蔗糖酯型阳离子类脂的设计合成及其基因转运研究

The major impediment to the application of gene therapy is lack of safe and high efficient gene delivery systems for human clinical trials. Sucrose esters have good biocompatibility and biodegradability, so they can provide a solution pathway which will overcome the issue of high toxicity of the traditional cationic lipid. However, there is not yet the study of sucrose ester-based cationic lipids for gene delivery. In view of structure characteristic of sucralose containing a single primary hydroxyl, it can be used as raw material to obtain sucrose ester with single structure instead of sucrose. A series of sucrose ester-based cationic lipids containing tertiary amine headgroup, the ester linker, the sucrose backbone and tails (long carbon chains and cholesterol) was designed and will be synthesized by sucralose. Cationic liposomes were prepared by sucrose ester-based cationic lipids and co-lipids, and then sucrose ester-based gene complexes were formulated with gene at different molar ratios. The structure and morphology of complexes of liposomes and gene will be investigated. The relationship between the structure of cationic lipids, the morphology and the size of complexes and transfection efficiency and cytotoxicity will be clarified through in vitro transfection and cytotoxicity evaluation. The molecular transfer mechanism for delivering and toxicity gene will also be discussed. It will provide novel vectors for delivery of gene, and pioneer a new route for non-viral gene vectors.

基因治疗的最大障碍之一是缺乏安全、高效的基因载体。蔗糖酯良好的生物相容性和降解性为克服传统阳离子类脂较高的毒性提供了解决途径，由于单一结构蔗糖酯难以化学合成，目前尚未有蔗糖酯型阳离子化合物用于基因转运的相关研究。本项目鉴于三氯蔗糖具有单一伯羟基的结构特点，建立一种以三氯蔗糖为原料合成单一结构蔗糖酯型阳离子类脂化合物的方法。三氯蔗糖能与胆固醇衍生物或脂肪酸酯进行酯交换反应，再与仲胺进行胺基化，获得单一结构蔗糖酯型阳离子类脂；利用蔗糖酯型阳离子类脂与助类脂结合，制备阳离子脂质体，再与核酸按不同比例复配，构建蔗糖酯型基因复合体，用于基因转运研究。通过上述研究将获得高效、低毒，具有进一步研究价值和应用潜力的蔗糖酯型类脂化合物，并可阐明类脂结构与转染效率及细胞毒性之间的关系；还可诠释其基因转运机制及其毒性作用机制，为研究非病毒载体运载基因提供新思路和理论参考。

基因治疗的最大障碍之一是缺乏安全、高效的基因载体。蔗糖酯具有良好的生物相容性和降解性，为克服传统阳离子类脂较高的毒性提供了解决途径。但是由于单一结构蔗糖酯难以化学合成，目前尚未有蔗糖酯型阳离子化合物用于基因转运的相关研究。本项目鉴于三氯蔗糖具有单一伯羟基的结构特点，建立一种以三氯蔗糖为原料合成单一结构蔗糖酯型阳离子类脂化合物的方法。将三氯蔗糖能与胆固醇衍生物或脂肪酸酰氯进行反应，再与胺类化合物进行胺基化，获得单一结构的蔗糖酯型阳离子类脂，采用ESI-MS、Q-TOF-MS、IR、1H NMR和13C NMR表征，证明结构正确。利用蔗糖酯型阳离子类脂与助类脂结合，制备阳离子脂质体，并采用透射电镜、动态光散射以及Zeta电位仪等手段对其进行研究，发现所制备的脂质体基本呈椭球形，尺寸在80-200 nm之间，脂质体的表面都带正电荷，电位在35-80 mV之间。再与核酸按不同比例复配，构建蔗糖酯型基因复合体，十二和十四碳尾部的脂质体转染效率明显优于十六碳尾部的脂质体；当类脂与助类脂Chol的比例为3/1时，转染效率最高，明显优于商品试剂2,3-二油氧基丙基三甲基氯化铵（DOTAP），与商品试剂Lipofectamine 2000相当。将其通过尾静脉注射入裸鼠体内，蔗糖酯型脂质体介导IGF-1R-siRNA转染组的Bcl-2蛋白表达量比空白对照下降了42%，显著地抑制了这条抗凋亡信号转导通路。而对比空白对照和DOTAP，蔗糖酯型脂质体介导IGF-1R-siRNA转染组的Bax蛋白表达量分别上调了22% 和 5%，显著地激活了这条促凋亡信号转导通路。脂质体介导IGF-1R-siRNA下调IGF-1R蛋白后能够显著地促进A549细胞的凋亡，可以有效抑制肿瘤的生长，获得了高效低毒的基因递送载体。