Fabrication of strontium Eucommia ulmoides polysaccharides and in vitro evaluation of their osteoimmunomodulatory property

The osteoimmune environment plays indispensable roles in bone regeneration because it determines subsequent osteogenesis and osseointegration. Eucommia ulmoides polysaccharide (EUP) was proved to be an effective biomaterial that has immunomodulatory effects for improving the biomechanical quality of bone. Strontium is a trace element that inhibits inflammation and promotes bone growth. To develop a novel EUP-based osteoimmunomodulatory biomaterial with potentially enhanced bone regeneration, we synthesized strontium Eucommia ulmoides polysaccharides (EUP-Sr) and evaluated its morphology, structure and thermal stability. The materials characterization results confirmed that strontium was successfully introduced into the EUP and formed a new complex with thermal-stable property. The cytocompatibility evaluation of different concentrations of EUP-Sr by CCK8 assay suggested that EUP-Sr is beneficial to the macrophages proliferation. We further evaluated the gene expressions of RAW 264.7 cells treated with EUP-Sr. It was found that EUP-Sr could suppress inflammatory factors and osteoclastogenesis, and enhance the expressions of osteogenic factors of RAW 264.7 cells. Therefore, EUP-Sr should be a promising bioactive compound with the capability to create a positive pro-regenerative environment for skeleton tissue engineering.