Fabrication of strontium-incorporated protein supramolecular nanofilm on titanium substrates for promoting osteogenesis

The inherent biological inertness of Ti substrates is a general challenge in orthopedic and dental clinical application. In this study, the strontium-containing phase change lysozyme coating was prepared on titanium via a supramolecular self-assembly method for accelerating osseointegration. Successful preparation of the Sr-incorporated lysozyme nanofilm onto the Ti substrate (Ti-Ly-Sr) was proved by tests of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Contact angle (CA). Furthermore, the results of cell morphology observation, cell viability assay, alkaline phosphatase staining and quantitative analysis showed that Ti-Ly-Sr substrate enhanced early adhesion, proliferation and osteogenic differentiation of bone marrow stromal cells (BMSCs). The quantitative real-time polymerase chain reaction (qRT-PCR) assays confirmed that Ti-Ly-Sr enhanced the expression of osteogenic related genes (BMP2, OPG, Runx2 and COL-1) of BMSCs at the molecular level. Moreover, Micro-CT and histological analysis proved that the strontium-incorporated lysozyme nanofilm modified Ti implants had significant capability of new bone formation in vivo after implantation for 4 weeks. We anticipate that the present system would provide a facile and effective means for surface modification of Ti-based implants. Relevant ideas and techniques in this study will contribute to the development of new implant devices.