**5.4 Transdermal**

The transdermal administration of drugs improves their bioavailability and is useful for systemic and local treatment as in pulmonary application. Takeuchi et al. [119] evaluated the in vivo permeability of 40 nm SFN through the skin using mice and demonstrated that the particles are capable of reaching the dermis in 6 hours in addition to the stratum corneum, hair follicles and epidermis that surrounds them.
