Photoelectrochemical immunoassay of squamous cell carcinoma antigen based on CuO/nitrogen-doped porous carbon-ZnO biolabeling and a type-II In 2 O 3 /AgBiS 2 heterojunction.

AgBiS 2 was hydrothermally synthesized, In 2 O 3 was synthesized by hydrothermal method and calcination, and the type-II In 2 O 3 /AgBiS 2 heterojunction material of an optimized composition ratio was cast-coated on a fluorine-doped tin oxide (FTO) slice to fabricate an In 2 O 3 /AgBiS 2 /FTO photoanode. The signal-attenuated photoelectrochemistry sandwich immunoassay of squamous cell carcinoma antigen (SCCA) was realized on this photoanode, on the basis of a bovine serum albumin/secondary antibody/CuO nanoparticles/nitrogen-doped porous carbon-ZnO bionanocomposite that can competitively absorb light and deplete the electron donor ascorbic acid as well as show the steric hindrance and p-n quenching effects. Under the optimized conditions (e.g., at a bias of 0 V vs. SCE), the photocurrent was linear with the common logarithm of SCCA concentration from 2.00 pg mL -1 to 50.0 ng mL -1 , with a limit of detection (LOD) of 0.62 pg mL -1 (S/N = 3). The immunoassay of SCCA in human serum samples gave satisfactory recovery (92.0~103%) and relative standard deviation (5.1~7.8%) results.