Observing, Understanding, and Manipulating Biological Membranes

The phospholipid bilayer is one of the hallmarks of eukaryotic life. This complicated two dimensionally fluid surface is composed of a double layer of lipids which have a region that is hydrophobic and a region that is hydrophilic. The lipid bilayer membranes of a cell act as a barrier that distinguishes the cells and the organelles interiors from the outside environment. In order for the cell to be able to effectively communicate across these impermeable barriers they have evolved many intricate systems of lipid and protein interaction that serve to transmit information from one side of the membrane to the other. The abundance of functionality in the membrane has made them incredibly complicated and intricate structures. This complexity makes the study of any one membrane associated signaling pathway or system more often than not very challenging if not impossible. Because of this a simplified analogue of the biological membrane is necessary for controlled and quantitative studies. The amphiphilic nature of phospholipids allows researcher to create lipid bilayer that can be controlled for composition and placed on a surface that is accessible to many investigative systems. These supported lipid bilayer (SLB) systems have been used for decades to figure out the intricate series of actions and reactions that occur in a natural biomembrane. While there is still a lot to be learned from simple lipid bilayer systems there is also now the need to produce bilayers that incorporate more of the functions of a living cell. These will permit the study of signaling systems involving multiple molecules, the direct observation of cellular responses to surface stimuli, and even the control of cellular behavior. Along with providing greater versatility in the study of cells and membrane mediated systems these enhanced lipid bilayers will have major biomedical applications. Given that a lipid bilayer is the exterior presented by cells in nature there can be no more biocompatible surface than a lipid bilayer, for the surface treatment of medical devices this could have great implications. For instance, if sufficient knowledge is developed about these systems, then all types of medical implants could have a customized lipid bilayer based coating that would help it to integrate perfectly with the tissue to which it is embedded. Joint replacements could have a surface that would promote the growth of osteoblast cells, a cardiac stent could have a coating to prevent clot formation while promoting epithelial cell growth and discouraging smooth muscle cell growth, perhaps even neural implants capable of two way communication for the treatment of paralysis.;It is with this long term vision that we set out to advance the field of lipid bilayer systems to increase the capacity for dynamic control, artificial enhancement, and tissue interface. A series of investigations were undertaken with the goal of promoting each one of these facets. (Abstract shortened by UMI.).