Construction of Wogonin Nanoparticle-Containing Strontium-Doped Nanoporous Structure on Titanium Surface to Promote Osteoporosis Fracture Repair.

M2 polarization of macrophage is an important immunomodulatory event that attenuates inflammation. To regulate the immune microenvironment in osteoporotic conditions for enhancing bone healing, strontium-doped nano-structure is fabricated on the surface of titanium implant via microarc oxidation and electrochemical deposition technology, followed by the addition of multiplayer coatings embedded with silk fibroin-based wogonin nanoparticles (Ti-MAO/Sr/LBL ) by layer-by-layer self-assembly technique (LBL). It is found that Ti-MAO/Sr/LBL can release wogonin and Sr in a sustainable manner for more than 7 and 21 days. In vitro studies show that Ti-MAO/Sr/LBL significantly upregulates the expression of CD206 while reducing the expression of CD86. Meanwhile, Ti-MAO/Sr/LBL can promote the expression level of M2 macrophage anti-inflammatory factor (TGF-β1, Arg-1), which improves the proliferation and osteogenic differentiation of osteoblasts through paracrine signaling. Compared to bare titanium, Ti-MAO/Sr/LBL significantly inhibits the expression of inflammatory factors around the implant and effectively promotes new bone formation at pre-implant interface after implantation for 4 weeks. This study provides a simple and effective method to develop functional titanium alloy materials for osteoporotic fracture repair.