Planar lipid bilayers formed from thermodynamically-optimized liposomes as new featured carriers for drug delivery systems through human skin.

The fundamental objective pursued in this work is to investigate how liposomes formed with a thermodynamically optimized molar composition formed by the main components of the stratum corneum matrix behave on the human skin surface when used as drug delivery systems. To this purpose we engineered liposomes using phosphatidylcholines, ceramides and cholesterol. The specific molar ratio of the three components was established after studying the mixing properties of the lipid monolayers of the lipid components formed at the air-water interface. Liposomes loaded and unloaded with ibuprofen and hyaluronic acid were characterized by quasi-elastic light scattering and fluorescence polarization. Optimized liposomes, with and without drugs, were applied onto human skin and the structures formed evaluated using atomic force microscopy. Since penetration enhancers improve the permeation of the drugs encapsulated, we also examined the effects of Tween® 80 on the physical properties of the liposomes and on their extensibility over skin. In the present work we were able to observe the deposition and extension of liposomes in suspension onto human skin demonstrating the potential of liposomes without a secondary vehicle for releasing drugs in transdermal applications.

Enhanced topical delivery of hyaluronic acid encapsulated in liposomes: A surface-dependent phenomenon.

In the present study, we investigated the release and permeation of hyaluronic acid (HA) encapsulated in liposomes when deposited onto two surfaces: cellulose, a model widely used for investigating transport of drugs; and human skin, a natural biointerface used for transdermal drug delivery. We prepared and characterised liposomes loaded with HA and liposomes incorporating two penetration enhancers (PEs): the non-ionic surfactant Tween 80, and Transcutol P, a solubilising agent able to mix with polar and non-polar solvents. In vitro and ex vivo permeation assays showed that PEs indeed enhance HA-release from liposomes. Since one of the possible mechanisms postulated for the action of liposomes on skin is related to its adsorption onto the stratum corneum (SC), we used atomic force microscopy (AFM) topography and force volume (FV) analysis to investigate the structures formed after deposition of liposome formulations onto the investigated surfaces. We explored the possible relationship between the formation of planar lipid structures on the surfaces and the permeation of HA.

Improving ex vivo skin permeation of non-steroidal anti-inflammatory drugs: enhancing extemporaneous transformation of liposomes into planar lipid bilayers.

Transdermal delivery of active principles is a versatile method widely used in medicine. The main drawback for the transdermal route, however, is the low efficiency achieved in the absorption of many drugs, mostly due to the complexity of the skin barrier. To improve drug delivery through the skin, we prepared and characterized liposomes loaded with ibuprofen and designed pharmaceutical formulations based on the extemporaneous addition of penetration enhancer (PE) surfactants. Afterwards, permeation and release studies were carried out. According to the permeation studies, the ibuprofen liposomal formulation supplemented with PEs exhibited similar therapeutic effects, but at lower doses (20%) comparing with a commercial formulation used as a reference. Atomic force microscopy (AFM) was used to investigate the effect caused by PEs on the adsorption mechanism of liposomal formulations onto the skin. Non-fused liposomes, bilayers and multilayered lipid structures were observed. The transformation of vesicles into planar structures is proposed as a possible rationale for explaining the lower doses required when a liposome formulation is supplemented with surfactant PEs.