Hair follicles - a long-term reservoir for drug delivery.

Nanoparticles represent an important drug carrier system. Recently, we have reported on the penetration and storage behavior of particular and non-particular substances revealing the superiority of particular substances in the range of 300-400 nm. In this regard, it was assumed that the rigid hair shaft acts as a geared pump, moving the particles deeper into the hair follicle. In the present investigation, the storage reservoir capacity of the stratum corneum and the hair follicle infundibulum and canal are compared. Interestingly, we could demonstrate a 10 times longer storage within the hair follicles. These results underscore the importance of the hair follicle for drug delivery purposes, mainly highlighting new possibilities for the future concerning retarded delivery, application frequency, and galenic design. Copyright (c) 2006 S. Karger AG, Basel.