【作者】 叶新羽；

【导师】 蔡舒；

【作者基本信息】 天津大学 ， 材料学， 2013， 博士

【摘要】 作为新一代可降解骨修复材料，镁合金具备良好的力学性能、生物相容性以及可降解特性，近年来引起了广泛关注和研究。但是，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。通过制备保护涂层，可以有效保护镁合金基体，控制其腐蚀行为。与传统涂层材料相比，介孔材料具备窄的孔径分布、大的比表面积以及良好的亲水性等特点，可以显著提高材料的生物性能。为此，在镁合金表面制备介孔涂层有望获得具有良好综合性能的骨修复材料。本文采用溶胶凝胶法结合浸渍提拉的工艺分别在载玻片和镁合金表面制备出介孔羟基磷灰石涂层以及添加45S5玻璃陶瓷的介孔羟基磷灰石/45S5玻璃陶瓷复合涂层，优化出结构均匀、无缺陷裂纹涂层的制备工艺。以CTAB或F127做为模板剂制备的介孔羟基磷灰石，可通过改变pH值或模板剂浓度调控其介孔结构；其中，使用0.192g/mL的F127模板剂制得了孔径、孔容和比表面积分别为3.17nm，0.38cc/g，211.7m2/g的介孔羟基磷灰石，并在镁合金表面制得了厚度约为1.0μm，结构均匀、无裂纹的介孔涂层。以模拟体液为腐蚀介质，研究了不同结构和组成的包覆涂层对材料降解行为的影响，并探索了介孔涂层抑制镁合金基体快速降解的作用机理。结果表明：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。介孔涂层包覆的镁合金，在浸泡10d后仅出现部分涂层的剥落，腐蚀速率为0.050mm/d，表现出较好的耐蚀性能。添加45S5玻璃陶瓷可以减小涂层和基体之间热膨胀系数的差异，降低复合涂层中的热应力。介孔复合涂层在浸泡10d后只开裂而未剥落，试样的腐蚀速率为0.012mm/d，进一步提高了对基体的保护。同时，研究了介孔涂层的结构对材料亲水性和生物性能的影响。引入介孔结构提高了羟基磷灰石涂层的比表面积和表面粗糙度，使涂层的水接触角从67.8°下降到30.1°。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)。综上所述，介孔结构在延缓涂层的开裂、剥落的同时，提高了涂层的亲水性和细胞相容性，介孔涂层包覆的镁合金具有良好的耐蚀性能和生物性能，有望作为骨修复材料使用。更多还原

【Abstract】 Due to the good mechanical properties, in vitro and in vivo biocompatibility, anddegradability, magnesium (Mg) and its alloys have been regarded as the candidate forthe application as the biodegradable bone repair materials recently. However, theclinic use of Mg alloys is mainly restricted owing to the too fast initial corrosion ratein body fluids. Surface modification is an efficient way to protect Mg alloys andcontrol their corrosion behavior. Compared with the conventional coatings materials,mesoporous materials have the narrow distribution of pore size, large specific surfacearea and enhanced surface wettability, which favor for the promotion of biologicalproperties of the substrates. It could be hypothesized that Mg alloys coated withmesoporous coatings would exhibit suitable properties for bone repair.In this paper, mesoporous hydroxyapatite (HA) and mesoporous HA/45S5glass-ceramic composite coatings were respectively prepared on the glass or Mg alloysubstates using a sol-gel dip-coating method, and the process was optimized toprepare the uniform and crack-free coatings. Mesoporous HA with different porestructure was prepared using CTAB or F127as the templates by varing pH value andtemplate concentration. Therein, the mesoporous HA prepared using0.192g/mL ofF127template achieved the mesopores sized in3.17nm, and its pore volume andspecific surface area were0.38cc/g and211.7m2/g. The uniform and crack-freemesoporous coating with the thickness in~1.0μm was prepared on Mg alloysubstrate.Using simulated body fluids (SBF) as the corrosion medium, the influence of theporous structure and composition of the coatings on the corrosion behavior of Mgalloy was studied, and the mechanism of the mesoporous coatings to prevent Mg alloyfrom rapid corrosion was explored. The immersion tests showed that the presence ofmesoporous structure would decline the elastic modulus of the coating and the effectof residual stress on its breakdown, preventing the rapid cracking and peeling of HAcoating in the initial soaking stage and promoted the protection of the mesoporous HAcoating to the substrate. After soaking in SBF for10days, the corrosion rate of themesoporous HA coated Mg alloy was0.050mm/d, revealing that the coated sample has good corrosion resistance. Furthermore, the addition of glass-ceramic into themesoporous coating would decrease the difference of thermal expansion coefficientsbetween the coatings and substrates. Due to the downtrend of the residual stress, themesoporous composite coating didn’t peel after immersed in SBF for10days andprovided the enhanced protection to the substrate, that is, the corrosion rate of themesoporous composite coating coated Mg alloy was decreased to0.012mm/d.Meanwhile, the effect of the mesoporous structure on the surface wettability andbiological properties of the coatings was evaluated. The introduction of mesoporespromoted the specific surface area and surface roughness of the coatings, which led tothe decrease of water contact angle from67.8°to30.1°. In vitro cell assay revealedthat the improved surface area and wettability favored for the adsorption of proteins inculture media, being beneficial for the adhesion, spreading, proliferation ofosteoblasts and bone-related proteins expression. After being cultured for designedperiods, the cell density and proteins concentration in the mesoporous groups weremarkedly higher than those of the non-mesoporous group (*p<0.05).In conclusion, the mesoporous structure could prevent the rapid cracking andpeeling of the coatings, and promote their surface wettability and in vitrocytocompatibility. Therefore, the mesoporous coatings coated Mg alloy, being withgood corrosion resistance and biological properties, could be used as the bone repairmaterials.更多还原