Controlling phospholipid self-assembly and film properties using highly fluorinated components--fluorinated monolayers, vesicles, emulsions and microbubbles

Abstract

Use of fluorinated components instead or along with standard phospholipids in film, vesicle, bubble and emulsion engineering, can cause drastic modifications of the formation processes, structure and dynamics, and functional behavior of these systems. Perfluoroalkyl chains provide a powerful driving force for self-assembly and ordering. They allow, for example, obtainment of thermally stable vesicles from single-chain phosphocholine derivatives, tubules from non-chiral amphiphiles, faceted vesicles with fluid bilayer membranes, exceptionally stable and narrowly dispersed emulsions and microbubbles. Contact of a monolayer of DPPC with a fluorocarbon gas modifies the monolayer's phase behavior, suppressing the liquid expanded/liquid condensed transition. Phospholipid absorption kinetics at an air/water interface can be substantially accelerated, and the equilibrium interfacial tension reduced by exposure to a fluorocarbon gas. Perfluoroalkyl chains induce nanocompartmentation in films and membranes, allowing, for example, polymerization within vesicular membranes. Vesicles involving highly fluorinated components generally exhibit stability, permeability, fusion and recognition characteristics, different from those of their hydrogenated analogues. Drastic stabilization can be gained for phospholipid-coated emulsions through a co-surfactant effect of (perfluoroalkyl)alkyl diblocks. Stable, size-controlled, narrowly dispersed populations of microbubbles have been obtained using fluorinated wall and/or internal gas components, allowing progress in the understanding of microbubble physics, and open new application perspectives.