Plasma Technology for Health
"Für den Betrieb der 10mm-Al2O3-Elektrode wurde nach einer spektralen Gewichtung der Strahlung entsprechend der physiologischen Wirksamkeit festgestellt, dass eine tägliche Behandlung unter Verwendung des gleichen Parametersatzes von 22 Stunden unbedenklich erscheint. Da sich in der spektralen Verteilung der beiden Experimente keine wesentlichen Unterschiede zeigten und die Intensitäten beim Betrieb mit der flexiblen Spritzguss-Elektrode um ein Vielfaches niedriger liegen, kann davon ausgegangen werden, dass sich keine Reglementierung der täglichen Behandlungsdauer aufgrund der Plasma-UV-Emission während der Behandlung ergibt."
"Ozone is a major component produced by low-temperature plasmas operating in oxygen-containing gas mixtures. For correlation with biological or clinical results of plasma medical therapies as well as for evaluation of application security, tempo-spatially resolved ozone concentrations need to be considered. When operating a single-electrode dielectric barrier discharge (SE-DBD), the electric field characteristics are dependent on the geometrical setup as well as the electrical properties of the counter electrode. Thus, the counter electrode also affects the plasma input power and hence the total production of chemical species. Therefore, we studied the power input and the tempo-spatial characteristics of ozone concentrations during operation of a SE-DBD operated at voltage pulses in the us regime against a clean metal electrode and a metal electrode covered with porcine skin samples. At energy densities of up to 1.85 J/cm2, the ozone concentrations in the plasma volume amount to as much as 293 ppm whereas at a distance of 5 and 20 cm, respectively, from the discharge, concentrations have decreased beneath recommended safety limits of 0.1 ppm. Furthermore, significantly lower ozone concentrations could be observed when skin samples were used as part of the counter electrode"
"The effects of low-temperature plasma treatment on microorganisms typically related to skin diseases are studied qualitatively by the inhibition of growth and viability assays to evaluate the potential for classifying as a prospective antiseptic agent. A variety of microorganisms enveloping gram- negative and gram-positive bacteria as well as one genus of yeast and fungus each were exposed to plasma in vitro. In a comparative approach, two power supplies, both of which produce high voltage pulses yet at different temporal characteristics, are applied for the growth study. While operation with both devices led to growth inhibition of all microbes, the results indicate a superior antimicrobial efficacy for high voltage pulse lengths in the nanosecond scale. Fluorescence assays reveal the efficacy of nanosecond-pulse driven plasma in reducing germ viability. Furthermore, the technical background for patents related to low-temperature plasma technology in the field of plasma medicine is discussed."
"In the frame of plasma source development for dermatological applications in the field of plasma medicine, operational safety of the devices is of superior priority. For sources based on the concept of dielectric barrier discharges (DBD), electric potentials with amplitudes in the range of some kV are arranged in close proximity to the skin of patients, wherein dielectric strength of the electrodes and leakage currents are crucial for electrical applicability. In this work, ceramic electrodes of 10 mm in diameter and varying ceramic thickness are operated at input powers up to 300 mW against non‐biological counter electrodes. In a combined experimental and numerical approach, electric fields inside the ceramic are determined, whereas values are well below the dielectric strength of the material. The spectrally weighted plasma emission is within limit values of exposure to human skin as long as daily treatment does not exceeded 7 h. Neutral gas temperatures of up to 310 K are determined which underline the minor thermal impact of the plasma exposure. In contrast, values for reduced electric fields are of the order of some hundred Townsend and thus the electrons can initiate various secondary effects such as chemical reaction chains. Consequently, ozone concentrations in the discharges are quantified between 230 ppm and 1140 ppm in close proximity to the actual discharge volume and the results are discussed in the frame of risk assessment for therapeutic applications in dermatology."
" Dielectric barrier discharge (DBD) devices generate air plasma above the skin containing active and reactive species including nitric oxide (NO). Since NO plays an essential role in skin physiology, a topical application of NO by plasma may be useful in the treatment of skin infections, impaired microcirculation and wound healing. Thus, after safety assessments of plasma treatment using human skin specimen and substitutes, NO-penetration through the epidermis, the loading of skin tissue with NO-derivates in vitro and the effects on human skin in vivo were determined. After the plasma treatment (0-60 min) of skin specimen or reconstructed epidermis no damaging effects were found (TUNEL/MTT). By Franz diffusion cell experiments plasma-induced NO penetration through epidermis and dermal enrichment with NO related species (nitrite 6-fold, nitrate 7-fold, nitrosothiols 30-fold) were observed. Furthermore, skin surface was acidified (~pH 2.7) by plasma treatment (90 s). Plasma application on the forearms of volunteers increased microcirculation fourfold in 1-2 mm and twofold in 6-8 mm depth in the treated skin areas. Regarding the NO-loading effects, skin acidification and increase in dermal microcirculation, plasma devices represent promising tools against chronic/infected wounds. However, efficacy of plasma treatment needs to be quantified in further studies and clinical trials."
" The dielectric barrier discharge (DBD) plasma source for biomedical application is characterized using optical emission spectroscopy, plasma-chemical simulation and voltage–current measurements. This plasma source possesses only one electrode covered by ceramic. Human body or some other object with enough high electric capacitance or connected to ground can serve as the opposite electrode. DBD consists of a number of microdischarge channels distributed in the gas gap between the electrodes and on the surface of the dielectric. To characterize the plasma conditions in the DBD source, an aluminium plate is used as an opposite electrode. Electric parameters, the diameter of microdischarge channel and plasma parameters (electron distribution function and electron density) are determined. The gas temperature is measured in the microdischarge channel and calculated in afterglow phase. The heating of the opposite electrode is studied using probe measurement. The gas and plasma parameters in the microdischarge channel are studied at varied distances between electrodes. According to an energy balance study, the input microdischarge electric energy dissipates mainly in heating of electrodes (about 90%) and partially (about 10%) in the production of chemical active species (atoms and metastable molecules)."
“Atmospheric-pressure dielectric barrier discharge (DBD) in air is investigated for medical applications, especially for skin treatment. When the DBD was tested on mouse skin, a homogeneous discharge accompanied by filamentary microdischarges is observed. For characterization of the homogeneous discharge, averaged plasma parameters (namely electron density and electron velocity distribution function) and gas temperature are determined by optical emission spectroscopy, microphotography and numerical simulation. Chemical kinetics in the active plasma volume and in the afterglow is simulated. Fluxes of biologically useful molecules like nitric oxide (NO) and ozone reaching the treated surface and irradiation by UV photons are determined. Skin biopsy results show that DBD treatment causes no inflammation and no changes in the skin-collagen.”