| In recent years, as the extent of people’s health concerns and the continuous improvement of clinical need, magnesium alloys as biomaterials show many superior properties to other metal materials. To prepare the biological medical materials and select Mg, Zn, Sr three elements, combined with the already existing research results, design optimization Mg-4.0Zn-1.0Sr(wt.%) alloys was prepared in this paper. Further study the corrosion degradation behavior of magnesium alloy and biocompatibility, and through implanting magnesium alloy on animals to evaluate the impact on animal physiology and effect on fracture healing, to provide basic reference data for degradable medical magnesium material and its application technology research and development. The experimental data were as follows:(1) Optimize the designation of the Mg-4.0Zn-1.0Sr(wt.%) alloy. And the Mg-4.0Zn-1.0Sr(wt.%) alloy was prepared by solution treatment at 440℃,12h:the grain was refined, most of precipitates at intragranular and the grain boundaries were soluted to the matrix, improving the uniformity of the structure. By artificial aging treatment, we can improve the mechanical properties of the alloy, whose best aging condition is:180 ℃,18h. After aging treatment, the hardness value can reach 57.78HV, tensile strength can reach 180.4MPa, elongation rate maximum can reach 6.5%.(2) In the DMEM solution vitro immersion test, the corrosion law of Mg-4.0Zn-1.0Sr (wt.%) alloy was the cycle process of pitting corrosionâ†'deepening pitting corrosionâ†'pitting corrosion in new surface. The white corrosion products present on the surface, and the main component of MgO and calcium phosphate. Mg-4.0Zn-1.0Sr(wt.%) alloy demonstrated good corrosion resistance after immersed in DMEM solution, Zn, Sr elements can conducive passivation film informed on the alloy surface, the second phase of intermittent shape can prevent corrosion expanding and improving the corrosion resistance of magnesium alloys. The average corrosion rate is reduced from the initial 3.08mm/yr to 0.58mm/yr at 8d. The pH value of DMEM solution increased with time, and the rate of increasing gradually decreased; the rate of increase leveled off after 5d, the change is consistent with the corrosion rate.(3) It took hemolysis rate test and cytotoxicity test to study vitro biocompatibility of the Mg-4.0Zn-1.0Sr(wt.%) alloy. The hemolysis rate was 4.70% and the hemolysis didn’t occur, which satisfied the requirement of biocompatibility. In 3d cytotoxicity test indicated that the cell toxicity of the Mg-4.0Zn-1.0Sr(wt.%) alloy was approximately at 1 level, and the value of RGR>90%, which satisfied the requirement of cell toxicity biomaterials.(4) Using the method of simulated fracture to study vivo biocompatible of Mg-4.0Zn-1.0Sr(wt.%) alloy after implanting into the rabbit femur. After the rabbits implanted Mg-4.0Zn-1.0Sr(wt.%) alloy, systemic physiological conditions unaffected, surgical site healed well. The rabbit’s heart, liver, kidney, spleen had no adverse effects, the concentration of magnesium ions continuously excreted out of the body with the degradation of the magnesium alloy, which has no significant increase in serum, keeping within a reasonable range, the circulation and urinary system of rabbits, has no significant effect, and showing good biocompatibility.(5) With the continuous degradation of Mg-4.0Zn-1.0Sr(wt.%) alloy, the degradation products remain in the interface between alloy and bone material, the degradation products of Ca, P, C gathered for the growth of new bone to provide favorable conditions. The trabeculae of new bone has a good distribution, neat, although the osteolysis appeared at early stage, but the osteogenesis obviously later and have no adverse effects on the surrounding tissues, the Mg-4.0Zn-1.0Sr(wt.%) alloy exhibits good osteoinductive and conduction activity. |
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