A Class-Specific Enzyme-Linked Immunosorbent Assay Based on Magnetic Particles for Multiresidue Organophosphorus Pesticides

A magnetic particle-based enzyme-linked immunosorbent assay (mp-ELISA) to detect multiresidue organophosphorus pesticides (OPs) was developed and evaluated in parallel with a conventional competitive indirect ELISA utilizing the same pair of antibodies. The antibody was immobilized by chemical coupling on the ferroferric oxide nanoparticles coated with 3-aminopropyl triethoxysilane (APTES). Comparative studies demonstrated that mp-ELISA exhibited both significantly improved sensitivity and better class specificity than conventional ELISA, although the reproducibility and repeatability of the two assays were equivalent. As compared with data from the conventional ELISA, the averages of the midpoint inhibition (IC50) decreasing rate of mp-ELISA were 81.1 and 62.1% for the magnetic first antibody (MFA) and magnetic second antibody (MSA), respectively. The class specificity of MFA was broader than that of MSA. The results demonstrated the high potential of mp-ELISA based on the MFA as a tool to improve sensitivity and broad specificity in multiresidue immunoassay.