Evaluation of colloidal and polymeric routes in sol-gel synthesis of a bioactive glass-ceramic derived from 45S5 bioglass

This work studied the influence of two sol-gel synthesis routes in obtaining a bioactive glass-ceramic derived from the 45S5 composition: a polymeric and a colloidal route. The main difference between the routes is in the silica precursor employed. The tetraethyl orthosilicate metal alkoxide (Si(OC2H5)(4) - TEOS) is used in polymeric route and the silicic acid (H4SiO4) was used in the colloidal route. The synthesized xerogels were calcined at different temperatures to eliminate undesirable compounds and to verify the crystallization behavior. Afterwards, the calcined xerogels were submitted to in vitro bioactivity assay. The samples were also characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and laser diffraction. After calcination, the glass-ceramics obtained by the colloidal route showed greater number of bioactive phases and, consequently, of NBO bonds. The larger amount of NBO bonds resulted in a higher bioactivity of the materials synthesized by the colloidal route. In addition, the long hydrolysis step of the metal alkoxides was eliminated with colloidal synthesis. This allowed a significant reduction in the total synthesis time from 13 days to 24 h. To the best of our knowledge, this seems to be the first time this colloidal route has been employed in the synthesis of bioglass 45S5.