胶体纳米胶囊介导可降解性血管支架体内原位组织再生

Tissue engineered blood vessels (TEBVs) are potential vascular grafts for the treatment of cardiovascular diseases, such as coronary heart disease and aneurism. TEBVs are also found applications in the construction of arteriovenous shunts. However, previous strategies for TEBV fabrication usually require long wait times, and the TEBVs made from these methods showed low long time patency rates. In our proposed research, we will explore an alternative mode that rely on the combination of colloidal nanocapsules we reported in a recent work with electrospun nanofiber membrane, cell growth factor and cell growth regulating drugs to fabricate a degradable scaffold that can regenerate blood tissue in situ. We hope the proposed strategy could address the challenges that the current TEBVs confronted. Firstly, nanocapsule A with endothelial progenitor cell proliferation promotion drug and CD34 monoclonal antibody loaded inside and on the wall of thecapsule, nanocapsule B with TGF-β1 conjugated on the capsule wall, and nanocapsule C with anti-intimal hyperplasia drug embedded inside of the capsule are going to be prepared. Secondly, the prepared nanocapsules will be integrated into biodegradable polymers of low molecular weight chitosan, high molecular weight chitosan and poly(ε-caprolactone) respectively through co-electrospinning method, which result in three-layered electrospun nanofiber scaffold. Thirdly, the scaffold will be tested in a minipig model of coronary artery bypass. The scaffold capture the CD34+ cells in the peripheral blood automaticlly. The nanocapsules embedded in the scaffold induce the cells to generate endothelial cell layer, smooth muscle cell layer and extra cellular matrix layer. finally, as the matrix of the scaffold degrade with time resulting in neovessel with equivalent properties and functions compare with the natural blood vessels.

组织工程血管在冠心病、动脉瘤等心血管疾病的治疗，以及肾透析病人动静脉瘘的构建等领域有重要应用价值，但现有组织工程血管普遍存在构建周期长、远期通畅率低的问题。本项目拟用我们前期报道的胶体纳米胶囊整合静电纺丝纳米纤维膜、细胞生长因子和细胞生长调控药物，研究构建可在体内原位组织再生的血管支架，以解决组织工程血管存在的上述问题。项目主要研究内容为：首先构建囊壁和囊芯分别搭载抗CD34单抗和促内皮祖细胞增殖药的纳米胶囊A、囊壁搭载TGF-β1的纳米胶囊B、囊芯搭载抗内膜增生药的纳米胶囊C；然后用静电纺丝技术将上述纳米胶囊依次混纺到低分子量壳聚糖、高分子量壳聚糖和聚己内酯纳米纤维中，构建由内、中、外三层膜组成的血管支架；最后将血管支架用于小型猪冠状动脉搭桥，使其捕获循环血中的CD34+细胞，并使该细胞在支架上有序的生长出内皮细胞层、平滑肌细胞层和细胞外基质层，支架降解后得到具有完整仿生性能的再生血管。

构建周期长和远期通畅率低是组织工程血管普遍存在的问题。用胶体纳米胶囊整合静电纺丝纳米纤维膜、细胞生长因子和细胞生长调控药物，构建可克服以上问题的血管支架是本项目的立项初衷。项目启动后，项目组首先合成了Fe3O4纳米颗粒，并用PEG对其表面进行修饰，以期得到用于构建胶体纳米胶囊的原料，项目组研究后发现需用较长的PEG链对Fe3O4纳米颗粒进行修饰才能使其稳定的分散于水溶液中，然而长链PEG对纳米颗粒的界面自组装过程有抑制作用，导致纳米颗粒无法稳定的组装到油酸乳滴表面。针对该问题，项目组用氧化铈纳米颗粒替代Fe3O4纳米颗粒进行项目研究，但项目组随即发现目前还没有较好的方法可对氧化铈纳米颗粒进行表面修饰，而要实现氧化铈纳米颗粒在油酸乳滴界面自组装，必须在其表面锚定可与油酸的羧基形成稳定氢键的功能基团。为解决该问题，项目组筛选了大量小分子化合物，最终发现阿仑膦酸的双磷酸基团可通过多齿配位稳定的结合在氧化铈纳米颗粒表面，用阿仑膦酸作为锚定分子，可将不同分子量大小的配体共价结合到纳米颗粒表面，除具有锚定配体分子的功能外，阿仑膦酸还可改变氧化铈纳米颗粒表面的晶体结构，使其表面Ce3+/Ce4+的比例发生改变，由此使其酶学活性得到显著提升。成功筛选出高效的修饰氧化铈纳米颗粒的阿仑膦酸小分子为后期构建胶体纳米胶囊和血管支架奠定了重要研究基础。由于项目组耗费了大量时间在筛选修饰氧化铈纳米颗粒的小分子化合物上，导致血管支架的构建和生物性能评价研究工作稍微滞后，但项目组目前仍按照原定计划继续进行血管支架的构建及其体内外性能评价研究工作。在本项目的支持下，目前项目组已发表SCI论文1篇，获授权发明专利1项。