Detection of pesticides in the environment using biosensors based on cholinesterases

Amperometric biosensors based on acetylcholinesterase or butyrylcholinesterase were used for the kinetic determination of organophosphate and carbamate pesticides. The current of the biosensor I-ss was measured continuously with substrate; the addition of samples with pesticides resulted in the time decrease of the current dl/dt. The relative inhibition RI = (dl/dt)/I-ss was used as the signal for evaluations. For several pesticides, different calibration curves (dependencies of RI on concentration c) were obtained depending on the affinity of the individual pesticide to the cholinesterase used. This affinity was described using the bimolecular inhibition constant k(i). The single calibration curve independent on the type of pesticide was obtained as the dependence of RI on the product k(i)c, thus indicating the effects of both concentration and inhibiting properties on the response of the biosensor. The relative inhibition was used to characterise anticholinesterase toxicity of the sediments collected from the Morava River and its tributary streams. The influence of both point (large cities) and nonpoint (agriculture) sources of pollution was identified.