Layer-by-Layer Assembly of Bio-functionalized Carbon Nanotubes for Rapid and Discriminate Detection of Organophosphate Neurotoxins

Abstract

Layer-by-layer assembly is a self-assembly nanofabrication technique that has been used to build electrochemical amperometric sensors to detect pesticides. Organophosphorus hydrolase (OPH) is an enzyme which catalyzes the hydrolysis of organophosphate compounds (e.g. pesticides and chemical warfare agents). Acetylcholinesterase (AChE) biosensors are traditionally used to detect neurotoxic compounds, which inhibit its ability to hydrolyze acetylcholine and acetylthiocholine. However, these biosensors suffer from non-selectivity; many different compounds are able to inhibit AChE activity. AChE and OPH have been immobilized onto carbon nanotubes to stabilize the enzymes and provide scaffolding support for sensor construction. Multi-analyte detection has been realized through the layer-by-layer assembly process by using multiple enzymes within the layers such as Glucose Oxidase and AChE. A multi-layered sensor shows the capability to discriminate between organophosphate neurotoxins and non-OP compounds, through comparison of the activity of AChE and the signal response from the products of OPH hydrolysis. Evidence is provided which suggests that OPH could be used in this fashion to protect acetylcholinesterase from OP compounds, preventing significant inhibition of AChE from up to 10^-4 M paraoxon.