Enzyme-linked immunosorbent assay for detection of organophosphorylated butyrylcholinesterase: a biomarker of exposure to organophosphate agents

A sandwich enzyme-linked immunosorbent assay (sELISA) has been developed for detection of organophosphorylated butyrylcholinesterase (OP-BChE), a potential biomarker for human exposure to organophosphate insecticides and nerve agents. A pair of antibodies specific to OP-BChE adduct were identified through systematic screening of several anti BChE antibodies (anti-BChE) and anti-phosphoserine antibodies (anti-P(ser)) from different sources. The selected anti-BChE (set as capture antibody) antibodies recognize both phosphorylated and nonphosphorylated BChE. These antibodies can therefore be used to capture both BChE and OP-BChE from the sample matrices. The anti-P(ser) (set as detecting antibody) was used to recognize the OP moiety of OP-BChE adducts. With the combination of the selected antibody pair, several key parameters (such as the concentration of anti-BChE and anti-P(ser), and the blocking agent) were optimized to enhance the sensitivity and selectivity of the sELISA. Under the optimal conditions, the sELISA has shown a wide linear range from 0.03 nM to 30 nM, with a detection limit of 0.03 nM. Furthermore, the sELISA was successfully applied to detect OP-BChE using in vitro biological samples such as rat plasma spiked with OP-BChE with excellent adduct recovery (z>99%). These results demonstrate that this novel approach holds great promise to develop an ELISA kit and offers a simple and cost-effective tool for screening/evaluating exposure to organophosphate insecticides and nerve agents.