CATIONIC LIPID PHASE BEHAVIOR AND ITS IMPORTANCE TO TRANSFECTION

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心机构，不一定为研究者机构。重要的治疗程序，如基因转染和基因沉默，需要有效地传递遗传物质的细胞。人工合成的阳离子脂质，与聚阴离子DNA形成复合物（脂质复合物），是很有前途的基因载体。了解脂质介导的DNA递送（脂质转染）的机制对于它们的成功应用以及合理设计和合成用于增强基因递送的新型阳离子脂质化合物至关重要。合成了两种新型的具有不对称烃链的阳离子磷脂衍生物：油酰癸酰乙基磷脂酰胆碱（C18：1/C10-EPC）和硬脂酰癸酰乙基磷脂酰胆碱（C18：0/C10-EPC）。前者作为DNA转染剂（HUAEC细胞）比后者有效50倍，尽管它们具有相似的化学结构和几乎相同的lipoplex组织。C18：1/C10-EPC相对于C18：0/C10-EPC（以及许多其它阳离子脂质）的上级有效性的可能原因是当这些脂质与带负电荷的膜脂质制剂混合时演变的相。如通过使用小角X射线衍射观察到的，饱和的C18：0/C10-EPC在与生物膜模拟脂质制剂（MM：DOPC/DOPE/DOPS/Chol 45：20：20：15，w/w）的混合物中保持其层状结构;相反，不饱和的C18：1/C10-EPC在这样的混合物中表现出层状-非层状相变。具体而言，在C18：1/C10-EPC与MM和肝脂质提取物的混合物中，在生理温度约37 ℃下发生向非层状相（分别为立方Pn 3 m和六方HII相）的相变。这些结果突出了作为转染成功的决定性因素的载体脂质/细胞脂质混合物的相性质，并提出了合理设计上级阳离子脂质载体的新策略。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Important therapeutic procedures, such as gene transfection and gene silencing, require efficient delivery of genetic material to cells. Synthetic cationic lipoids, which form complexes (lipoplexes) with polyanionic DNA, are promising gene carriers. Understanding the mechanism of lipid-mediated DNA delivery (lipofection) is essential for their successful application, as well as for rational design and synthesis of novel cationic lipoid compounds for enhanced gene delivery. Two novel cationic phospholipid derivatives with asymmetric hydrocarbon chains were synthesized: oleoyldecanoyl-ethyl-phosphatidylcholine (C18:1/C10-EPC) and stearoyldecanoyl-ethylphosphatidylcholine (C18:0/C10-EPC). The former was 50x more effective as a DNA transfection agent (HUAEC cells) than the latter, despite their similar chemical structure and virtually identical lipoplex organization. A likely reason for the superior effectiveness of C18:1/C10-EPC relative to C18:0/C10-EPC (and to many other cationic lipoids, as well) was suggested by the phases that evolved when these lipoids were mixed with negatively-charged membrane lipid formulations. As observed by using small-angle X-ray diffraction, the saturated C18:0/C10-EPC preserved its lamellar structure in mixtures with a biomembrane-mimicking lipid formulation (MM: DOPC/DOPE/DOPS/Chol 45:20:20:15, w/w); in contrast, the unsaturated C18:1/C10-EPC exhibited a lamellar-nonlamellar phase transition in such mixtures. Specifically, in mixtures of C18:1/C10-EPC with MM and liver lipid extract, phase transitions to nonlamellar phases (cubic Pn3m and hexagonal HII phase, respectively) took place at physiological temperatures, ~37¿C. These results highlight the phase properties of the carrier lipid/cellular lipid mixtures as a decisive factor for transfection success, and suggest a novel strategy for the rational design of superior cationic lipid carriers.