Nanoparticles, Nanomaterials and Nanocarriers

Nanoparticles have been considered for a while as unlikely to penetrate healthy (undisrupted) skin [1]. It is universally accepted now that their size is an important factor which determines their absorption into the skin. In 2008 a European forum, the Scientific Committee on Consumer Products, made public their opinion about interactions between nanostructures and the skin. Their statements were made based on the sizes involved [2] and showed that only for particles smaller than 10 nm there is evidence of penetration as far as the dermis. For particles of 20 nm or larger there is no evidence of penetration into viable (undisrupted) skin layers. The conclusion summarizes experiments done on both human and porcine skin. The same document states that the situation is different for hair follicles which allow deep penetration of particles 20 nm or larger and can function as reservoirs for nanoparticles. Mechanical effects on the skin (e.g. wrinkles, flexing) affect (modulate) penetration as well.