新型稀土镁合金螺钉体内促骨修复及体外生物相容性研究

为测试新型稀土镁合金的生物相容性及降解产物致敏性; 评价新型稀土镁合金螺钉对骨伤模型的治疗效果, 基于NZ30K镁合金添加Mn元素制成新型稀土镁合金, 并通过后期加工制成不同规格的螺钉. 将稀土镁合金螺钉浸入磷酸盐缓冲液中制作浸提液, 于大鼠后肢背部皮下注射, 观察浸提液皮下致敏性. 将螺钉打磨制成圆片植入到大鼠皮下, 观察皮下降解产气情况, 以可吸收骨蜡作为对照同位置皮下植入. 建立兔骨损伤模型, 将稀土镁合金植入, 定期拍摄X光检查螺钉降解情况, 按照时间顺序分别于8周、12周、16周处死实验兔制作肝肾切片、骨切片, 评价肝肾毒性及体内降解情况; 同期以ZA75镁合金为基础添加0.3% Mn元素制成新镁合金, 作为对照组对比稀土镁合金对大鼠骨髓间充质干细胞成骨分化效果. 将浸提液过滤稀释后添加至细胞培养板中, 加入成骨诱导液培养, Westernblot蛋白电泳实验测定骨保护蛋白(OPG)表达情况. 新型稀土镁合金浸提液未表现出致敏性, 皮下降解结果显示植入初中期有气腔产生, 中后期气腔消失, 镁合金完全降解; 组织切片显示, 兔股骨螺钉植入在前中期有一定肝肾毒性, 植入中期促骨生长效果相较于前期更为明显, 植入后期未见明显肝肾毒性, 螺钉降解完全, 植入部位骨质增强; 兔股骨植入降解结果显示植入前期未观察到明显的促进骨生长效果, 螺钉与骨质嵌合紧密, 植入中期促骨生长修复效果呈现, 局部骨组织出现膨隆包裹住螺钉降解产物, 植入后期螺钉完全降解, 植入位置有一小孔未闭合, 股骨近端明显膨隆; 蛋白电泳实验显示, 新型稀土镁合金浸提液可增加OPG表达, 具有良好的生物相容性. 基于NZ30K开发的新型稀土镁合金在动物实验及细胞实验阶段表现出良好的生物相容性, 可为临床应用提供一定参考.

Study on bone promoting repair and biocompatibility of new rare earth magnesium alloy screws in vitro

To test the biocompatibility and sensitization of degradation products of new rare earth magnesium alloys and evaluate the therapeutic effect of new rare earth magnesium alloy screw on bone injury model, new rare earth magnesium alloy was made based on NZ30K magnesium alloy by adding Mn element, and screws of different specifications were made through post-processing. The extract was prepared by immersing rare earth magnesium alloy screws into phosphate buffer and injected subcutaneously into the back of hind limbs of rats to observe the subcutaneous sensitization of the extract. The screws were polished into discs and implanted into the subcutaneous skin of rats, and the gas production was observed under the subcutaneous degradation. The absorbable bone wax was used as the control to implant the discs at the same position. The rabbit bone injury model was established, the rare earth magnesium alloy was implanted, and the screw degradation was examined by X-ray taking regularly. The experimental rabbits were sacrificed at 8 weeks, 12 weeks and 16 weeks for liver and kidney sections and bone sections, respectively, to evaluate the liver and kidney toxicity and in vivo degradation. At the same time, ZA75 magnesium alloy was added 0.3% manganese to prepare new magnesium alloy, and the effect of rare earth magnesium alloy on osteogenic differentiation of rat bone marrow mesenchymal stem cells was compared as the control group. The extract was filtered and diluted, then added to the cell culture plate, cultured with osteogenic induction solution. The expression of osteoprotegerin (OPG) was determined by Western blot. The new rare earth magnesium alloy extract did not show sensitization, and the subcutaneous degradation results showed that there were air cavities in the early and middle stage of implantation, and the air cavities disappeared in the late stage, and the magnesium alloy was completely degraded. Tissue sections showed that femoral screw implantation had certain hepatorenal toxicity in the early and middle stages, and the effect of promoting bone growth in the middle stage was more obvious than that in the early stage. There was no obvious hepatorenal toxicity in the late stage, during which screw degradation was complete and the bone was enhanced at the implantation site. Rabbit femoral implant degradation observation results show that the implantation at early stage did not significantly promote bone growth effect, and screws and bone chimeric interlocked closely; while at medium-term stage, the repair effects on promoting bone growth were obvious, and local bone tissue wrapped in occurrence of screw degradation products. At late stage, the implanted screws were fully biodegraded, and there was a small hole in the implanation that is not closed, with proximal femur expanding obviously. Protein electrophoresis experiments showed that the new rare earth magnesium alloy extract could increase OPG expression and had good biocompatibility. It can be concluded that the new rare earth magnesium alloy developed based on NZ30K shows good biocompatibility in animal and cell experiments, which can provide some reference for clinical application.