Biossensor potenciométrico para a determinação de pesticidas inibidores da Acetilcolinesterase

Abstract

It was investigated in this work the use of ruthenium dioxide film (RuO2) as a potentiometric transducer of an enzymatic biosensor based on acetylcholinesterase (AChE). Electrodes of nominal composition Ru]Ti0O2 (100% RuO2 m/m) and Ru0,3Tio,702 (30% RuO2 m/m) had been prepared by the immobilization of RuO2 on the titanium support, by thermal decomposition, at 450 °C, of chloride precursors mixture solution, which was previously spilled on titanium surface. The equilibrium potential of both electrodes, 30% RuO2 and 100% RuO2, in KNO3 0.1 mol L'1, is in according to the solid State transition of redox pair Ru (IV) / Ru(III), that occurs with the participation of H+. The results had shown that both RuO2 electrodes enable fast measurements for small variations in the acetic acid concentration, either in solution of KNO3 0.1 mol L'1 as in 2.0 x 10'3 mol L phosphate buffer Solutions. The AChE enzyme from electric eel was immobilized on the surface of 100% RuO2 electrode by a glutaraldehyde in vapours and bovine serum albumin cross-linking procedure. The biosensor has shown good sensitivity for the acetic acid produced in the enzymatic hydrolysis of acetylcholine chloride, in the 5.0 x 10'3 mol L'1 phosphate buffer (pH 7.3). The calibration graph was linear from 1.0 x 10'4 to 1.0 x 10'1 mol L’1 of acetylcholine chloride. The stability of the biosensor was high and even after repetitive use for tree months the biosensor retained 80% of its original response. Inhibition studies of the biosensor by parathion methyl as a model organophosphate pesticide was investigated. Incubation of the biosensor for 10 min in parathion methyl solution resulted in a calibration plot of the inhibition versus the log of parathion methyl that was linear over range 5.0 x 10’8 to 1.8 x 10'7 mol L'1. The results have shown that the biosensor can be used to detect organophosphate pesticides in real samples.