A novel calcium phosphate-based ceramic scaffolds with unexpected high osteogenic activity by strontium doping

The effective restoration of local bone homeostasis is a key factor in successfully treating pathological bone defects, which can be attributed to conditions such as osteoporosis or bone tumors. To address this challenge, we prepared a strontium calcium phosphate (SrCaP) ceramic using an ion doping method that demonstrated both osteogenic promotion and osteoclastic inhibition. In this study, we systematically evaluated the physicochemical properties, in vitro cell responses and in vivo osteogenesis for this material. Our results demonstrate that a higher purity SrCaP can be obtained when the strontium doping content in hydroxyapatite is equal to or greater than 25 mol.%. The long-term release of strontium ions from SrCaP significantly promoted osteogenic differentiation of stem cells. Furthermore, in vitro experiments revealed that SrCaP scaffolds doped with 30 mol.% of strontium (Sr30–S) demonstrated the most effective performance in promoting osteogenic differentiation and inhibiting osteoclast formation, thus providing effective support for the restoration of local bone homeostasis. Although Sr30–S inhibited the formation of osteoclasts, which hindered active material absorption, its faster passive degradation rate ensured a more rapid in vivo degradation rate than that of hydroxyapatite scaffold, thereby promoting the generation and growth of new bones. In summary, the innovative SrCaP ceramic scaffolds synthesized in this study demonstrate superior capabilities in promoting osteogenic differentiation and inhibiting osteoclastic resorption activity. These scaffolds not only hold potential in facilitating the restoration of local bone homeostasis but also exhibit a degradation rate that aligns with new bone growth. As a result, they represent an excellent candidate for repairing pathological bone defects characterized by high osteoclastic absorption activity, offering promising clinical applications.