Study On Preparation And Biological Properties Of Porous Strontium-doped Hydroxyapatite Bone Repair Materials Prepared By Spark Plasma Sintering

ObjectivePorous strontium-doped hydroxyapatite (Sr-HA) material with different strontium-containing were prepared by spark plasma sintering (SPS). The invistigation of pore characteristics and mechanical properties on optimal preparation process parameters and different amount of strontium of materials were explored. Combination of the materials and rabbit bone marrow mesenchymal stem cells (BMSCs). Detect the degradability, toxicity, hemolytic and cytocompatibility of this composite material, and observe it under electron microscope. Comparing different strontium content which have influence on the properties of biological materials. To providing the experimental basis and data for animal experiments and clinical studies.MethodsMixing the different amounts of Sr-HA powder with pore-forming agent into the stainless steel mold, and preparing the green body in automatic pressure tester under the pressure of 180 MPa. The sintering was accomplished by SPS at a temperature of 1050℃ for 10min, after cooling mold and then obtained the Sr-HA material with different porosities. The porosities, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and mechanical property testing were determined. Subsequencely, combining the materials with BMSCs in vitro. Study on the degradation of porous Sr-HA through PBS soaking. Study on the cytotoxicity of porous Sr-HA through MTT. Observing the cytocompatibility of porous Sr-HA through SEM. Detecting the hemolyticity of porous Sr-HA in vitro. Research of the differentiating capacity of the porous Sr-HA on the BMSCs’ through vitro induction experiment. Comparing the biological properties of porous Sr-HA, which containing different amount of strontium.Results1. The results of XRD showed that the main phase of the sample was not changed, their respective position and width of the diffraction peaks were match with pure Sr-HA standard atlas sintered by SPS;2. The results of SEM showed that the sample have an interconnected porous structure, with the increase of strontium content, the pore structure of the material did not have a significant impact;3. The results of mechanical properties test showed that with the increase of strontium content, the elastic modulus and compressive strength of the Sr-HA porous material are strengthened. When strontium content reached 5 wt%, aperture size is about 300-500 μm and the compressive strength reached 5.35 MPa. It can matched with the medical clinic requirements of bone repair material on the mechanical performance;4. The porous Sr-HA, which pore-forming agent particle size is 300～500 μm, the pore-forming agent added an amount of 50%, a porosity from 50% to 70% sintered at 1050℃ for 10 min achieved the best mechanical properties and the best biological porous structure;5. The degradation results of porous Sr-HA sintered by SPS become slow down gradually. After 10 weeks later, the degradation rates were basically unchanged. This is in conformity with the time of bone tissue repair. With the increase of strontium content, the degradation rate of porous Sr-HA increased;6. The hemolysis rate of different strontium content porous Sr-HA sintered by SPS did not exceed 5%. With the increase of strontium content, the hemolysis rate of material is slightly increased;7. After the OD values measured by MTT assay, the statistical analysis showed that the porous Sr-HA are non-toxic.8. Observing materials and BMSCs cells after co-cultured for 7 days by SEM, we found that different amounts of strontium porous Sr-HA can make cells grow well.9. The results of Alizarin Red staining, alkaline phosphatase and oil red O staining showed that BMSCs, which co-cultured with Sr-HA can induce to osteoblasts and adipocytes. With the increase of strontium content, the osteogenic activity of material increased, while the adipogenic effect not obvious.ConclusionsThe porous Sr-HA prepared by SPS not only has a interconnect porous structure and mechanical properties, but also exhibits good cytocompatibility, nontoxicity, non-hemolytic reaction. The degradation rate matched with the bone tissue. BMSCs can be successful adhesion and differentiation of osteoblast and adipocyte in Sr-HA. Under the circumstance of strontium content below 10 wt%, with the increase of strontium content, the degradation rate increased, the Value-added role of cells increased. Porous Sr-HA materials prepared by SPS are a promising artificial bone repair materials.