Liposomes

Liposomes are self assembled structures formed by lipids. The use of lipid vesicles in topical delivery systems has many advantages, such as increases drug permeation through stratum corneum; lowers skin irritation caused by drugs and metabolites; extends the effective time within the skin by interaction of phospholipid bilayer with the similarly structured cell membrane; for hydrophobic drugs, liposome formulation increases overall solubility without the use of skin irritating solvents.

However, it has been proved that classic liposomes are of little or no value as carriers  for transdermal drug delivery because they do not deeply penetrate the skin, but rather remain on the upper layer of the stratum corneum. For liposomes to pass through and reach to the deeper layers of the skin, many new strategies have been developed. Among these, deformable liposomes have gained many attentions in the past twenty year. Deformable liposomes are prepared by combining a lipid, e.g., a phosphatidylcho line (PC) with a denaturant such as a surfactant or an alcohol.

We have conducted extensive research to develop various deformable liposomes using NSAIDs as model drug. Liposomes were prepared by the thin film hydration method followed by sonication (Figure 1).

These deformable liposomes were composed of phospholipid, edge activator, cholesterol and/or permeation enhancer.

Figure 1
Lipid Film of Various Liposomal Formulations

These NSAID loaded liposomes demonstrated high drug entrapment rate, homogeneous particle size and improved solubility and skin permeability compared to classic liposomes.

Figure
2 shows the TEM image of the deformable formulations.
Figure 2
TEM Image of Deformable Liposome

The dermal and transdermal delivery using deformable liposomes can be a promising alternative to conventional oral delivery of NSAIDS with enhanced local and systemic onset of action and reduced side effects. Our current research goal is to incorporate these liposomal suspensions into a delivery vehicle, such as hydrogel, cream or transdermal patch to eventually develop a commercially viable formulation.