Strontium hydroxyapatite/magnesium oxychloride cement with high strength and high osteogenic activity for bone defect repair

Abstract

Strontium is a kind of element which can promote the increase of bone density and benefit the growth of bone tissue. This study combined strontium hydroxyapatite (Sr-HAp) with magnesium oxychloride cement (MOC) to prepare a bioactive material with good osteogenic activity and degradability. The results revealed that the incorporation of 10 wt.% Sr-HAp densified the structure of MOC, slowed down the degradation rate of hydration product phase 5 in water, and enhanced the water resistance of MOC. After soaking for 28 days, the compressive strength of Sr-HAp/MOC decreased by 53%, which was lower than that of MOC (93%) and HAp/MOC (61%) without adding Sr-HAp. During the degradation process in vitro, Sr-HAp/MOC continuously released Sr2+ and the cumulative concentration of Sr2+ released in vitro after seven days of immersion was 1.27 ± 0.15 ppm. When Sr-HAp/MOC was soaking in simulated body fluid, Sr-HAp induced the growth and deposition of bone-like component hydroxyapatite crystals on MOC’s surface, improving MOC’s bioactivity. After implantation of femur defect in rats, the new bone tissue grew from outside to inside around Sr-HAp/MOC, which showed Sr-HAp/MOC had better osteogenic activity. MOC was containing 10 wt.% Sr-HAp can not only provide strong support for bone defects but also have the potential to promote bone regeneration.