A novel amperometric immunosensor for the determination of carcinoembryonic antigen (CEA) based on DNA/nano Ag composite and poly-thione has been fabricated. The composite, which contains DNA (negatively charged) and nano Ag, can not only be immobilized to the glass carbon electrode surface modified with poly-thione (positively charged) through negatively charged DNA, but also adsorb carcinoembryonic antibodies through nano Ag particles with large specific surface areas and good biocompatibility. The modification procedure was electrochemically monitored by cyclic voltammetry. The performance and influencing factors of the resulting immunosensor were studied in detail. Under optimal conditions, the developed immunosensor exhibited fast response to CEA and the linear ranges were 1.0～10.0 and 10.0～80.0 ng•mL^－1 with correlation coefficients of 0.9983 and 0.9970, respectively, and a detection limit of 0.24 ng•mL^－1 (at 3σ). Moreover, the precision, reproducibility and stability of the as-prepared immunosensor were acceptable. Importantly, the proposed methodology would be valuable for diagnosis and monitoring of carcinoma and its metastasis.

Key words: carcinoembryonic antigen, poly-thione, DNA/nano Ag composite, amperometric immunosensor, differential pulse voltammetry