A sandwich electrochemical immunosensor based on polypyrrole microspheres for the detection of the cancer marker CA125†

In this study, a sensitive sandwich electrochemical immunosensor for the detection of the cancer marker cancer antigen 125 (CA125) was developed using polypyrrole (PPy) microspheres for amplifying the sensing signal. The PPy microspheres provided a larger surface area for gold nanoparticle (Au NP), CA125 antibody and signal molecule adriamycin immobilization. In 0.10 M PBS of pH 7.4, a well-shaped oxidation peak for adriamycin at −0.83 V (vs. SCE) was obtained in a differential pulse voltammogram. Signal intensity was related to the level of CA125. Under optimal conditions, the immunosensor showed a wide linear response range of 10–100 U mL⁻¹ with a detection limit of 2.4 μU mL⁻¹ (at 3σ/N), and recovery was 98.1–101.2%, as evaluated using human serum samples. Furthermore, the immunosensor was applied to measure real serum samples, and the results obtained were in accordance with those of enzyme-linked immunosorbent assay (ELISA), indicating that the proposed immunosensor is an ideal platform for clinical diagnosis application.