The self-spreading double bilayer/Advances in lipid membrane nanotechnology

Abstract: In my thesis I describe the generation, characterization and uses of self-spreading double bilayers. This new type of solid-supported model membrane combines features and properties of the 2D lipid bilayer membrane, and the 3D phospholiposome. The double bilayer membrane, i.e., a fully closed, parallel stack of two lipid bilayers, is essentially a surface-adhered flat giant unilamellar vesicle (FGUV) with a very small internal volume. It possesses features of supported membranes, such as flatness, large area coverage and high mechanical stability, and of giant vesicles, such as the ability to encapsulate nanoparticles in its interior volume. In the experimental work towards this thesis, I have probed the response of the FGUV to chemical or physical cues, and studied dynamic features reminiscent of complex cell behavior. A number of examples are discussed, including protrusion formation as a response to a chemical gradient, directed and reversible movement in a temperature gradient, spontaneous nanotube formation in response to the adhesion of virus-like particles, and repair of large area membrane pores. An important outcome of my work is the discovery of two non-trivial pore formation modes in membranes, which links biomembrane materials properties to fundamental properties of thin solid materials. One of the modes displays crackling noise dynamics, featuring sudden intermittent bursts over a broad size range (avalanches), similar to earthquakes. I consider the FGUV to be an experimental model system for studying various aspects of cell like behavior on intact model membranes, as well as a nanotechnological platform, useful to construct mesoscale membrane architectures and networks.