Self-enhanced photocathodic matrix based on poly-dopamine sensitized TiO2 mesocrystals for mycotoxin detection assisted by a dual amplificatory nanotag

Abstract

The photoelectrochemical performance of rutile TiO₂ mesocrystals has been demonstrated to be significantly improved by a chelating-assembly of poly-dopamine on the surface of the TiO₂ mesocrystals. The formed benzoquinone groups on poly-dopamine could act as electron receivers to take over the photo-induced electrons of TiO₂ mesocrystals, thereby constituting a self-reinforced functionality transducing interface to enhance the cathode photocurrent. Herein, zearalenone as a representative mycotoxin was used as a model analyte to assist the immunoassay establishment. The bioconjugates of secondary antibody integrated ordered mesoporous Co₃O₄ were introduced through immunoreaction. The Co₃O₄, as a powerful scaffold, could load more bioactive molecules due to its mesoporous structure. Owing to the inevitable steric hindrance caused by the bioconjugates, the photo-initiated electrons in the TiO₂ mesocrystals/poly-dopamine composite were inaccessible to reduce the oxygen in the electrolyte, thus depressing the photocurrent density. Meanwhile, partial exciting light found it difficult to arrive at the TiO₂ mesocrystals due to Co₃O₄ with a felicitous band gap of 2.07 eV which consumed the partial light energy. Under optimal conditions, this immunosensor had a wide linear range from 10⁻⁶ to 20 ng mL⁻¹ for zearalenone detection. The specificity, precision, and reproducibility were satisfactory for this biosensor, which offered a valuable and versatile protocol in photoelectrochemical immunoassay development.