Different cellulose nanofibers impact properties of calcium phosphate silicate cement for bone tissue engineering

Aging-related abnormal bone metabolism can have detrimental effects on bone microstructure and significantly increases fracture occurrence in the older population. Injectable bone cement has been commonly used to augment porous and fragile bones. The self-setting calcium phosphate silicate cement (CPSC) has recently been proven suitable for bone tissue engineering. Unfortunately, the inadequate mechanical properties of CPSC limit its utilization as implants for load-bearing applications. One primary purpose of this study is to improve the mechanical properties of CPSC using different cellulose nanofibers (CNFs). It is shown that the mechanical properties of CPSC could be enhanced by adding 2% mass fractions of CNFs, carboxylate CNFs (CNF-C) and silanized CNFs (CNF-SH), and the reinforcing effects on the mechanical property of CPSC could be ranked as CNF-SH > CNFs > CNF-C. In addition, the Young's modulus of the CPSC pellet modified with CNF-SH (similar to 10 GPa) was proved to be close to that of trabecular bone (similar to 11.4 GPa). Unlike other studies, where the mechanical properties of bone cement were improved at the cost of decreasing handleability, our approach could simultaneously increase both qualities of the CPSC paste. Furthermore, the in vitro biocompatibility analyses proved that the nanofiber-modified CPSC was biocompatible and encouraged the proliferation and differentiation of osteoblast cells. In summary, the injectable CPSC bone cement can be better enhanced by CNF-SH than CNFs or CNF-C, and the resultant nanofiber-reinforced bone cement is a promising candidate as a bone substitute biomaterial.