Nanocarriers for drug delivery into and through the skin - Do existing technologies match clinical challenges?

The topical application of drug-loaded particles has been explored extensively aiming at a dermal, follicular or transdermal drug delivery. This review summarizes the present state of the field of polymeric nanocarriers for skin application, also covering methodologies to clinically characterize their interaction and penetration in skin in vivo. Furthermore, with a focus on a clinical perspective, a number of questions are addressed: How well are existing nanoparticle systems penetrating the skin? Which functions of new carrier concepts may meet the clinical requirements? To which extend will instrumental imaging techniques provide information on the biological functions of nanocarriers? Which issues have to be addressed for translating experimental concepts into a future clinical application?