Development of a class-specific immunochromatographic strip test for the rapid detection of organophosphorus pesticides with a thiophosphate group

In recent decades, organophosphorus (OP) pesticides are widely used in agricultural and domestic fields. There is increasing demand for more rapid and economical methods of detecting pesticide residues. We have developed a gold immunochromatography assay (GICA) strip test for detecting a group of OP pesticides based on monoclonal antibodies (MAb) against a generic hapten, O,O-diethyl O-(4-carboxy-3-methylphenyl) phosphorothioate. The MAb showed desirable properties for use in indirect competitive ELISA, and the minimum IC50 value (93ng/mL) was observed in chlorpyrifos-ethyl curve. The partially purified monoclonal antibodies were conjugated with colloidal gold particles. The conjugation of the colloidal gold and antibodies was monitored by ultraviolet-visible (UV-vis) spectroscopy and fluorescence spectroscopy, while the transmission electron microscopy (TEM) images were used to characterize the particle size and shape of the conjugates. Dynamic light scattering (DLC) was applied as a less expensive and faster method to substitute TEM. The colloidal gold and antibody conjugates were used for the production of a GICA strip test to detect OP pesticides. Preliminary assessment suggests that the OP pesticide, chlorpyrifos-ethyl (CE), in environmental samples could be detected by the GICA strip. This assay could potentially be used for screening large volume of samples and on-spot monitoring before the precise analysis. But the homogeneity of the detection needs to be improved further.