In vivo skin treatment with tissue-tolerable plasma influences skin physiology and antioxidant profile in human stratum corneum.

The antimicrobial treatment of wounds is still a major problem. Tissue-tolerable electrical plasma (TTP) is a new approach for topical microbial disinfection of the skin surface. The aim of the present study was to investigate the influence of TTP on a carotenoid profile in relation to skin physiology parameters (epidermal barrier function, stratum corneum (SC) hydration, surface temperature and irritation parameters). We were interested in the interaction of TTP and the antioxidative network, as well as the consequences for skin physiology parameters. These parameters are also indicative of TTP safety in vivo. For plasma application, 'Kinpen 09' was used (surface exposure 30-43°C) for 3 s. Beta-carotene and water profiles were assessed by in vivo Raman microspectroscopy (skin composition analyzer 3510). Skin physiology parameters were measured with Tewameter TM 300, Corneometer CM 825, skin thermometer and Chromameter CR 300. All parameters were assessed non-invasively on seven healthy volunteers before and after plasma application in vivo. We could show that TTP application leads to a decrease in beta-carotene especially in the superficial SC. Skin-surface temperature increased by 1.74°C, while the transepidermal water loss (TEWL) increase indicated an impaired barrier function. SC hydration decreased as seen in water profile especially in the superficial layers and capacitance values. A slight increase in skin redness was measurable. The induction of reactive oxygen species is probably the major contributor of TTP efficacy in skin disinfection. Skin physiology parameters were influenced without damaging the skin or skin functions, indicating the safety of TTP under in vivo conditions.

Drug delivery through the skin barrier enhanced by treatment with tissue-tolerable plasma.

Most treatments in dermatology and cosmetology are based on the penetration of topically applied drugs into the skin or through the skin barrier to the target structure in the living tissue. In the case of healthy skin, scarcely 1% of the applied drugs pass the skin barrier, depending on their chemical properties. Therefore, different physical and chemical methods have been developed to stimulate the penetration process. All these methods are based on the partial destruction of the barrier. In this study, an electrical tissue-tolerable plasma (TTP) was used to increase the penetration of a topically applied model drug (fluorescent dye) through the skin barrier. Using laser scanning microscopy, the distribution of the model drug in different depths of the skin was investigated. It was found that the plasma treatment of the skin is a very efficient process to deliver topically applied substances into the living tissue. In the case of the non-plasma-treated skin, it was found that the fluorescent dye could be detected exclusively on the skin surface. If the dye was applied to the TTP-treated skin, it could be observed in high concentration also in deeper parts of the skin extending down to the stratum basale and the papillary structure.

Risk assessment of the application of a plasma jet in dermatology.

Regardless of the fact that several highly efficient antiseptics are commercially available, the antiseptic treatment of chronic wounds remains a problem. In the past, electrical plasma discharges have been frequently used in biometrical science for disinfection and sterilization of material surfaces. Plasma systems usually have a temperature of several hundred degrees. Recently, it was reported that "cold" plasma can be applied onto living tissue. In in vitro studies on cell culture, it could be demonstrated that this new plasma possesses excellent antiseptic properties. We perform a risk assessment concerning the in vivo application of a "cold" plasma jet on patients and volunteers. Two potential risk factors, UV radiation and temperature, are evaluated. We show that the UV radiation of the plasma in the used system is an order of magnitude lower than the minimal erythema dose, necessary to produce sunburn on the skin in vivo. Additionally, thermal damage of the tissue by the plasma can be excluded. The results of the risk assessment stimulate the in vivo application of the investigated plasma jet in the treatment of chronic wounds.