各向异性木纤维水凝胶及其在临界骨缺损修复的应用研究

骨是一种天然的羟基磷灰石/胶原蛋白复合材料，表现出特殊的多层次各向异性结构。在临床骨缺损治疗领域，传统的自体或者同种异体骨移植具有一定的局限性，而植入骨组织工程支架能够避免这些问题。但大多数基于胶原蛋白的骨组织工程支架与天然骨结构特征差异较大，导致治疗效果不理想。针对该问题，本研究利用天然木材的多层次各向异性结构作为模板，制备一种具有良好骨诱导性的木材纤维基仿生水凝胶支架，通过结合机械刺激和生化刺激的方法，促进支架的骨修复性能。

本课题对松木和杨木两组木材进行脱木素处理，再使用2,2,6,6-四甲基哌啶氧化物介导的氧化体系进行表面改性，制备羧基化木质模板。通过脱木素处理，使支架管壁变薄并增大孔隙率，有利于后续氧化反应。羧基化后松木和杨木的孔隙率分别达到62.7%和78.1%，压缩模量约为430 kPa，并且均表现出木材特有的X射线衍射峰和红外吸收谱，保留了木材的基本结构。根据骨修复支架的结构需求，本课题选择羧基化杨木作为结构模板。

通过偶联反应交联胶原蛋白与羧基化杨木，获得复合支架（WH）；而胶原蛋白水凝胶（Col）作为实验对照。扫描电镜图像表明，胶原与模板结合紧密，并且沿纤维分布，而红外吸收光谱和X射线光电子能谱证明两者以酰胺键方式交联。模拟矿化后Col和WH均能沉积钙盐，且形态分别呈球形和片状。在细胞实验中，Col与WH的细胞存活率相近但形态存在差别，WH表面的细胞表现出明显的轴向性。此外，WH可显著增强碱性磷酸酶等成骨细胞活性标志物的基因表达。通过构建大鼠颅骨缺损模型发现，WH组的再生骨的骨体积和骨密度均高于其余实验组，说明WH对体内骨再生有明显的刺激作用。

本课题证明了与骨具有相似各向异性结构的材料能促进骨再生，讨论了各向异性结构诱导细胞成骨分化的机理，探究了一种多尺度模拟骨组织具备的多级取向结构的新方法，有利于推动具有取向性结构的骨修复支架的构建和应用。

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