A Comparison of the Penetration and Permeation of Caffeine into and through Human Epidermis after Application in Various Vesicle Formulations.

A range of vesicles is now widely used to carry various solutes into and through the epidermis. These usually have the active solute encapsulated within and may be modified to confer flexibility and skin penetration enhancement. Here, we compared the ability of five different vesicle systems to deliver a model hydrophilic drug, caffeine, into and through excised human skin. In addition to lipids, the vesicle excipients included eucalyptol or oleic acid as penetration enhancers, and decyl polyglucoside as a non-ionic surfactant. Vesicle particle sizes ranged between 135 and 158 nm, and caffeine encapsulation efficiencies were between 46 and 66%. Caffeine penetration and permeation were measured using high-performance liquid chromatography. We found that niosomes, which are liposomes containing a non-ionic surfactant, and transferosomes (ultraflexible vesicles) showed significantly greater penetration into the skin and permeation across the stratum corneum. Significant enhancement of caffeine penetration into hair follicles was found for transferosomes and those liposomes containing oleic acid. We conclude that targeted delivery of the hydrophilic drug caffeine into the skin compartments can be modified using optimized vesicular formulations.