Desenvolvimento e caracterização de filmes de poli(ácidos hidroxifenilacéticos) para aplicação na biodetecção de Neisseria meningitidis e Anaplasma marginale

Abstract

In this study we investigated the electropolymerization isomers hydroxyphenylacetic acid, for their application in the construction of polymeric systems, by immobilizing synthetics molecules for development of biological sensors. The graphite electrodes electrochemically modified were characterized for morphology and electrochemical behavior showing that the poly(2-hydroxyphenylacetic acid), poly(3-hydroxyphenylacetic acid) and poly(4-hydroxyphenylacetic) are electroactive, and the latter showed a lower yield in electrosynthesis in agreement with the images of atomic force microscopy showed that the surface of graphite electrodes were changed less with this material compared to its isomers. The electrochemical impedance spectra of poly (4-hydroxyphenylacetic acid) showed that this material is more resistive with respect to its other isomers which are more conductive in accordance with the values of current and voltage shown by tests ion exchange the probes positive and negative. The ratio between the masses electrodeposited and the loads required to carry out the redox process these materials remained constant demonstrating that the same number of electrons are involved in reduction and oxidation of these materials according to the diagnostic reversibility applied by cyclic voltammetry are unanimously reversible systems, however poly(3-hydroxyphenylacetic acid) was more stable during repeated cycling electrochemically in perchloric acid. The optimized tridimensional structures justify the electrochemical and morphologic behavior of these three platforms, wherein the poly(2-hydroxyphenylacetic acid) and poly(3-hydroxyphenylacetic acid) have structures with a more ordered arrangement, unlike poly(4-hydroxyphenylacetic acid), which has a rather more disordered structure and therefore more resistive, while isomers are more conductors. The mechanistic proposal begins with the anodic oxidation of monomers whose square wave voltammetry experiments showed the loss of an electron. The couplings between cation radicals promote a formation of ether leaving the acetate groups exposed on the structure. The pairing occurs between the phenolic oxygen and carbon of the aromatic ring whose potential were studied by spin density and consistent with the resonance structures of the cation-radical that are in the suggested mechanisms. In tests incorporation of nitrogenous bases found that poly(3-hydroxyphenylacetic acid) also proved more effective in the retention of the same and for this reason associated with their better electrochemical behavior described above, it was selected among others for applying isomers polimeric systems by immobilizing synthetics molecules by physical adsorption. In the first system froze synthetic oligonucleotides that mimic fragments of DNA from the bacterium Neisseria meningitidis able to recognize their genomic DNA in samples of pure cultures by differential pulse voltammetry and electrochemical impedance spectroscopy, and this latter showed a better response sensitivity signal in relation to the increasing concentration of the target. In the second system, there immobilization of synthetic peptides compatible to the cell membrane of Anaplasma marginale able to selectively recognize antibodies in their sera samples from cattle. The images made by atomic force microscopy of the two procedures backing the effective recognition of both polimeric systems developed for the detection of Neisseria meningitidis and Anaplasma marginale bacteria causing bacterial meningitis and bovine anaplasmosis, respectively.