Label-free photoelectrochemical immunosensor for sensitive detection of Ochratoxin A

Abstract A general label-free photoelectrochemical (PEC) platform was manufactured by assembly of CdSe nanoparticles (NPs) sensitized anatase TiO 2 -functionalized electrode via layer-by-layer (LBL) strategy. CdSe NPs were assembled on anatase TiO 2 -functionalized electrode through dentate binding of TiO 2 NPs to –COOH groups. Ascorbic acid (AA) was used as an efficient electron donor for scavenging photogenerated holes under visible-light irradiation. The photocurrent response of the CdSe NPs modified electrode was significantly enhanced as a result of the band alignment of CdSe and TiO 2 in electrolyte. Ochratoxin A (OTA), as model analyte, was employed to investigate the performance of the PEC platform. Antibodies of OTA were immobilized on CdSe sensitized electrode by using the classic 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride coupling reactions between –COOH groups on the surfaces of CdSe NPs and –NH 2 groups of the antibody. Under the optimized conditions, the photocurrent was proportional to OTA concentration range from 10 pg/mL to 50 ng/mL with detection limit of 2.0 pg/mL. The employed PEC platform established a simple, fast and inexpensive strategy for fabrication of label-free biosensor, which might be widely applied in bioanalysis and biosensing in the future.