电刺激控制药物顺序释放的三维石墨烯神经电极材料的研究

Neural electrode has great potential as a therapeutic tool for the repair of nervous system injury. The lack of electrode material with high efficiency, good biocompatibility, and superior flexibility is the key issue. Due to the high electrical conductivity, excellent mechanical properties and good chemical stability, graphene was expected to offer an opportunity to develop novel neural electrodes. However, two major challenges facing functional recovery following nervous system injury are to increase the charge injection capacity and improve the bioactivity for neural regeneration. We propose here a strategy based on three-dimensional (3D) graphene combined with a sequential delivery of dexamethasone, an anti-inflammatory molecule, and brain-derived neurotrophic factor (BDNF). Hopefully, the 3D graphene could offer higher charge injection capacity, and the sequential delivery of dexamethasone and BDNF could attenuate the acute inflammatory response during the initial period and enhance neural regeneration for a long term period. In order to achieve the sequential delivery, we propose here electrically controlled drug delivery of dexamethasone, which was physically adsorbed on graphene, and long term delivery of BDNF, which was chemically conjugated onto graphene. We thus hypothesize that initial release of dexamethasone followed by a sustained release of BDNF could be achieved. Drug release will be monitored over time in vitro, the in vitro study of neural stem cell and astrocyte culture will be conducted, and furthermore, the 3D graphene-based neural electrodes with sequential delivery of dexamethasone and BDNF for hemisection spinal cord injury repair in rats will be evaluated. The present study will contribute to a better design of neural electrodes with drug delivery system and better understand of nervous system injury repair with electrical stimulation, and provide valuable information for their clinical use.

神经电极在神经系统疾病治疗中发挥重要作用，但开发高效、生物相容性良好的柔性神经电极材料是制约其临床应用的瓶颈问题。石墨烯具有良好的电学性能、力学性能和化学稳定性，有望成为一种新型神经电极材料。但其电荷注入效率有限，难以实现高效的神经刺激效果；同时生物活性不高，难以实现理想的神经功能修复，这些都严重阻碍了石墨烯神经电极的发展。本项目拟采用具有高比表面积的三维网络结构石墨烯为电极材料，以提高电荷注入效率，并复合药物顺序释放体系以提高生物活性，期望电刺激协同药物治疗能促进神经功能修复。为了满足神经修复不同阶段的需求，药物顺序释放体系采用电刺激调控物理吸附的抗炎药物地塞米松早期定时释放，以降低前期炎症反应；化学交联的神经营养因子(BDNF)缓慢释放，以促进神经长期修复。研究以三维石墨烯为电极基底材料，电刺激协同药物顺序释放对神经细胞的作用和大鼠脊髓损伤修复效果，为开发新型神经电极奠定基础。

发展高效、生物相容性良好的新型柔性神经电极对神经系统疾病治疗具有重要价值和经济意义。通过在细菌纤维素微生物发酵的过程中加入三维石墨烯材料的方法制备细菌纤维素/石墨烯三维导电复合材料，作为神经干细胞的培养支架。三维石墨烯通过化学气相沉积法制备，在复合材料中起骨架作用，能为细胞的生长分化提供良好的空间，复合材料中BC纳米纤维可模拟细胞外基质，促进干细胞的增殖。结果表明，所制备的复合材料显著促进神经干细胞的增殖。通过在所制材料上的分化神经干细胞电刺激实验，发现柔性神经电极能够和神经细胞形成良好电耦合，通过石墨烯传递的电脉冲能够诱导细胞内钙离子浓度显著变化。其次，将抗炎药物负载在柔性神经电极材料中，以PC12细胞为细胞模型，通过电刺激控制药物的释放行为；结果发现电刺激可加速药物释放，药物释放速度可控。同时通过对石墨烯表面羧基的选择性保护和脱保护，分别将疏水小分子 (十八烷基异氰酸酯，ODI) 和亲水性良好的树枝状大分子 (dendrimer) 顺序接枝到石墨烯材料表面，制得内部疏水外部亲水的双亲性石墨烯界面 (Dendrimer-GO-ODI)，并通过π-π堆叠作用将抗炎药物姜黄素负载到石墨烯表面；研究了负载姜黄素的Dendrimer-GO-ODI的药物释放规律，以及对BV2神经小胶质细胞的炎症治疗效果。与纯石墨烯相比，Dendrimer-GO-ODI的载药率远远高于纯石墨烯，而且，Dendrimer-GO-ODI负载的姜黄素可实现逐渐缓慢释放，与纯药对照组相比，具有更好的抗炎治疗效果。另外，制备了矿化三维石墨烯支架，发现可以支持干细胞粘附和生长，并促进向成骨细胞分化。综上所述，本研究发展的新型柔性神经电极具有优异的生物相容性和电活性，有望成为一种潜在的脊髓损伤修复材料；已发表高水平SCI收录论文6篇，申请发明专利3项，其中相关实用新型专利获授权2项。