The poly 2,6-pyridinediamine (pPA) film was formed on the glassy carbon electrode by utilizing electropolymerization, which yielded an interface with amine groups for the assembly of thionine (Thi) and colloidal Au. The electrochemical characteristics of the immunosensor were studied by cyclic voltammetry. The factors influencing the performance of the resulting biosensor were studied in detail. Under the optimized conditions, the current response of the proposed immunosensor decreased linearly in two concentration ranges of CEA from 0.5 to 10 ng/mL and from 10 to 120 ng/mL with a detection limit of 0.2 ng/mL. Moreover, the studied immunosensor exhibited simple fabrication, good reproducibility and a broad linear range, which made it potentially application for determination of CEA in clinical analysis.

Key words: immunosensor, poly(2,6-pyridinediamine), thionine, gold nanoparticle, carcinoembryonic antigen