Enhancement of osteogenic differentiation and bone regeneration by Total flavonoids of Rhizoma Drynariae -loaded magnesium phosphate cement /Co-doped hydroxyapatite composites.

The total flavonoids of Rhizoma Drynariae (TFRD) are traditionally used to repair bone defects. Magnesium phosphate cement (MPC) features high early strength, fast setting, good biocompatibility and osteoconductivity. Cobalt-doped hydroxyapatite (Co-HA) exerts a significant role in guiding the osteogenic and angiogenic differentiation of bone marrow stromal cells (BMSCs). We herein hypothesize that incorporating TFRD into MPC/Co-HA yields composite scaffolds with sustained drug release and self-setting capacity, capable of inducing osteogenesis in vitro and accelerating bone repair in vivo. Accordingly, MPC/Co-HA/TFRD composites were fabricated with various TFRD loadings. The results showed that TFRD was uniformly dispersed in the MPC/Co-HA matrix. It cleared that MPC/Co-HA/TFRD composites exhibited characteristic chemical constitution of MPC，Co-HA and TFRD, with no new phases formed. In addition, the weight loss ratio of the MPC/Co-HA/TFRD composites increased with increasing TFRD content, and the pH of the composite soaking solution remained within a range suitable for the human physiological environment throughout the immersion period. Drug release studies demonstrated that the MPC/Co-HA/TFRD composites exhibited an initial burst release within 48 h, followed by a sustained slow-release pattern. In vitro cellular experiments verified that the 5 wt% TFRD-loaded MPC/Co-HA/TFRD5 composite remarkably enhanced BMSCs proliferation. The incorporation of TFRD into MPC/Co-HA enhanced alkaline phosphatase (ALP) activity and accelerated calcium nodule formation, indicating that the composites effectively induced osteogenic differentiation of BMSCs. The introduction of TFRD into MPC/Co-HA upregulated the expression of osteogenic-related proteins (IBSP, Runx2, and Osterix) and angiogenesis-related proteins (OPN, HIF-1α, and HO-1) in BMSCs. In vivo results revealed that the MPC/Co-HA/TFRD5 scaffold implanted into femoral condyle bone defects in New Zealand white rabbits significantly accelerated bone regeneration 8 weeks after surgery and exhibited favorable osteoconductivity. Hence, the MPC/Co-HA/TFRD composite represents a promising candidate scaffold for bone tissue regeneration applications.