脑靶向有机控释丙泊酚-丙酸酯直链淀粉纳米螺旋系统的研究

Propofol is the most important clinical intravenous anesthetic at home and abroad. However, the clinical used lipid-emulsion propofol has the shortages of instability and sereve side effects. The main reasons are that the lipid-emulsion is sensitive to environmental impact to prematurely leak prpofol, it can not specifically target to blood brain barriar (BBB) and central nervous system, and it can not quickly release propofol at targeted site. This project was inspired by the nano helical complex of starch and hydrophobic iodine and supported by preliminary experimental validation. In this project, we obtain propionic acid modified amylose through esterification reaction, which forms nano helix by specific hydrophilic-hydrophobic interaction. Then, lactoferrin (Lf) is conjugated to the amylose of nano helix and propofol is loaded inside the nano helix, getting the propofol-propionic acid amylose nano helical complex with brain targeting and organic phase controlled release(nano helical complex). Its chemical structure is measured by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. Its helical crystal conformation is measured by X-Ray Diffraction. Its morphology is measured by Transmission Electron Microscope and Scanning Electron Microscope. Meanwhile, animals are used to test the acute toxicity, effectiveness, metabolism and distribution of the nano helical complex. Its mechanism is explored through the fluorescent probe, Liquid Chromatography-Mass Spectrometry and so on. Our nano helical complex is less susceptible to environmental impact, so it could stably carry propofol. It could target to BBB by lactoferrin and rapidly release prpofol by the trigger of organic phase in BBB. In one word, the nano helical complex is a promising propofol formulation with good stability, rapid onset and low side effect.

丙泊酚是国内外临床主要静脉麻醉剂，临床使用的丙泊酚脂肪乳有稳定性差、副作用大等不足。主要原因是其微乳结构易受体内外环境影响而过早释放丙泊酚，也不能特异靶向到血脑屏障和中枢神经系统，更不能短时间在靶部位快速释放。受淀粉与疏水性碘形成纳米螺旋启发并结合前期实验验证，本项目设计采用丙酸酐与直链淀粉羟基酯化反应生成丙酸酯直链淀粉，通过特定的亲水-疏水作用形成纳米螺旋结构，将具有脑靶向性质的乳铁蛋白连接到直链淀粉上，将丙泊酚负载其中制成脑靶向有机相控释纳米螺旋体。用红外、核磁共振确定其化学结构，用X射线衍射测量纳米螺旋晶体结构，用透射电镜、扫描电镜观察形态，用动物实验检验急毒、有效性、代谢分布，用荧光探针、液质联用等探索作用机制。这种纳米螺旋体不易受环境影响，从而稳定载药；其通过乳铁蛋白靶向到血脑屏障处，在有机相触发下快速释放丙泊酚，使丙泊酚快速通过血脑屏障；达到稳定性好、起效快、毒副作用低的目的。

中枢神经系统疾病是造成健康生命损失最高的疾病，且发病人数呈上升趋势。其治疗的主要困难是药物很难通过血脑屏障（BBB），无法高效快速作用于病变的脑实质。疏水中枢神经系统药物如果直接静脉注射，无法均匀分散于亲水的血液系统，当药滴直径大于5μm易引起血管栓塞，因此需要制成亲水制剂，但是亲水改性后又引起了BBB通过率低、包材代谢不良等其他问题。目前临床最常用的疏水中枢镇静药物丙泊酚，采用的策略是制备成脂肪乳亲水制剂，但是它的呼吸、循环的抑制作用明显、体系不稳定易破乳有明显注射痛，大量使用会使患者产生高脂血症、胰腺炎甚至致死性的丙泊酚注射综合征，主要原因一是不能实现脑靶向，无法减少丙泊酚的使用量，二是包裹材料本身对代谢的不良影响。.针对该科学问题，本课题组研究利用具有良好生物相容性和降解性的淀粉材料，制备了丙酸酯直链淀粉纳米螺旋载体并负载疏水药物（HLPAH螺旋载体系统），形成高效快速通过BBB的药物载体系统。通过分子模拟与实验论证了该系统由BBB部位丰富的脑磷脂特异触发释放，而其它内皮由于脑磷脂含量低而不能使之释放，其机理是在BBB脑磷脂氢键作用下载体解螺旋快速释放疏水药物，再利用疏水药物自身的疏水性和局部浓度梯度通过BBB，作用于中枢神经系统。与丙泊酚脂肪乳制剂比较，该系统可以快速实现脑靶向，可将丙泊酚BBB通过率提高了6-8倍；单次注射可加快诱导、维持、苏醒时间分别到0.5倍、0.61倍、0.26倍，而且减轻循环抑制作用；持续给药药量减少到0.13倍。达到了“高低短快”四个特性：即高BBB渗透性和特异性、低给药量、短的作用时间、快速起效和恢复。该载体为疏水中枢神经系统药物提高药效提供了新策略，为进一步研究药物高效、快速通过血脑屏障提供了依据。该研究成果已在生物材料学顶级期刊Biomaterials发表，详细机理部分已成文投稿Journal of controlled release。后续工作在前期载药体系上交联乳铁蛋白靶头，形成LHLPAH脑靶向缓释体系。交联反应形成乳铁蛋白-直链淀粉相互交错的网状结构，限制了螺旋载体的释放，从而实现缓释功能，该部分工作已经完成初稿。