Solid lipid nanoparticles for topical drug delivery

Solid lipid nanoparticles (SLN) have shown interesting potential as a drug delivery system for the topical delivery of various drugs. However, their performance when applied to the skin has not been fully investigated because of the complexity of their composition and structure. Theoretically, drug can be targeted systemically to the vasculature in the dermis, locally to the skin strata, or superficially to the surface of the skin. Therefore, the topical delivery vehicle should be designed according to the desired therapeutic purposes. To understand drug permeation behavior, it is essential to elucidate the pattern of drug release from the SLN formulations. A number of different drug release patterns have been outlined in the literature, and these patterns have been found to be related to the manufacturing process of the vehicle. In this paper, we summarize the results of SLN-mediated skin penetration data in the literature and illustrate several theoretical mechanisms of SLN-skin interactions that might take place at the site of action. Substantial research dedicated to the development of this promising drug delivery system is still required.