Highly sensitive immunosensor based on polydopamine-nanofilm modified 3D gold nanoelectrode for α-fetoprotein detection

Abstract

The sensitivity and selectivity of the electrochemical immunosensor (ECIS) are the key aspect for the biomolecular detection of ultratrace tumor markers. Here we fabricated a novel ECIS for the detection of tumor marker α-fetoprotein (AFP) by a dual electrochemical signal amplification strategy involving 3D gold nanowire electrode (3D-GNE) and recycling redox polydopamine (PDA) nanofilm on 3D-GNE (PDA-3D-GNE). The electrochemical signal was first amplified by depositing Au nanowires on the bare electrode, the as-prepared 3D-GNE possessed a quadrupled active area, 2.6 times increase in oxidation current and fast electron transfer ability. The electrochemical signal was further amplified by reversible redox PDA nanofilm on 3D-GNE, which achieved a sixfold increase in capacitance, excellent binding strength to antibody (Ab) and great biocompatibility. The electrochemical performance and interfacial kinetic property of the immunosensor were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The optimized AFP ECIS exhibited a wide linear range from 0.1 pg·mL−1 to 50 ng·mL−1, a low detection limit of 0.01 pg·mL−1, excellent stability and reproducibility as well as selectivity. Furthermore, it was successfully demonstrated to work well for analyzing AFP in complex real human serum samples.