Liposomes: From the pioneers to Epigenetic Therapy

Abstract

The nanoscience is the discipline that explains the behavior of systems at nanoscopicscale. The liposomes were one of the first nanostructures developed which were rapidlyapplied in different areas. These systems are structures formed by self-closingphospholipid bilayers in aqueous solutions. The strategies used for their developmenthave leaded them to reach a place of preponderance in drug delivery systems design.For analyzing the properties of liposomes, physicochemical concepts such as thoseused to describe liquid crystals, must be used. Owing to their amphiphilic nature, thephospholipids form aggregates giving an auspicious framework for the interaction withhydrophilic and lipophilic substances. These properties encouraged the emergence ofinnumerable modifications and thus, different types of liposomes have already beenreported since seventies to present. The main strategies have been focused on increasingtheir time of permanence in blood circulation and on decreasing their removal by the cellsof the mononuclear phagocyte system (MPS) in liver and spleen. For reaching this aimtheir size was reduced and their membrane fluidity was modified using cholesterol and sphingomyelins. However, one of the most successful strategies was the development ofPEGylated liposomes which have been named ?stealth liposomes.?Therefore, this book chapter is addressed to a comprehensive revision of thebibliography regarding to the emergence of liposomes and the first steps in their design,the type of systems (components and structures), their classification and properties.Their experimental physicochemical stability and also theoretical, using DLVOtheory, was analyzed. Furthermore, this text reviews some of the desired properties ofliposomes: the loading and the release of drugs, and their relationship with cells whichcan be mediated or not by receptors among other properties.The lipids, sterols, drugs or other different types of molecules which are able tointeract with the liposome membranes can be studied by biophysics techniques becausethey modify the self-organization at the air-water interface and the states of thesesystems. Therefore, this point is discussed in a separate section of this chapter.Finally, some approaches about the use of liposomes in the biomedicine field andapproved commercial formulations are revised. Additionally, some proposed perspectivesbased on their capability to carry molecules, such as silencing RNA (siRNA), which is astrategy used in pharmacoepigenetics therapy, are shown.