Au@SiO₂ SERS nanotags based lateral flow immunoassay for simultaneous detection of aflatoxin B₁ and ochratoxin A

Agricultural products are frequently contaminated by mycotoxins. Multiplex, ultrasensitive, and rapid determination of mycotoxins is still a challenging problem, which is of great significance to food safety and public health. Herein, a surface-enhanced Raman scattering (SERS) based lateral flow immunoassay (LFA) for the simultaneous on-site determination of aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) on the same test line (T line) was developed, in this study. In practice, two kinds of Raman reporters 4-mercaptobenzoic acid (4-MBA), and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) encoded silica-encapsulated gold nanotags (Au^4-MBA@SiO₂ and Au^DNTB@SiO₂) were used as detection markers to identify the two different mycotoxins. Through systematic optimization of the experimental conditions, this biosensor has high sensitivity and multiplexing with the limits of detection (LODs) at 0.24 pg mL^-1 for AFB₁ and 0.37 pg mL^-1 for OTA. These are far below the regulatory limits set by the European Commission, in which the minimum LODs for AFB₁ and OTA are 2.0 and 3.0 μg kg^-1. In the spiked experiment, the food matrix are corn, rice, and wheat, and the mean recoveries of the two mycotoxins ranged from 91.0% ± 6.3%-104.8% ± 5.6% for AFB₁ and 87.0% ± 4.2%-112.0% ± 3.3% for OTA. These results demonstrate that the developed immunoassay has good stability, selectivity, and reliability, which can be used for routine monitoring of mycotoxin contamination.