Silver nanowire-graphene hybrid nanocomposites as label for sensitive electrochemical immunoassay of alpha-fetoprotein

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 0.05-400 ng/mL with a low detection limit (LOD) of 5 pg/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. (C) 2011 Elsevier Ltd. All rights reserved.