Permeabilization of human stratum corneum and full-thickness skin samples by a direct dielectric barrier discharge

A direct ex vivo treatment of human skin with cold atmospheric plasma, specifically a dielectric barrier discharge (DBD) using skin as the ground electrode, is able to permeabilize the stratum corneum (SC) throughout a treated area of 0.5 cm2. Silver sheet oxidation subsequent to a plasma treatment of isolated human SC revealed a regular pattern of local permeabilized regions greater in number than the expected number of skin appendages. The transepithelial electrical resistance showed a long-term overall drop for treatments ≥ 90 s in isolated SC as well as full-thickness skin. In view of drug delivery, a desirable prospective application of plasma permeabilization, permeation study results indicate that relatively small hydrophilic substances with Stokes' radii up to 1.4 nm are efficiently transported through human SC subsequent to 2 × 90 s treatment with direct cold atmospheric plasma at a power density of about 0.2 W cm−2. A moderate permeation of particles up to 6 µm in diameter is evident for the occasional formation of large pores in the µm-range. Finally, a mechanism for DBD plasma permeabilization of skin is proposed and discussed.