Development of a novel electrochemical pesticide sensor

Project Summary/Abstract Organophosphate and carbamate (OPaC) compounds account for the largest class of pesticides in the world and accumulate in the environment and food chain. OPaCs cause toxicity by interacting with the acetylcholinesterase enzyme (AchE), which inhibits acetylcholine (ACh) hydrolysis. This results in the buildup of ACh in nerve synapses and can lead to uncoordinated movements, tremors and paralysis making them a major public health concern. In turn, domestic and international governmental agencies have instituted regulatory limits and guidelines to closely monitor OPaC residues to protect the population from unintended excessive exposure which can negatively impact health. To ensure these limits and guidelines are met and enable simple testing by laboratories, sample collection personnel, first responders, warfighters, and concerned citizens it is important to have the methods and kits available to rapidly, cheaply, quickly and easily monitor their concentration on-site. The methods for monitoring OPaCs are not currently sufficient to enable on-site, rapid, easy to use, and low- cost screening applications. For example, low throughput, time consuming, expensive, and highly technical methods for detecting OPaCs may be performed with the help of analytical equipment such as liquid chromatography, mass spectroscopy or gas chromatography. These instruments are extremely expensive and are not practical for screening large numbers of samples. On the other hand, enzymatic test kits utilizing Elman’s reaction, while less expensive, also require technical staff, expensive equipment, a laboratory, and thus can’t be performed on-site. We intend to solve these limitations by developing a low-cost, rapid, highly sensitive, portable, user-friendly electrochemical biosensor that uses recombinant AChE derived from ticks. Our tick derived AChE has several key benefits over vertebrate AChE. As opposed to vertebrate AChE which needs to be purified from source animals (e.g. eel) tick AChE can be produced with recombinant protein expression techniques and can be made reliability. Vertebrate AChE derived from eel also lose activity quickly while the tick enzyme is stable and amendable for use in an electrochemical biosensor assay. Lastly, the tick derived AChE is more sensitive to OPaCs than their vertebrate counterparts and therefore, due to these reasons, a superior enzyme to be used in an electrochemical biosensor. Our Phase I efforts will create a truly novel portable electrochemical assay for the sensitive and selective detection of OPaC compounds with several important advantages over currently available tools including convenience, robustness and simplicity.