新型两性离子/聚酯骨组织工程支架的构建及其生物学性能研究

Design high-efficiency delivery systems for bone morphological protein-2 (BMP-2) to resolve the severe side effects that caused by the supra-physiological dose clinic treatment is the focus of the bone tissue engineering scaffolds’ research. Current strategies in reducing the BMP-2 dosage are mainly through the adjusting its loading & release manners. However, the dosages that below 1 µg/scaffold (single growth factor treatment) are believed to be insufficient for the functional healing of non-union critical-sized bone defects. Based on the merit of zwitterionic materials that they can maintain the native conformation of proteins, combined with the preliminary findings that zwitterionic motifs are efficient ligands for templated biomineralization of hydroxyapatite (HA), the current project will fabricate novel zwitterion/polyester scaffolds for bone tissue regeneration. In this project, the relationship between the physicochemical properties of the zwitterion/polyester scaffolds and the release profile of BMP-2 will be established, the osteoconductivity and osteoinductivity of the BMP-2 bearing scaffolds will also be exploited. In addition, the healing behavior of the critical-sized rat bone defects with the zwitterion/polyester scaffolds bearing super-low BMP-2 dose (orders of magnitude lower than that required for the current delivery systems) will be evaluated and the mechanism of the promoted bone healing associated with zwitterionic scaffolds will also be elucidated. This study will not only provide new approaches for the construction of efficient bone tissue engineering scaffolds, but also offer promising candidates for the high-efficiency delivery of other bioactive molecules.

构建骨形态发生蛋白-2（BMP-2）的高效缓释体系以解决临床中因高剂量BMP-2的使用所致的严重副作用是当前骨组织工程支架材料研究的热点与难点。针对目前普遍采用通过调节BMP-2的释放方式中所面临的低于1µg/支架的剂量（单一BMP-2治疗）不足以修复临界尺寸骨缺损的瓶颈，并基于两性离子材料能维持蛋白正常构象的特性，结合其特殊双离子结构能促进生物矿化的前期研究基础，本项目拟从载体材料对BMP-2活性保持这一新的角度来构建骨组织工程支架材料。研究两性离子/聚酯复合支架物化性能与BMP-2缓释效果之间的关系；探索支架/BMP-2复合体系的骨传导、骨诱导功能；结合大鼠临界骨缺损模型评价超低BMP-2剂量下（数量级地低于现有缓释体系）复合支架对骨缺损的修复行为并最终阐明其作用机制。本研究不仅为高效骨组织工程支架的研发提供新的途径，而且可为其他生物活性分子的高效缓释载体的设计提供新的思路和科学依据。

针对目前普遍采用通过调节BMP-2的释放方式来降低其用量所面临的低剂量BMP-2（低于1μg/支架的剂量）不足以修复临界尺寸骨缺损的瓶颈，本项目从载体材料对BMP-2活性保持这一新的角度设计并制备了一类新型的两性离子水凝胶/聚酯复合支架。由于复合支架中三维构建的两性离子结构（水凝胶）具备特殊的双离子型化学结构，能实现对离子型蛋白质的缓慢释放。结合两性离子材料能维持蛋白正常构象的特性，所制备的新型复合支架实现了在450 ng/支架的剂量下有效引导5-mm大鼠头盖骨缺损的功能性修复，为高效骨组织工程支架的研发提供新的途径。圆满完成了项目的既定目标。在此基础上，进一步开发了矿化的两性离子/聚酯骨组织工程复合支架，具备优异的骨传导及对于rhBMP-2缓释性能。与此同时，开发了两种技术工艺分别制备了两类新型的可分别用于聚氨酯、金属器件表面改性的两性离子聚合物涂层材料，为下一步在聚氨酯、金属支架表面构建两性离子蛋白缓释层打下良好的基础。本项目共申请中国发明专利3项（1项已授权）；发表SCI论文3篇，另有2篇在投稿或待投；培养研究生5名（2名已获得硕士学位）。