个性化丝胶神经导管的设计及其在外周神经损伤模型中的应用研究

Peripheral nerve injury is usually caused by various types of trauma. The functional recovery of peripheral nerve injury remains challenging. The grafting of tissue-engineering nerve guidance conduit is considered as a promising approach for treating peripheral nerve injury. Some tissue-engineering conduits have been used in repairing peripheral nerve injury. We also have previously fabricated a sericin nerve conduit that has excellent effects on promoting regeneration of injured peripheral nerves. However, the main functional properties of these conduits, such as mechanical properties, degradation rate of and releasing capability of therapeutic factors, cannot be conveniently adjusted to accommodate diverse repair requirements of each patient (e.g. site of injured nerves, and distance of injured nerve). Therefore, this project is focused on developing an on-demand, customized sericin nerve conduit, which may offer precise and effective treatment for repairing different peripheral nerve injuries. To do so, we will fabricate a new nerve conduit by rolling a sericin film with microgrooves on its surface. Using a mathematical modeling approach, we will dissect the relationships between various influencing factors (such as the number of layers, the concentration of sericin or crosslinkers) and the main properties of the sericin nerve guidance conduit, thereby establishing the relevant mathematical models for designing purposes. To meet the repair requirements of different nerve injuries, we will use those mathematical models to calculate the best fitting parameters for fabricating the customized nerve guidance conduit for an individual injury. We will use this customized nerve conduit to repair the nerve injury in vivo in an animal model and exam nerve regeneration so as to evaluate the application value of a customized nerve guidance conduit.

外周神经损伤通常由各种原因的创伤导致，其功能修复仍是创伤修复领域的难题。组织工程神经导管移植被认为是治疗外周神经损伤的新方法，已有一些组织工程神经导管应用于外周神经损伤修复并取得一定效果。我们前期研发了具有良好神经修复功能的丝胶神经导管。但这些导管的主要特性（机械性能、降解性能和缓释性能）很难根据患者神经损伤的具体情况（神经直径、损伤部位、损伤距离、治疗药物）进行调节，难以达到最佳修复效果。为此，本项目旨在研制性能个性化的丝胶神经导管，以期精确高效修复受损神经。我们将通过卷绕丝胶膜制成神经导管，利用数学建模的方法分析导管主要理化参数（导管层数、丝胶液浓度、交联剂浓度和冻干温度等）与主要特性之间的关系，建立相应数学模型。根据受损神经修复的具体要求，计算出导管的最佳参数，制备个性化神经导管，用神经损伤动物模型评价其修复效果，探索个性化导管的设计和应用。

我们利用蚕茧天然成分丝胶通过与壳聚糖交联的方式研制出具有优越性能的壳聚糖-丝胶复合支架，通过调整壳聚糖与丝胶不同配比可以对该复合支架的孔隙率和机械性能进行精细调控，以满足神经修复材料的个性化需求。该材料可以作为载体搭载并缓释神经细胞因子（NGF），并上调施旺细胞胶质源性神经生长因子（GDNF）、生长反应素-2（EGR-2）和神经细胞粘附分子（NCAM）的表达，显著改善神经卡压伤后再生神经的密度和再生髓鞘的厚度，促进神经功能学恢复，明显减轻靶肌组织的萎缩状况。此外，我们利用戊二醛化学交联丝胶的方法开发新型丝胶神经导管，该生物材料可上调施旺细胞神经营养因子-3（NT-3）和神经营养因子-4（NT-4）的mRNA和蛋白表达水平，并通过搭载氯倍他索增强髓鞘相关基因（NRG-1和EGR-2）的表达，显著促进髓鞘再生。在治疗长距离（10mm）外周神经离断损伤可显著促进髓鞘再生，获得良好的神经再生效果和功能恢复。本课题组还运用低功率长时程超声的方式在丝胶水凝胶中均匀地掺入碳纳米微管（CNTs），成功制备碳纳米丝胶复合神经导管。碳纳米管的加入未明显改变该复合材料的孔隙率和傅立叶红外光谱，但显著增强其机械性能。通过调整碳纳米管的掺入量可以对该复合神经导管的机械性能进行精细调控。碳纳米丝胶复合神经导管联合电刺激疗法显著增强有髓神经纤维的密度，增加再生髓鞘的厚度，促进神经功能学恢复并改善腓肠肌萎缩状况。在碳纳米丝胶复合材料的基础上，我们还探究并揭示了该生物材料记忆形变性能、可注射性和促干细胞分化的性能。建立的数学模型显示，调整碳纳米管的含量可以对该复合生物材料的记忆形变性能进行精准调控。运用核磁共振扫描、三维重构、三维打印和倒模技术可以个性化定制碳纳米丝胶复合支架，体内移植后该生物支架可以恢复原有形状并与神经缺损部位相匹配。本项目研发的这类新型个性化神经导管与生物支架为神经再生提供了性能优越的生物材料，有望推动神经再生与修复领域的进展。