Amperometric sandwich immunoassay for the carcinoembryonic antigen using a glassy carbon electrode modified with iridium nanoparticles, polydopamine and reduced graphene oxide

The authors describe a sandwich-type electrochemical immunoassay for sensitive determination of the carcinoembryonic antigen (CEA). It is based on the use of iridium nanoparticles (Ir NPs) acting as electrochemical signal amplifier on the surface of a glassy carbon electrode. At first, polydopamine-reduced graphene oxide (PDA-rGO) was employed to immobilize primary antibody (Ab(1)) against CEA. Secondly, Ir-NPs were used as a support for the immobilization of secondary antibody (Ab(2)) to afford signal labels. The large surface area of PDA-rGO and the excellent electro-oxidative H2O2-sensing properties of Ir NPs result in a sensitive assay for CEA. Operated best at a working voltage of -0.6 V (vs. SCE), the assay has a linear range that extends from 0.5 pgai...mL(-1) to 5 ng center dot mL(-1), and the lower detection limit is 0.23 pgai...mL(-1). The immunosensor displays satisfactory reproducibility and stability, thus demonstrating a reliable immunoassay strategy for tumor biomarkers. It was applied to the determination of CEA in spiked serum samples.