Cathodic photoelectrochemical immunoassay based on glucose-oxidase mediated biocatalysis to inhibit the exciton trapping of cupric ions for PbS quantum dots

The integration of photocathodes with enzymatic label tracer for the development of amplified PEC immunoassays is attractive for different diagnosis applications. Herein, we induce a novel strategy for the construction of cathodic PEC immunoassay on the basis of enzymatic reaction inhibited exciton trapping for PbS quantum dots (QDs). The cathodic photocurrent of the PbS QDs sensitized NiO was inhibited by cupric ions due to the formation of exciton trapping centers of CuS on their surface. In the presence the model target of carcinoembryonic antigen (CEA), a sandwich-type immunoreaction occurred with the detection antibody labeled glucose oxidase (GOx) as the signal tracer. The enzymatic reduction of ferricyanide ([Fe(CN)(6)](3-)) by GOx produced ferrocyanide ([Fe(CN)(6)](4-)), which easily combined with cupric ions to form cupric hexacyanoferrate (CuHCF, Cu-2[Fe(CN)(6)]) aggregates, and thus interrupted the formation of the exciton trapping centers of CuS. The enhanced photocurrent of the system was linear with the CEA concentration ranging from 0.5 pg/mL to 30 ng/mL with a detection limit of 0.17 pg/mL. Moreover, the PEC immunosensor also displayed high specificity and good reproducibility toward the target protein. It was also evaluated to analyze CEA in real samples of human serum specimens, which gave well matched results with the commercially available enzyme-linked immunosorbent assay (ELISA) kits. (C) 2018 Elsevier B.V. All rights reserved.