Preparation of an anti-thiamethoxam monoclonal antibody for development of an indirect competitive enzyme-linked immunosorbent assay and a colloidal gold immunoassay

In this study, we developed an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) for determination of thiamethoxam residues. We prepared a specific highly sensitive monoclonal antibody (mAb) based on a thiamethoxam-derived hapten. After mouse immunisation and cell fusion, we obtained three monoclonal cell lines: 3B2, 3G6, and 4D2. The antibodies produced by cell line 4D2 had the highest affinity and sensitivity. The half-maximal inhibitory concentration was 0.87 ng/mL, and the cross-reactivity was <1%. We optimised the ic-ELISA method and the optimal conditions for ic-ELISA consisted of pH 7.4, 0.8% NaCl, and 0% methanol in PBS buffer. Using this mAb, an ic-ELISA and immunochromatographic strip (ICS) assay were used to detect thiamethoxam residues in cucumbers. The working range of ic-ELISA was 0.5-1.7 ng/mL, and the cut-off vaule of the ICS was 10 ng/mL. The recovery of thiamethoxam in cucumber samples ranged from 89% to 97%. Both methods can serve as rapid tools for the detection of thiamethoxam in vegetables.