Development of a monoclonal antibody-based immunoaffinity chromatography and a sensitive immunoassay for detection of spinosyn A in milk, fruits, and vegetables

Spinosad has been extensively used for insect control in agricultural crops. In the present study, a novel succinic derivative of spinosyn A as the hapten was synthesized, and an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed using a new monoclonal antibody (designed as mAb3E6) specifically against spinosyn A. A mAb3E6-based immunoaffinity column was developed for enrichment extraction of spinosyn A and reduction of matrix interference. The half maximum inhibitory concentration and limit of detection (LOD) of the icELISA were 4.11 ng/mL and 0.63 ng/mL, respectively. The icELISA had average fortified recoveries from 78.1% to 103.2% and the validation results correlated well with high-performance liquid chromatography. The mAb3E6 showed cross reactivity of 80.4%, 75.7% and less than 0.1% with spinosyns B, D and other macrolides, respectively. Interactions of the antibody and macrolides were further analyzed by molecular docking. The developed immunoaffinity chromatography-assisted icELISA is potentially a sensitive and convenient tool for monitoring spinosad residues in milk, fruits, and vegetables.