基于水凝胶多级结构仿生设计关节软骨替代材料及其粘弹性力学行为研究

Now, large area articular cartilage defect is still a clinically tough problem, urgently needs the suitable articular cartilage substitute materials. New polymer hydrogels have many excellent functions, such as anti-fatigue, self-repair, high strength and toughness, and its network structures, viscoelasticity and water content are similar to the extracellular matrix. So polymer hydrogels are ideal articular cartilage substitute materials. This project is based on the mechanical characteristics and biological behavior of chondrocytes controlled by multistage structures of hydrogels, such as the chemical composition, crosslinking network, aggregation structures and mineralized structures. The internal mechanism of properties controlled by the structure of hydrogels is studied by means of multistage structures characterization technologies and mechanical properties test methods. New hydrogels could be developed which satisfy the requirements of articular cartilage and the cartilage cell growth. Then, articular cartilage substitute materials are in-situ formed by imitating the structure and function of articular cartilage, and it is constituted by the self-healing shallow surface, hard and tough middle layer, high viscous calcification layer and high elastic liner layer. The experimental methods of tensile, compression, stress relaxation, creep, nano-indentation and dynamic thermomechanical analysis are used to study the mechanical behaviors. The mechanical behaviors corresponds the mechanism of molecular motion is analyzed based on the multistage structural features of hydrogels, and the multicomponent model describing the viscoelasticity of multistage structural hydrogels is explored by numerical calculation methods. These researches provide material and theory basis for polymer hydrogels used in the clinical treatment of large area defects of articular cartilage.

目前大面积关节软骨缺损仍是临床治疗的难题，迫切需要合适的关节软骨替代材料。新型高分子水凝胶具有抗疲劳、自修复、高强韧等优异性能及与细胞外基质类似的网络结构、粘弹性、含水量，是理想的关节软骨替代材料。本项目基于水凝胶的化学组成、交联网络、聚集态及矿化结构调控力学特性和软骨细胞生物学行为，通过结构表征和性能测试方法分析结构调控性能的内在机制，研制满足关节软骨功能及软骨细胞生长要求的水凝胶。仿关节软骨的结构和功能，构筑由自修复浅表层、硬韧性中间层、高粘性钙化层及高弹性衬垫层原位成型的水凝胶关节软骨替代材料。利用拉伸、压缩、应力松弛、蠕变及纳米压痕、动态热机械分析等实验方法研究其力学行为，基于水凝胶多级结构特征分析其力学行为对应的分子运动机理；辅以数值计算方法，研究多级结构水凝胶的粘弹性力学行为，探索描述其粘弹性的多元件模型。上述研究将为水凝胶用于大面积关节软骨缺损的临床治疗提供材料和理论基础。

目前大面积关节软骨缺损仍是临床治疗的难题，迫切需要合适的关节软骨替代材料，临床使用的人工软骨多采用塑料、金属或陶瓷材料，植入体内后难以与骨或软骨界面产生良好结合，同时金属的耐腐蚀性、塑料的耐磨性等问题仍待解决。新型高分子水凝胶具有抗疲劳、自修复、高强韧等优异性能及与细胞外基质类似的网络结构、粘弹性、含水量，是理想的关节软骨替代材料。本项目结合人工软骨替代材料的要求和组织工程方法的优势仿生设计基于高分子水凝胶的一体化关节软骨替代材料，包括关节软骨层替代材料及软骨下骨层修复材料。基于多重氢键和Hofmeister协同效应制备了聚乙烯醇/聚丙烯酸(PVA/PAA)高强度水凝胶，满足关节软骨替代材料的要求的同时兼具良好的细胞相容性。PVA/PAA Cold-Drawn水凝胶的抗拉强度和拉伸弹性模量达到了到14.54 ± 0.89 MPa和2.67 ± 0.47 MPa，80%应变下抗压强度及压缩弹性模量达到了22.04 ± 0.67 MPa和2.12 ± 0.11 MPa。同时对高强度水凝胶的应力松弛特性、动态黏弹性及耐疲劳性能进行了初步研究。采用光引发和热引发的自由基聚合方法制备了具有多孔结构的聚丙烯酰胺（PAM）和PAM-Mineralized水凝胶，其表面形成了稳定的羟基磷灰石矿化涂层，MC3T3-E1细胞在其表面能够良好的黏附生长和成骨分化能力，适合用于软骨下骨修复材料。采用一体化成型方法制备了PVA/PAA-PAM一体化水凝胶，解决了单一成分水凝胶难以满足关节软骨替代材料和软骨下骨修复的需求，避免了通常多层水凝胶的复合界面间移位的缺点。本项目的实验研究和理论分析成果为水凝胶用于大面积关节软骨缺损的临床治疗提供材料基础和理论依据，达到了项目预期研究目标。在项目执行期，以第一及通讯作者发表SCI论文7篇、中文EI两篇、核心一篇；参加国内学术会议8人次，并做分会报告3人次；申请国家发明专利6项，指导硕士研究生6人（毕业3人），超额完成了项目制定的预期研究成果。