Transfersomes, liposomes and other lipid suspensions on the skin: permeation enhancement, vesicle penetration, and transdermal drug delivery.

Agents with MW < or = are being delivered transdermally with the aid of skin permeation enhancers that increase the agent's diffusivity and/or partitioning in the organ. Use of composite, lipidic agent-carriers (liposomes, niosomes) was not successful to date, due to the inability of such vehicles to pass through the narrow (< or = 30 nm) intercellular passages (virtual pores) in the outer skin layers. A solution to this problem are the orders of magnitude more deformable supramolecular aggregates, transfersomes. Such innovative drug-carriers are driven across the skin by the noturally occurring, concentration-insensitive, and probably hydration based, transepidermal gradient(s) and transport very efficient (> > 50%) and reproducibly various agents (200 < or = MW < or = 10(6); lipophilic/hydrophilic) into the body. Transfersomes were successfully used in animals and humans, also for the transcutaneous peptide and protein delivery. The theoretical rational for this is described together with the corresponding experimental models and practical examples.