生物玻璃陶瓷涂层包覆镁合金材料的界面结合、降解和生物学性能的研究

Magnesium alloys/coating materials have been considered as the revolutionary biodegradable materials used as orthopedic implants due to their desirable mechanical properties and biocompatibility. However, too fast corrosion rate, being associated with the large amount of H2 production in vivo and the low bonding strength between the coatings and the magnesium alloy substrate, limits the clinical application. In the present investigation, an attempt will be made to develop mesoporous glass-ceramic coatings on magnesium alloys through a sol gel technique for improving stress match of magnesium alloy substrate to inorganic coatings, with the aim to increase the adhesion and corrosion resistance of metallic clinical implants. The effects of mesoporous structure of the coatings on the ductility of magnesium alloy matrix, crack formation in the mesoporous coatings during the corrosion processes, as well as the degradation and bioactivity of the glass-ceramics coated magnesium alloys will be investigated in this study. Meanwhile, based upon the alloy superplastic deformation/diffusion bonding theory and technology, and the adjustable soft points of Ca-P-Si glasses, the composition and processing parameters of glass-ceramics coated magnesium alloys with high adhesion strength will be optimized. Moreover, the diffusion mechanism of the interface atom under superplastic conditions will be explored, which helps to recommend the fabrication of glass-ceramic coated alloys. On this basis, the controlled degradation of the coated magnesium alloys can be achieved by adjusting the composition and structural properties of the mesoporous glass-ceramic coatings. And the influrence of degradation, structure of mesoporous coatings on biorelated functions will be investiaged as well. The novel design strategy of mesoporous coatings on magnesium alloy substrates and the substrate-coating bondings proposed in this project can be further extended to the synthesis of functional coatings on the other superplastic alloys, and it can also offer a useful guide for the surface modification and new product development of medical alloys.

镁合金/涂层材料有望成为最重要的可降解吸收的骨科植入材料，然而较低的基-膜结合强度和在体液中的快速降解一直是亟待解决的问题。本项目提出利用溶胶凝胶方法在镁合金基体上制备介孔生物玻璃陶瓷涂层，改善涂层与镁合金基体的应力匹配；研究介孔涂层的结构特性对涂层的开裂行为和镁合金基体延展性的影响，及其对材料降解和生物活性的调控作用。同时依据合金超塑变形/扩散连接理论和技术，以及玻璃软化点的可调变特性，研究形成基-膜牢固结合的钙磷硅玻璃体系和工艺条件，探讨超塑性条件下界面原子的扩散途径和结合机理。本项目在形成牢固基-膜结合的基础上，利用介孔玻璃陶瓷涂层的组成和结构性能的调变作用，实现镁合金/涂层材料的可控降解。并研究材料降解、介孔涂层结构对生物学性能的影响。本研究提出的介孔涂层设计方案和基-膜连接思路可以进一步拓展到其它具有超塑性（医用）合金表面功能涂层的制备、改性和产品研发上，具有普遍的指导作用。

镁合金具备良好的力学性能、生物相容性以及可降解特性，作为可降解骨修复材料，已引起了广泛的关注和研究。但镁合金在生理体液环境中的初期腐蚀速度较快，限制了其临床应用。本项目通过涂层改性的方法在镁合金基体上制备涂层，控制镁合金基体的腐蚀行为，改善其生物活性。以生物活性玻璃或玻璃陶瓷，如硅基玻璃、钙磷玻璃等为涂层材料，采用溶胶-凝胶法结合浸渍提拉工艺，以及热处理在镁合金表面制备出致密的，具有介孔结构的涂层。研究了介孔涂层结构和组成的可控制备，涂层与镁合金基体的界面结合及其机理，以及涂层组成和结构对材料降解、矿化和生物性能的影响。.在镁合金上（AZ31）成功制备了表面形貌均匀、结构完整的多种介孔玻璃或玻璃陶瓷体系的涂层，如45S5、 58S和羟基磷灰石/45S5的生物玻璃陶瓷。高温、加压热处理促进了Mg、Ca、Na原子的扩散，同时镁合金因超塑性变形促进晶界滑移和晶粒转动，在界面处产生互扩散和固溶反应，使涂层与基体形成了强的界面结合，结合强度为18-27MPa。介孔结构的存在可以降低涂层的弹性模量，减小残余应力对涂层失效的影响，避免介孔涂层在浸泡初期的开裂、剥落，延长涂层对镁合金基体的保护作用。如介孔羟基磷灰石/45S5玻璃陶瓷涂层在SBF中浸泡10 d后只开裂而未剥落，试样的腐蚀速率为0.012 mm/d，呈现出良好的耐蚀性能。研究了介孔涂层的结构对材料亲水性和生物性能的影响。涂层中的介孔结构提高了涂层的比表面积和表面粗糙度。在体外细胞实验中，介孔涂层比表面积的增大和亲水性的改善促进了材料对培养基中蛋白质的吸附，有利于成骨细胞在涂层表面的黏附、伸展和增殖，以及骨相关蛋白的表达。在一定的培养周期后，介孔涂层试样的细胞密度和蛋白质浓度显著高于非介孔涂层试样 (*p<0.05)。.本项目研制的介孔结构涂层能够显著延长镁合金基体的降解周期，提高涂层的亲水性和细胞相容性，具有良好的耐蚀性能和生物性能，有望作为可降解骨修复材料使用。