Search

The promising potential of cold atmospheric plasma (CAP) treatment as a new therapeutic option in the field of medicine, particularly in Otorhinolaryngology and Respiratory medicine, demands primarily the assessment of potential risks and the prevention of any direct and future cell damages. Consequently, the application of a special intensity of CAP that is well tolerated by cells and tissues is of particular interest. Although improvement of wound healing by CAP treatment has been described, the underlying mechanisms and the molecular influences on human tissues are so far only partially characterized. In this study, human S9 bronchial epithelial cells were treated with cold plasma of atmospheric pressure plasma jet that was previously proven to accelerate the wound healing in a clinically relevant extent. We studied the detailed cellular adaptation reactions for a specified plasma intensity by time-resolved comparative proteome analyses of plasma treated vs. nontreated cells to elucidate the mechanisms of the observed improved wound healing and to define potential biomarkers and networks for the evaluation of plasma effects on human epithelial cells. K-means cluster analysis and time-related analysis of fold-change factors indicated concordantly clear differences between the short-term (up to 1 h) and long-term (24-72 h) adaptation reactions. Thus, the induction of Nrf2-mediated oxidative and endoplasmic reticulum stress response, PPAR-alpha/RXR activation as well as production of peroxisomes, and prevention of apoptosis already during the first hour after CAP treatment are important cell strategies to overcome oxidative stress and to protect and maintain cell integrity and especially microtubule dynamics. After resolving of stress, when stress adaptation was accomplished, the cells seem to start again with proliferation and cellular assembly and organization. The observed strategies and identification of marker proteins might explain the accelerated wound healing induced by CAP, and these indicators might be subsequently used for risk assessment and quality management of application of nonthermal plasma sources in clinical settings.

The applications of low-temperature plasma are not only confined to decontamination and sterilization but are also found in the medical field in terms of wound and skin treatment. For the improvement of already established and also for new plasma techniques, in-depth knowledge on the interactions between plasma and microorganism is essential. In an initial study, the interaction between growing Bacillus subtilis and argon plasma was investigated by using a growth chamber system suitable for low-temperature gas plasma treatment of bacteria in liquid medium. In this follow-up investigation, a second kind of plasma treatment-namely air plasma-was applied. With combined proteomic and transcriptomic analyses, we were able to investigate the plasma-specific stress response of B. subtilis toward not only argon but also air plasma. Besides an overlap of cellular responses due to both argon and air plasma treatment (DNA damage and oxidative stress), a variety of gas-dependent cellular responses such as growth retardation and morphological changes were observed. Only argon plasma treatments lead to a phosphate starvation response whereas air plasma induced the tryptophan operon implying damage by photooxidation. Biological findings were supported by the detection of reactive plasma species by optical emission spectroscopy and Fourier transformed infrared spectroscopy measurements., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Plasma medicine and also decontamination of bacteria with physical plasmas is a promising new field of life science with huge interest especially for medical applications. Despite numerous successful applications of low temperature gas plasmas in medicine and decontamination, the fundamental nature of the interactions between plasma and microorganisms is to a large extent unknown. A detailed knowledge of these interactions is essential for the development of new as well as for the enhancement of established plasma-treatment procedures. In the present work we introduce for the first time a growth chamber system suitable for low temperature gas plasma treatment of bacteria in liquid medium. We have coupled the use of this apparatus to a combined proteomic and transcriptomic analyses to investigate the specific stress response of Bacillus subtilis 168 cells to treatment with argon plasma. The treatment with three different discharge voltages revealed not only effects on growth, but also clear evidence of cellular stress responses. B. subtilis suffered severe cell wall stress, which was made visible also by electron microscopy, DNA damages and oxidative stress as a result of exposure to plasma. These biological findings were supported by the detection of reactive plasma species by OES measurements., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This paper deals with the analysis of nanoparticles polymerized in nitrogen/acetylene and argon/acetylene gas mixtures in low temperature rf discharges. The polymerization process was monitored by means of mass spectroscopy. The chemical characteristics of the material were obtained in situ by infrared absorption spectroscopy and ex situ by means of near edge x-ray absorption fine structure spectroscopy. These data were supported by complimentary elemental analyses such as deuteron induced gamma emission, Rutherford backscattering, and nuclear reaction analysis. Although morphology showed no differences, further material analysis shows clearly nitrogen incorporation in the nanoparticles, mostly by multiple bonds. In comparison with the nanoparticles from argon/acetylene plasma, the amount of carbon in carbon-nitride nanoparticles remains unchanged, whereas hydrogen content strongly decreases. The results of mass spectroscopy on neutrals and ions lead to the assumption that carbon-nitride nanoparticles are formed by copolymerization of two kinds of precursors: hydrocarbon and nitrogen containing hydrocarbon species. [ABSTRACT FROM AUTHOR]

Plasma-enhanced chemical vapor deposition methods are frequently used to deposit barrier layers, e.g. on polymers for food packaging. These plasmas may suffer from particle (dust) formation. We report on a flexible monitoring system for dust. It is based on scanning a 3D plasma volume for particles by laser light scattering. The lower size limit of particles detected in the presented system is 20 nm. We report on existence diagrams for obtaining dust free or dust loaded capacitively or inductively coupled rf-plasmas in C2H2 depending on pressure, flow and rf-power. We further present growth rates for dust in these plasmas and show that monodisperse particles are only obtained during the first growth cycle. [ABSTRACT FROM AUTHOR]

A non-invasive diagnostic technique for measurements of ion fluxes and ion densities in low-pressure pulsed radio-frequency (RF) discharges is described. The ion flux towards an electrode is determined from the change in electrode dc-bias in the plasma afterglow. The measurements in various gas mixtures (Ar, N2, Ar/C2H2 and Ar with nanoparticles) show an increase in ion flux with the applied RF power. Ion densities are estimated from the ion fluxes and the plasma density at the plasma–sheath boundary, assuming the afterglow electron temperature to be known. Very good agreement between the estimated ion densities and independently measured electron densities is found in the bulk of dust-free plasmas assuming an afterglow electron temperature of 0.05 eV for argon and argon/acetylene plasmas and 0.2 eV for the nitrogen plasma. In dusty plasmas, the ion density at the plasma–sheath boundary can be determined from the measured ion flux and assuming an afterglow electron temperature of 0.05 eV. For the estimation of ion density in the dusty plasma bulk, the ion density distribution, influenced by the negatively charged dust particles, has to be taken into account. [ABSTRACT FROM AUTHOR]

Space resolved concentrations of helium He* (S) and argon Ar* (P) metastable atoms in an atmospheric pressure radio frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. Even small absorptions down to 10 could be measured using lock-in technique. The absolute density of metastable atoms densities at different rf-power, flow rate and gas mixture was deduced from measured absorption rates. Metastable concentrations range from 10 to 10 cm. Analysis of spectral profiles provided the pressure broadening coefficients of both metastable atoms by helium. The spatial distribution of metastable atoms in the plasma volume was obtained for various discharge conditions. Density profiles between the electrodes reveal the sheath structure and reflect the plasma excitation distributions in the discharge volume. It reveals the dominance of the α-mode discharge. [ABSTRACT FROM AUTHOR]

The influence of dust particles on the properties of a capacitively coupled Ar–C2H2 discharge is studied both experimentally and theoretically. The results of measurements of the intensity and spatial distribution of the emitted light, the line width of the fast component of Hα line and of the electron density during the particle growth are presented. To analyze the experimental results a one-dimensional discharge model is developed. Using the model the effects of dust grains on the power absorption (taking into account stochastic and Ohmic heating in the plasma sheaths), the optical emission intensity profile, the sheath size, the rf electric field and on the energy of positive ions bombarding the electrodes are investigated. In particular, it is shown that the decrease of the power absorption in the sheaths of complex plasmas is due to the dependence of the stochastic and Ohmic heating in the plasma sheaths on the electron temperature and the current flowing across the discharge plates. The results of the calculations are compared with the available experimental data and found to be in good agreement. [ABSTRACT FROM AUTHOR]

In this paper a spectroscopic investigation of an expanding surface wave produced plasma is presented. The electron temperature is evaluated by means of emission spectroscopy. The results show a strong and sharp increase of the electron temperature toward the end of the discharge, where the plasma is expanding into a region with lowered gas pressure. [ABSTRACT FROM AUTHOR]

Studies the power exhaust and the role of impurities in the Torus Experiment for Technological Oriented Research. Establishment of a quasistationary radiating boundary layer; Use of silicon as a condensing element; Underlying mechanisms for the buildup of a radiating plasma mantle and the interdependences of neon and silicon on other impurities.

The axial light distributions in parallel-plate dc microdischarges in argon show similar behavior to large-scale discharges. Between the low-current Townsend mode and the high-current glow mode exists a large region of currents where different oscillations appear and the dynamic volt–ampere characteristic shows hysteresis behavior. During the oscillations, the maximum peak intensity moves closer to the cathode, which is characteristic for the abnormal glow regime even though the average current is considerably smaller. [ABSTRACT FROM AUTHOR]

Abstract: In a fusion reactor like ITER, in-vessel materials are subjected to interactions with the plasma. One of the main consequences of these plasma-material interactions is the creation of co-deposited layers. Due to internal stresses, part of these layers can crack leading to micro particle creation. The purpose of the following paper is to review the Tokamak operation processes which lead to erosion and layer creation. Then, the proportion of these layers that is converted into micro-particles will be evaluated in the case of Tore Supra experiments and extrapolated for ITER. It is major importance to measure the ITER mobilizable dusts present in the Vacuum Vessel and compare the measured quantity with the safety limits. When approaching these limits, removal systems must be used in order to control the in-vessel dust inventory. In the second part of the paper, diagnostics and removal system under development will be presented. [Copyright &y& Elsevier]