医用镁合金表面多元耦合仿生膜层构建及其可控降解机理研究

The controllable degradation and compatibility are two serious problems faced by magnesium (Mg) and its alloys for potential orthopaedic applications. Surface modification with bioactive materials is one of the promising ways to resolve these problems simultaneously. Scapharca subcrenata shell owns a perfect combination of interface bonding strength, wear and corrosion resistance, and biomineralization inducing function, which is attributed to the coupling roles of its specific multi-layered “brick-bridge-mortar” structure, non-smooth micro-nano hierarchical features, together with the inorganic and organic compositions. Inspired by this biological coupling functions, multi-layered calcium phosphate (CaP) / collagen (Col) / calcium carbonate (CaCO3) composite coatings with micro-nano hierarchical surface features will be designed and fabricated on biomedical Mg alloys in the present project, with the aim to fix the insufficient corrosion resistance and bioactivities of the composite coatings due to their poor coating adhesion during the practical applications. To obtain a bioactive composite coating with high coating adhesion and layer-by-layer controllable degradation behavior, the effects of multi-layered structures, surface features and coating compositions on the coating adhesion, degradation behavior, wettability, cytocompatibility and histocompatibility will be studied, and the interaction mechanisms of these behaviors will be further discussed. This project will provide novel conception and method for the design and fabrication of the composite coatings on biomedical Mg alloys.

镁合金植入体在人体内的可控降解与生物相容性是医用植入材料领域亟待突破的重要科学问题，表面制备生物活性膜层是有望同时改善上述问题的有效方法之一。自然界毛蚶壳中多层交替的砖泥桥结构和非光滑微纳分级形态以及无机、有机材料有序复合，赋予其优异的界面结合力、耐蚀耐磨和生物矿化诱导功能。本项目依据仿生学原理，模仿毛蚶壳结构、形态和材料多因素耦合作用，在镁合金表面构建由钙磷/胶原/碳酸钙组成的多层交替微纳分级复合膜层，着力解决医用镁合金表面膜层因结合力不足导致植入体耐腐蚀性和生物相容性无法完全满足临床应用要求的基础问题。通过探索多层结构、微纳形态以及材料组成对复合膜层结合力、润湿性、腐蚀降解行为、细胞和组织相容性等的影响规律，揭示耦合变量、制备参数与功能特性之间的相互作用机制，最终获得兼具逐层可控降解功能和高结合强度的生物活性复合膜层，为生物医用镁合金表面复合膜层的创新设计与制备提供新原理和新途径。

生物医用金属植入体可帮助修复或替换人体中病变或受损的承重骨骨骼组织。与传统的金属植入材料(如不锈钢、钴铬合金和钛合金)相比，镁及其合金具有良好的机械性能、可降解性以及生物相容性。镁植入体在体内能够缓慢降解，不需要进行二次取出手术，加速手术愈合的同时也减少了病人痛苦和医疗费用。然而，在生理环境中的快速降解和潜在的细胞毒性阻碍了它们在临床上的进一步应用。表面改性是提高镁合金耐腐蚀性能以及生物相容性能最常用的方法，也是最有效的方法之一。本项目基于生物耦合机制与规律，通过对膜层结构、形态与材料多个耦元进行耦合仿生设计与制备，在镁合金表面制备了由磷酸钙（CaP）、二氧化钛（TiO2）、胶原蛋白（Col）等组成的多种复合涂层。通过体外降解实验以及电化学分析检测了不同涂层的耐腐蚀性能以及矿化性能，并使用小鼠前成骨细胞（MC3T3-E1）分析了不同涂层试样的体外生物相容性能。研究表明，不同仿生复合涂层不仅明显降低了镁合金的腐蚀速率，而且大大提高了植入体材料表面的生物相容性和抗菌性。本项目立足于生物医用金属植入体的临床需求和生物活性膜层失效机制，围绕腐蚀降解、生物相容和仿生研究的基础理论，拓宽了镁合金在耦合仿生领域和生物医学领域的交叉复合应用。