Nanogold-functionalized g-C3N4 nanohybrids for sensitive impedimetric immunoassay of prostate-specific antigen using enzymatic biocatalytic precipitation

This work reports on a new impedimetric immunosensing strategy for sensitive detection of prostate-specific antigen (PSA) in biological fluids. The assay was carried out on monoclonal anti-PSA capture antibody-modified glassy carbon electrode with a sandwich-type detection format. Gold nanoparticles-decorated g-C3N4 nanosheets (AuNP/g-C3N4), synthesized by the wet-chemistry method, were utilized for the labeling of polyclonal anti-PSA detection antibody and horseradish peroxidase (HRP). Upon target PSA introduction, the sandwiched immunocomplex could be formed between capture antibody and detection antibody. Followed by the AuNP/g-C3N4, the labeled HRP could catalyze 4-choloro-1-naphthol into benzo-4-chlorohexadienone. The as-generated insoluble product was coated on the electrode surface, thus increasing the Faradaic impedance of Fe(CN)64−/3− indicator between the solution and the base electrode. Under the optimal conditions, the impedance increased with the increasing target PSA in the sample, and exhibited a wide linear range from 10 pg mL−1 and 30 ng mL−1 with a detection limit of 5.2 pg mL−1. A repeatability and intermediate precision of <14% was accomplished. The specificity and method accuracy in comparison with commercial PSA ELISA kit for analysis of human serum specimens were relatively satisfactory.