A self-supported electrochemical immunosensor based on Cu₂O/CuO@AuNPs heterostructures for sensitive and selective...

Accurate and rapid detection of ochratoxin A (OTA) residues in food can significantly reduce cancer risk due to their potent renal and liver toxicity. Herein, a heterojunction structure material used as enhanced antibody load labels is modified on flexible carbon paper to construct a novel self-supported electrochemical immunoassay for ultrasensitive OTA detection in foods. The heterojunction structure was constructed on Cu₂O hexagonal crystal with exposed high-energy facets through galvanic exchange reaction, in which the surface of Cu₂O was oxidized to CuO, and Au³⁺ was reduced to Au⁰. The Cu₂O/CuO@AuNPs/anti-OTA modified electrode exhibited good sensitivity and selectivity for OTA detection due to the synergistic effect of exposed (110) crystallographic facets, the increase of active sites, the copper mixed valence that promotes redox reactions at the interface between electrode and analyte, along with the immune effect of OTA antibody to specific recognition. The OTA sensor shows a linear range spanning 0.05-200 ng mL^-1 and a low detection limit of 0.2 pg mL^-1, which could be further applied in corn and soybean solution with good recovery ranging from 94 % to 106 %. Moreover, the elliptical joint confidence region result shows that the OTA sensor has good accuracy.