Physical properties and biocompatibility effects of doping SiO 2 and TiO 2 into phosphate-based glass for bone tissue engineering

Phosphate glass is continuing to gain more attention as potential bone substitutes. The ternary (P₂O₅-CaO-Na₂O) is investigated in terms of both physical properties and biocompatibility by doping different percentages of SiO₂ and TiO₂. Two groups were prepared; the first has different percentages of TiO₂ and SiO₂, whereas the second group compositions have 5 mol% TiO₂ and 5 mol% SiO₂ being added to compensate the network-forming oxide P₂O₅ and the network-modifying oxide CaO. Density, mass loss, pH, DTA, XRD, and cation release experiments were performed to study the physicochemical properties of the compositions, while MG63 and hMS cells were used within in vitro cell culture to study their biocompatibility. Results showed that an increase in TiO₂ content correlated with an increase in glass density, decreased mass loss, increased trend of Tg and Tm values, and Na⁺ and Ca²⁺ release in group 1. There was no improvement in the MG63 viability or the ability of hMSCs to differentiate into osteoblasts where TiO₂ decreased in favour of SiO₂. Furthermore, in group 2, 50P₂O₅–25CaO was less dense than 45P₂O₅–30CaO, degraded dramatically less, had lower Tg and Tm values and released less Na⁺ and Ca⁽²⁺⁾. The synergistic effect of doping 5 mol% TiO₂ and 5 mol% SiO₂ increased the MG63 viability in both compositions and was found 45P₂O₅–30CaO to have promising results in terms of the ability of hMSCs to differentiate into osteoblasts. To conclude, substituting TiO₂ in place of SiO₂ improved the physical properties and the biocompatibility of (P₂O₅-CaO-Na₂O) glass system, whereas doping 5 mol% SiO₂ and 5 mol% TiO₂ together in place of P₂O₅ and CaO had a synergistic effect in controlling their degradation rate and improving their biological responses.