In-situ synthesized porphyrinic zirconium MOF-derived multilayered nanocomposite probe for ultra-sensitive immunosensor.

Aflatoxin B1 (AFB1) is a major concern due to its widespread contamination and potential harm. Colorimetric lateral flow immunoassays (LFIAs) incorporating gold nanoparticles (AuNPs) are widely used for on-site analyte detection. However, it remains challenging due to the limited brightness of AuNPs. Herein, we introduce an immunosensor for highly sensitive AFB1 detection utilizing a multilayered nanocomposite probe (PCN-224@Fe3O4@PDA@Ab/HRP), created by sequentially modifying Fe3O4 nanoparticles, polydopamine layers, and horseradish peroxidase on a porphyrinic metal-organic framework, which offers magnetic separation, high signal brightness, and strong catalytic activity. Integrated with a competitive assay format, the immunosensor achieved ultrasensitive detection of AFB1, with a detection range of 0.003-3 ng/mL and a limit of detection (LOD) of 0.0014 ng/mL. Moreover, our immunosensor exhibited satisfactory recoveries and successful detection of AFB1 in cereal samples. Therefore, this work offers innovative strategies for designing multi-functional nanocomposite probes that enhance detection sensitivity, holding great promise in food safety monitoring.