BMP2-loaded titania nanotubes coating with pH-responsive multilayers for bacterial infections inhibition and osteogenic activity improvement

Bacterial infection and surface biointertness are two main causes for titanium (Ti)-based orthopedic implants failure. To improve the antibacterial ability and enhance poor osteogenic property of Ti substrates, in this work, we employed titania nanotubes (TNTs) as Bone Morphogenetic Protein 2 (BMP2) carrier, and a pH-responsive multilayer film composed of alginate dialdehyde-gentamicin (ADA-Gen) and chitosan (Chi) was constructed onto BMP2-loaded TNTs substrates through layer-by-layer (LBL) assembly technique, resulting in TNT-BMP2-LBLg samples. The release experiments revealed that acidic environment could trigger the release of Gen from the multilayer films and in turn accelerate the release of BMP2 from TNTs. Moreover, antibacterial assay against E. coli and S. aureus confirmed that the TNT-BMP2-LBLg had excellent antibacterial capacity both in early (6 h) and in long-term (72 h). Meanwhile, in vitro cellular tests demonstrated that TNT-BMP2-LBLg had good cytocompatibility toward osteoblasts even co-cultured with S. aureus. Importantly, the obtained TNT-BMP2-LBLg promoted differentiation of osteoblasts, including enhanced alkaline phosphatase activity, improved mineralization capability and stimulated osteogenic-relative gene expression. This study thus provides a promising strategy to develop pH-responsive antibacterial and enhance bone integrative Ti-based implants for potential orthopedic application.