Production and characterization of a monoclonal antibody against organophosphate pesticides for residue analysis

Immunoassay methods have been used as analytical tools for residue pesticide analysis of environmental samples recently. The immunoassay is a relatively simple, effective and low-cost analytical method and can be used for field testing. The basics of the immunoassay is a special reaction between an analyte and an antibody specific to this analyte. The key reagents are the polyclonal and/or monoclonal antibodies. In this study, the investigation focused on a monoclonal antibody's binding behavior to a low molecular weight organophosphate pesticide, paraoxon. Various factors governing the binding process were assessed using structural analogs of paraoxon. The results provided information which may be useful in development of an immunochemical method for residue analysis.; Two mice were immunized with amino paraoxon bovine serum albumin (BSA) conjugate. Hybrid cells were prepared by fusion of mouse's splenic cells with myeloma cells. One hundred and fifteen hybridoma cell lines were produced. From these 115 cell lines, four were found to secrete monoclonal antibodies against the organophosphate pesticide (paraoxon). A modified enzyme linked immunoassay (EIA) was developed. One of four cell lines which produced the most sensitive monoclonal antibody was selected for the binding study. A hypothetical binding model of this monoclonal antibody was proposed. It was assumed that this antibody might have four binding sites, the aromatic ring, the ethyl groups, the phosphoryl oxygen and the nitro group on the aromatic ring, based on the chemical structure of paraoxon. These binding sites were explored using various analogs of paraoxon. Each analog had a particular structural character. The results indicated that the aromatic ring of paraoxon was a major determinant and the ethyl groups were also important. The phosphoryl oxygen and the nitro group affected the antibody's binding weakly or not at all. It was found that the antibody's binding power was much affected by the molecular shape of the analyte. Binding decreased significantly for test compounds whose shapes were different from that of paraoxon or parathion, even if this difference was slight.; The antibody cross-reacted with parathion but it did not significantly cross-react with the pesticides, diazinon, ethion, disyston, EPN, trithion and chlorpyrifos oxon. This antibody can be used as a reagent to detect paraoxon and parathion in residue analysis.