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Gas plasma is an approved technology that generates a plethora of reactive oxygen species, which are actively applied for chronic wound healing. Its particular antimicrobial action has spurred interest in other medical fields, such as periodontitis in dentistry. Recent work has indicated the possibility of performing gas plasma-mediated biofilm removal on teeth. Teeth frequently contain restoration materials for filling cavities, e.g., resin-based composites. However, it is unknown if such materials are altered upon gas plasma exposure. To this end, we generated a new in-house workflow for three commonly used resin-based composites following gas plasma treatment and incubated the material with human HaCaT keratinocytes in vitro. Cytotoxicity was investigated by metabolic activity analysis, flow cytometry, and quantitative high-content fluorescence imaging. The inflammatory consequences were assessed using quantitative analysis of 13 different chemokines and cytokines in the culture supernatants. Hydrogen peroxide served as the control condition. A modest but significant cytotoxic effect was observed in the metabolic activity and viability after plasma treatment for all three composites. This was only partially treatment time-dependent and the composites alone affected the cells to some extent, as evident by differential secretion profiles of VEGF, for example. Gas plasma composite modification markedly elevated the secretion of IL6, IL8, IL18, and CCL2, with the latter showing the highest correlation with treatment time (Pearson's r > 0.95). Cell culture media incubated with gas plasma-treated composite chips and added to cells thereafter could not replicate the effects, pointing to the potential that surface modifications elicited the findings. In conclusion, our data suggest that gas plasma treatment modifies composite material surfaces to a certain extent, leading to measurable but overall modest biological effects. [ABSTRACT FROM AUTHOR]

The uncured carbon nanotube/epoxy composite was treated with an atmospheric pressure argon plasma jet. The discharge characteristics of argon plasma jet were characterized by measuring voltage and current waveforms, luminescent images, and optical emission spectra. The effects of applied voltage, treatment time, and inter-electrode distance on volume resistivity of the composite were studied. The results showed that the argon plasma jet is a typical diffuse streamer discharge. The optical emission intensities of main active particles are increased with the increasing of applied voltage. The composite was most effectively treated by atmospheric pressure argon plasma jet under the following conditions: inter-electrode distance 14.5 mm, treatment time 18 s, and applied voltage 10.4 kV. As compared with the untreated composite, the treated composite had lower volume resistivity and better electrical conductivity due to the improved dispersion of carbon nanotubes in epoxy resin after argon plasma jet treatment. The aging test result showed that the electrical resistivity of the composite is very stable and unchanged within 30 days. [ABSTRACT FROM AUTHOR]

A comparative study of two plasma sources (floating-electrode dielectric barrier discharge, DBD, Drexel University; atmospheric pressure argon plasma jet, kINPen, INP Greifswald) on cancer cell toxicity was performed. Cell culture protocols, cytotoxicity assays, and procedures for assessment of hydrogen peroxide (HO) were standardized between both labs. The inhibitory concentration 50 (IC50) and its corresponding HO deposition was determined for both devices. For the DBD, IC50 and HO generation were largely dependent on the total energy input but not pulsing frequency, treatment time, or total number of cells. DBD cytotoxicity could not be replicated by addition of HO alone and was inhibited by larger amounts of liquid present during the treatment. Jet plasma toxicity depended on peroxide generation as well as total cell number and amount of liquid. Thus, the amount of liquid present during plasma treatment in vitro is key in attenuating short-lived species or other physical effects from plasmas. These in vitro results suggest a role of liquids in or on tissues during plasma treatment in a clinical setting. Additionally, we provide a platform for correlation between different plasma sources for a predefined cellular response. [ABSTRACT FROM AUTHOR]

Exposure to cold physical plasma has been proposed to be of therapeutical value in oncology via the generation of a number of biologically relevant redox-active molecules. Cancer cells can be recognized and eliminated by cells of the immune system, and accordingly many tumors are populated with these cells, among them T helper cells (TH cells). These lymphocyte population is crucial for effector immune responses against tumor antigens, in response to immunogenic cell death in malignant cells. However, a number of TH populations exists, each having distinct phenotypical features. Using a cold atmospheric pressure argon plasma jet, its redox activity was tested in different TH cell subpopulations to better understand the immunological consequences of potential antitumor plasma treatments in vivo. [ABSTRACT FROM AUTHOR]