Interaction of inorganic nanoparticles with the skin barrier: current status and critical review.

Integration of nanotechnology with biology leads to various advantages in applied pharmaceutical and medical sciences. In that regard, the behavior of nanoparticles (NPs) in relation to the skin, an important biological barrier, has been the target of several recent studies. Yet the potential ability of NPs to penetrate into the underlying viable tissue lies at the center of debate. This review briefly highlights the current applications of inorganic NPs, then discusses the current status of their skin penetration in view of the vast variation among the experimental setups in use. Determinants of particle penetration, adopted approaches for enhanced penetration, the underlying mechanism, as well as qualitative and quantitative analysis of NPs present in the skin are also within the scope of this review article. We emphasize analyzing the data generated from experiments on human skin, the "gold standard" for assessment of in vitro skin penetration. Based on this, we include some recommendations for future research. FROM THE CLINICAL EDITOR: Transdermal application of inorganic nanoparticle-based medications is of growing interest in nanomedicine research. This critical review discusses the knowns and the unknowns of this field, providing insightful recommendations for future research.