55S bioglass stimulates in vitro osteoblast differentiation and creates a favorable template for bone tissue formation

In this study, we have investigated the behavior of fetal rat osteoblasts cultured on bioactive glasses with 55wt% silica content (55S) and on a bioinert glass (60S). When rat bone cells were cultured on both substrata, they formed multi-layered nodular structures by day 10 in culture. In addition, the specific activity of AP determined biochemically was significantly higher in 55S cultures than in the controls. SEM observations of the material surfaces after scraping-off the cell layers showed that mineralized bone nodules remained attached on 55S surfaces but not on 60S. The 55S/bone interfaces were also analyzed on transverse sections. The interfacial analysis showed a firm bone bonding to the 55S surface through an intervening apatite layer, confirmed by the X-ray mappings. All these results indicated the importance of the surface composition in supporting differentiation of osteogenic cells and the subsequent apposition of bone matrix allowing a strong bond of the bioactive materials to bone.