▎ 摘　　要

A rapid and sensitive one-step electrochemical immunoassay for the determination of a-fetoprotein (AFP, as a model biomarker) was developed by immobilizing anti-AFP antibody on a nanogold-functionalized graphene interface. Initially, thionine molecules as electron mediators were conjugated onto the surface of graphene nanosheets, then gold nanoparticles were sandwiched onto the graphene, and then horseradish peroxidase-anti-AFP (HRP-anti-AFP) conjugates were immobilized on the nanogold surface. The presence of two-dimensional graphene nanosheets with high conductivity not only increased the surface coverage of the electrode, but also enhanced the immobilized amount of biomolecules. With the AFP analyte, the formed antigen-antibody complex was coated on the electrode surface, which partially hindered the immobilized HRP toward the catalytic reduction of H2O2 in the solution. Under optimal conditions, the electrochemical immunosensor displayed a wide dynamic range of 0.1-200 ng mL(-1) with a detection limit (LOD) of 0.05 ng mL(-1) AFP at 3s(B). The reproducibility, selectivity and stability of the immunosensor were investigated with the acceptable results. In addition, the one-step immunoassay was evaluated and validated by assaying 5 positive and 5 negative serum specimens, and the obtained results were compared with those by the referenced electrochemiluminescent, receiving a good correlation between the two methods.