Preparation of bright fluorescent metal-organic framework immunoprobes for highly sensitive lateral flow immunoassay...

Carbendazim, a broad-spectrum benzimidazole fungicide, is extensively applied in agriculture but poses carcinogenic risks due to its slow degradation and persistence in food. Rapid and sensitive on-site detection is therefore critical for food safety monitoring. Fluorescent metal-organic frameworks (MOFs) show significant potential for applications in fluorescent sensing; however, they have rarely been applied in lateral flow assay (LFA) for food safety monitoring so far.

Herein, we synthesized zirconium-based MOFs (ZrMOFs) using the AIE ligand and Zr⁴⁺ ions, achieving a high quantum yield of 40.6% and intense blue fluorescence. The ZrMOFs directly conjugated with antibodies via electrostatic adsorption without additional surface modification, forming stable immunoprobes. A ZrMOFs-based fluorescent LFA (FLFA) was constructed for carbendazim detection. Under optimal conditions, the assay exhibited a visual limit of detection (vLOD) of 10 ng/mL, which is 5-fold lower than that of traditional AuNP-LFA. Quantitative analysis gave an LOD of 0.46 ng/mL with a linear range of 0.5-10 ng/mL. The method showed excellent selectivity over six structurally related fungicides, good batch-to-batch reproducibility and storage stability (RSD <10%), and satisfactory recoveries (96.9-105.4%) in spiked Pisum sativum samples, consistent with ELISA results.

This work provides a convenient method for preparing fluorescent immunoprobes and a strategy for developing highly sensitive FLFA for small-molecule residues in food.