Vanadium-doped metal-organic framework@Znln₂S₄ core-shell heterojunction-attenuated photoelectrochemical immunoassay

Considering that cancer has become the second leading cause of death in humans, it is essential to develop an analytical approach that can sensitively detect tumor markers for early detection. We report an attenuated photoelectrochemical (PEC) immunoassay based on the organic-inorganic heterojunction 10MIL-88B(FeV)/ZnIn₂S₄ (10M88B(FeV)/ZIS) as a photoactive material for monitoring carcinoembryonic antigen (CEA). The 10M88B(FeV)/ZIS heterojunctions have excellent light-harvesting properties and high electrical conductivity, which are attributed to the advantages of both organic and inorganic semiconductors, namely, remarkable photogenerated carrier separation efficiency and long photogenerated carrier lifetime. Horseradish peroxidase (HRP) in the presence of H₂O₂ can catalyze 3,3'-diaminofenamide (DAB) producing brown precipitates (oxDAB), which is then loaded onto the 10M88B(FeV)/ZIS heterojunction to reduce the photocurrent and enable the quantitative detection of CEA. Under optimal conditions, the photocurrent values of the PEC biosensor are linearly related to the logarithm of the CEA concentrations, ranging from 0.01 ng mL^-1 to 100 ng mL^-1 with a detection limit (LOD) of 4.0 pg mL^-1. Notably, the accuracy of the PEC biosensor is in agreement with that of the human CEA enzyme-linked immunosorbent assay (ELISA) kit.