Liposome-Mediated In Situ Formation of Ag3PO4/AgBr/Br-CN Ternary Nanostructures on Photoanodes for Photoelectrochemical Immunoassay

A dual-photoelectrode self-powered photoelectrochem-ical (PEC) biosensing system for protein was proposed based on the liposome-assisted signal amplification strategy. The dual-photoelec-trode self-powered device was constructed by integrating Ag3PO4 with bromine-doped g-C3N4 (Ag3PO4/Br-CN) as a photoanode and CuInS2 as a photocathode synchronously. Ag nanoparticle (AgNP)-encapsulated liposomes as tags were labeled on the target protein through a sandwich immunoreaction implemented in a 96-well plate. The AgNP-encapsulated liposomes were used to generate the signal regulator Ag+ for PEC detection. In the presence of Ag+, the reaction between Ag+ and Ag3PO4/Br-CN occurred to form Ag3PO4/AgBr/Br-CN ternary heterostructures. The compact contact and the matchable band-edge levels of Ag3PO4, AgBr, and Br-CN in the ternary heterostructures broaden the light absorption range and efficiently restrain the electron-hole recombination of the photoanode, producing an enhanced photocurrent response. The large loading capacity of liposomes, the fine performance of the formed ternary heterostructures, and the well-designed dual-photoelectrode self-powered PEC device endows the biosensing system with high sensitivity for protein detection. Using prostate-specific antigens as model proteins, the biosensing system exhibited a low detection limit of 3.4 x 10-13 g mL-1 with a linear range of 1.0 x 10-12 g mL-1 to 5.0 x 10-8 g mL-1. The marriage of the self-powered system with the liposome-assisted strategy not only represented a generic method for protein detection but also provided a path to fulfill the requirement of high sensitivity in PEC analysis.