Nanogold/mesoporous carbon foam-mediated silver enhancement for graphene-enhanced electrochemical immunosensing of carcinoembryonic antigen

• An ultrasensitive electrochemical immunosensor with a novel tracing tag is prepared on a graphene modified GCE.
• The tracing tag is nanogold functionalized mesoporous carbon foam which can induce silver deposition after immunoreaction.
• The silver deposition process produces a mass of silver for signal ampilification by electrochemical stripping analysis.
• This method avoids the shortcoming of the enzyme-related immunoassay and the need of deoxygenation.

Nanogold functionalized mesoporous carbon foam (Au/MCF) coupling with a signal amplification by C–Au synergistic silver enhancement was designed for sensitive electrochemical immunosensing of biomarker. The Au/MCF was prepared by in situ growth of nanogold on carboxylated MCF and used as a tracing tag to label signal antibody via the inherent interaction between protein and nanogold. The immunosensor was prepared by covalently immobilizing capture antibody on an electrochemically reduced graphene oxide/chitosan film modified glassy carbon electrode. Through a sandwich-type immunoreaction, Au/MCF tags were captured on the immunoconjugates to induce a silver deposition process. The electrochemical stripping signal of the deposited silver was used to monitor the immunoreaction. The Au/MCF-mediated silver enhancement along with the graphene-promoted electron transfer led to high detection sensitivity of carcinoembryonic antigen. Under optimal conditions, the proposed immunoassay method showed wide linear range from 0.05 pg mL−1 to 1 ng mL−1 and a detection limit down to 0.024 pg mL−1. The newly designed amplification strategy holds great potential for ultrasensitive electrochemical biosensing of other analytes.