The sustained-release agent of total flavonoids of Rhizoma drynariae prepared by nano-mesoporous silica can still promote osteogenesis and angiogenesis in vitro

Total flavonoids of Rhizoma drynariae (TFRD) possess the ability to enhance bone formation by promoting the coupling of angiogenesis and osteogenesis. However, the limited duration of serum concentration necessitates frequent oral administration. Designing TFRD as a sustained-release agent could enhance patient's compliance and extend efficacy. Mesoporous silica nanoparticles (MSNPs) were used as a carrier for the preparation of a sustained-release agent containing TFRD (TFRD@MSNPs). Material characterization confirmed the successful loading of TFRD onto MSNPs. Subsequently, HUVECs were treated with varying concentrations of TFRD or TFRD@MSNPs to evaluate their effects on proliferation and migration ability. The secretion levels of VEGF, VCAM-1, EGF, TGF-β1, and type H endothelial markers (CD31 and EMCN) were assessed. BMSCs were cultured in conditioned medium derived from HUVECs induced by either TFRD or TFRD@MSNPs to evaluate their osteogenic potential in vitro. Gene expressions of ALP, OCN, and RUNX2, alkaline phosphatase activity, and calcium deposition were measured. The mass fraction of TFRD in the sustained release system TFRD@MSNP was approximately 60%. An appropriate concentration (< 400 µg/mL) of TFRD promoted the proliferation and migration of HUVECs, inhibited the secretion of TGF-β1, and increased the expression levels of VEGF, VCAM-1, EGF, CD31, and EMCN. The conditioned medium from HUVECs induced by TFRD significantly enhanced the osteogenic differentiation potential of BMSCs. An appropriate concentration of TFRD@MSNPs promoted the proliferation and migration of HUVECs, as well as the expression levels of CD31 and EMCN, but had no significant effect on VEGF, VCAM-1, EGF, or TGF-β1 secretion. The conditioned medium from HUVECs induced by TFRD@MSNPs increased ALP, OCN, and RUNX2 gene expression in BMSCs to varying degrees. Compared to the conditioned medium induced by TFRD in HUVECs, the conditioned medium induced by TFRD@MSNPs resulted in more calcium deposits in BMSCs. The sustained-release agent TFRD prepared by MSNPs can effectively promote the osteogenic differentiation of BMSCs through the coupling effect of angiogenesis and osteogenesis in vitro. These findings suggest that using MSNPs to formulate TFRD as sustained-release agent holds potential for clinical application, but the specific mechanism remains to be elucidated.