Delivery of drugs applied topically to the skin

The stratum corneum is a formidable physical, environmental and microbial barrier, protecting mammalian organisms from external insult and maintaining homeostasis. If the skin is to be used as a route of topical drug delivery, the barrier must be overcome, but this can normally only be achieved with small, relatively lipophilic molecules. Strategies to increase the range of substances that are suitable for transdermal delivery and to improve the permeation of particular substances include advanced formulation and the use of chemical and physical enhancement techniques. Nanomaterials are increasingly being exploited as carriers to deliver materials such as drugs, dyes, vaccines or gene fragments to specific cell targets for therapeutic or diagnostic purposes.