TRANSFERSOMES ULTRA FLEXIBLE VESICLES FOR TRANSDERMAL DELIVERY

Molecules greater than 500 Da normally do not cross the skin. This prevents epicutaneous delivery of the high molecular weight therapeutics as well as non-invasive transcutaneous immunisation. Transfersomes are a form of elastic or deformable vesicle, which were first introduced in the early 1990s. Elasticity is generated by incorporation of an edge activator in the lipid bilayer structure. The original composition of these vesicles was soya phosphatidyl choline incorporating sodium cholate and a small concentration of ethanol. Transfersomes are applied in a non-occluded method to the skin and have been shown to permeate through the stratum corneum lipid lamellar regions as a result of the hydration or osmotic force in the skin. They have been used as drug carriers for a range of small molecules, peptides, proteins and vaccines, both in vitro and in vivo. Transfersomes penetrate through the stratum corneum and the underlying viable skin into the blood circulation in intact form. However, this has not been substantiated by other research groups who have extensively probed the mechanism of penetration and interaction of elastic vesicles in the skin. Structural changes in the stratum corneum have been identified, and intact elastic vesicles visualised within the stratum corneum lipid lamellar regions, but no intact vesicles have been ascertained in the viable tissues. Extremely deformable vesicles prepared by the judicious combination of several materials provide a solution to this problem: the resulting agent carriers, transfersomes, are the only tested colloidal system that can transport even large macromolecules spontaneously through the skin in immunologically active form.