A novel fluorescence based assay for the detection of organophosphorus pesticide exposed cholinesterase activity using 1-naphthyl acetate.

Acetylcholinesterase (AChE) is the primary target of organophosphorus pesticides (OPs). Ellman's method using Acetylthiocholine (ATCh) is the standard approach for the detection of AChE activity. Though ATCh is a popular substrate, it has certain drawbacks as well. Because of these limitations, there is a need for the development of reliable and rapid assays for determination of AChE activity in cases of OP poisoning. In the present work, we have used 1-Naphthyl acetate (1-NA) as a fluorogenic substrate for the estimation of AChE activity of human erythrocytes. It is well known that due to inter-individual variation in AChE activity, the baseline value cannot be correctly predicted. Therefore, using 1-NA, we have developed a rapid, sensitive and baseline free assay for the estimation of AChE activity. The assay is based on reactivation and fluorescence quenching using a cocktail of oximes for the determination of cholinesterase activity in a post-exposure sample. Moreover, it is free from interference due to oximolysis which is an established limitation of ATCh. We feel that such an assay using 1-NA has the potential to be explored at the point of care for rapid detection of OP poisoning.