Controlled multi-stage self-assembly of vesicles

The association of lipid or surfactant molecules into spherical vesicles in solution constitutes a primary self-assembly process, although typical vesicles are not the equilibrium form of aggregation for most lipids. Such meta-stable vesicles can undergo a secondary self-assembly into higher order structures in a controlled and reversible manner by means of site-specific ligand-receptor coupling. Cryo-electron microscopy shows these structures to be composed of tethered vesicles in their original, unstressed state. In contrast, vesicles aggregated by non-specific forces are deformed. In this work, we show that equilibrium vesicles can also undergo a secondary self-assembly via ligand-receptor interactions, as evidenced by freeze-fracture electron microscopy. Such site-specific vesicle aggregation provides a practical mechanism for the production of stable, yet controllable, microstructured materials.