人工关节固定表面生物活性涂层仿生构筑及其性能研究

Stable fixation of artificial joint implants with bone system are believed to have significant effect on their osteointegration. To achieve stable and effective fixation of these artificial joint implants with bone tissues, novel bioactive coating materials with strong and high toughness, excellent osteoconductivity and wear resistance should be developed，and deep understanding of the biological responses and regulating mechanisms of the implant/bone fixation interface are also required. On the basis of excellent mechanical properties, good biocompatibility and antibacterial properties of graphene nanosheets (GNSs)，and the typically lamellar structure of plasma sprayed coatings, the primary emphasis of this proposal is to develop key techniques of bionic manufacturing for plasma sprayed GNS/HA composite coating with bimodal microstructure under the guidance of material design concept of "Multi-scale synergistic reinforcing and toughening splat boundaries and splats", which are expected to impart the composite coating excellent biomechanical properties and osteointegration to bone tissues. The objective will be achieved by dividing research plan into the following broad categories: 1.Optimization of plasma spray processing maps: The degree of melting and re-solidification of the in-flight agglomerated particles and the selection mechanisms of splat morphology should be well controlled, regulating mechanisms of both multiple interface structure and bionic building will be also highlighted. 2.Evaluation of mechanical properties: Mechanical properties such as bond strength of GNS/HA/Ti6Al4V, elastic modulus, fracture toughness, wear resistance of these composite coatings will be evaluated. Fracture surfaces, surface morphologies of indent marks and scratch tracks, worn surface and wear debris will also be characterized to reveal reinforcing and toughening mechanisms. 3.Evaluation of in-vitro biocompatibility: Osteoblast functions on the surface of composite coating will be investigated through cell attachment, adhesion, proliferation, differentiation, cytotoxicity, alkaline phosphatase (ALP) activity; Adhesion force of osteoblast on the coating will be assessed by nanoscratching technique; Biomineralization behaviors will be investigated through immersion in SBF; More importantly, some gene expression such as ALP, Bone sialoprotein, Collagen Ⅰ, Osteocalcin, Osteonectin, osteopontin will be highlighted to reveal the interfacial regulating mechanisms of osteointegration.

人工关节植入假体与骨组织固定界面稳定形成决定了假体在人体环境中的骨整合质量。为从根本上解决人工关节植入假体的稳定性固定，急需掌握人工关节/骨组织固定界面骨整合行为及其调控机理，并开发出同时具有高强韧性、优异骨传导和抗摩擦磨损性能的生物活性涂层新材料。依据石墨烯优异的力学性能和良好的生物相容性与抗菌性能，针对等离子喷涂涂层层状结构特点，本项目以"扁平粒子界面及扁平粒子内部协同强韧化"多尺度结构仿生构筑植入假体固定表面生物活性涂层为设计思路，重点研究石墨烯/HA生物涂层多尺度结构仿生制备关键技术、涂层生物力学性能及其表面物理化学性质对成骨细胞贴附、增殖、分化行为、骨形成过程中骨相关基因有序表达的影响机制，阐明复合材料涂层强韧化的物理、力学机制，揭示涂层/骨组织固定界面骨整合行为及其调控机理，获得植入假体固定理论新认识。

本项目重点研究石墨烯(Graphene nanoplatelet, GNS)/HA生物涂层多尺度结构仿生制备技术、涂层力学性能及成骨细胞贴附、增殖、分化行为。...结果表明，等离子喷涂GNS/HA 涂层中GNS均匀分布于HA基体，且涂层呈现了双态结构（微米晶和纳米晶共存）。涂层物相组成主要为HA、TCP、CaO及非晶相，随着涂层中GNS含量的增加，涂层中HA结晶度略有增加（最高为~51.3%）。与HA涂层相比，1.0wt.% GNS/HA和2.0wt. %GNS/HA涂层的压入屈服强度分别提高了~54.7%和~60.8%，涂层扁平粒子间的滑移阻力则提高了~8.7%和~6.5%，断裂韧性提高了~32.2和~44.1，并具有较好的摩擦磨损性能。上述结果充分说明GNS对等离子喷涂HA涂层具有显著的强韧化作用，且奥罗万机制、GNS拔出、GNS阻碍裂纹扩展、GNS裂纹桥接、裂纹偏转等是等离子喷涂GNS/HA涂层的重要强韧化机制。体外生物学性能测试表明，石墨烯的添加在一定程度可改善成骨细胞的贴附及其贴附强度，这主要源于GNS/HA涂层表面粗糙度、润湿性及其刚度的改善。此外，GNS/HA涂层对成骨细胞的增殖、分化及在模拟体液中类骨磷酸钙盐的沉积均有一定的促进作用。..等离子喷涂GNS/HA涂层中HA结晶度较低，本项目采用热处理+水热反应（后面简称为热处理）对等离子喷涂涂层进行后处理。结果表明，热处理后等离子喷1.0wt.%GNS/HA及2.0wt.%GNS/HA涂层中晶态HA的体积分数分别为~71.6%、~75.4%，而且有助于等离子喷涂涂层中扁平粒子界面的消除，并使热处理后2.0wt%GNS/HA 涂层的表面粗糙度较未处理前提高了2倍。与等离子喷涂GNS/HA涂层相比，热处理后两种成分的GNS/HA涂层的压入屈服强度分别提高了~27.7%、~29.4%，但断裂韧性无明显改善。发现高温热处理不仅在石墨烯中引入较多的结构缺陷，还使石墨烯发生氧化造成其厚度、长度方向上的明显减小，导致其增韧效果显著降低。并且，热处理后GNS/HA涂层的摩擦磨损性能得到明显改善。研究发现，热处理对GNS/HA涂层的成骨细胞贴附、贴附强度、成骨细胞的增殖与分化无显著改善，且对GNS/HA涂层在模拟体液中类骨磷酸钙盐的沉积产生较大的副作用。