ESTUDO DE VIDROS BOROFOSFATOS DO SISTEMA B₂O₃–P₂O₅– CaF₂–Na₂O MODIFICADOS COM K₂O E Li₂O PARA APLICAÇÕES COMO BIOMATERIAIS REGENERATIVOS: Da síntese aos testes in vitro

Abstract

The development of bioactive materials is guided by the continuous demand for effective solutions for tissue repair and regeneration, especially in cases of bone diseases, trauma, or infections. In this context, the incorporation of elements with physiological importance constitutes a promising strategy to adjust properties such as bioactivity, degradation rate, and cytocompatibility. This work aimed to synthesize and characterize borophosphate glasses with the composition 50B2O3–20P2O5–15CaF2–(15–x)Na2O–xMO (MO = K2O or Li2O, between 0– 15 mol%), using the melt-cooling method, to evaluate their potential as biomaterials. The study was developed in two stages. In the first, the progressive substitution of Na2O by K2O (0–15 mol%) was investigated, evaluating its effects on physical, structural, vibrational, and thermal properties, as well as on in vitro bioactivity behavior and cytocompatibility. In the second stage, the partial substitution of Na2O by Li2O (0–10 mol%) was analyzed, focusing on the physical, structural, thermal, mechanical, and bioactive properties of the glasses, as well as cytocompatibility and antibacterial activity. The samples were characterized by volumetric density, molar volume, oxygen packing density (OPD), powder X-ray diffraction (PXRD), FTIR spectroscopy, DTA, DSC, SEM-EDS, and Vickers microhardness (Hv). In vitro assays included bioactivity tests in SBF solution for 28 days, cell viability, and antibacterial activity. In the glass series containing K2O, structural expansion, depolymerization of the glass network, increased glass transition temperature (Tg), and high thermal stability were observed. Higher concentrations of K2O promoted increased reactivity in SBF and rapid formation of calcium phosphate and boric acid phases. Compositions containing both Na2O and K2O exhibited nonlinear behavior in the N4 fraction, indicating the occurrence of the mixed alkali effect (MAE). Furthermore, increasing K2O improved bioactive behavior, and the simultaneous presence of alkali oxides in the network favored cell viability. For the glass series containing Li2O, the occurrence of MAE was also observed in the physical properties, structural depolymerization, accompanied by a reduction in Tg. Increasing the Li2O concentration resulted in an increase in Vickers microhardness (Hv), indicating improved mechanical strength of the glasses. All compositions containing Li2O showed bioactivity, confirmed by PXRD and FTIR, and antibacterial activity. Finally, the results demonstrate that incorporating different alkali oxides in the structure of borophosphate glasses is a promising strategy for adjusting structural, mechanical, and bioactive properties, highlighting the potential of these glasses for applications as regenerative biomaterials.