A photoelectrochemical/colorimetric immunosensor for broad-spectrum detection of ochratoxins using bifunctional copper oxide nanoflowers

The detection of ochratoxins is of great significance for rapid and accurate food safety screening. This work was aimed to design a photoelectrochemical/colorimetric immunosensor for the broad-spectrum detection of ochratoxin A (OTA), ochratoxin B (OTB) and ochratoxin C (OTC). In order to provide a comprehensive and accurate assessment of ochratoxins contamination, the broad spectrum antibodies were used as recognized elements and the bifunctional copper oxide nanoflowers (CuO NFs) were used as dual-signal probe to trigger the response of photoelectrochemical (PEC) and colorimetric detection. In PEC mode, Cu2+ released by CuO NFs can replace Cd2+ in photoactive material to form a new band gap, which accelerated the electron-hole recombination to change the PEC current. In colorimetric mode, Cu2+ efficiently assisted etching of Au nanorods (Au NRs), causing multiply color changes and localized surface plasmon resonance (LSPR) shifts of Au NRs. Two independent modes from different detection mechanisms were used to reflect the concentrations of ochratoxins with more accuracy and reliability. Therefore, this work not only realized the broad-spectrum detection of OTA, OTB and OTC, but also provided a new strategy for the development of accurate, visual and multi-signal immunosensing platform.