pH-Responsive silk protein/ZIF-8@bacitracin composite coating on strontium-doped nanorod surface for combating...

Titanium-based bone repair materials often face bacterial infections, resulting in inflammation and impaired osseointegration. To address this issue, we developed a multifunctional coating by encapsulating bacitracin within a metal-organic framework (ZIF-8@B) and incorporating it into a strontium-doped titanium dioxide nanorod (STN) structure using silk protein (SF). This coating, termed STN-SF/ZIF-8@B, was applied to titanium surfaces. It demonstrated outstanding hydrophilicity, corrosion resistance, hemocompatibility, and biosafety. The synergistic effects of bacitracin and Zn²⁺ achieved over 80 % inhibition against both E. coli and S. aureus. Additionally, STN-SF/ZIF-8@B effectively reprogrammed inflammatory macrophages into an anti-inflammatory M2 phenotype. The combined actions of Sr²⁺ and Zn²⁺ significantly enhanced the migration, lumen formation, and expression of angiogenic growth factors in HUVEC. Moreover, STN-SF/ZIF-8@B upregulated the expression of genes and proteins related to osteogenesis, promoting the osteogenic differentiation of MC3T3-E1 cells. In vivo experiments utilizing a rat bone defect model revealed that STN-SF/ZIF-8@B exhibited superior anti-inflammatory, antibacterial, pro-angiogenic, and osteogenic properties. This study provided a promising approach for the development of advanced biomaterials that simultaneously address infection control, immune modulation, angiogenesis, and bone regeneration, offering significant potential for improving the outcomes of bone defect repair in clinical applications.