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

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

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.