Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Mater Sci Eng C Mater Biol Appl. 2016 Jun;63:429-38. doi: 10.1016/j.msec.2016.02.059. Epub 2016 Mar 11.
Ionic substitutions in hydroxyapatite (HA) scaffolds and self-setting cements containing Sr(2+) ions incorporated are particularly of interest in bone regeneration. To date, the approach widely used to incorporate Sr(2+) ions into HA cements has been the addition of Sr(2+) containing salts, such as SrCO3, SrCl2∙6H2O, or SrHPO4. However, this approach is dependent upon the relative solubility of Sr(2+) containing salts with respect to calcium phosphate (CaP) precursors. Therefore, in the current study Sr(2+) substituted dicalcium phosphate dihydrate (DCPD) was first synthesized and directly reacted with tetracalcium phosphate (TTCP) to form Sr(2+) substituted HA forming cements. Rietveld refinement indicated that after one week of aging in phosphate buffered saline, cements prepared with and without Sr(2+) were composed of 75% HA and 25% unreacted TTCP by weight. Cements prepared with 10% Sr(2+) DCPD exhibited increased compressive strengths in comparison to unsubstituted cements. Increased MC3T3-E1 proliferation and differentiation were also observed on the cements prepared with increasing Sr(2+) content. It was concluded that both the scaffold microstructure and Sr(2+) ion release supported osteogenic differentiation. With respect to osteoclastic differentiation, no statistically significant differences in TRAP activity or cell morphology were observed. This suggests that the amount of Sr(2+) released may have been too low to influence osteoclast formation in comparison to unsubstituted cements. The results obtained herein demonstrate that the use of Sr(2+) substituted DCPD precursors rather than individually separate Sr(2+) containing salts may be a useful approach to prepare Sr(2+) containing HA cements.
在羟基磷灰石 (HA) 支架中进行离子取代，以及在含有 Sr(2+) 离子的自凝固水泥中进行取代，对于骨再生特别有意义。迄今为止，将 Sr(2+) 离子掺入 HA 水泥中广泛使用的方法是添加含有 Sr(2+) 的盐，如 SrCO3、SrCl2·6H2O 或 SrHPO4。然而，这种方法取决于含有 Sr(2+) 的盐相对于磷酸钙 (CaP) 前体的相对溶解度。因此，在本研究中，首先合成了 Sr(2+) 取代的二水磷酸二钙 (DCPD)，并直接与磷酸四钙 (TTCP) 反应形成 Sr(2+) 取代的 HA 形成水泥。Rietveld 精修表明，在磷酸盐缓冲盐水中老化一周后，不含和含 Sr(2+) 的水泥的重量组成分别为 75%的 HA 和 25%的未反应 TTCP。与未取代的水泥相比，含有 10% Sr(2+) DCPD 的水泥表现出更高的抗压强度。在含有 Sr(2+) 的水泥上，MC3T3-E1 增殖和分化也有所增加。研究得出结论，支架的微观结构和 Sr(2+) 离子的释放都支持成骨分化。关于破骨细胞分化，在 TRAP 活性或细胞形态方面没有观察到统计学上的显著差异。这表明与未取代的水泥相比，释放的 Sr(2+) 量可能过低，无法影响破骨细胞的形成。本研究结果表明，使用 Sr(2+) 取代的 DCPD 前体而不是单独使用含有 Sr(2+) 的盐可能是制备含有 Sr(2+) 的 HA 水泥的一种有用方法。
