Sol-gel-entrapped cholinesterases: A microtiter plate method for monitoring anti-cholinesterase compounds

Herein is reported the successful entrapment of three esterase enzymes within silica, by means of the sol-gel process. The enzymes were acetylcholinesterase (AChE) from electric eel (ee), AChE from bovine erythrocytes (er), and butyrylcholinesterase (BChE) from horse serum. Enzyme entrapment was carried out in a novel configuration by casting the doped sol-gel material in 96-well microtiter plates. The study determined the apparent kinetics of the activity and inhibition of the three entrapped enzymes and elucidated the optimal sol-gel matrix composition and preparation procedure. The enzyme mode of action within the sol-gel matrix was compared with that obtained in solution, under various experimental conditions. The activity of entrapped ee-AChE was found to depend on the concentration of the entrapped enzyme and on the sol-gel preparation procedure and composition. It was found that whereas the activity of ee-AChE was 3-4-times lower than that in solution, one gained significantly higher stability. The entrapped enzymes were sensitive to various organophosphates and to the carbamate carbaryl, with inhibition patterns similar to those obtained in aqueous reactions.