Surface characteristics and primary bone marrow stromal cell response of a nanostructured strontium-containing oxide layer produced on a microrough titanium surface

Strontium (Sr) has been successfully used for the treatment of osteoporotic bone, increasing new bone formation while reducing bone resorption by stimulating proliferation and differentiation of osteoblastic cells and inhibiting osteoclast function. In this study, Sr-incorporated Ti oxide layer was produced on clinically relevant osteoconductive implant surface, that is, a grit-blasted microrough Ti surface, by a simple hydrothermal treatment with the expectation of utilizing the osteoblast response enhancement effect of Sr for the future applications as a more osteoconductive surface of the permanent load-bearing endosseous implants, without altering the original microrough surface features of grit-blasted Ti at the micron-scale. This surface exhibits a hierarchical structure (i.e., a nanoscale surface architecture of the Sr-incorporated Ti oxide layer (SrTiO ₃) imposed on micron-scale rough Ti structure) and Sr ion release into physiological solution. In vitro experiments using primary mouse bone marrow stromal cells (BMSCs) revealed that the hydrothermally produced SrTiO ₃ coating promotes both the early and late cell response of BMSCs grown on a microrough Ti surface, with notably enhanced attachment, spreading, focal adhesion, alkaline phosphatase activity, and expression of critical integrins and osteoblastic phenotype genes. These results indicate that a hydrothermally produced SrTiO ₃ coating improves the osteoconductivity of the microrough Ti surface by enhancing both the early and late cell response of BMSCs.