Effect of the immune responses induced by implants in a integrated three-dimensional micro-nano topography on osseointegration.

In order to explore the abilities of an integrated three-dimensional micro-nano topography in immunomodulation and promoting bone formation, present study focuses on the titanium sheets used in the micro-nano topography by treating them with the sandblasted, large-grit and acid-etched (SLA)and alkaline thermal reaction. Further, we characterized and obtained the surface morphology, roughness, and hydrophilicity of the titanium sheets. Moreover, we detected their in vitro cytocompatibility and cell proliferation as well. In addition, investigation was carried out for the immunomodulatory ability of the titanium sheets in a micro-nano topography by observing the expression of M1 (classical activated macrophage) and M2 (alternatively activated macrophage) type marker factors, inflammatory factors, and morphological changes of RAW264.7 cells cultured on the titanium sheets in different topographies. Through cell migration experiments and coculture, we observed the effects of different titanium sheet immune environments on osteoblast migration, extracellular matrix mineralization, and osteoblast gene expression. These results showed that the micro-nano topography constructed through SLA and alkaline thermal treatment improved the hydrophilicity and promoted the cell proliferation. Moreover, it promoted RAW264.7 cells to polarize as M2 phenotype, thereby leading to the anti-inflammatory effect of local microenvironments. This facilitated osteoblasts to secrete bone morphogenetic protein-2 (BMP2) and vascular endothelial growth factor. Nonetheless, these findings provided a theoretical basis for the molecular biological mechanism related to implants in a micro-nano topography which promoted the osteointegration while offering a meaningful theoretical basis for the clinical treatment of such implants.