Triple strategy-enhanced immunochromatographic assay based on APCB and AIEFM for the ultrasensitive detection of AFM1

Aflatoxin M1 (AFM1) is highly toxic, widely distributed, and difficult to monitor, posing a serious threat to human health. Therefore, a highly sensitive, rapid, convenient, and low-cost detection method must be urgently established. In this study, a triple strategy-enhanced immunochromatographic assay (ICA) was developed to satisfy these detection requirements. First, a turn-on signal output mode of the fluorescence quenching ICA substituted the turn-off mode of the traditional ICA for sensitive response to trace AFM1, with the limit of detection (LOD) reduced by approximately 4.9-fold. Then, a novel Au and polydopamine (PDA) cogrowth chrysanthemum-like blackbody was prepared as the quenching probe to reduce the background signal. This probe combined the excellent properties of Au nanoparticles with PDA. Thus, its fluorescence quenching constant was higher than that of single Au and PDA nanoparticles by 25.8- and 4.9-fold, respectively. Furthermore, an aggregation-induced emission fluorescence microsphere with a 5.7-fold higher relative quantum yield than a commercial fluorescence microsphere was selected as the signal output carrier to improve the signal-to-noise ratio. The integration of the above triple strategies established a 53.4-fold sensitivity-enhanced fluorescence quenching ICA (LOD = 0.9 pg/mL) for detecting AFM1 in milk, providing a strong technical guarantee for the safety monitoring of milk products.