Development of Peptide Nanotube-Modified Biosensors for Gas-Phase Organophosphate Detection

• Main Author: Baker, Peter A
• Format: Report
• Language: English
• Subjects: ACETYLCHOLINE; ACETYLCHOLINESTERASE; Biochemistry; BIOLOGICAL DETECTION; CALIBRATION; CARBON NANOTUBES; CATALYSIS; CHEMICAL AGENT DETECTION; CHEMICAL AGENT DETECTORS; Chemical, Biological and Radiological Warfare; CHOLINESTERASE BIOSENSORS; CONCENTRATION(COMPOSITION); ELECTRODES; ENZYMES; GAS CHROMATOGRAPHY; HYDROLYSIS; MALATHION; Miscellaneous Detection and Detectors; NANOSTRUCTURES; NERVE AGENTS; ORGANOPHOSPHATE DETECTION; ORGANOPHOSPHATES; OXIDATION; PEPTIDE NANOTUBES; PEROXIDASES; THESES; THIOCHOLINE; VAPOR PHASES; VOLTAMMETERS; VOLTAMMETRY

Vapor-phase detection of the model organophosphate malathion was achieved using enzymes encapsulated in peptide nanotubes and attached to gold screen-printed electrodes. Malathion was chosen as the model for this experiment because its binding mechanism with acetylcholinesterase (AChE) is identical to its more potent counterparts (such as sarin or VX), but it has an extremely low human toxicity, which makes it both practical and easy to use. The peptide nanotubes had horseradish peroxidase encapsulated inside and were coated with both acetylthiocholine (ASCh) and AChE on the outside. ASCh hydrolysis, which produces thiocholine, was catalyzed by the AChE. The thiocholine was then oxidized by the electrodes to produce a signal that could be measured by a cyclic voltammeter. This signal was inhibited in the presence of malathion vapor, with the extent of inhibition proportional to the malathion concentration. A calibration curve was first established in order to determine the concentration of malathion vapor in a given environment using standards of known concentrations of liquid malathion in a gas chromatograph. Once the vapor concentration was established, peptide-nanotube-modified, gold screen-printed electrodes were used to detect organophosphate vapor. The nanotube-modified electrodes were exposed to both AChE and ASCh and inserted into an airtight vial with a known concentration of malathion. Cyclic voltammograms were taken at each step to monitor the changes in activity. This research demonstrates the ability to use nano-modified biosensors for the detection of organophosphate vapor, an important development in countering weaponized organophosphate nerve agents and detecting commercially-used pesticides. The original document contains color images.