ABSTRACT
I. INTRODUCTION Liposomes (1,2) are flexible membrane shells enclosing aqueous compartments. The membranes are spontaneously formed in water by self-assembly of phospholipid molecules into bimolecular layers. Each liposome may have a single membrane (unilamellar vesicle) (Fig. 1) or contain a number of concentric bilayer shells separated by aqueous layers (multilamellar vesicle). The sizes of liposomes range from tenths of nanometers to micrometers. Small liposomes are thermodynamically unstable due to the curvature of the bilayer, whereas larger liposomes show higher stability, although they tend to fuse or aggregate at high liposome concentration.
