In vitro bioactivity and gene expression by cells cultured on titanium dioxide doped phosphate-based glasses

In our previous study, glasses with 50 P2O5-(20-15) Na2O-30 CaO-(0-5 mol%) TiO2 have been prepared by the conventional melt-quenching process. MG63 cell proliferation, gene expression, in vi vo biocompatibility, and bioactivity of these glasses is the concern of this study. The results showed that addition of TiO2 in small amounts up to 5 mol% enhanced the biocompatibility of these glasses. The cell metabolic activity was conspicuous, on 3 and 5mol% TiO2 compositions in particular, with no significant difference from Thermanox((R))) control over a period of 21 days. The findings from the gene expression study showed that, at day I and on 5 mol% TiO2 glass, core binding protein factor alpha 1 (Cbfa1) and alkaline phosphatase (ALP) showed significantly lower transcription level; however, collagen type I alpha subunit I (COLIAI) and Osteonectin (Sparc) showed no significant differences compared to the control. At day 7, all these genes transcription levels were not significantly different form the control, but at day 14, they were significantly higher than the control. Moreover, there were no significant differences detected in these genes on both 3 and 5 mol% TiO2 glasses up to 7 days. At day 14; however, 5 mol% TiO2 glasses showed significantly higher level than 3 mol% TiO2 composition. This was also correlated by the presence of new bone tissue at the bone-particles interface for 5 mol% TiO2 composition after 5 weeks of implantation in rat calvarium. Regardless of this favourable cell response and gene up-regulation, these glasses showed no evidence of apatite layer formation after 14 days incubation in SBF. (C) 2007 Elsevier Ltd. All rights reserved.