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.

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.

Recently, it was reported that a plasma-jet could be efficiently applied for the antisepsis of wounds. In this case, the discharge in an argon gas stream was used to produce a so-called "cold plasma" on the skin surface. The thermal action of the plasma on the skin was investigated in the present study by means of laser scanning microscopy (LSM) and by histological analysis. Consequently, the plasma beam was moved with a definite velocity at an optimal distance over the skin surface. The structural changes of the tissue were analyzed. It was found by LSM that a thermal damage could be detected only in the upper cell layers of the stratum corneum (SC) at moving velocities of the plasma beam, usually applied in clinical practice. Deeper parts of the SC were not damaged. The structural changes were so superficial that they could be detected only by LSM but not by analysis of the histological sections.Plasma-jet under working conditions

The application of tissue-tolerable electrical plasma (TTP) is highly efficient in skin antisepsis. However, the germs are not only located on the skin surface, but also in the hair follicles, from where they re-colonize the skin surface after antisepsis, e.g. The objective of the present study was to show that plasma is able to reach the follicular reservoir for antisepsis. For this purpose, a solution containing particulate chlorophyll dye had been applied onto porcine skin samples. The fluorescent properties of the dye changed during the plasma tissue interaction. The results demonstrate that TTP penetrates deep into the hair follicles, whereupon the hairs act as a conductor for the plasma. Therefore, it can be concluded that micro-organisms of the follicular reservoir are destroyed more efficiently by the plasma than by conventional liquid antiseptics. μmHistological image of a hair follicle colonized with fungi (pityrosporon ovale, PAS staining)

Cold physical plasmas ignited a technological spark in industry, biotechnology, and medicine. Especially the field of hygiene benefited of the plasma's exceptional activity against pathogenic microorganisms. Together with plasma-based surface functionalization, these qualities are highly relevant in a variety of processes in health care, such as the decontamination or sterilization of medical devices, food, packaging materials, waste water, or indoor air. In medicine, plasma has proven to show promising antiseptic results on skin and mucosal membranes in infection-related diseases in dermatology and dentistry. This comprehensive review will discuss the current applications of cold plasma in the fields of hygiene, and will provide a promising outlook on many applications yet to come.