Direct and discriminative detection of organophosphate neurotoxins for food and agriculture products

Abstract

Organophosphate neurotoxins are well known as a class of acute toxins with significant immediate and delayed impacts on human health. There is a growing need for the development of simple and reliable methods for the identification and detection of neurotoxins (both pesticides and agents of warfare or terrorist activity) in agriculture and food industry. We used the ability of the class of enzymes known as organophosphate hydrolases (OPH) to selectively hydrolyze the various phosphotriester neurotoxins to develop “kinetic-mode” biosensors for specific detection and discrimination of these compounds. Here we presented an example of organophosphorus hydrolase functionalized CNT conjugates provided the platform for direct amperometric detection of paraoxon, a model organophosphate. For biosensor development we used an easily renewable nanocomposite interface based on layer-by-layer (LbL) assembled cationic/anionic layers of carbon nanotubes customized with biopolymers. A simple approach was developed to fabricate a nano-scale structure composed of alternating layers of oxidized multiwalled carbon nanotubes upon which was immobilized either the cationic enzyme organophosphorus hydrolase (OPH) (MWNT-OPH) or the anionic DNA (MWNT-DNA). This approach results in a biosensor with excellent sensitivity, a reliable calibration profile, and stable electrochemical response. Additionally, organophosphate hydrolase may be used in combination with acetylcholine esterase (AChE), to realize a new strategy for the detection and discrimination of neurotoxins from different classes.