No abstract

A novel nonenzymatic electrochemical immunosensor was fabricated for quantitative detection of -fetoprotein (AFP). The immunosensor was constructed by modifying gold electrode with electrochemical reduction of graphene oxide-carboxyl multi-walled carbon nanotube composites (ERGO-CMWCNTs) and electrodeposition of gold nanoparticles (AuNPs) for e®ective immobilization of primary antibody (Ab 1 Þ. Ferroferric oxide-manganese dioxide-reduced graphene oxide nanocomposites (Fe 3 O 4 @MnO 2 -rGO) were designed as labels for signal ampli¯cation. On one hand, the excellent electroconductivity and outstanding electron transfer capability of ERGO-CMWCNTs/AuNPs improved the sensitivity of the immunosensor. On the other hand, introduction of rGO could not only increase the speci¯c surface area for immobilization of secondary antibody (Ab 2 Þ but also build a synergetic e®ect to reinforce the electrocatalytic properties of catalysts. Fe 3 O 4 @MnO 2 -rGO nanocomposites were characterized by scanning electron microscope, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Using AFP as a model analyte, the proposed sandwich-type electrochemical immunosensor exhibited a wide linear range of 0.01-50 ng Á mL À1 with a low detection limit of 5.8 pg Á mL À1 . Moreover, the Fe 3 O 4 @MnO 2 -rGO-based peroxidase mimetic system displayed an excellent analytical performance with low cost, satisfactory reproducibility and high selectivity, which could be further extended for detecting other disease-related biomarkers.