanoparticles could be conducted in a homemade detection cell. Under optimal conditions, the dynamic concentration range spanned from 0.1pM to 10nM ATP with a detection limit of 0.06pM ATP. The electrochemical aptasensor showed good reproducibility, selectivity, and stability. In addition, the methodology was evaluated for the analysis of ATP spiked serum samples, and the recoveries was 81-140%.
    Biosensors & bioelectronics 10/2013; 53C:390-398. · 5.43 Impact Factor
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    ABSTRACT: Prostate-specific antigen (PSA), one of the indications of possible prostate malignancy, is used as a biomarker for the diagnosis and prognosis of prostate cancer. Herein, we develop a new homogeneous potentiometric immunoassay for sensitive detection of low-concentration PSA without the need of sample separation and washing step. Two nanostructures including positively charged polyethyleneimine-poly(styrene-co-acrylic acid) (PEI-PSAA) nanospheres and negatively charged gold nanoparticles conjugated with anti-PSA antibody (Ab-AuNP) were first synthesized by using mulsifier-free emulsion copolymerization and wet chemistry method, respectively. Thereafter, the as-prepared PEI-PSAA was used as a pseudo hapten for the construction of immunosensing probe based on an electrostatic interaction between PEI-PSAA and Ab-AuNP. Upon target introduction, the added PSA competed with PEI-PASS for Ab-AuNP based on a specific antigen-antibody interaction, and displaced Ab-AuNP from PEI-PASS. The dissociated PEI-PASS was captured through the negatively charged Nafion- modified electrode, thereby resulting in the change of membrane potential. The fabrication process was characterized by using high-resolution transmission electron microscope (HRTEM), scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDX), surface plasmon resonance (SPR) and dynamic laser scattering (DLS) technique. Under optimal conditions, the output signal was indirectly proportional to the concentration of target PSA in the sample and exhibited a dynamic range from 0.1 to 50ng/mL with a detection limit (LOD) of 0.04ng/mL. Intra- and inter-assay coefficients of variation (CVs) were 6.8 and 7.5%, respectively. In addition, the methodology was evaluated for analysis of 12 clinical serum samples and showed good accordance between the results obtained by the developed immunosensing protocol and a commercialized enzyme-linked immunosorbent assay (ELISA) method.
    Biosensors & bioelectronics 10/2013; 53C:465-471. · 5.43 Impact Factor
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    ABSTRACT: A new fluorescence immunoassay strategy based on target-induced displacement reaction with cargo release from protein-gated carbohydrate-functionalized magnetic mesoporous silica nanoparticles (MMSN) was developed for sensitive detection of small molecular mycotoxins (aflatoxin B1, AFB1 used in this case). To construct such an assay system, MMSN was initially functionalized with mannose-terminated silanes, then capped with biotinylated concanavalin A (Con A) entrapping rhodamine B (RB) within the pores through the carbohydrate-protein interaction, and then biotinylated monoclonal anti-AFB1 capture antibody was conjugated to Con A-functionalized MMSN by the avidin-biotin chemistry. Gold nanoparticles (AuNP) heavily functionalized with invertase and bovine serum albumin-AFB1 conjugate was utilized as the trace tag. With target AFB1 introduction, a competitive immunoreaction was carried out between the immobilized anti-AFB1 on the MMSN and the labeled AFB1 on the AuNP. Accompanying with AuNP, the carried invertase hydrolyzed sucrose in glucose and fructose. The generated glucose competed with the mannose for Con A, and displaced the Con A-antibody complex from the MMSN, resulting in the open of molecular gates owing to the uncapping of MMSN, thereby the entrapping RB could release from the pores. The released RB could be quantitatively determined by a fluorometer. Under optimal conditions, the fluorescence intensity decreased with the increasing AFB1 concentration in the range from 0.01 to 5 ng mL-1 with a detection limit (LOD) of 8 pg mL-1 at the 3sblank criterion. Intra- and inter-batch assay precisions were lower than 9% and 9.5% (CV), respectively. The method featured unbiased identification of negative (blank) and positive samples. No significant differences at the 95% confidence level were encountered in the analysis of naturally contaminated peanut samples between the fluorescence immunoassay and a commercialized enzyme-linked immunosorbent assay (ELISA) method.
    Analytical Chemistry 09/2013; · 5.70 Impact Factor
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    ABSTRACT: A novel homogeneous immunoassay protocol was designed for quantitative monitoring of small molecular biotoxin (brevetoxin B, PbTx-2, as a model) by using target-responsive cargo release from polystyrene microsphere-gated mesoporous silica nanocontainer (MSN). Initially, monoclonal mouse anti-PbTx-2 capture antibody was covalently conjugated onto the surface of MSN (mAb-MSN), and the electroactive cargo (methylene blue, MB) was then trapped in the pores of mAb-MSN by using aminated polystyrene microspheres (APSM) based on the electrostatic interaction. Upon addition of target PbTx-2, the positively charged APSM was displaced from the negatively charged mAb-MSN owing to the specific antigen-antibody reaction. Thereafter, the molecular gate was opened, and the trapped methylene blue was released from the pores. The released methylene blue could be monitored by using a square wave voltammetry (SWV) in a home-made micro-electrochemical detection cell. Under optimal conditions, the SWV peak current increased with the increasing of PbTx-2 concentration in the range from 0.01 to 3.5 ng mL-1 with a detection limit (LOD) of 6 pg mL-1 PbTx-2 at the 3Sblank criterion. Intra- and interassay coefficients of variation with identical batches were ≤ 6% and 9.5%, respectively. The specificity and sample matrix interfering effects were acceptable. The analysis in 12 spiked seafood samples showed good accordance between results obtained by the developed immunoassay and a commercialized enzyme-linked immunosorbent assay (ELISA) method. Importantly, the target-responsive controlled release system-based electrochemical immunoassay (CRECIA) offers a promising scheme for the development of advanced homogeneous immunoassay without the sample separation and washing procedure.
    Analytical Chemistry 09/2013; · 5.70 Impact Factor
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    ABSTRACT: A new signal-on immunoassay protocol for sensitive electronic detection of alpha-fetoprotein (AFP) was developed by coupling with metal sulfide nanolabels and silver nanocluster (AgNC)-based rolling circle amplification (RCA) strategy. Initially, a sandwiched immunocomplex was formed on primary antibody-coated microplate using PbS nanoparticle-labeled polyclonal anti-AFP antibody (PbS-pAb2) as detection antibody, and then the carried PbS-pAb2 was dissolved by acid to release a large number of lead ions, which could induce the cleavage of lead-specific DNAzyme immobilized on the electrode. The residual single-stranded DNA on the electrode could be used as the primer to produce numerous repeated oligonucleotide sequences via the RCA reaction for the hybridization with many AgNC-labeled detection probes, resulting in the amplification of electronic signal due to the unique properties of silver nanoclusters. Under optimal conditions, the developed immunoassay exhibited high sensitivity for the detection of AFP with a dynamic range of 0.001 - 200 ng mL-1 and a detection limit (LOD) of 0.8 pg mL-1. Intra-assay and interassay coefficients of variation were below 8.0% and 10%, respectively. Importantly, the methodology was evaluated by analyzing 12 clinical serum specimens, and no significant differences were encountered in comparison with conventional enzyme-linked immunosorbent assay (ELISA) method.
    ACS Applied Materials & Interfaces 04/2013; · 5.01 Impact Factor
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    ABSTRACT: This work reports a novel electrochemical immunoassay protocol with signal amplification for determination of low-abundance protein (free prostate-specific antigen, PSA, used as a model) with high sensitivity and high selectivity by coupling metal sulfide (PbS)-based nanolabels with cleavage of the corresponding lead ion-induced DNAzymes. The assay mainly consists of an antigen-antibody immunoreaction with metal nanolabel in a transparent 96-well polystyrene microplate, the release of metal ions from the nanolabel, and cleavage of metal ion-induced DNAzyme. The signal is amplified by the labeled redox tag (ferrocene) on the DNAzyme-based sensor. In the presence of target analyte, the sandwiched immunocomplex can be formed between the primary antibody on the microplate and the corresponding metal sulfide nanolabel. The carried nanolabel can release numerous metal ions by acid, and induce the cleavage of the corresponding DNAzyme, thus resulting in the change of electrochemical signal. Under optimal conditions, the DNAzyme-based immunoassay presents an obvious electrochemical response for the detection of PSA, and allows detection of PSA at a concentration as low as 0.1 pg mL-1. Intra-assay and inter-assay coefficients of variation (CV) were less than 9.5% and 10%, respectively. No significant differences at the 0.05 significance level were encountered in the analysis of 12 clinical serum specimens between the developed immunoassay and a commercially available enzyme-linked immunosorbent assay (ELISA).
    Bioconjugate Chemistry 03/2013; · 4.58 Impact Factor
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    ABSTRACT: Methods based on sandwich-type immunosensors and immunoassays have been developed for detection of multivalent antigens/analytes with more than one eptiope due to the use of two matched antibodies. High-affinity antibodies and appropriate labels are usually employed for the amplification of detectable signal. Recent research has looked to develop innovative and powerful novel nanoparticle labels, controlling and tailoring their properties in a very predictable manner to meet the requirements of specific applications. This articles reviews recent advances, exploiting nanoparticle labels, in the sandwich-type immunosensors and immunoassays. Routine approaches involve noble metal nanoparticles, carbon nanomaterials, semiconductor nanoparticles, metal oxide nanostructures, and hybrid nanostructures. The enormous signal enhancement associated with the use of nanoparticle labels and with the formation of nanoparticle-antibody-antigen assemblies provides the basis for sensitive detection of disease-related proteins or biomolecules. Techniques commonly rely on the use of biofunctionalized nanoparticles, inorganic-biological hybrid nanoparticles, and signal tag-doped nanoparticles. Rather than being exhaustive, this review focuses on selected examples to illustrate novel concepts and promising applications. Approaches described include the biofunctionalized nanoparticles, inorganic-biological hybrid nanoparticles, and signal tage-doped nanoparticles. Further, promising application in electrochemical, mass-sensitive, optical and multianalyte detection are discussed in detail.
    Analytica chimica acta 01/2013; 758:1-18. · 4.31 Impact Factor
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    ABSTRACT: We have designed a new molecularly imprinted co‐polymer (MIP) for the sensitive detection of streptomycin (STR) in food using enzymes as signal amplification. The MIP was fabricated via co‐polymerization of aniline and o‐phenylenediamine on gold substrate in the presence of STR as template. The assay is based on competitive binding of free STR and glucose oxidase‐labeled STR (GOx‐STR) to the imprinters on the MIP. On addition of glucose, hydrogen peroxide is formed that is detected by differential pulse voltammetry. Under optimal conditions, the decrease of the catalytic current is proportional to the STR concentration in the range from 0.01 to 10 ng mL−1, with a detection limit (LOD) of 7.0 pg mL−1 STR (at 3s B). Intra‐ and inter‐assay coefficients of variation (CVs) are Document Type: Research Article DOI: http://dx.doi.org/10.1002/elan.201200468 Affiliations: Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Department of Chemistry, Fuzhou University, Fuzhou 350108, P. R. China Publication date: February 1, 2013 $(document).ready(function() { var shortdescription = $(".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } $(".descriptionitem").prepend(shortdescription); $(".shortdescription a").click(function() { $(".shortdescription").hide(); $(".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher By this author: Que, Xiaohua ; Liu, Bingqian ; Fu, Libing ; Zhuang, Junyang ; Chen, Guonan ; Tang, Dianping GA_googleFillSlot("Horizontal_banner_bottom");
    Electroanalysis 01/2013; 25(2). · 2.82 Impact Factor
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    ABSTRACT: Redox-active magnetic molecularly imprinted polymer (mMIP) nanospheres were first synthesized and functionalized with streptomycin templates for highly efficient electrochemical determination of streptomycin residues (STR) in food by coupling with bioelectrocatalytic reaction of enzymes for signal amplification. The mMIP nanospheres were synthesized by using Au(III)-promoted molecularly imprinted polymerization with STR templates on magnetic beads. Based on extraction of template molecules from the mMIP surface, the imprints toward STR templates were formed. The assay was implemented with a competitive-type assay format. Upon addition of streptomycin, the analyte competed with glucose oxidase-labeled streptomycin (GOX-STR) for molecular imprints on the mMIP nanospheres. With the increasing streptomycin in the sample, the conjugation amount of GOX-STR on the mMIP nanospheres decreased, leading to the change in the bioelectrocatalytic current relative to glucose system. Under optimal conditions, the catalytic current was proportional to STR level in the sample, and exhibited a dynamic range of 0.05-20ngmL(-1) with a detection limit of 10pgmL(-1) STR (at 3s(B)). Intra- and inter-assay coefficients of variation were below 12%. The assayed results for STR spiked samples including milk and honey with the mMIP-based sensor were received a good accordance with the results obtained from the referenced high-performance liquid chromatography (HPLC) method.
    Biosensors & bioelectronics 09/2012; · 5.43 Impact Factor
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    ABSTRACT: Marine toxins from microscopic algae can accumulate through the food chain and cause various neurological and gastrointestinal illnesses for human health. Herein, we designed a new ultrasensitive multiplexed immunoassay protocol for simultaneous electrochemical determination of brevetoxin B (BTX-2) and dinophysistoxin-1 (DTX-1) in seafood using distinguishable metal nanocluster-labeled molecular tags as traces on bifunctionalized magnetic capture probes. To construct such a bifunctionalized probe, monoclonal mouse anti-BTX-2 (mAb(1)) and anti-DTX-1 (mAb(2)) antibodies were co-immobilized on a magnetic bead (MB-mAb(1,2)). The distinguishable metal nanoclusters including cadmium nanoclusters (CdNC) and copper nanoclusters (CuNC) were synthesized using the artificial peptides with amino acid sequence CCCYYY, which were used as distinguishable signal tags for the label of the corresponding bovine serum albumin-BTX-2 and bovine serum albumin-DTX-1 conjugates. A competitive-type immunoassay format was adopted for the online simultaneous monitoring of BTX-2 and DTX-1 on a homemade flow-through magnetic detection cell. The assay was based on the stripping voltammetric behaviors of the labeled CdNC and CuNC at the various peak potentials in pH 2.5 HCl containing 0.01 M KCl using square wave anodic stripping voltammetry (SWASV). Under optimal conditions, the multiplexed immunoassays enabled simultaneous detection of BTX-2 and DTX-1 in a single run with wide working ranges of 0.005-5 ng mL(-1) for two marine toxins. The limit of detection (LOD) and limit of quantification (LOQ) were 1.8 and 6.0 pg mL(-1) for BTX-2, while those for DTX-1 were 2.2 and 7.3 pg mL(-1), respectively. No non-specific adsorption and electrochemical cross-talk between neighboring sites were observed during a series of procedures to detect target analytes. The covalent conjugation of biomolecules onto the nanoclusters and magnetic beads resulted in good repeatability and intermediate precision down to 9.5%. The method featured unbiased identification of negative (blank) and positive samples. No significant differences at the 0.05 significance level were encountered in the analysis of 12 spiked samples, including Sinonovacula constricta , Musculista senhousia , and Tegillarca granosa , between the multiplexed immunoassay and commercially available enzyme-linked immunosorbent assay (ELISA) for analysis of BTX-2 and DTX-1.
    Journal of Agricultural and Food Chemistry 08/2012; 60(36):8974-82. · 2.91 Impact Factor
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    ABSTRACT: Methods based on nanomaterial labels have been developed for electrochemical immunosensors and immunoassays, but most involved low sensitivity. Herein a novel class of molecular tags, nanogold-polyaniline-nanogold microspheres (GPGs), was first synthesized and functionalized with horseradish peroxidase-conjugated thyroid-stimulating hormone antibody (HRP-Ab(2)) for sensitive electrochemical immunoassay of thyroid-stimulating hormone (TSH). X-ray diffraction, confocal Raman spectroscopy, scanning electron microscope and transmission electron microscope were employed to characterize the prepared GPGs. Based on a sandwich-type immunoassay format, the assay was performed in pH 5.0 acetate buffer containing 6.0mmolL(-1) H(2)O(2) by using GPG-labeled HRP-Ab(2) as molecular tags. Compared with pure polyaniline nanospheres and gold nanoparticles alone, the GPG hybrid nanostructures increased the surface area of the nanomaterials, and enhanced the immobilized amount of HRP-Ab(2). Several labeling protocols comprising HRP-Ab(2), nanogold particle-labeled HRP-Ab(2), and polyaniline nanospheres-labeled HRP-Ab(2), were also investigated for determination of TSH and improved analytical features were obtained by using the GPG-labeled HRP-Ab(2). With the GPG labeling method, the effects of incubation time and pH of acetate buffer on the current responses of the immunosensors were also studied. The strong attachment of HRP-Ab(2) to the GPGs resulted in a good repeatability and intermediate precision down to 7%. The dynamic concentration range spanned from 0.01 to 20μIUmL(-1) with a detection limit (LOD) of 0.005μIUmL(-1) TSH at the 3s(B) criterion. Significantly, no significant differences at the 0.05 significance level were encountered in the analysis of 15 spiking serum samples between the developed electrochemical immunoassay and the commercially available enzyme-linked immunosorbent assay (ELISA) method for determination of TSH.
    Analytica chimica acta 08/2012; 738:76-84. · 4.31 Impact Factor
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    ABSTRACT: A novel class of redox-active molecular tags, poly(o-phenylenediamine)-carried nanogold particles (GPPDs), was first synthesized and functionalized with horseradish peroxidase-anti-prolactin conjugates (HRP-anti-PRL). Thereafter, a specific sandwich-type electrochemical immunoassay was designed for determination of prolactin (PRL) by using GPPD-labeled HRP-anti-PRL conjugates as molecular tags on anti-PRL antibody-modified glassy carbon electrode. Compared with pure gold nanoparticles and poly(o-phenylenediamine) microspheres, the as-prepared GPPDs increased the surface coverage of the nanostructures, and enhanced the immobilization amount of biomolecules. Several labeling protocols compromising GPPD-labeled HRP-anti-PRL, nanogold particles-labeled HRP-anti-PRL and poly(o-phenylenediamine) microspheres-labeled HRP-anti-PRL, were investigated for detection of PRL, and improved analytical features were obtained with the GPPD-based strategy. With the GPPD labeling method, dependence of the electrochemical signals on the incubation time and pH of the assay solution were also studied. The strong attachment of HRP-anti-PRL to the GPPDs resulted in a good repeatability and intermediate reproducibility down to 9.8%. The dynamic concentration range spanned from 0.5 to 180 ng mL(-1) PRL with a detection limit of 0.1 ng mL(-1) at the 3S(blank) level. No significant differences at the 95% confidence level were encountered in the analysis of 10 spiked blank cattle serum samples between the developed immunoassay and enzyme-linked immunosorbent assay method for determination of PRL.
    Analytica chimica acta 05/2012; 728:18-25. · 4.31 Impact Factor
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    ABSTRACT: This work reports a novel electrochemical immunoassay protocol with signal amplification for determination of proteins (human IgG here used as a model target analyte) at an ultralow concentration using DNA-based hybridization chain reaction (HCR). The immuno-HCR assay consists of magnetic immunosensing probes, nanogold-labeled signal probes conjugated with the DNA initiator strands, and two different hairpin DNA molecules. The signal is amplified by the labeled ferrocene on the hairpin probes. In the presence of target IgG, the sandwiched immunocomplex can be formed between the immobilized antibodies on the magnetic beads and the signal antibodies on the gold nanoparticles. The carried DNA initiator strands open the hairpin DNA structures in sequence and propagate a chain reaction of hybridization events between two alternating hairpins to form a nicked double-helix. Numerous ferrocene molecules are formed on the neighboring probe, each of which produces an electrochemical signal within the applied potentials. Under optimal conditions, the immuno-HCR assay presents good electrochemical responses for determination of target IgG at a concentration as low as 0.1 fg mL(-1). Importantly, the methodology can be further extended to the detection of other proteins or biomarkers.
    Analytical Chemistry 05/2012; 84(12):5392-9. · 5.70 Impact Factor
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    ABSTRACT: A novel redox-active magnetic nanostructure was synthesized by using a wet chemical method for high-efficiency electrochemical immunoassay of carcinoembryonic antigen (CEA, as a model analyte). The nanostructures based on the combination of a magnetic nanocore, a layer of electroactive poly(o-phenylenediamine) (PPD), and a silver metallic shell displayed good adsorption properties for the attachment of anti-CEA antibody selective to CEA. The magnetic nanostructure presented good redox behaviors to facilitate and modulate the way it was integrated into a magnetic carbon paste electrode. The assay was based on a sandwich-type immunoassay protocol by using nanogold-patterned graphene oxide nanoscales (AuNP-GO), conjugated with horseradish peroxidase-labeled anti-CEA, as secondary antibodies and biofunctionalized magnetic nanostructures as immunosensing probes. Under optimal conditions, the nanoparticle-based immunocomposites exhibited good electrochemical responses for the determination of CEA, and allowed the detection of CEA at a concentration as low as 1.0 pg mL(-1) at a signal-to-noise ratio of 3. In addition, the magnetic immunosensing had good reproducibility, and acceptable accuracy, and could be successfully applied for the detection of CEA in the clinical serum specimens. Significantly, by controlling the target biomolecules, this assay can be easily extended for use with other immunosensings, and thus represents a versatile design routine.
    Talanta 03/2012; 91:95-102. · 3.50 Impact Factor