Chapter 16 Bionanotubules Formed from Liposomes

Bionanotubules are lipid-bound cylindrical structures with typical diameters in the tens of nanometers and length than can span up to hundreds of micrometers. Besides being observed in nature, bionanotubules can be prepared synthetically by various methods, some of which involve the extension of these structures from lipid vesicles. We describe the formation of lipid nanotubules from liposomes prepared with various lipid mixtures including phosphatidylcholine, phosphatidic acid, and various fluorescent phospholipids. We depict the methods used to extend bionanotubules from surface-attached vesicles, using electric fields as the driving force for bilayer extension and tubular growth. These methods include liposome preparation, surface attachment, and tubular extension by applying modest electric fields (<30 V/cm). Methods in which lipid tubules are extended from liposomes that are free in solution and subject to higher magnitude fields are also described. In addition, we summarize other protocols of bionanotubule formation from liposomes, including various modes of micromechanical manipulation of lipid vesicles.