Multiplex fluorescence quenching immunoassay based on multicolor magnetic quantum dot and dual spectral-overlapped polydopamine nanospheres for ultrasensitive detection of aflatoxin B1, zearalenone, ochratoxin A, and fumonisin B1

Due to the increasing fungal infections and the implementation of strict food safety regulations, the demand for sensitive, rapid, and easy assays for testing co-contaminated mycotoxins in food has grown in recent years. In this study, a multiplex fluorescence quenching immunoassay is developed to simultaneously detect prevalent mycotoxins in cereals, namely aflatoxin B1 (AFB1), zearalenone (ZEN), ochratoxin A (OTA), and fumonisin B1 (FB1). Four spherical nanocomposites with magnetic core and three-layer quantum dot (QD) shell (MagTQD) are fabricated. These nanocomposites exhibit different maximum emission peaks without overlap and interference at the same excitation wavelength. Four MagTQD conjugated with corresponding coating antigens to prepare four fluorescence signal probes with rapid magnetic enrichment ability, respectively. Moreover, polydopamine nanospheres (PDANs) with dual-spectral overlapped fluorescence quenching properties are conjugated with four mycotoxin antibodies to prepare four fluorescence quenching probes, respectively. The established immunoassay has the low detection limit at 1.29 pg mL-1 for AFB1, 0.80 pg mL-1 for ZEN, 1.97 pg mL-1 for OTA, and 13.89 pg mL-1 for FB1, respectively. This developed assay can provide a new approach to realize the efficient detection of multi-mycotoxins in food safety supervision.