CYCLODEXTRIN-CATALYZED EXCHANGE TO CONTROL LIPID COMPOSITION AND LIPID ASYMMETRY: FROM LIPOSOMES TO CELLS

非技术部分：活细胞被一层由脂质（专门的脂肪分子）和蛋白质组成的薄膜所包围。人造膜泡，称为脂质体，由膜脂和蛋白质组成，形成类似细胞膜的包膜。天然膜有两层脂质，就构成膜的两层脂质中每一层都有不同类型的脂质组成而言，它们是不对称的。但人工脂质体的一个关键限制是它们缺乏脂质不对称性。PI和小组的早期研究发现了一种制备不对称脂质体的新方法。本项目的重点将是发展对材料科学的基本理解，以各种非天然脂质体制备不对称脂质体，然后比较它们的功能特性。利用从拟议材料研究中获得的知识，该项目还将定义如何调整已开发的方法来改变生物细胞中的脂质，这将使来自天然细胞膜的生物材料用于传递分子和其他应用成为可能。就更广泛的影响而言，该项目将对未来科学家的职业发展产生强烈影响，包括来自代表性不足群体的学生，通过培训研究生和本科生（包括通过与其他当地机构的联系）进行研究，实验原理和膜研究中使用的专业实验技术。学生还将接受科学研究、科学写作和科学演讲的训练。这将反过来为他们在研究、教学和相关领域的专业成长和职业生涯做好准备。脂质不对称，即生物膜的内外小叶（单层）中脂质组成的差异，是许多细胞膜的重要特性。含有脂质双层的人工囊泡（脂质体）是一种生物材料，已被证明是生物膜的宝贵模型，并可能在许多应用中使用，但缺乏制备脂质分布不对称的脂质体的方法限制了它们的应用。本项目涉及开发利用改性环糊精开发不对称囊泡的新方法。第一个目标是制备不对称脂质体，其中含有非天然的带正电的阳离子脂质或聚乙二醇衍生的脂质，仅在其内部或外部单层中。含有这些脂质的脂质体可以应用于将生物分子和药物输送到细胞中，从而改变细胞特性或基因表达。通过将这些非天然脂质限制在两层脂质中的一层，这些研究将通过将分子困在脂质体中来最大限度地将分子输送到细胞中，并定制这些脂质体以最大限度地发挥与生物系统的相互作用和兼容性。第二个目标是将这些研究扩展到生物细胞。允许在细胞膜外层脂质替换的条件，以及这如何改变膜的物理结构和膜的完整性，将被定义。这将使以天然膜为起点的新型生物材料的制备成为可能。在这些研究中，学生将接受各种用于研究膜蛋白和脂质的生化和光谱技术的专门培训，包括新开发的方法。学生还将接受适当的科学研究行为、写作技巧和口语技巧的训练。这将为他们在生物/生物物理研究和/或教学领域的职业生涯做好准备。该项目将广泛影响膜生物学领域，包括药物传递和纳米材料的应用。

Non-Technical Section: Living cells are surrounded by a thin membrane composed of lipids (specialized fat molecules) and proteins. Artificial membrane vesicles, called liposomes, are composed of membrane lipids and proteins which form an envelope similar to a cell membrane. Natural membranes have two layers of lipids and are asymmetric in terms of composition with different types of lipids in each of the two lipid layers that form the membrane. But a key limitation in the utility of artificial liposomes has been their lack of lipid asymmetry. Earlier studies by the PI and group discovered a novel method on how to prepare asymmetric liposomes. The focus of this project will be in developing a basic understanding of materials sciences in the preparation of the asymmetric liposomes with a variety of unnatural lipids, and then compare their functional properties. With the knowledge gained from the proposed materials research, this project also will define of how to adapt the methods developed to change the lipids in biological cells, which should enable applications in which biomaterials derived from natural cell membranes are used to delivery molecules and other applications. With respect to broader impacts, this project will have a strong impact on career development of future scientists, including students from underrepresented groups, by training graduate and undergraduate students (including via contacts with other local institutions) in the conduct of research, experimental principles, and the specialized experimental techniques used in membrane research. Students will also be trained in proper conduct of scientific studies and scientific writing and speaking. This will in turn prepare them for their professional growth and careers in research, teaching and allied fields.Technical Section: Lipid asymmetry, a difference in the lipid composition in the inner and outer leaflets (monolayers) of a biological membrane, is a crucial property of many cell membranes. Artificial vesicles (liposomes) containing lipid bilayers are biomaterials that have proven invaluable models of biological membranes, and possible use in a number of applications, but a lack of methods to prepare liposomes with asymmetric lipid distributions has limited their utility. This project involves developing novel methods in developing asymmetric vesicles using modified cyclodextrins. The first goal will to prepare asymmetric liposomes containing unnatural and positively charged cationic lipids or polyethylene glycol derivized-lipids in only their inner or outer monolayers. Liposomes containing these lipids have applications in delivery of biomolecules and drugs into cells that in turn could modify cell properties or gene expression. By restricting these unnatural lipids to only one of the two lipid layers, these studies will maximize the amount of molecules that can be delivered into cells by trapping them within liposomes, and tailoring these liposomes to maximize interactions and compatibility with biological systems. The second goal involves extending these studies to biological cells. Conditions allowing replacement of the lipids in the outer layer of cell plasma membranes, and how this alters membrane physical structure and membrane integrity, will be defined. This will enable the preparation of novel biomaterials having natural membranes as their starting point. In these studies, students will receive specialized training in a variety of biochemical and spectroscopic techniques used to study membrane proteins and lipids, including newly developed methods. Students will also be trained in proper conduct of scientific studies, and writing skills and speaking skills. This will prepare them for careers in field of biological/biophysical research and/or teaching. This project should broadly impact the field of membrane biology, including drug delivery and nanomaterial applications.