Acetylcholinesterase in organic solvents for the detection of pesticides: Biosensor application

Abstract

Acetylcholinesterase (AChE) from electric eel, in a free or immobilized state, can be used for the detection of insecticides. This system is convenient because of the selectivity and specificity of the inhibition of AChE by organophosphorus and carbamate insecticides. However, these pesticides are highly soluble only in organic solvents. This article deals with the determination of the activity of AChE in organic solvents. Firstly, the effect of different organic solvents on activity was determined using the free enzyme. The AChE activity was maintained using the free enzyme. The AChE activity was maintained depending on the nature of the solvent. The results were applied to the biosensing system and a new method for the detection of organophosphorus and carbamate insecticides was developed. A correlation between the AChE activity and a physico-chemical parameter, was found in order to predict the effect of the solvent on enzyme activity. Upon comparison of the correlation curve obtained with free and immobilized enzyme, it appeared that immobilization enhanced the stability of the enzyme and increased the number of usable organic solvents. The inhibition of AChE by organophosphorus and carbamate insecticides was tested in organic solvents and the limit of detection determined. The inhibitory capacity of AChE was maintained in most organic solvents. The reactivation of immobilized enzyme with 2-pyridine aldoxime methiodide (2-PAM) allowed the repeated use of the same enzyme electrode. The application of the biosensor for the detection of organophosphorus and carbamate insecticides in organic solvents using chemical knowledge will be useful for the detection of pesticide residues present in water and food at very low levels.