Electrochemical detection of two tumor markers based on functionalized polypyrrole microspheres as immunoprobes

Abstract

In this study, a sandwich-type electrochemical immunosensor for the simultaneous detection of two tumor markers has been reported using functionalized polypyrrole microspheres as immunoprobes. The polypyrrole microspheres, which were synthesized through an one step chemical oxidative polymerization approach, showed high adsorption ability to redox probes such as thionine and adriamycin. Meanwhile, the polypyrrole microspheres functionalized with redox probes and gold nanoparticles (Au NPs) provided a larger surface area for the two different antibodies immobilization. The reduced graphene oxide sheet (rGO) was decorated with Au NPs as a substrate to immobilize two different antibodies. Carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) were used as model analytes in this study. Two well resolved reduction peaks, one at about −0.26 V (corresponding to thionine), another at about −0.69 V (corresponding to adriamycin, both vs. SCE) can be obtained in differential pulse voltammograms. Under optimal conditions, CEA and AFP can be simultaneously detected in the range from 1.0 pg mL⁻¹ to 50 ng mL⁻¹. The limit of detection for CEA and AFP was 0.40 pg mL⁻¹ and 0.33 pg mL⁻¹ (at S/N = 3), respectively. Further, the immunosensor was evaluated using a human serum sample, and the recovery was within 99.5–107% for CEA and 96.3–99.9% for AFP. The analysis results with the serum sample using the immunosensor were in accordance with those of an enzyme linked immunosorbent assay (ELISA), indicating the immunosensor has a potential application in real sample analysis.