Strong light-trapping probes with high antibody activity for sensitive detecting FB1 by “turn-on” lateral flow immunoassay

Due to the insufficient chromaticity, traditional Au nanoparticles (AuNPs) are usually unsatisfactory in the lateral flow immunoassay (LFIA) for tracing targets. Polypyrrole nanoparticles (PPyNPs), known for their excellent optical properties, have a limited chemical surface, which is unsuitable for use in LFIA. PPyNPs@metal-phenolic materials (PMNPs) were designed to break the restriction, which were then applied in fluorescence quenching LFIA to detect fumonisin B1 (FB1). PMNPs, as an efficient fluorescence quencher, with strong absorption in the ultraviolet–visible region, had the molar extinction coefficient of 2.47 × 1011 M−1 cm−1 and 1.86 × 1011 M−1 cm−1 at 335 nm and 620 nm. Meanwhile, the quenching constant of PMNPs was 2.30 × 10−10, 23.6-fold higher than that of AuNPs. After the surface modification with the Au-TA structure, PMNPs exhibited higher hydrophilicity than PPyNPs, making them more favorable to antibody binding. Compared with AuNPs-mAb and PPyNPs-mAb, the PMNPs-mAb had a higher affinity constant and lower equilibrium dissociation constant. The visual limit of detection (vLOD) and LOD of the "turn-on" LFIA based on PMNPs were 25 ng mL−1 and 1.58 ng mL−1, which were 20-fold and 4.82-fold lower than that of AuNPs-LFIA, respectively. Furthermore, the method demonstrated satisfactory recoveries in detecting FB1 in food samples, confirmed by LC-MS.