Desenvolvimento e caracterização de um novo material polimérico para aplicação em biossensores eletroquímicos na detecção de derivados fenólicos

Abstract

This work reports studies on the 2-hydroxyphenylacetic acid (2-HPA) electropolymerization over graphite electrodes in order to biomolecule immobilization for biosensor construction. The polymeric film formed over the graphite electrode was characterized piezoelectrically, spectroscopically, morphologically and electrochemically. The analysis pointed a redox peak relative area increase, suggesting a polymeric film formation with larger surface area for the 2-HPA modified electrode formed at 20mv.s-1, comparing to films formed in different scan rates. Polymeric films formation experiments were performed at different pH values from the monomeric solution due the monomer present different protonation states of phenol and carboxyl groups according the medium pH. These studies pointed that the polymer prepared in acid conditions favors the formation of a material with conductive properties. The polymers formed at different pH values presented two oxidation and two reduction waves, ordinary result to all studies performed. Analysis of atomic force microscopy showed that the films formed at different pH values show distinct morphological characteristics. The piezoelectric analysis pointed that during the polymer preparation in acid medium, a linear mass increase occurred, reaching a deposit material mass over the electrode of 477,60 ng at the end of 20 cycles. Poly(2-HPA) as well 2-HPA presented fluorescence high intensity and a bathochromic shift from the monomer to the polymer, pointing a polymeric chain formation with larger conjugation extent. The FTIR data suggests that electropolymerization produces a polymer with an oxygen atom from phenol hydroxyl group forming the bond between the aromatic rings. Poly(2-HPA) presented biocompatibility for horseradish peroxidase (HRP) enzyme immobilization since the bare graphite electrodes did not retained it during the flow analysis. However the polymeric film modified electrode containing the enzyme was stable for more than twenty injections. For HRP immobilization it was necessary to drive the electrode at a reduction potential in order to improve the incorporation response and minimize lixiviation. The poly(2-HPA)/HRP modified electrode presented response in guaiacol presence with detection limit of 1.89 mmol.L-1 and quantification limit of 6.31 mmol.L-1. The results showed that the biosensor can also be used in hydrogen peroxide analysis beyond the phenolic derivatives analysis.