Photoelectrochemical immunoassay of aflatoxin B1 in foodstuff based on amorphous TiO2 and CsPbBr3 perovskite nanocrystals

Abstract

Aflatoxin B₁ (AFB₁) pollution is one of the most serious problems for food safety. In this paper, a split-type photoelectrochemical (PEC) immunoassay was designed for sensitive detection of AFB₁ in foodstuffs by using amorphous TiO₂ with all-inorganic perovskite CsPbBr₃ nanocrystals (CsPbBr₃/a-TiO₂). The a-TiO₂ layer not only improved the stability of CsPbBr₃ nanocrystals, but also facilitated charge transfer, which resulted in the increasing photocurrent of the nanocomposites. Initially, a competitive-type enzyme immunoreaction was executed on a high-binding microplate between the analyte and alkaline phosphatase (ALP)-labeled AFB₁-bovine serum albumin (AFB₁–BSA) conjugate. Accompanied by the formation of the immunocomplex, the carried ALP triggered enzymatic hydrolysis to generate ascorbic acid (AA, as an electron donor) for increasing the photocurrent of the CsPbBr₃/a-TiO₂-modified electrode. Coupling with the competitive enzyme immunoassay, the photocurrent of the modified electrode decreased with the increase of target AFB₁ concentration in a dynamic working range from 0.01 ng mL⁻¹ to 15 ng mL⁻¹ with a limit of detection (LOD) of 2.8 pg mL⁻¹ under optimum conditions. Furthermore, the photoelectrochemical immunoassay was also utilized to detect AFB₁ in peanut and corn samples, giving acceptable accuracy in comparison with the referenced AFB₁ enzyme-linked immunosorbent assay (ELISA) method.