A multimodal lateral flow immunoassay driven by a “all-in-one” Au@Pt@ZIF-8 nanocomposite for trace monitoring of 3-phenoxybenzoic acid

A “all-in-one” nanolabel APZ was constructed. • High Nbs coupling, dual spectral overlap, visible absorption, pH-triggered catalysis. • The three orthogonal signals enhance reliability and enable flexible applicability. • ZIF-8 “enrichment–confinement–pH-triggered collapse” synergy boosts catalysis. • Stabilize Au Pt heterostructure via ZIF-8–enabled physical isolation and protection. Conventional lateral flow immunoassay (LFIA) suffers from limited sensitivity due to single-signal readout, low antibody conjugation efficiency, and steric hindrance associated with bulky conventional antibodies. Herein, we developed a multimodal LFIA employing Au@Pt@ZIF-8 (APZ) as a multifunctional nanolabel, prepared by encapsulating flower-like Au@Pt nanoparticles (Au@Pt NPs) within a ZIF-8 framework. Benefiting from its high specific surface area and mesoporous structure, APZ significantly enhanced the coupling efficiency and stability of anti-3-phenoxybenzoic acid nanobodies (3-PBA Nbs), achieving a coupling efficiency of 94.75% under identical conditions, compared with 69.61% for Au@Pt NPs. APZ further exhibits a broad absorption spectrum, fluorescence quenching due to dual spectral overlap, and high catalytic activity arising from the intrinsic peroxidase-mimicking activity of Au@Pt, synergistically enhanced by ZIF-8 enrichment/confinement and pH-triggered framework collapse. These features enabled the integration of three orthogonal readout modes, namely aggregation-induced coloration, catalysis-induced chromogenesis, and fluorescence quenching, into a single test strip. The resulting multimodal APZ-LFIA attains limits of detection (LOD) for 3-PBA of 0.004 ng/mL, 0.001 ng/mL, and 0.0003 ng/mL, respectively. By integrating multiple complementary signals, this strategy offers a flexible and reliable platform for trace 3-PBA analysis and shows great promise for on-site food safety monitoring. Download: Download high-res image (87KB) Download: Download full-size image