Hydrazone molecules as mimics for acetylcholinesterase. A new route towards disposable biosensors for pesticides?

Acetylcholinesterase has been widely used in the development of biosensors for pesticide detection. However, there are few reports approaching the application in real samples, mainly due to the low stability, high cost and lack of enzymatic activity by pesticides adsorption. An alternative is the replacement by a low cost molecule that mimics the enzymatic behavior and allows the development of disposable devices, as those used for glucose evaluation in human blood. In this study, different hydrazone molecules were synthesized and tested as mimics for the acetylcholinesterase enzyme. Their actions in the hydrolysis of acetylthiocholine were demonstrated by UV–vis absorption measurements. The nucleophilic reaction was characterized by FTIR and the reaction products (acetate and thiocholine) identified. The mimetic behavior was confirmed comparing the kinetic of the hydrolysis reaction of 4-[(1E)ethanehydrozanoyl]benzoic acid to that of other molecules as cyclopropyl methyl ketone hydrazone, 3-methyl-2-butanone hydrazone and hydrazine. The proposed molecules catalyzed acetylthiocholine hydrolysis being the 4-[(1E)ethanehydrozanoyl]benzoic acid faster than anyone else. Computational studies showed the substrate is attracted by the aromatic ring followed by the nucleophilic attack through the hydrazone group. This mimetic molecule can be used in order to develop a disposable biochemical sensor to be applied in the determination of acetylcholine or in the indirect determination of organophosphorous or carbamate pesticides.