Gold-based immunochromatographic strip assay for detecting dimethomorph in vegetables†
Dimethomorph (DMM) is a novel therapeutic fungicide, which is mainly used to control downy mildew, phytophthora, and other fungal diseases of grapes, leeks, and cucumbers. Its residue is harmful to the human body and the soil environment. In this study, the optimum monoclonal antibody (mAb) against DMM was prepared after routine fusion and selection. Based on the mAb, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a gold nanoparticle immunochromatographic assay (GNP-ICA) were developed for detecting DMM in leek samples. The 50% inhibitory concentration (IC50) of the mAb was 1.823 ng mL−1, and its cross-reactivity with structurally related analogs was less than 3%. Under optimal conditions, the visible detection limit of this ICA method was 10 ng g−1, and the cutoff value of DMM in leeks was 100 ng g−1. The analysis of DMM in leeks showed that the results of the strip analysis were highly comparable with those of ic-ELISA and liquid chromatography–mass spectrometry LC-MS. Therefore, the GNP immunoassay is a sensitive screening method for detecting DMM residues in foods.