Non-Thermal Atmospheric Pressure Plasma-Assisted Bone Morphogenetic Protein-2 Immobilisation on Titanium Nanotube Surface Promotes Osteogenesis Differentiation by Influencing Macrophage Polarisation

Implant restoration is widely adopted for addressing dentition defects, but the failure rate due to insufficient bone integration remains high. This is often attributed to the low osteogenic efficiency and prolonged osseointegration periods associated with pure titanium (Ti) implants that lack surface treatments. Enhancing the surface of these implants could potentially improve their integration. This study aims to investigate the effects of non-thermal atmospheric pressure plasma (NTAP) in immobilizing bone morphogenetic protein-2 (BMP-2) onto Ti nanotubes (TNTs), examining its osteoinductive capabilities through the immune response pathway. Ti nanotubes (TNTs) were fabricated on the surface of Ti discs using a secondary anodic oxidation process. The capability of NTAP to facilitate the immobilization of BMP-2 on TNTs was assessed. The study further evaluated the influence of different Ti substrates on the polarization of macrophages and the osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs), particularly through macrophage-induced polarization. The application of TNTs/NTAP/BMP-2 substantially reduced the presence of M1 macrophages while promoting M2 macrophages. The secreted products from macrophages treated with TNTs/NTAP/BMP-2 enhanced the migration and osteogenic differentiation of BMMSCs, as evidenced by increased cell migration, higher alkaline phosphatase activity, more mineralized nodules, and the up-regulation of osteogenesis-related genes and proteins. NTAP treatment effectively promotes the immobilization of BMP-2 on TNTs. This surface-modified Ti substrate significantly enhances the osteogenic differentiation of BMMSCs by modulating macrophage polarization. This approach could lead to improved outcomes in implant restoration by fostering better bone integration. This study provides new ideas and theoretical basis for the design of novel bone implant materials, which is expected to enhance the speed and strength of implant osseointegration, thus increasing the success rate of dental implants in the clinic.