A High Throughput Method to Predict Skin Penetration and Screen Topical Formulations

By: Konstantin Tsinman, PhD, Pion Inc.; Bálint Sinkó, PhD, SinkoLAB Scientific Bt.

Posted: March 5, 2013, from the March 2013 issue of Cosmetics & Toiletries.

In past decades, the understanding of mechanisms for skin penetration has significantly improved.¹ Studies have identified the stratum corneum (SC), the outermost layer of the skin, as the main barrier for penetration of pharmaceutical and cosmetic ingredients,² and due to its unique composition—i.e., about 50% ceramides, 35% free fatty acids and 15% cholesterol—the SC differs from other biological membranes.³ To facilitate the development of transdermal delivery for the compounds of interest, estimations of skin penetration rates and comparisons of dermatological formulations have become crucial to pharmaceutical and cosmetics research.⁴

Several methods have been developed for the prediction of skin penetration. Although the most useful data is obtained from in vivo studies in humans, such measurements are expensive, labor-intense and slow to perform. This makes their application in lead selection and optimization impractical. In vivo measurements using rodents⁵ are well-known to overestimate the penetration rate since compounds can permeate down the hair follicle,⁶ and although pig ear skin is also used for in vitro tests based on its structural equivalence to human skin,⁷ the most generally accepted in vitro permeation models are based on human skin as the membrane.

This is only an excerpt of the full article that appeared in Cosmetics & Toiletries, but you can purchase the full-text version.