Effects of Sr doping on biodegradation and bone regeneration of magnesium phosphate bioceramics

The present work reports the effects of strontium (Sr) addition on in vitro degradability, cytocompatibility, and in vivo bone regeneration of magnesium phosphate (MgP) bioceramics. Pure and Sr doped MgP bioceramis were prepared by solid state sintering at 1200 degrees C. Nearly 50% reduction in degradability of MgP ceramics was noticed for 1 wt.% Sr doped samples which was further confirmed by both FESEM and micro computed tomography (mu-CT) analysis. In vitro cell-materials interactions were studied using human osteoblast like cells (MG-63) and it was found that 2 wt.% Sr doped samples had highest cell proliferation as indicated by both alamar blue assay and Live/Dead imaging. Biocompatibility and degradability was further studied by implanting the samples in rabbit femur. mu-CT analysis of the retrieved bone samples showed an enhanced in vivo degradability of higher Sr doped samples whereas bone regeneration was optimum for 2 wt.% Sr doped MgP samples. Quantitative analysis using oxytetracycline labeling indicated 82 +/- 3% bone regeneration for MgP-2Sr samples compared to 56 +/- 3% for pure MgP samples, after 90 days of implantation. The present results indicated that MgP ceramics has good biocompatibility and suitable degradability to be used for bone regeneration that can further be tuned by Sr doping to make it more patient specific.