A split-type photoelectrochemical immunosensor based on a high-performance In2O3/BiVO4 photoelectrode modulated by a ZIF-8 protective layer

Herein, a split-type photoelectrochemical (PEC) immunosensor is designed to detect neuron-specific enolase (NSE), which is a tumor marker for small cell lung cancer present in nerve and neuroendocrine tissues. In this study, a heterogeneous In2O3/BiVO4 structure is developed with coral-like BiVO4 films adsorbed onto In2O3 based on simplified successive ionic layer adsorption and reaction (s-SILAR). Moreover, immune recognition occurs in a 96-well plate in the split-type PEC immunosensor, thus effectively avoiding interference with the recognition of biomolecules. However, the sensitivity of zeolitic imidazolate framework (ZIF)− 8 molecules to pH varies, and most of the degradation of ZIF-8 molecules can be achieved by a reaction at a pH of 5.5–6.5 for > 30 min. Therefore, SiO2-glucose oxidase is selected as a regulatory switch to act on ZIF-8 molecules by catalyzing the conversion of glucose to gluconic acid, whereas In2O3/BiVO4 is selected as the photoactive substrate and ZIF-8 protective layer as the signal switch. By constructing a split-type PEC immunosensor, gluconic acid of different concentrations is released in the 96-well plate through the change of NSE concentration to regulate the degradation of the ZIF-8 protective layer and achieve the sensitive detection of NSE. The constructed PEC sensor exhibits an excellent photocurrent response between 0.1 pg mL–1 and 100 ng mL–1, with a detection limit of 0.03 pg mL–1. Simultaneously, the accuracy, specificity, stability, and reproducibility of this split-type PEC sensing platform predict its promising application in the future in the field of biomolecules.