Giant Janus Liposomes: Preparation, Self-Assembly and Motion

Abstract

Presented in this Dissertation are a series of studies on Janus liposomes, their formation, self-assembly and motion behaviors. Liposomes are closed, spherical lipid bilayer assemblies dispersed in water. Since their discovery in the 1960s, liposomes have become indispensable tools and ingredients not only in basic research but also in industry. Janus liposomes, on the other hand, are liposomes containing broken symmetry and surface heterogeneity in their structures. These less studied lipid structures are the focus of this Dissertation, specifically. In Chapter 1, a literature survey is given on research topics mostly related to this work. Through the survey, the feasibility of preparing Janus liposomes is determined. In Chapter 2, I describe a high-yield procedure for preparing micro-sized (giant) Janus liposomes via gel-assisted lipid swelling. An optimized formation procedure is presented, which reproducibly yields large liposome populations dominated by a single domain configuration. In Chapter 3, by combining gel-assisted lipid hydration with membrane-based lipid extrusion, I demonstrate a general procedure for size-controlled preparation for giant unilamellar liposomes, including homogeneous and Janus liposomes. In Chapter 4, I describe a straightforward strategy to incorporate biotin-conjugated lipids into Janus liposomes’ formation and clustering behavior of these liposomes directed by biotin-avidin affinity binding. In Chapter 5, I present the first report on dipolar Janus liposomes – liposomes that contain opposite surface charged decorating the two hemispheres of the same colloidal body. Using confocal fluorescence microscopy, the electrokinetic motion as well as electrostatic self-assembly of these new dipolar Janus particles are followed. Finally, in Chapter 6, I draw the main conclusion of my studies and offer an outlook of what might be accomplished in the near future along this direction.