The incorporation of β-tricalcium phosphate nanoparticles within silk fibroin composite scaffolds for enhanced bone regeneration: An in vitro and in vivo study

To investigate the osteogenesis of beta-tricalcium phosphate nanoparticles-incorporated silk fibroin (SF/beta-TCP) composite scaffolds, SF-based scaffolds with different beta-TCP proportion (2/1, 1/1, and 1/2) were fabricated by freeze-drying technology in the present study. Structural and physicochemical properties of SF-based scaffolds were evaluated by using scanning electron microscope, X-ray diffraction, Fourier transformed infrared spectroscopy (ATR-FTIR) and transmission electron microscope. Biocompatibility and osteogenesis of SF/beta-TCP scaffolds were investigated by using bone marrow mesenchymal stem cells (BMSCs). Eight New Zealand rabbits were selected, while four 8-mm-diameter calvarial defects were created in each rabbit to place SF/beta-TCP scaffolds. The harvested specimens at 4 and 12 weeks were used to evaluate the bone forming ability by micro-CT and histological examination. The results suggested incorporation of beta-TCP displayed flake-like pore morphology with proper pore sizes. With the increasing proportion of beta-TCP, composite scaffolds exhibited higher compressive strength, lower swelling ratio and degradation rate, as well as enhanced biomineralization capacity. Alkaline phosphatase activity and collagen type I expression levels of BMSCs were significantly increased in the presence of beta-TCP nanoparticles. All composite scaffolds with different beta-TCP proportion had good bone formation ability at 12 weeks. Among them, SF/beta-TCP (1/2) scaffold exhibited the favorable osteogenesis capability which had great potential for applications in bone regeneration.