Bioactivity evolution of calcium-free borophosphate glass with addition of titanium dioxide

• The titanium dioxide was added in calcium-free bioactive borophosphate glasses.
• Structural rearrangements take place in the main phosphate network.
• The TiO2 content influences the growth of the apatite-like layer.

The addition of titanium dioxide in the bioactive phosphate glass composition is intended to control the rate of dissolution, but nevertheless, the TiO2 presence may affect the glass bioactivity. Therefore, in this study the bioactivity response of the calcium-free borophosphate glasses by varying the titania content was evaluated. The glass system belonging to the compositional range (100 − x)[10B2O3·30Na2O⋅60P2O5]·xTiO2, with 0 ≤ x ≤ 12 mol%, was obtained by the conventional melt quenching method and the structural changes were assessed by performing X-ray diffraction, Raman and Fourier Transform Infrared measurements. The Raman and Fourier Transform Infrared spectra show the presence of TiOP bonds once the titania was added to the glass composition. This result indicates that structural rearrangements take place in the main phosphate network due to the replacing of POP by TiOP bonds. Regarding in vitro assessment of bioactivity, the results obtained by analysing the information derived from X-ray diffraction, Fourier Transform Infrared, Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy point out that the increase of titanium dioxide content has as consequence the occurrence of a more pronounced apatite layer. However, in the case of the samples with the highest TiO2 content, the crystallization of apatite layer does not occur in the first 14 days. The solubility test data indicated a clear decrease of glass solubility for titania amounts of 8 and 12 mol%.