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Lin D.,Nanjing University | Wu J.,Nanjing University | Ju H.,Nanjing University | Yan F.,Jiangsu Institute of Cancer Prevention and Cure
Biosensors and Bioelectronics | Year: 2014

Nanogold functionalized mesoporous carbon foam (Au/MCF) coupling with a signal amplification by C-Au synergistic silver enhancement was designed for sensitive electrochemical immunosensing of biomarker. The Au/MCF was prepared by in situ growth of nanogold on carboxylated MCF and used as a tracing tag to label signal antibody via the inherent interaction between protein and nanogold. The immunosensor was prepared by covalently immobilizing capture antibody on an electrochemically reduced graphene oxide/chitosan film modified glassy carbon electrode. Through a sandwich-type immunoreaction, Au/MCF tags were captured on the immunoconjugates to induce a silver deposition process. The electrochemical stripping signal of the deposited silver was used to monitor the immunoreaction. The Au/MCF-mediated silver enhancement along with the graphene-promoted electron transfer led to high detection sensitivity of carcinoembryonic antigen. Under optimal conditions, the proposed immunoassay method showed wide linear range from 0.05pgmL-1 to 1ngmL-1 and a detection limit down to 0.024pgmL-1. The newly designed amplification strategy holds great potential for ultrasensitive electrochemical biosensing of other analytes. © 2013 Elsevier B.V. Source


Ji H.,Nanjing University | Yan F.,Jiangsu Institute of Cancer Prevention and Cure | Lei J.,Nanjing University | Ju H.,Nanjing University
Analytical Chemistry | Year: 2012

An ultrasensitive protocol for electrochemical detection of DNA is designed with quantum dots (QDs) as a signal tag by combining the template enhanced hybridization process (TEHP) and rolling circle amplification (RCA). Upon the recognition of the molecular beacon (MB) to target DNA, the MB hybridizes with assistants and target DNA to form a ternary "Y-junction". The target DNA can be dissociated from the structure under the reaction of nicking endonuclease to initiate the next hybridization process. The template enhanced MB fragments further act as the primers of the RCA reaction to produce thousands of repeated oligonucleotide sequences, which can bind with oligonucleotide functionalized QDs. The attached signal tags can be easily read out by square-wave voltammetry after dissolving with acid. Because of the cascade signal amplification and the specific TEHP and RCA reaction, this newly designed protocol provides an ultrasensitive electrochemical detection of DNA down to the attomolar level (11 aM) with a linear range of 6 orders of magnitude (from 1 × 10-17 to 1× 10-11 M) and can discriminate mismatched DNA from perfect matched target DNA with high selectivity. The high sensitivity and specificity make this method a great potential for early diagnosis in gene-related diseases. © 2012 American Chemical Society. Source


Dong H.,Nanjing University | Ding L.,Nanjing University | Yan F.,Jiangsu Institute of Cancer Prevention and Cure | Ji H.,Nanjing University | Ju H.,Nanjing University
Biomaterials | Year: 2011

A simple nanocarrier of polyethylenimine-grafted graphene nanoribbon (PEI-g-GNR) was proposed as an effective gene vector. The GNR was formed by longitudinally unzipping multiwalled carbon nanotubes (MWCNTs), and treated with strong acids and sonication to obtain surface carboxylic acid groups for graft of PEI via electrostatic assembly. The PEI-g-GNR appeared to protect locked nucleic acid modified molecular beacon (LNA-m-MB) probes from nuclease digestion or single-strand binding protein interaction, thus could be used as a nanocarrier of the probes for more efficient transfection of cells than PEI or PEI-g-MWCNTs due to the large surface area of the GNR and high charge density of PEI. The cytotoxicity and apoptosis induced by the PEI-g-GNR were negligible under optimal transfection conditions. Combining with the remarkable affinity and specificity of LNA to microRNA (miRNA), a delivery system by the LNA-m-MB/PEI-g-GNR was proposed for effectively transferring LNA-m-MB into the cells to recognize the target miRNA. Using HeLa cells as model, a method for detection of miRNA in single cell was developed. These results suggested that PEI-g-GNR would be a promising nonviral vector for in situ detection of gene in cytoplasm and gene therapy in clinical application. © 2011 Elsevier Ltd. Source


Xu Q.,Nanjing University | Yan F.,Jiangsu Institute of Cancer Prevention and Cure | Lei J.,Nanjing University | Leng C.,Nanjing University | Ju H.,Nanjing University
Chemistry - A European Journal | Year: 2012

This work designed a simple, sensitive, and low-cost immunosensor for the detection of protein marker by using a carbon sphere/gold nanoparticle (CNS/AuNP) composite as an electrochemical label. The nanoscale carbon spheres, prepared with a hydrothermal method by using glucose as raw material, were used to load AuNPs for labeling antibody by electrostatic interaction, which provided a feasible pathway for electron transfer due to the remarkable conductivity. The disposable immunosensor was constructed by coating a polyethylene glycol (PEG) film on a screen-printed carbon-working electrode and then immobilizing capture antibody on the film. With a sandwich-type immunoassay format, the analyte and then the CNS/AuNP-labeled antibody were successively bound to the immunosensor. The bound AuNPs were finally electro-oxidized in 0.1M HCl to produce AuCl 4 - for differential pulse voltammetric (DPV) detection. The high-loading capability of AuNPs on CNS for the sandwich-type immunorecognition led to obvious signal amplification. By using human immunoglobulin G (IgG) as model target, the DPV signal of AuNPs after electro-oxidized at optimal potential of +1.40 V for 40 s showed a wide linear dependence on the logarithm of target concentration ranging from 10 pgmL -1 to 10 ngmL -1. The detection limit was around 9 pgmL -1. The immunosensor showed excellent analytical performance with cost effectivity, good fabrication reproducibility, and acceptable precision and accuracy, providing significant potential application in clinical analysis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Lin D.,Nanjing University | Wu J.,Nanjing University | Wang M.,Nanjing University | Yan F.,Jiangsu Institute of Cancer Prevention and Cure | Ju H.,Nanjing University
Analytical Chemistry | Year: 2012

A triple signal amplification strategy was designed for ultrasensitive immunosensing of cancer biomarker. This strategy was achieved using graphene to modify immunosensor surface for accelerating electron transfer, poly(styrene-co-acrylic acid) microbead (PSA) carried gold nanoparticles (AuNPs) as tracing tag to label signal antibody (Ab 2) and AuNPs induced silver deposition for anodic stripping analysis. The immunosensor was constructed by covalently immobilizing capture antibody on chitosan/ electrochemically reduced graphene oxide film modified glass carbon electrode. The in situ synthesis of AuNPs led to the loading of numerous AuNPs on PSA surface and convenient labeling of the tag to Ab 2. With a sandwich-type immunoreaction, the AuNPs/PSA labeled Ab 2 was captured on the surface of an immunosensor to further induce a silver deposition process. The electrochemical stripping signal of the deposited silver nanoparticles in KCl was used to monitor the immunoreaction. The triple signal amplification greatly enhanced the sensitivity for biomarker detection. The proposed method could detect carcinoembryonic antigen with a linear range of 0.5 pg mL -1 to 0.5 ng mL -1 and a detection limit down to 0.12 pg mL -1. The immunosensor exhibited good stability and acceptable reproducibility and accuracy, indicating potential applications in clinical diagnostics. © 2012 American Chemical Society. Source

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