VEGF/Si-HA/TiO2复合涂层多孔钛的构建及其在大段骨缺损修复中的促血管和骨生成效应

Repair of large bone defects resulted from high-energy trauma, resection of bone tumors, etc. is still a challenge of clinical treatments. Finding a bone graft with excellent mechanical property and endowing it with quick angiogenesis and osteogenesis are key factors to resolve this problem. In this project, we focus on porous titanium with good potential for repairing load-bearing bone defects and fabricate a VEGF/Si-HA/TiO2 composite coating on it by combining advanced processing techniques of porous materials with progressive surface modification methods. This composite coating could have excellent ability to promote angiogenesis and osteogenesis, because it is not only composed of bioactive TiO2 and HA, but also contains the doped Si ions and loaded VEGF, which has been proved to have good ability to promote angiogenesis. The key step to produce this multi-functional coating is the successful preparation of the unique nanotube-shaped Si-HA crystals by electrochemical deposition technique, as Si-HA nanotubes could load VEGF more efficiently than other Si-HA crystals. Then, we will investigate the ability of VEGF/Si-HA/TiO2 coated porous titanium to promote the in vitro angiogenesis of endothelial cells as well as the osteoblastic differentiation of mesenchymal stem cells by in vitro cellular experiments, and evaluate its effect on repair of large bone defects in load-bearing sites by in vivo animal experiments. In the present study, advanced materials characterization, cellular and molecular biology techniques, histological analysis and other methods will be used. The results would be helpful to reveal the working mechanism of the material and give the possible solution to resolve the clinical problems of treating load-bearing large bone defects.

因肿瘤切除及严重创伤等导致的大段骨缺损修复是临床治疗的难题，选择优异力学性能的骨移植材料，赋予其快速的血管化和促骨再生性能是解决问题的关键。本项目立足多孔钛在承重骨缺损修复上的应用潜能，通过先进的多孔材料制备与表面改性技术的集成和创新，在常规生物活性TiO2和HA涂层上，集成和装载可促血管生成的Si离子和促血管生成因子VEGF，从而在生物力学相容多孔钛表面构建出兼具促血管和骨生成作用的VEGF/Si-HA/TiO2复合涂层。其技术核心在于电化学沉积Si-HA晶体形貌的调控，形成独特的纳米管状结构以实现对VEGF的高效装载。同时，结合先进的材料表征技术、细胞及分子生物学技术、以及组织学分析技术等，分别从体内外研究该材料在促进内皮细胞血管化、间充质干细胞成骨分化、以及动物承力部位大段骨缺损修复中的作用和机制，为突破解决临床大段骨缺损修复难题提供材料基础及设计思路。

大段的承重骨修复是临床治疗的一大难题，修复体设计、快速血管化和成骨活性是影响其成功修复的重要因素。本项目在传统泡沫浸渍和3D打印多孔钛表面通过优化的化学处理及电化学沉积工艺，逐层构建不同形貌和化学组成的HA/TiO2涂层，系统研究HA形貌、Si掺杂、VEGF装载等对涂层多孔钛耐腐蚀性、成骨、成血管性能等的影响；进一步设计构建钢板内固定和髓内固定的兔和比格犬股骨临界尺寸的节段性骨缺损修复体，通过构建的动物模型评价上述涂层改性多孔钛在大节段骨缺损中的修复效果。研究结果显示，应用不同的电沉积模式和工艺参数，可实现不同形貌（类片状、类棒状、类针状）HA或Si-HA涂层的优化制备，在化学处理和电沉积步骤间引入特定的阳极氧化处理，在化学处理形成的疏松TiO2层（L-TiO2）与钛基底之间可形成一薄层致密的TiO2层（D-TiO2），并通过电沉积后的水热处理，可赋予涂层多孔钛以优异的耐腐蚀性能。体外细胞实验评价显示，所有三种形貌HA涂层中，具有更大表面粗糙度和更亲水的类片状EDHA-P更能促进MSCs的成骨分化；Si掺杂可降低HA晶体的结晶度，更有利于涂层中Si、Ca和P离子的释放，形成的离子微环境有利于HUVECs的成血管化，也有利于促进MC3T3-E1的成骨分化。EDHA-P涂层能有效装载VEGF并实现可控释放，60天时的累计释放率不到60%；基于VEGF装载构成的VEGF/SiHA/TiO2涂层相较于SiHA/TiO2涂层，更能促进HUVECs的成血管化。比格犬背肌内和股骨髁内植入实验证实，与酸碱处理（AA）相比，类片状的EDHA-P涂层多孔钛具有更优的骨诱导性、骨整合性和成骨能力；兔和比格犬股骨大节段缺损修复实验证实，纳米HA涂层的3D打印多孔钛可较好修复临界尺寸的节段骨缺损，既促进新骨沿修复体表面爬行生长，又诱导新骨在孔隙内形成；修复体的初始力学稳定性同样在节段骨缺损修复中具有重要的作用。因此，本项目构建的VEGF/SiHA/TiO2涂层多孔钛在临床大节段承重骨修复中有较好的应用潜能。