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Abstract: A facile and sensitive mediator-free electrochemical immunoassay was developed for determination of alpha-fetoprotein (AFP) in human serum with a sandwich-type mode by using silver nanowire–graphene hybrid nanocomposites (AgNW–GPs) as label. One-pot hydrothermal method was used for the synthesis of the AgNW–GPs with the aid of trisodium citrate. The as-prepared AgNW–GP was not only utilized for the label of horseradish peroxidase-conjugated anti-AFP (HRP-anti-AFP) with highly loading capacity, but also displayed good electrochemical behaviors. Compared with the conventional HRP-anti-AFP-based electrochemical immunoassay, the sensitivity of the proposed immunoassay by using the synthesized nanolabels was greatly improved. Under optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.05–400ng/mL with a low detection limit (LOD) of 5pg/mL AFP (at 3s B). Intra- and inter-assay coefficients of variation were below 10% and 8.5%, respectively. The selectivity and stability of the immunosensor were acceptable. In addition, the methodology was also validated by assaying 16 positive serum samples and 7 negative serum samples, receiving a good correlation with the results obtained from the referenced electrochemiluminescence method. [Copyright &y& Elsevier]

Abstract: A new sandwich-type electrochemical immunosensor with enhanced sensitivity was developed for detection of alpha-fetoprotein (AFP, as a model analyte) in biological fluids by using nanogold-enclosed titania nanoparticle (AuTi)-labeled secondary antibody on a gold–silver–graphene hybrid nanosheet (AuAgGP)-functionalized glassy carbon electrode (GCE). The presence of the AuAgGP nanosheets not only enhanced the immobilized amount of biomolecules, but also improved the electrochemical properties of the immunosensor. With the aid of AuTi nanolabels, the electrochemical signal was greatly amplified in comparison with pure nanogold or titania-based labels. Under optimal conditions, the sensitivity and dynamic range of the immunosensor were evaluated by using the labeled horseradish peroxidase on the AuTi as trace and H2O2 as enzyme substrate, and exhibited a wide dynamic range of 0.001–200ngmL−1 with a low detection limit (LOD) of 0.5pgmL−1 AFP (at 3σ). Both the intra- and inter-assay coefficients of variation were less than 10%. The current of the immunosensor at 13th day was as much as 90% of the initial current. In addition, the methodology was evaluated for 8 positive serum specimens obtained from hepatocarcinoma patients and 19 negative sera, and validated with the commercially available Roche 2010 Electrochemiluminescent (ECL) Automatic Analyzer. No significant differences at the 95% confidence level were encountered between two methods. [Copyright &y& Elsevier]