The effects of strontium incorporation on a novel gelatin/bioactive glass bone graft: In vitro and in vivo characterization

Growing evidence indicates that biomaterials that contain bioactive glass (BG) exert positive effects on bone tissue repair. Strontium-substituted BGs have been demonstrated to promote bone formation while inhibiting bone resorption by osteoclasts. In this study, we fabricated composites containing gelatin combined with different concentrations of strontium (Sr)-delivering glasses. We then investigated the in vitro effect of the presence of Sr in the polymer matrix on proliferation and differentiation of bone marrow mesenchymal stem cells (BMMSCs). The potential angiogenic effect of Sr was assessed by subcutaneous implantation in mice. Scanning electron microscopy (SEM) of prepared scaffolds showed an interconnected porous structure with an average diameter of 100-300 mu m; increasing the percentage of Sr decreased the average pore size. The stiffness of scaffolds containing Sr was about five times greater than that of scaffolds containing BG with no Sr. Cytocompatibility of the prepared scaffolds, assessed using BMMSCs, was confirmed with MTT assay. Secretion of alkaline phosphatase was significantly enhanced in cells cultured on Sr-containing scaffolds, compared with other samples, after 14 days. Imunohistofluorescence analysis indicated that the addition of Sr increased perivascular localization and cell migration, and stimulated sprouting angiogenesis. The results of this study highlight the enhanced mechanical and biological properties of our polymer matrix after the addition of Sr. Our results indicate that Sr-containing bioactive glasses could exert beneficial effects on bone tissue engineering.