Regulation of TiO2 nanotubes on titanium implants to orchestrate osteo/angio-genesis and osteo-immunomodulation for boosted osseointegration

The bio-inertness of titanium (Ti) and accompanying severe inflammation can extremely inhibit the coupled osteogenesis-angiogenesis regulation and result in an undesirable osseointegration of peri-implant during the implantation process. Herein, three types of TiO2 nanotubes (TNT) were prepared on native Ti substrate using an anodic oxidation approach, including TNT with a diameter of 30 nm (TNT-30), 70 nm (TNT-70), or 110 nm (TNT-110). Among the four substrates, TNT-70 was the most prominent to induce the differentiation of macrophages to the pro-healing M2 phenotype via significant down-regulation of pro-inflammation genes (CD86, iNOS, CD11c) and cytokines (TNF-α, IL-6), as well as up-regulation of anti-inflammation genes (CD206, Arg-1, IL-10) and cytokines (TGF-β, IL-10). Furthermore, TNT-70 could stimulate the osteogenic potential of mesenchymal stem cells (MSCs) and the angiogenic ability of human umbilical vein endothelial cells (HUVECs) via multiple paracrine signaling. In vivo experiments suggested that TNT-70 significantly relieved early inflammatory response around the implant, facilitated coupled osteogenesis and angiogenesis, and effectively promoted the osseointegration of peri-implant. This study provided a reference for fabricating surface topography on Ti implant for improving osseointegration and relieving associated excessive inflammatory response.