镁合金表面水滑石缓控释复合功能涂层的构筑及其体外降解机制研究

The coating on magnesium alloy surface is an effective way to solve the problem of its rapid corrosion and uncontrollable degradation , especially composite coating. The structure with multilayers of composite coating can not only improve the corrosion resistance of magnesium alloy effectively, but also control and regulate the degradation rate of magnesium alloy. Moreover, surface functionalization can satisfy the functional gradient requirements of metal after implantation such as antibacterial, controllable degradation and promoting tissue growth, for achieving the aiming of clinical magnesium alloy degradation rate matching bone healing. In this subject, Mg-Zn-Zr-Sr alloys are chosen as the research subject. The multilayer functional gradient composite coating consisted of nano silver particles-magnesium aluminum hydrotalcite/carboxyl polylactic acid/medicine-magnesium aluminum hydrotalcite is proposed to be fabricated by layer-by-layer assembly method. The mechanism of degradation of LDH conversion film in vitro is revealed and the influence of LDH inhibiting corrosion and delayed release, combining with the inhibition effect of drug on the corrosion process of magnesium alloys are investigated. Furthermore, the corrosion mechanism of magnesium alloy in each gradient degradation process are clarified and the gradient structure effects of multilayer functional coatings on regulating degrading corrosion of magnesium alloys in vitro are deep studied. In addition, the influence of degrading products and ambient from coating-magnesium alloy decomposing on osteoblast behavior and its ossification mechanism is also investigated, and the analyses of multiple gradient structure and its degradation effects on activity and differentiation of osteoblast are also performed. In summary, the topic may provide the suitable bone healing and functional gradient coating-magnesium alloy materials to achieve the clinical requirements for the match of magnesium alloy degradation and bone healing.

镁合金表面构筑涂层是解决其体内腐蚀过快、降解不可控的有效途径，特别是复合涂层，其多层结构不仅有效改善镁合金耐蚀性，更易实现其降解速率可控，并可通过表面功能化满足植入后抗菌-降解特性-调控组织生长等功能梯度需求、实现临床所需镁合金降解特性匹配骨愈合。本项目以前期研究Mg-Zn-Zr-Sr系镁合金为基础，采用层层组装法在其表面构筑纳米银颗粒-镁铝水滑石/端羧基聚乳酸/药物-镁铝水滑石多层功能梯度复合涂层，通过体外降解实验揭示各功能梯度LDH体外降解溶蚀机制，深化其基于缓蚀/缓释特性、结合药物缓蚀对镁合金体外腐蚀进程影响机制的认识；明晰降解过程中镁合金腐蚀演变机理，探讨多层功能梯度结构调控镁合金体外降解的作用机制；结合细胞实验，阐明梯度涂层-镁合金降解产物、协同镁离子浓度变化对成骨细胞行为影响的生物学机制，最终获得适配骨愈合、具有功能梯度的涂层-镁合金材料，实现临床意义上镁合金降解-骨愈合匹配。

镁合金表面构筑涂层是解决其体内腐蚀过快、降解不可控的有效途径。复合涂层的多层结构不仅有效改善镁合金耐蚀性，调控其降解速率，同时引入功能化表面解决植入体抗菌、降解、促进组织生长等功能需求。本课题在医用镁合金表面成功制备了具有良好耐蚀性、抗菌性和细胞相容性等功能性的以纳米银-层状镁铝氢氧化物、微弧氧化涂层为主体的复合涂层。项目首先通过微弧氧化涂层对基体预处理，有效提升了基体的耐蚀性；设计在硅-磷混合电解液中预处理制备了微弧氧化涂层，揭示了硅酸钠含量对涂层质量的影响规律，阐明了硅-磷混合体系中涂层形成对于硅/磷原子比、磷酸根和硅酸根离子竞争关系的依懒机制，从而获得耐蚀性、生物相容性良好的预处理涂层。在提升基体耐蚀性基础上，进一步合成功能化抗菌原位纳米银-镁铝氢氧化物涂层和药物缓蚀聚毗咯涂层；研究了原位水热纳米银-镁铝氢氧化物双相涂层各种工艺参数对涂层组织形貌和耐蚀性的影响，获得了具有良好生物相容性、抗菌性和显著提升基体耐蚀性的原位涂层，阐明了银-镁铝氢氧化物涂层的耐蚀性随原位水热反应工艺参量的变化规律，揭示了原位一步形成银和镁铝氢氧化物的反应生成机制和硝酸根插层交换阻滞氯离子的缓蚀、以及抗菌银离子的缓释机制；阐明了微弧氧化涂层表面化学制备负载地塞米松的聚吡咯涂层的工艺参量的变化规律，揭示了药物缓释剂量随体外离子浓度变化的响应机制。所获得涂层具有优异耐蚀性、抗菌性及细胞相容性，有望为骨创伤提供更好的修复与治疗材料，为研发综合性能更优异的可降解骨修复材料奠定了理论和技术基础。