Skin penetration behaviour of liposomes as a function of their composition

Deformable liposomes have been developed and evaluated as a novel topical and transdermal delivery system. Their mechanism of drug transport into and through the skin has been investigated but remains a much debated question. The present study concerns ex vivo diffusion experiments using pig ear skin in order to explain the penetration mechanism of classical and deformable liposomes. Classical and deformable vesicles containing betamethasone in the aqueous compartment through the use of cyclodextrin inclusion complexes were compared to vesicles encapsulating betamethasone in their lipid bilayer. Deformable liposomes contained sodium deoxycholate as the edge activator. Liposomes were characterised by their diameter, encapsulation efficiency, deformability, stability (in terms of change in diameter) and release of encapsulated drug. Exvivo diffusion studies using Franz diffusion cells were performed. Confocal microscopy was performed to visualise the penetration of fluorescently labelled liposomes into the skin. This study showed that liposomes do not stay intact when they penetrate the deepest layers of the skin. Betamethasone is released from the vesicles after which free drug molecules can diffuse through the stratum corneum and partition into the viable skin tissue.

Schematic representation of fluorescently labelled liposomes encapsulating calcein in their inner cavity (A), liposomes encapsulating NBD-PC in their lipid bilayer (B) and liposomes encapsulating rhodamine B and NBD-PC in their lipid bilayer (C). Skin penetration of these liposomes is shown in the corresponding confocal images.Figure optionsDownload as PowerPoint slide