Vancomycin-loaded silica coatings for controlled release of drug and Si ions to repair infected bone defects

Promoting bone regeneration while inhibiting bacterial infection is still clinical challenge in the repair of infectious bone defects. Herein, a vancomycin-loaded silica coating with controlled release of drug and Si ions was prepared on polymer matrix via layer-by-layer assembly, to construct a functional composite coating scaffold with antibacterial function and enhanced bone regeneration capacity. Different release behavior and antibacterial effect were achieved by alternating or sequential deposition on the scaffold surface. In vitro study showed that both the alternating and the sequential coatings could promote osteogenic differentiation of bone mesenchymal stem cells, and the sequential coating exhibited a higher bacteriostatic rate of 97 % against Staphylococcus aureus. In vivo study of infectious bone defect model demonstrated that the sequential coating with an outer layer of vancomycin allowed more sufficient antibacterial treatment in the early stage of infection and achieved superior bone regeneration consequently. Transcriptomic analysis indicated that the vancomycin loading in the silica coating played an antibacterial role without interfering with the bone-promoting process of silicon ions, and revealed that the mechanism of osteogenic promotion was based on the activation of osteo/angio-genic related genes expression and corresponding signaling pathways. This study demonstrates an effective strategy to design functional composite scaffolds for complex infectious bone repair.