经鼻靶向递送超顺磁铁氧纳米颗粒增强经颅磁刺激治疗脑梗死疗效的机制研究

Noninvasiveness, better convenience and improved feasibility are remarkable advantages of repetitive transcranial magnetic stimulation (rTMS) over direct electric stimulation in treating central nervous system diseases. But weaker therapeutic efficacy, lack of targetability and shorter reach of stimulation effects are obvious disadvantages of rTMS. The present study aims to investigate the possibility of enhancing therapeutic effects of rTMS in treating cerebral infarction by intranasally delivering magnetic nanoparticles into rat brain. Chitosan-PEG coating superparamagnetic iron oxide nanoparticles (SPIONs) will be synthesized and hypoxia inducible factor-1 (HIF-1) antibody will be linked to the complex to increase the targetability to ischemic brain tissues. These new SPIONs will be delivered via intranasal pathway in order to bypass the blood-brain barrier(BBB). An external magnet will be placed on the head to drive SPIONs into infarction areas in rats with middle cerebral artery occlusion (MCAO). Ischemic tissues near infarction will produce HIF-1, which will combine with HIF-1 antibody on SPIONs. This action will make SPIONs target to ischemic neurons. With the help of external magnet and HIF-1 antibody, SPIONs will concentrate in the ischemic brain tissues. After intranasal delivery of SPIONs, the local eddy current produced by rTMS will be amplified due to interaction between magnetic nanoparticles and alternating electromagnetic field. The targetability of rTMS to ischemic tissue will be actualized with the combination of HIF-1 and its antibody. The results of this study may help to establish a new strategy for boosting the therapeutic effects of TMS in treating ischemic stroke and other CNS diseases.

经颅磁刺激用于治疗中枢神经系统疾病具有无创、便捷、适应症宽泛等优点，但也具有刺激效应弱、靶向性差、刺激深度不足等缺点。本研究拟将超顺磁氧化铁纳米颗粒递送至脑内，利用电磁效应增强经颅磁刺激治疗的反应性。同时采用壳聚糖包裹超顺磁氧化铁纳米颗粒，并将抗缺氧诱导因子抗体结合在磁纳米颗粒上，因为只有缺血缺氧神经元可表达缺氧诱导因子，这样给药后就能使磁纳米颗粒靶向结合到缺血脑组织，实现经颅磁刺激治疗的靶向性。在脑梗死大鼠模型中，采用经鼻嗅觉通路递送超顺磁铁氧纳米颗粒以绕开血脑屏障，通过颅外放置永磁铁将磁纳米颗粒定向吸引到梗死脑区，加上缺氧诱导因子的靶向结合作用，这样就能使磁纳米颗粒在缺血组织中富集。这时再实施重复经颅磁刺激，超顺磁铁氧纳米颗粒将定向放大缺血组织内的涡电流，有可能增强磁刺激的反应性，提高刺激针对缺血组织的靶向性。本研究有望克服目前经颅磁刺激的技术缺陷，显著改善经颅磁刺激治疗脑梗死的效果。

经颅磁刺激已用于多种中枢神经系统疾病的治疗，其突出优点是无创、便捷、适应症宽泛，其突出缺点是刺激效应弱、靶向性差、刺激深度不足。本研究拟将超顺磁氧化铁纳米颗粒递送至脑内，利用电磁效应增强经颅磁刺激治疗的反应性。为了促进血脑屏障（BBB）的跨越，本项目在超顺磁性氧化铁纳米颗粒（SPIONs）外包裹上羧化壳聚糖和聚乙二醇。为了促进纳米颗粒通过血脑屏障并抵达治疗脑区，在静脉注射SPION之前，在大鼠前额安置一个外部永久性磁铁。神经电生理学测试发现，SPIONs+磁体组大鼠记录的最大MEP振幅显著高于盐水组（5.78±2.54 vs.1.80±1.55 mV，P=0.015）。在M1区域，免疫组织化学法检测到SPIONs+磁体组c-fos阳性细胞的数量密度是盐水组的3.44倍。这些结果表明，静脉注射SPION可以增强TMS治疗神经系统疾病的效果。