Broad-specificity immunoassay for O,O-diethyl organophosphorus pesticides: Application of molecular modeling to improve assay sensitivity and study antibody recognition

Authors: XU, ZHEN-LIN - South China Agricultural University; SHEN, YU-DONG - South China Agricultural University; ZHENG, WEN-XU - South China Agricultural University; Beier, Ross; XIE, GUI-MIAN - South China Agricultural University; DONG, JIE-XIAN - South China Agricultural University; YANG, JIN-YI - South China Agricultural University; WANG, HONG - South China Agricultural University; LEI, HONG-TAO - South China Agricultural University; SHE, ZHI-GANG - Sun Yat-Sen University; SUN, YUAN-MING - South China Agricultural University

Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2010
Publication Date: 10/19/2010
Citation: Xu, Z., Shen, Y., Zheng, W., Beier, R.C., Xie, G., Dong, J., Yang, J., Wang, H., Lei, H., She, Z., Sun, Y. 2010. Broad-specificity immunoassay for O,O-diethyl organophosphorus pesticides: Application of molecular modeling to improve assay sensitivity and study antibody recognition. Analytical Chemistry. 82:9314–9321.

Interpretive Summary: Organophosphorus pesticides (OPs) have been widely used in agricultural and domestic applications for more than six decades. However, OP intoxication can occur in humans and animals. We have developed antibodies that recognize a broad-group of eight commonly used OPs. Antibodies are substances that are produced by the immune system in response to foreign substances that enter the body. Once the antibodies to a foreign substance are isolated, they can be used in a method to detect the presence of that foreign substance. The antibodies that we isolated may be used in an easy-to-use test called an enzyme-linked imunosorbent assay, or ELISA, for broad-specificity detection of eight OPs. A broad-specificity ELISA is an analytical method that can identify more than one target and detect positive samples among hundreds of negative samples in one simple test. A broad-specific determination of pesticides can be a very cost-effective way of pre-screening hundreds of samples prior to more expensive confirmatory methods. This method could be an attractive approach for a broader pesticide monitoring program that is needed worldwide. Also, a computer model was constructed using molecular parameters of the OPs tested to help study how the antibody recognized the OPs. The results from this computer model allowed improvements to be made in the assay, which helped make it more sensitive.

Technical Abstract: A monoclonal antibody (MAb) against 4-(diethoxyphosphorothioyloxy)benzoic acid (hapten 1) was raised and used to develop a broad-specificity competitive indirect enzyme-linked immunosorbent assay (ciELISA) for 14 O,O-diethyl organophosphorus pesticides (OPs). Computer-assisted molecular modeling was used to model two-dimensional (2D) and three-dimensional (3D) quantitative structure-activity relationships (QSARs) to study antibody recognition. Based on insights obtained from the QSAR models, two heterologous coating haptens, 4-(diethoxyphosphorothioylamino)butanoic acid (hapten 2) and 4-(diethoxyphosphorothioyloxy)-2-methylbenzoic acid (hapten 3) were designed, synthesized, and used to develop heterologous ciELISAs with significantly improved sensitivity. The heterologous ciELISA using hapten 2 as the coating hapten showed good sensitivity in a broad-specific manner for eight O,O-diethyl OPs, and may be used as a screening method for the determination of these OPs. Our studies demonstrated that molecular modeling can provide insights into the spatial and electronic effects of molecular structures that are important for antibody activity, which can then be used to improve immunoassay sensitivity.