Preparo, caracterização e estudo da bioatividade de compósitos de hidroxiapatita – vidro borato bioativo

Abstract

Composites of hydroxyapatite (HA) and bioactive borate glass doped with silver, of composition 59.5B2O3-2P2O5-9.5CaO-19.5Na2O-9CaF-0.5Ag2O (% in mol) were studied, with the aim of exploring the combined action of compatibility and stability of HA as an initial structural reinforcement, combined with the dissolution kinetics and quick conversion of borate glass to apatite in order to assess whether these composites can serve as an inducing substrate for bone self-regeneration and/or allow the replacement of damaged. The composites were prepared from powders of precursor materials in proportions of 25% and 50%, in mass, of glass, thermally treated at 530 ºC and 1000 ºC and had their bioactivity, in vitro, evaluated in periods of 14 and 28 days of immersion in simulator body fluid. At 530 ºC the amorphous nature of the glass is preserved and the analysis of diffractograms and FTIR spectra indicates the predominance of the apatite structure without the formation of additional phases. At 1000ºC, NaCaPO4 appears as an additional phase resulting from the heat treatment, and, in all composites, the characteristic structure of HA is confirmed by X-ray diffraction, before and after bioactivity testing in a simulator body fluid. At this temperature of 1000 °C, ionic substitutions occur in the HA structure with changes in its hydroxylation, from the incorporation of borate groups in OH- and PO4³ 3- sites, which ware confirmed by the FTIR spectra and allow to indicate boroapatite formation. The diffractograms of composites containing 50% glass and thermally treated at 530 °C showed the silver chloride phase even after 28 days of immersion in a simulator body fluid, indicating greater potential, among the composites and conditions studied, of antibacterial action. The analysis of diffractograms, FTIR spectra, pH measurements and the crystallinity index calculated by the FTIR technique for HA showed the bioactive behavior of composites thermally treated at 530 ºC and of boroapatite obtained from composites thermally treated at 1000 ºC. The studied composites showed bioactive behavior, in vitro, and therefore, have the potential to be used as biomaterials in bone treatment; and the composite containing 25% of glass and thermally treated at 1000 ºC, longer in days of immersion to stabilize the measured pH value, indicating a more controlled interaction or resorption of the resorbable phase after immersion in a simulator body fluid.