Photocurrent quenching by competitive consumption of surface electron donor and light absorption for immunosensing

This work designs a competitive consumption strategy of surface electron donor and light absorption for quenching the photocurrent of ZnSnO₃ nanocubes/BiOI nanoarrays/polydopamine (ZnSnO₃ NCs/BiOI NAs/PDA) as a photoactive material. This material can be formed on electrode surface by successive coating and deposition to provide a substrate for immobilization of capture antibody, and producing strong photocurrent in the presence of ascorbate acid as a surface electron donor due to the well matching structure of band gaps between ZnSnO₃ NCs and BiOI NAs, the excellent light absorption ability and high photo-electron conversion efficiency of BiOI NAs and PDA, and the accelerated electron transfer. Using ascorbate oxidase loaded dopamine-melanin nanosphere (DAM-AAO) as a label of the signal (secondary) antibody, the sandwich-type immunoreaction leads to dual photocurrent quenching of the label through the competitive consumption of ascorbate acid with enzymatic oxidation and the light absorption by DAM nanosphere. Thus, a sensitive "On-Off" photoelectrochemical (PEC) immunosensing method is constructed for the analysis of neuron specific enolase (NSE). The proposed method shows a detection range of 0.1 pg/mL -50 ng/mL and a detection limit of 0.03 pg/mL. The excellent performance and the recovery text demonstrated the practicability of the designed strategy and label in immunoassay of different protein biomarkers.