We designed a signal-on photoelectrochemical (PEC) immunoassay for the sensitive monitoring of prostate-specific antigen (PSA) based on the etching reaction of hydrogen peroxide (H2O2) toward oxygen/phosphorus co-doped graphitic C3N4/AgBr/MnO2 nanosheets (OP-g-C3N4/AgBr/MnO2). Initially, glucose oxidase (GOX)-labeled detection antibodies were introduced into the capture antibody-coated microplate with a sandwich-type immunoreaction in the presence of PSA. Then, the as-generated H2O2 from the decomposition of glucose by GOX etched the manganese dioxide (MnO2) nanosheets into manganese ions (Mn2+), thereby causing the exposure of the underlying OP-g-C3N4/AgBr. Meanwhile, H2O2 could be also used as an electron scavenger, and restrain the recombination of the electron-hole pairs of OP-g-C3N4/AgBr. Two advantages of H2O2 enhanced the photocurrent synergistically. Under optimum conditions, the PEC immunoassay showed high sensitivity toward target PSA within a dynamic working range of 0.05-50 ng mL-1 with a limit of detection of 17 pg mL-1. In addition, our system possessed high specificity, favorable selectivity, and good stability. Relative to commercialized PSA ELISA kits, the accuracy of our strategy was acceptable. More importantly, our strategy can be easily extended to screen other biomarkers by controlling the corresponding antibodies.
Keywords: Etching reaction; MnO(2) nanosheets; O/P co-doped g-C(3)N(4)/AgBr; Photoelectrochemical immunoassay; Prostate-specific antigen.
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