【作者】 孔丽丽；

【导师】 林昌健；

【作者基本信息】 厦门大学 ， 物理化学， 2009， 硕士

【摘要】 医用金属钛及其合金的表面改性和性能优化一直是生物材料研究领域的焦点之一。虽然钛及其合金具有较好的生物相容性,但缺乏生物活性,亟需通过表面修饰改性使之具备诱导骨组织长入并与植入部位实现骨性结合的能力。医用钛表面涂覆羟基磷灰石（HA）是一种重要的生物活性改性优化技术。商用等离子体喷涂法存在高温相变分解及无法实现复杂形状基体的均匀涂覆等难以克服的技术缺点,电化学沉积技术作为一种温和的非直线涂覆技术,可避免等离子体喷涂技术中HA相变分解等问题,有望发展成为一种重要的替代表面技术。然而,一般电化学沉积的HA涂层结构疏松,与基底结合力较弱,且仍存在由于基体钛或钛合金的热膨胀系数和HA的热膨胀系数差异较大,所导致的界面物理性能突变,应力集中的问题。TiO₂的热膨胀系数8.7×10^-6K^-1,介于Ti(8.2×10^-6K^-1)和HA(15×10^-6K^-1)之间。钛基阳极氧化和水热制备TiO₂,操作简单,条件温和,也可实现在复杂形状基体表面的均匀涂覆,涂层结合强度高,能够阻挡体液对钛基体的生理腐蚀。另一方面,运用阳极氧化法或水热法对钛基体表面进行纳米化处理,构筑有序结构,可为进一步羟基磷灰石的电沉积提供定向成核和生长的模板。本论文主要研究内容有:a)通过对医用钛金属的设计和改性,发展阳极氧化和水热处理的方法,在钛基体表面构筑纳米结构的TiO₂膜层;b)基于仿生学的观点,发展电化学沉积方法,在钛基TiO₂膜层表面实现可控制备有序结构、组分和结构确定的HA膜层,制备具有良好力学性能和优异生物性能的仿生骨膜层;c)运用各种物理化学和细胞培养方法对经电化学新技术改性的生物材料的理化性质、力学性能和生物学特性进行考察,探明材料表面的构—性关系。主要研究结果如下:1.通过两步电沉积（脉冲—恒流）法,首次实现了在TiO₂纳米管内和纳米管阵列膜表面定向沉积HA纳米晶,研究表明,TiO₂纳米管内有大量纯HA晶体沉积,较低的电流密度下,HA颗粒主要在TiO₂纳米管管间和管内壁定向沉积。控制电化学沉积参数,制备了不同结构形貌的纳米羟基磷灰石膜层,并跟踪观测了电化学沉积过程的纳米羟基磷灰石膜层形貌结构变化。还采用划痕实验对材料力学性能进行了测试,应用Tafel极化曲线和电化学阻抗技术对表面经过电化学改性的医用钛金属在Tyrode’s生理溶液中的耐蚀性进行了评价。2.采用水热法加后处理,改变反应条件,在医用钛表面制备了两种不同微—纳米形貌的多孔锐钛矿型TiO₂膜层。发展了结构有序HA的电沉积制备技术,在不同水热处理所得的TiO₂膜层表面构筑了HA纳米棒膜层,成功地对医用钛金属表面进行了生物活性修饰,并考察了不同沉积时间对HA膜层性能的影响。细胞实验表明,HA/TiO₂复合膜层可显著增强MG63细胞的粘附和生长,其生物相容性明显优于单一的TiO₂膜层。且随着HA/TiO₂复合膜层中HA含量的增加,其生物相容性和生物活性增强,HA晶粒结构和尺度对细胞伪足的伸展影响明显。3.采用乳液聚合法和分散聚合法,通过改变反应参数,制备了0.1～5μm不同粒径的单分散的聚苯乙烯（PS）微球。结合电化学阳极氧化和表面磺化法分别对金属钛和聚合物微球进行表面改性,使微球在钛表面组装成规整的模板。在组装了不同粒径磺化聚苯乙烯（SPS）微球的TiO₂纳米管阵列表面电沉积HA膜层,并通过退火处理,使羟基磷灰石膜层充分陶瓷化,并且进一步增强羟基磷灰石膜层与基底的结合力,同时去除SPS微球,成功获得到了均一致密的微—纳米有序多孔HA膜层。形成的HA膜层一级结构为微米尺度排列有序的孔结构,电化学沉积的HA纳米晶须形成纳米尺度的二级结构。膜层内部孔洞间完全贯通,这种结构一方面能为骨生长因子、成骨细胞等生物活性物质提供几何空间和相对稳定的微环境;另一方面,有利于体液和营养物质在材料内部流动,与体循环连通,增加材料与体液的接触面积,加速材料与组织的融合过程。且HA颗粒在TiO₂纳米管管内和管间沉积,进一步改善界面间的结合强度。细胞培养实验表明,多孔HA膜层可显著增强细胞的黏附与生长,其生物相容性优于直立HA膜层和TiO₂纳米管阵列。这种生物活性的显著差异与多孔HA膜层独特的微—纳米多级结构以及与骨类似的组分密切相关。更多还原

【Abstract】 Surface modification and functional optimization of medical titanium（Ti） and its alloys are one of the most focal topics in biomaterials.Titanium and its alloys have no sufficient bioactivity themselves,it is necessary to conduct surface modifications to endow them with abilities of induction of bone tissue ingrowth and osseointegration at the implantation site.Preparing hydroxyapatite（HA） coating on titanium substrate is an important technology to improve the bioactivity,and plasma spraying technique has been commercially used to deposit HA coating on Ti surface.However the heat effect during the coating process unavoidably causes decomposition of HA,and the HA can not be uniformly coated on the Ti substrates with complicated shape.As a moderate non line coating technology,the electrodeposition method is proposed as one of the most promising alternatives.However,the HA coating obtained by electrodeposition remains loose structure and poor bonding with the substrate,and a great difference between the coefficients of thermal expansion（CTE） of Ti substrate and HA may result in sudden changes of physical property and stress concentration on their interface.The coefficient of thermal expansion of TiO₂ is 8.7×10^-6 K^-1,between Ti(8.2×10^-6 K^-1) and HA(15×10^-6 K^-1).So proper anodic oxidation or hydrothermal treatment for Ti has distinct advantages including simple and moderate preparation conditions,and facile to obtain a uniform coating on the substrates with complicated shape.The bonding strength between Ti substrate and prepared TiO₂ coating is high, ant it is able to resist its physiological corrosion in body fluids.On the other hand,the nano-structured TiO₂ derived form anodic oxidation or hydrothermal method on Ti is possible to provide oriented nucleation and growth template with an ordered structure for electrodeposition of HA.The main works in this thesis includes:a) development of anodic oxidation and hydrothermal method to construct nano-structured TiO₂ coatings on titanium substrate; b) controllable electrodeposition to prepare HA coating with ordered structure and definite composition on Ti-based TiO₂ film,and to obtain a biomimetic bone film of HA/TiO₂ with good mechanical properties and excellent biological properties,based on the views of bionics;c) the physicochemical,mechanical and biological characteristics of the coatings prepared by electrochemical methods were studied to learn the relationship of structure and properties of materials.The main findings and progresses are as follows:1.The hydroxyapatite nanocrystals were electrochemically-oriented deposited inside and onto the TiO₂ nanotubes by using the two-step electrodeposition for the first time.It is indicated that,thers is a large number of pure HA crystals deposited in TiO₂ nanotubes.At a lower cathodic current density,HA was mainly deposited between and on the walls of the TiO₂ nanotubes. Controlling electrochemical deposition parameters,the nano-HA coatings with different structures were prepared.And the morphology and structural changes of the nano-HA in the electrodeposition process was studied by SEM and XRD observations.The mechanical properties of the prepared materials were tested by the scratch analysis of nanoindentation.Tafel polarization and electrochemical impedance spectroscopy（EIS） were applied to study the electrochemical corrosion behavior of the modified medical titanium in Tyrode’s physiological solution.2.Two different micro-nano structured anatase TiO₂ on medical titanium surface were prepared by hydrothermal method and post-treatment.The electrodeposition was developed to construct an orderly structured HA coating on the different TiO₂ films prepared by hydrothermal method.The effect of the deposition parameters on HA coating was studied.It is indicated, from in vitro cell culture,that the HA/TiO₂ composite is able to significantly enhance the ability of MG63 cell to adhere and grow on the coating,and its biocompatibility is superior to a single layer of TiO₂.And with increasing of HA in HA/TiO₂ composite coating,the biocompatibility and bioactivity are clearly improved.The HA grains has a significant impact on the extension of pseudopodia of cells.3.Using emulsion polymerization and dispersion polymerization,the monodisperse PS microspheres with different sizes of 0.1～5μm in diameter were prepared.Combination of anodic oxidation of titanium and sulfonation of the PS microspheres surface,the PS microspheres were successfully self-assembled on the prepared TiO₂ nanotube arrays surface.The uniform micro-nano structured interconnected porous HA was obtained by electrodepositing HA coating on TiO₂ nanotube arrays,through the templates of self-assembled and sulfonated PS（SPS） microspheres,and then annealing to remove the SPS microspheres and to further increase the bonding strength of the substrate and the coatings.The primary structure of prepared HA coating shows an ordered micron-scale pore structure derived from SPS microspheres,and the secondary structure is the HA nano-whisker formed from the electrodeposition of HA.And the HA coating has a completely interconnective structure,that is able to provide the geometric space and a relatively stable microenvironment for bioactive substances such as bone growth factors and osteoblasts.On the other hand,this structure is conducive to the flow of body fluids and nutrients within the material,and to increase the contact area between the material and the body fluids,which is helpful to accelerate the integration process of materials and organizations.The HA nanoparticles deposited inside and between the TiO₂ nanotubes will not only further improve the bonding strength at the interface,but also enhance the corrosion resistance of materials against the body fluids.In vitro cell culture showed that the prepared porous HA coatings are able to significantly enhance the ability of MG63 cell to adhere and grow on the surface.The biocompatibility and bioactivity of the porous HA coating is superior to the vertically oriented HA coating and TiO₂ nanotube arrays as well.This significant differences of biological activity is closely related to their unique two-level ordered structure of porous HA coating on medical Ti surfaces.更多还原