掺锶硫酸钙复合骨修复材料的制备及体外特性研究

In Vitro Study of Strontium-Calcium Sulfate Compounds as Bioactive Bone Grafted Substitute

将锶元素与医用硫酸钙复合以增加材料的生物活性,并初步验证掺锶硫酸钙复合骨修复材料的理化性能和体外降解性能,旨在为后续的进一步研究提供基础。用α-半水硫酸钙(-αcalcium sulfate hemihydrate,-αCSH)和氯化锶(SrCl2)采用混合共结晶法制备6组不同掺锶量的掺锶硫酸钙骨修复材料,其锶元素摩尔含量分别为0%、0.1%、0.3%、0.5%、1%和2%。扫描电镜观察材料的晶体形态,测试各组材料的抗压强度。用模拟体液(Stimulatebody fluid,SBF)作为降解液对材料进行降解实验,观测降解过程中材料的重量变化、抗压强度变化以及降解液pH值的变化和锶离子浓度的变化。氯化锶的掺入会影响到α-半水硫酸钙的晶体形态。随着掺锶量的增加,抗压强度有逐渐下降的趋势。各组材料在降解前4周重量变化相对较小,4周后失重率增加的趋势。随着掺锶量的进一步增加,材料的失重率变化增加趋势更为明显(P<0.05)。掺锶量为0%、0.1%、0.3%和0.5%的材料在降解前4周强度下降比较缓慢,而当掺锶量增加到1%和2%时,材料降解过程中强度下降明显增快。降解液中锶离子浓度从第4周开始快速增长,且材料的掺锶量越大,降解液中锶离子浓度越高(P=0.000)。实验结果提示,用α-半水硫酸钙和氯化锶混合固化制得的均质骨修复材料———掺锶硫酸钙具有一定力学强度。材料体外降解性能稳定,当掺锶量在0.5%以内时,材料降解前4周内能保持重量和力学强度的相对稳定,并在4周后开始大量释放具有骨诱导活性的锶元素,有利于植入体内后诱导成骨。

This study was aimed to create strontium-calcium sulfate compounds for making a new bioactive material with osteoconductive and osteoinduceable activity for bone repairing. Its mechanics and degradation features were assessed in vitro. Powders of α-calcium sulfate hemihydrate （α-CSH） and SrCl2 were mixed completely to make Srcalcium sulfate compounds materials with 6 different concentrations （0%,0.1%,0.3%,0.5%,1% and 2%） of Sr. Scanning electron microscope was used to observe the configuration of the new materials. The compressive strength of each material was tested. The materials were soaked into simulated body fluid （SBF） to test the features of degradation, which included pH, weight loss, declination of compressive strength and the changes of strontium ion concentration. The crystal appearances were influenced by incorporating of strontium. The compressive strength of nonstrontium incorporating calcium sulfate was 36.65±2.22 MPa. When the concentration of strontium was increasing, the compressive strength measurements of the materials tended to decline. The compressive strength declined to 20.56±2.64 MPa when the strontium concentration reached to 2%. The pH value of the SBF declined when the time of degradation increased, but both of them were very stable. All of the materials got weight loss after being soaked in SBF for several weeks. The weight loss was slight within 4 weeks and it became dramatic after 4 weeks. When the concentration of strontium was increasing, the weight loss became more rapid and significant（P〈0. 05）. During 0-4 weeks＂ degradation in SBF, the materials＂ compressive strength decreased much slower when the strontium concentration was below 0. 5%; however,when the decrement of strength became faster, the strontium concentration became higher. The concentration of strontium ion in SBF began to increase faster after 4 weeks＂ soaking in SBF. As the concentration of strontium was increasing, the strontium ion concentration in SBF became higher（P= 0. 000）. The new compound materials made by the mixing of α-calcium sulfate hemihydrate and SrCI2 can provide efficient compressive strength. The features of degradation of the materials are very stable. The new materials can release lots of bone inducible substance-strontium ions to repair bone defection after 4 weeks of degradation