| dc.description.abstract | Objective: Bioactive silicate glass-based Perioglas® has been used to treat periodontal-bony-defects. During glass degradation in body fluids, this glass generates a high pH>8. This high pH may enhance the growth of periodontopathic bacteria such as P.gingivalis which grows optimally at a pH ≈ 8.3. Furthermore, the high pH is likely to inhibit osteoblast activity, resulting in suppression of osteogenic differentiation/proliferation in the local biological environment. Therefore, this work aims to develop novel strontium-containing silicate/phosphate glass-mixtures where the phosphate glass generates an acidic pH to offset the alkaline pH arising from the silicate bioactive glass. The objective is being to (i) inhibit the alkaline periodontal bacterial growth of virulent P.gingivalis and (ii) create a neutral periodontal environment for osteoconductive bone regeneration. Strontium is known to stimulate osteoblasts and has a bactericidal action against P.gingivalis, it also provides radio-opacity enabling the dissolution process to be potentially followed clinically by X-rays.
Methods: Nine compositions of bioactive silicate/phosphate glass-mixtures were prepared. The glasses synthesised were ground and sieved to obtain a specific selection of particle size fractions for glass-mixtures preparation. The glass-bioactivity was performed by immersing the prepared glass mixtures in Tris, SBF and ALP containing Tris buffer solution. The pH change in solutions was measured and the ions release was quantified by ICP-OES as a function of time. The glass-mixtures degradation and apatite formation were investigated by Infrared-Spectroscopy-FTIR, MAS-NMR Spectroscopy and Solution-NMR Spectroscopy.
Results: The pH behaviour was modulated by immersing the nine compositions of glass-mixtures in buffers solution. The degradation of glass mixtures in Tris buffer was evaluated by MAS-NMR and revealed the transformation of the Q2 metaphosphate species into large amounts of Q1 species with a small amount of Q0 orthophosphate species. The rate of these transformations of glass mixtures depends on the mixture composition (the ratio of silicate glass to phosphate glass). ALP which is elevated in periodontal bony defects hydrolysed the terminal phosphate Q1 species of the Q2-metaphosphate chain of phosphate glass and converted it into Q0-orthophosphate species as demonstrated efficiently by Solid and Solution NMR spectroscopies.
Conclusion: Smart modulation of pH profile was essential to inhibit the alkaline bacterial growth of P.gingivalis. The transformation of Q2-metaphosphate species into Q1-species demonstrated by spectroscopy was significant finding as the emerging Q1-species was hydrolysed by ALP enabling hydroxyapatite precipitation for new bone formation. This extremely pioneering technology of mixing phosphate and silicate glasses and using them with ALP has potential for the development of new biomedical materials for different applications. | en_US |
