Photoelectrochemical immunoassay for prostate-specific antigen based on gasochromic reaction of Pd-MoO3

Exploiting new sensing mechanism for multiple signal responses has become an emerging research trend of gas-sensitive photoelectrochemical (PEC) immunoassay. Herein, we design a double-mode visual and PEC immunosensing system for the sensitive detection of prostate-specific antigen (PSA, as a model analyte) on the basis of gasochromic reaction with Pd-MoO3. As the sandwich immunoreaction progresses, a platinum nanoparticle-labeled detection antibody catalyzes the production of H2 from the substrate (NH3BH3). The resulting H2 undergoes a gasochromic reaction with Pd-MoO3, resulting in a change in color of the Pd-MoO3-coated electrode to provide a visual readout. Meanwhile, the photocurrent intensity of the product increases due to the reduction of the bandgap, which is positively related to the concentration of the analyte. Under optimal conditions, the developed sensing platform presented a high sensitivity for PSA in a dynamic working range of 0.1–50 ng mL−1 with a limit of detection of 76 pg mL−1. Impressively, this work not only presents a new protocol for the application of gasochromic materials but also gives a path for the developing dual signal readout in gas-sensitive PEC immunoassay.