Development of a monoclonal antibody-based ELISA and lateral flow immunoassay for the sensitive detection of fluroxypyr in corn

Fluroxypyr (FLU) is a widely used synthetic auxin-type herbicide. FLU residues in agricultural products pose potential risks to the environment and human health. Therefore, the development of rapid and sensitive fluroxypyr detection methods is highly important. In this study, a monoclonal antibody, 11D8 (mAb-11D8), capable of specifically recognizing FLU, was obtained via hybridoma technology. This antibody has a heavy chain subtype of IgG3 and a light chain subtype of κ, with a half-maximal inhibitory concentration (IC50) of 1.95 ng mL−1 and a linear detection range of 0.67–8.09 ng mL−1. Molecular docking revealed that SER L:44, TRP H:104, and LEU H:4 are predicted to be the key residues of mAb-11D8 involved in the recognition of FLU via hydrogen bonding. Two immunoassays, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a colloidal gold lateral flow immunochromatography assay (LFIA), were established for FLU detection. The LOD in the corn samples was 56.0 ng mL−1 for ic-ELISA and 180.8 ng mL−1 for LFIA. In spiked recovery experiments using corn samples, the recovery rates for ic-ELISA ranged from 87% to 92%, whereas the LFIA method yielded recoveries of 81–102%. These results were highly consistent with those obtained via liquid chromatography-tandem mass spectrometry validation. The results demonstrate that both developed immunoassays are suitable for the rapid, sensitive, and quantitative detection of FLU residues in corn.