Sr2+ Sustained Release System Augments Bioactivity of Polymer Scaffold

Strontium ion (Sr2+) enabled us to endow polymer bone scaffolds with bioactivity owing to its excellent osteoinductive capacity. Nevertheless, the burst release of Sr2+ hindered its further application. Herein, strontium substituted hydroxyapatite (SrHA) was constructed to achieve a sustained release system. Specifically, Sr2+ could substitute Ca2+ in a HA lattice framework through ion exchange due to their similar ion radius. The ionic bond formed by Sr2+ and surrounding ions could prevent the rapid escape of Sr2+ and thereby achieve the sustained release of Sr2+. Subsequently, SrHA was introduced into the poly-l-lactic (PLLA) scaffold fabricated by selective laser sintering. Results demonstrated that PLLA/SrHA scaffolds presented a sustained Sr2+ release with a cumulative concentration of 5.6 mg/L over 28 days. The released Sr2+ significantly promoted the cell proliferation and differentiation. Furthermore, the tensile and compressive strengths of PLLA/SrHA scaffolds were also greatly enhanced in comparison with that of PLLA scaffolds. These positive findings demonstrated that PLLA/SrHA scaffolds had considerable potential for bone repair.