Dynamic transformation of liposomes revealed by dark-field microscopy

Liposomes are micro compartments made of lipid bilayer membrane of which characteristics are quite similar to those of biological membrane. Direct observation of liposomes by optical dark-field microscopy revealed that membrane vesicles possess the ability to transform into a variety of cell organelle-like shape in response to alterations in the surface-to-volume ratio caused by osmotic pressure. Topological changes such as fusion and division of membrane vesicles also play an essential role in cellular activities. We investigated the mechanism of these topological transformations by visualizing their real-time processes. A variety of novel topological transformations were found, including the opening-up of liposomes, the direct expulsion of inner vesicles and the inside-out inversion.