Síntese e otimização dos parâmetros de eletroplimerização de ácido 2-hidroxibenzoico para o desenvolvimento de um biossensor para detecção de pesticidas

Abstract

The optimization of the parameters of electrochemical polymerization is an indispensable process in several applications as in the development of biosensors, which are most used in the most diverse areas such as environmental, food and health. Among the major difficulties in these studies are the high cost and conditioning of working electrodes, being circumvented in this work by the use of pencil carbon graphite electrodes. 2-hydroxybenzoic acid was the monomer chosen for cyclic voltammetry, yielding a polymeric film with carboxylic groups available for attachment to the enzyme alkaline phosphatase. Electrochemical and morphological studies were done to characterize the formed material. In the optimization the best values were 1.0 mM 2-hydroxybenzoic acid, 0.25M perchloric acid and 40 cycles. Experiments changing the pH value and scanning speed were used to propose a mechanism for electropolymerization. Four different forms of immobilization of the biomolecule were evaluated: adsorption on clean electrode, covalent bond on clean electrode, adsorption on modified electrode and covalent bond on modified electrode. Response analysis after immobilization was done by differential pulse voltammetry. The substrate 4-nitrophenylphosphate was evaluated by detecting the enzymatic reaction product, 4-nitrophenol. The system using covalent bond in modified electrode presented the highest response, showing to be an alternative for the development of biosensors for the detection of organophosphate pesticides.