Nanoparticles influence in skin penetration of drugs: In vitro and in vivo characterization

Abstract Topical application of drugs is the choice route of administration for treating skin diseases. The stratum corneum , a natural skin barrier, protects the body against external agents but also limits penetration of topically applied drugs into deeper skin layers. Nanoparticles are nano-sized drug delivery systems with several advantages for topical administration, including protection against drug degradation and sustained drug delivery, leading to a more effective and less toxic treatment, compared to conventional topically applied formulations. Nanoparticle interactions and distribution within the skin, whether associated or not with physical methods like iontophoresis, modifies drugs penetration. It is, consequently, important to evaluate nanoparticle characteristics which bring about these interactions. Therefore, this chapter will address nanoparticle characteristics affecting skin drug penetration, their possible penetration pathways, in addition to in vitro and in vivo techniques commonly used in assessing penetration and distribution of drugs into the skin when nanoparticles are used as topical delivery systems.