Potentials of new nanocarriers for dermal and transdermal drug delivery

A colloidal carrier system with an oily colloidal phase (O/W microemulsion) is shown on the right hand side which is used to improve dermal and transdermal drug delivery of extremely lipophilic drugs. On the left hand side a colloidal carrier system with an aqueous colloidal phase (W/O microemulsion) is shown suitable for dermal and transdermal drug delivery of extremely hydrophilic drugs such as peptides and proteins. Nanocarriers (NCs) are colloidal systems having structures below a particle or droplet size of 500 nm. In the previous years, the focus for the application of NCs was primarily placed on the parenteral and oral application. However, NCs applied to the skin are in the center of attention and are expected to be increasingly applied as the skin offers a lot of advantages for the administration of such systems. For the use of NCs to the skin, one has to differentiate between the desired effects: the local effect within the skin (dermal drug delivery) or a systemic effect accompanied by the permeation through the skin (transdermal drug delivery). Both for dermal and transdermal drug delivery, the stratum corneum (SC), the main barrier of the skin, has to be overcome. SC is one of the tightest barriers of the human body. Therefore, it is the primary goal of new NC to overcome this protective and effective barrier. For that purpose, new NCs such as microemulsions, vesicular (liposomes) and nanoparticular NCs are developed and investigated. This article evaluates the potentials of these NCs for dermal and transdermal drug delivery.