Biosensors for V-type nerve agents

Organophosphorus (OP) compounds are among the most toxic substances. They are widely used as pesticides, insecticides and chemical warfare agents. Many of these insecticides, malathion, demeton-S, acephate, azinophos-ethyl, and phosalone, are phosphorus thiolesters, which are widely used in insect pest management for crop production, municipal hygiene and disease control. VX, the highly lethal chemical warfare agent (CWA), also belongs to the phosphorus thiolester family. Because of their wide spread use, their occurrence in the environment and the risks that they pose, there is an urgent need for their selective, sensitive and rapid detection to protect our water supply, food and the environment.; Biosensor technology is well-suited to satisfy the demands for on-site environmental monitoring and the rapid detection of OP compounds. In this dissertation, first, a highly sensitive and selective transducer for thiol was developed based on pyrroloquinoline quinone (PQQ encapsulated sol-gel and carbon nanotubes (CNT) modified electrode as a prerequisite for the development of a novel biosensor for OP compounds. The CNT based transducer was then combined with the enzyme acetylcholinesterase (AChE) for the development of a highly sensitive and easily designed biosensor for OP compounds.; Inhibition enzyme electrodes based on the modulated biocatalytic activity of AChE have excellent sensitivity, but they have a number of limitations including poor selectivity, irreversible response, or a multistep protocol (involving a substrate addition, incubation and regeneration of the enzyme). To develop a rapid and direct sensor for OP compounds---such as the highly toxic and persistent V-type nerve agents, a mutant of the enzyme organophosphorus hydrolase (OPH) showing improved activity for these compounds was employed. The CNT based mediator free, membrane free biosensor developed was very sensitive, selective, fast and enabled low cost, field deployable detection of OP thiol esters.