Nanotube Vesicle Networks: Immobilization and Transport Studies

Abstract: Surfactant lipids are an essential element of living cells. They are the basis for the biomembranes that envelope and divide cells into compartments. In addition to this static function, lipid membranes also play a role in dynamic processes such as transport and signaling. The development of biomimetic lipid nanotube vesicle networks and the techniques involved has been an ongoing process for over 10 years. The techniques have expanded and our abilities to observe, handle, and predict nanotube vesicle network processes have increased. The applications of these systems range from the basic research of biological membrane behavior and cellular processes to the development of pharmaceutical drugs in a user friendly medical industry environment. This thesis explores and expands techniques and applications of lipid nanotube vesicle mainly with a focus on immobilization and transport. Networks of nanotubes and vesicles offer a platform for construction of biomimetic nanofluidic devices operating down to single molecule and particle level. Highly organized and well defined lipid vesicle networks can be constructed with control over connectivity, container size, content, tube lengths and angle between nanotubes. Transport of fluid and particles confined in the network nodes can be controlled with several methods as well as modifications of content by controlled injections or chemical reaction dynamics. Among these are the pipette writing principle described in paper I, allowing fast and efficient formation and immobilization of well defined networks with regard to size, geometry and connectivity. The method developed in paper II aid in the fabrication of fully integrated and multiplexed nanofluidic devices and expands the vesicle network connectivity to the third dimension. In paper III the use of electrophoretic transport show linear velocities of transported latex beads. Moreover it is proven that nanotubes adhered to a specific epoxy surface does not collapse and can sustain transport. Nanotubes wired to microfabricated substrates are shown to introduce new functionalities to vesicle networks. Based on the experimental observations and theoretical modeling in paper IV, we conclude that Y junctions observed in nanotube-vesicle networks forms by a zipper-like mechanism. Surfactants from two branches flow through the junction and form the extension of the third nanotube branch. The incorporation of an entirely biological component into the nanotube vesicle network in paper V not only shows proof of concept but also introduces new functionality to the system. The motile bacteria E. coli can be electroinjected into unilamellar lipid vesicles retaining both viability and motility. It is also suggested that they can be utilized to alter the chemical environment.