Ultrasensitive sandwich-type photoelectrochemical immunosensor based on CdSe sensitized La-TiO2 matrix and signal amplification of polystyrene@Ab2 composites

A novel and sensitive sandwich-type photoelectrochemical (PEC) sensor was fabricated using signal amplification strategy for the quantitative detection of the prostate specific antigen (PSA). CdSe nanoparticles (NPs) sensitized lanthanum-doped titanium dioxide (La-TiO 2 ) composites were used to bind the primary antibodies (Ab 1 ). The doping of lanthanum promoted the visible light absorption of TiO 2 and remarkably enhanced the photocurrent . Moreover, 0.3%La-TiO 2 displayed the highest photocurrent in the La-TiO 2 composites, which was twice as much as that of undoped TiO 2 . Carboxyl modified CdSe NPs were assembled onto La-TiO 2 composites via the dentate binding between –COOH and Ti atom in TiO 2 NPs, which dramatically promoted the photocurrent intensity by approximately 2.1 times. Carboxyl functionalized polystyrene (PS) microspheres were coated with the secondary antibodies (Ab 2 ). Owing to the better insulation property and steric hindrance of the prepared polystyrene@Ab 2 (PS@Ab 2 ) composites, the significant reduction of the photocurrent signal was achieved after the specific immune recognition. Under the optimum experimental conditions, the fabricated PEC sensor realized ultrasensitive detection of PSA in the range of 0.05–100   pg   mL −1 with a detection limit of 17   fg   mL −1 . Moreover, this well-designed PEC immunoassay exhibited ideal reproducibility, stability, and selectivity, which is a promising platform for the detection of other important tumor targets.