Liposomes are lipid vesicles made of phospholipids consisting of one or more bilayers surrounding aqueous compartments [New, 1990]. Etymology of the name liposome is derived from two Greek words: lipos = fat and soma = body. Since their discovery by Bangham et al. in 1960s, they were used mainly as models of cell membranes, due to their structural similarity with the biomembranes [Bangham, 1983].

The liposomes could be made by dispersing lipids in an aqueous medium. In the lipid bilayer that results from this process quickly and spontaneously by of a self-assembling process, amphiphilic molecules are oriented so that the hydrophilic heads of lipid molecules to be located at the lipid-water interface (Figure 1) and the hydrocarbon chains to be restricted within the bilayer inside, without contact with water media.

[caption id="attachment_696" align="aligncenter" width="300"]The lipid bilayer structure of a liposome Fig.1. The lipid bilayer structure of a liposome[/caption]

 

Starting 1970s, these lipid spheres have been used as drug delivery systems. The presence of two different environments in their structure: the aqueous compartment(s) and the hydrophobic inside of the lipid bilayer(s), liposomes could be versatile carriers for a wide variety of hydrophobic, hydrophilic or amphipathic therapeutic agents.

Liposomes are widely used in the pharmaceutical industry for the study of drug action, as well as in medicine: gene therapy, in establishing medical diagnoses (fluorescent liposomes), as adjuvant in vaccination [Couvreur & Vauthier, 2006] or as "vehicles" carrying oligonucleotides, antigens, drugs, thus decreasing drug toxicity [Hermanson, 2008]. Incorporating these drugs in liposomes extends their duration of action, reaching the target organ in the concentration required.

The liposomes are also employed in photodynamic therapy for photochemical eradication of malignant tumors [Derycke & Witte, 2004].

For extraction and detection of antibodies in biological samples, it is necessary the liposomes entrapping magnetic nanoparticles (magnetoliposomes) are very useful using [Vo-Dinh, 2003]. Magnetoliposomes are of high importance in drug delivery, as they can be guided and localized to the therapeutic site by external magnetic field gradients and used in cancer treatment by hyperthermia [Dandamudi & Campbell, 2007]. The studies of García-Jimeno et al. (2012) confirmed that it is possible to target drugs encapsulated in magnetoliposomes by means of an external magnet; this method can be used to treat the inflammatory process or other pathologies, and it can reduce the drug concentration administered and increase the efficacy of the treatment.

A number of arguments justify the use of liposomes as "carriers" of drugs [Swarbrick & Boylan, 1994]: liposomes are biocompatible due to their biodegradability and low toxicity, and can serve as a "device" for the controlled release of the drug in body fluids and in the cells. The liposomes may be administered in several ways: ocularly, pulmonary, nasally, orally, intramuscularly, subcutaneously, topically or intravenously.

Another interesting application is the use of liposomes as "bioreactors" [Nardin et al., 2001; Noireaux & Libchaber, 2004]. Liposomes are a model for many fundamental studies [Phillipot & Schuber, 1995; Lasic, 1995] in the following fields:

  • Mathematics (topology of two-dimensional surfaces in three-dimensional space, governed only by bilayer elasticity);
  • Physics (aggregation, fractal, soft and hard materials);
  • Biophysics (permeability, phase transitions, photophysical studies);
  • Physical chemistry (colloid behavior in a system with well-defined physical forces, inter- and intra-aggregate DLVO theory);
  • Chemistry (photochemistry, photosynthesis, artificial catalysis, micro-compartmentalization);
  • Biochemistry (reconstitution of membrane proteins into artificial membranes);
  • Biology (models of biological membranes, cell functioning study using liposomes as a tool for restoring biological membranes, the elucidation of the mechanisms of membrane fusion, cell recognition, immunological studies).

 

In cosmetics, liposomes are used as a platform delivering different ingredients or drugs, and also as penetration enhancers of different active substances into the skin; they can be included in creams, gels or lotions [Lasic, 1995; Paye et al. 2006]. Vyas et al. (2013) reported a novel liposomal gel formulation of caffeine that could reduce the cellulite depositions over human body.

Recently, liposomes bearing a natural porphyrin: chlorophyll a, were used as building blocks to design antioxidant and antimicrobial materials [Barbinta-Patrascu et al., 2014].

The liposomal composition can be infinitely modified and thus creating smart materials with multiple applications.

 

References

Bangham, A. D., ed., Liposome Letters, Academic Press, 1983.

Barbinta-Patrascu, M. E., Ungureanu, C., Iordache, S. M., Iordache, A. M., Bunghez, I. R., Ghiurea, M., Badea, N., Fierascu, R. C. and Stamatin, I., Mat. Sci. Eng. C 39 (2014) 177.

Couvreur, P. and Vauthier, C., „Nanotechnology: Intelligent Design to Treat Complex Disease”, Pharmaceutical Research, 23 (2006) 1417.

Dandamudi, S. and Campbell, R. B., Biomaterials, 28 (2007) 4673.

Derycke, A. S., de Witte, P. A., “Liposomes for photodynamic therapy”, Adv. Drug Deliv. Rev. 56 (2004) 17.

García-Jimeno, S., Escribano, E., Queralt, J. and Estelrich, J., Nanoscale Research Letters, 7 (2012) 452.

Hermanson, G. T., Bioconjugate Techniques, Edition: 2, revised, Academic Press, 2008.

Lasic, D. D., “Applications of Liposomes”, Handbook of Biological Physics, Vol. I, edited by Lipowsky and E. Sackmann, Liposome Technology, Inc., 1995.

Nardin, C., Widmer, J., Winterhalter, M., Meier, W., “Amphiphilic Block Copolymer Nanocontainers as Bioreactors”, European Physical Journal E 4 (2001) 403.

New, R. R. C. (ed.), Liposomes: A practical approach, IRL press, Oxford University, 1990.

Noireaux, V., Libchaber, A., “A vesicle bioreactor as a step toward an artificial cell assembly”, PNAS 101 (2004) 17669.

(www.pnas.org_cgi_doi_10.1073_pnas.0408236101)

Paye, M., Barel, A. O., Maibach, H. I., Handbook of cosmetic science and technology, Edition: 2, Informa Health Care, 2006.

Phillipot, J. R., Schuber, F., Liposomes as tools in Basic Research and Industry, CRC press, Inc., 1995.

Swarbrick, J., Boylan, J. C., Encyclopedia of Pharmaceutical Technology: Liposomes As Pharmaceutical Dosage Forms to Microencapsulation, Informa Health Care, 1994.

Vo-Dinh, T., Biomedical Photonics Handbook, CRC press, 2003.

Vyas, L. K., Tapar, K. K., Nema, R. K., Parashar, A. K., Int J Pharm Pharm Sci, 5(3) (2013) 512.