医用镁合金微弧氧化生物活化涂层构建及其腐蚀降解调控与生物相容性

The objective of the research is to propose a novel fabricating method of ceramic coatings with bioactive CaSiO3-Mg2SiO4-CaMgSiO4-CaP phases on magnesium alloy by simple one-step microarc oxidation technique, and further understand the interrelationship between bioactive coating interface and biocompatibility. Such special structural coatings are expected to be an effective way to resolve the two key issues on earlier mechanical failure due to the rapid degradation rate and poor biocomparativity of Mg alloy, by preventing the substrate from rapid release of magnesium ions at the interface and inducing faster bone response. This research will focus on: revealing effects of electrolyte composition design and processing parameters on microarc discharging behaviours, coating growth and microstructure; establishing the relationships between the formation of bioactive constitution and processing parameters, and investigating the effects of coating composition, structure and in vitro hemolysis and cytotoxicity compatibility; examing the effects of different structured coatings on Mg alloy surface on corrosion degradation and HA depositing mechanism through in vitro (SBF) experiments; taking the animal model implanted in the femur shaft of New Zealand white rabbits to understand the in vivo degradation behavior and induing bone response of Mg alloys samples coated with different coatings. Finally, making a comparative research on in-vitro and -vivo corrosion degradation evolution and and finding the difference with the purpose to clarify the mechanism involving corrosion degradation and inducing bioactivity. Based on the results, the process parameters and coating structure were optimized to obtain the matching of new bone induction and degradation rate. The proposed project has a broader societal impact on scientific disciplines and engineering applications. Not only will it enriches the theories of corrosion degradation and surface bioactivation, but will also explore and find the novel way to contol corrosion degradation rate of biomedical magnesiom alloy.

针对可降解镁合金在体内腐蚀降解速度过快及生物相容性差的关键问题，提出新颖的含CaSiO3-Mg2SiO4-CaMgSiO4-CaP生物活性组分陶瓷涂层的一步微弧氧化构建方法，实现降解速度可调控与改善组织治愈双重功能。研究微弧氧化电解液组成设计与工艺参数对涂层组织结构的影响，揭示工艺参数与活性物质定向生成的关系；研究涂层组成、微结构与体外溶血及细胞相容性的关系；通过体外（SBF）实验揭示不同涂层结构对镁合金腐蚀降解与诱导HA沉积过程的影响及机制；以动物模型考察不同涂层材料植入大白兔骨股裸后的降解行为、对骨裸部位的诱导成骨作用及对实验动物的全身影响。对比研究体外与体内腐蚀降解演变规律与差异性，阐明腐蚀降解与诱导生物活性的机理。对涂层进行优化设计，获得诱导骨组织生长及与降解速度相匹配的涂层结构与工艺。本课题对于探索医用镁合金腐蚀调控新方法、丰富腐蚀降解与表面活化理论具有重要的学术与应用价值。

针对可降解镁合金在体内腐蚀降解速度过快及生物相容性差的关键问题，本课题提出新颖的含CaSiO3-Mg2SiO4-CaMgSiO4-CaP 生物活性组分陶瓷涂层的一步微弧氧化构建方法，研究微弧氧化电解液组成设计与工艺参数对涂层组织结构的影响，研究涂层体外细胞相容性与腐蚀降解行为；以骨折模型与大节段骨缺损模型研究植入涂层镁合金的体内腐蚀降解与诱骨生长机理。.结果表明：通过电解液与电参数的匹配调节，制备出含MgO、Mg2SiO4、MgSiO3、CaSiO3、Ca2SiO4、Mg3(PO4)2相的涂层，腐蚀电流降低到1.767×10-5A/m2。在微弧氧化涂层基础上制备了微弧氧化-水热复合封孔涂层，涂层主要成分为CaHPO4等，涂层的腐蚀电流减小为9.695×10-6 A/cm2，腐蚀电位升高到-0.92V。浸泡腐8周后失重24.97mg/cm2，比镁合金降低了6倍，2周内可诱导生成Ca10(PO4)6(OH)2。细胞粘附与增值实验表明，无涂层镁合金细胞生长受到抑制， 而10μm、20μm厚微弧氧化涂层、水热封孔复合涂层均具有良好的细胞相容性，24h后细胞在材料表面铺展性良好。.针对多数骨折需要内固定以及大节段骨缺损机体不能自愈合的问题，采用新西兰大白兔桡骨3mm骨折模型、尺骨15mm骨缺损模型，评价镁合金支架在体内腐蚀降解及对骨愈合行为的影响。两个模型中各组镁合金植入体在体内植入12周时间内，血液学指标，心肾器官组织学检测等均表明镁合金板状支架的生物安全性良好。两个模型中体内降解结果均表明， 20μm涂层支架的耐蚀性能最好，镁合金支架表面腐蚀严重，在各组植入体支架中耐蚀性能最差。由于Mg2+的促进作用，8周时，骨折模型中，镁合金板支架植入组白兔骨折处骨髓腔已部分再通，愈合速度领先于10μm、20μm涂层支架组；12周后，骨缺损模型中，骨缺损各植入组新生骨组织基本填充缺损骨位置，上下骨组织已连通，表明镁合金网状支架对15mm骨缺损的治疗起到了良好的作用。研究成果可为开发新型医用镁合金腐蚀调控涂层新体系、拓展其在临时承载植入体、大节段骨缺损修复方面的应用等提供理论指导。