Liposomes and Drug Delivery

Abstract

Liposomes are vesicles in which an aqueous volume is entirely surrounded by a phospholipid membrane and their size can range between 30 and 50 nm up to several micrometers. Liposomes serve as a drug delivery system because of their versatile structure and because they are nontoxic, nonimmunogenic, and fully biodegradable. This chapter focuses on basic characteristics and applications of liposomes, their fate after in vivo administration by different routes, and other possible routes for in vivo administration of liposomes.

Liposomes in tissue engineering and regenerative medicine

“…This method can encapsulate large macromolecules, with high encapsulation efficiency (EE) (20-68%). The main disadvantage of this method is the exposure of the material to be encapsulated to organic solvents and to sonication conditions, which may result in denaturation of sensitive molecules [12,66].…”

“…This liposome preparation method has the advantage of avoiding chemical or physical treatment of lipids. However, the concentration of vesicles produced is low and it involves an extra step to remove ethanol [12].…”

“…An aqueous buffer is added to the deposited lipids, allowing their hydration, at a temperature above the T c of the lipid or of the highest melting component of the mixture [66]. Different MLVs can be produced depending on the hydration time, the re-suspension method, the lipid concentration and composition, and the volume of suspending the aqueous phase [12]. When comparing the thin-film hydration, the reverse-phase evaporation and the ethanol injection methods to prepare cationic liposomes, the results showed that liposomes prepared by the thin-film method were of the best quality and stability [63].…”

“…This liposome preparation method also presents some limitations such as low encapsulation ability and the difficulty in producing nano-size liposomes. However, sonication or extrusion through polycarbonate membranes can be employed to obtain ULVs [12,18,51].…”

“…In terms of the polar headgroups, phospholipids are classified as phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylglycerol (PG) and phosphatidic acid (PA). PC and PE are the most abundant phosphatides in plants and animals and are also the most used to produce liposomes [12]. However, natural Figure 2.…”