Strontium-loaded mineral bone cements as sustained release systems; Compositions, release properties, and effects on human osteoprogenitor cells

摘要

This study aims to evaluate in vitro the release properties and biological behavior of original compositions of strontium (Sr)-loaded bone mineral cements. Strontium was introduced into vaterite CaCCVdicalcium phosphate dihydrate cement via two routes: as SrCO_3 in the solid phase (SrS cements), and as SrCI_2 dissolved in the liquid phase (SrL cements), leading to different cement compositions after setting. Complementary analytical techniques implemented to thoroughly investigate the release/dissolution mechanism of Sr-loaded cements at pH 7.4 and 37degC during 3 weeks revealed a sustained release of Sr and a centripetal dissolution of the more soluble phase (vaterite) limited by a diffusion process. In all cases, the initial burst of the Ca and Sr release (highest for the SrL cements) that occurred over 48 h did not have a significant effect on the expression of bone markers (alkaline phosphatase, osteocal-cin), the levels of which remained overexpressed after 15 days of culture with human osteoprogenitor (HOP) cells. At the same time, proliferation of HOP cells was significantly higher on SrS cements. Interestingly, this study shows that we can optimize the sustained release of Sr~(2+), the cement biodegradation and biological activity by controlling the route of introduction of strontium in the cement paste.