A Magnet-Controlled and Renewable Amperometric Immunosensor for Carcinoembryonic Antigen Based on Magnetic Fe3O4(core)/Au(shell) Nanoparticles Modified Screen-Printed Carbon Electrode

Abstract

A novel amperometric immunosensor for carcinoembryonic antigen (CEA) was fabricated. Firstly, multi-walled carbon nanotubes with carboxyl groups (MCNTs)-thionine (Thi)-Nafion composite was prepared and dropped on the surface of a screen-printed working electrode (SPCE) to prepare the basic electrode (SPCE|MCNTs-Thi-Nafion). Secondly, horseradish peroxidase (HRP) labeled carcinoembryonic antigen antibody (HRP anti CEA) and bovine serum albumin (BSA) were assembled on Fe₃O₄(core)/Au(shell) nanoparticles (GMPs) to form the nanoprobes, which were introduced on the surface of the basic electrode by permanent magnet. Through one-step immunoassay format, the immunosensor was incubated with carcinoembryonic antigen. The formed antigen-antibody complex inhibited partly the active center of horseradish peroxidase labeled on anti carcinoembryonic antigen, which led to a linear decrease in the catalytic efficiency of horseradish peroxidase to the oxidation of immobilized thionine by H₂O₂. Under optimized conditions, the decreased current was proportional to the carcinoembryonic antigen concentration from 0.1-5.0 and 5.0-80 ng mL^-1 with a detection limit of 0.03 ng mL^-1 at signal/noise ratio of 3.