Bulletin of the American Physical Society
68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015; Honolulu, Hawaii
Session ET1: Reactive Species for Plasma Medicine |
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Chair: David Graves, University of California, Berkeley Room: 301 B |
Tuesday, October 13, 2015 10:00AM - 10:30AM |
ET1.00001: TBD Invited Speaker: Deborah O'Connell |
Tuesday, October 13, 2015 10:30AM - 10:45AM |
ET1.00002: Reactive species profile in an atmospheric pressure plasma jet ignited in He and He/O2 mixture -- implications for surface sterilization Krishna Priya Arjunan, Brendan Jones, Sylwia Ptasinska The enhanced chemistry and low temperature of cold atmospheric plasma (CAP) makes it a promising alternative to conventional sterilization techniques. Of the various configurations used for generating cold plasma, atmospheric pressure plasma jets (APPJs) are particularly interesting for biomedical applications since they can be used for targeted treatment of intricate geometries such as catheters due to their small dimensions. The present study shows the efficacy of an APPJ ignited in helium or He/O2 mixture in inactivating \textit{Escherichia coli} (\textit{E.coli}) bacterium on agar plate. To study the dependence of helium flow rate and sample distance on the inactivation area, \textit{E.coli} spread on agar was treated for 10 min at various combinations of helium flow rates and sample distances from the nozzle. A ring-shaped inactivation area was observed in samples treated close to the jet nozzle. Addition of O2 significantly increased the inactivation area. The ring shaped inactivation area observed with only helium feed gas vanished with oxygen addition. The optical emission spectra of the core and jet region of the APPJ in helium and He/O2 were obtained. The profile of H2O2, NO2-, NO3- and O3 reaching the sample were determined using test strips arranged in a 3x3 array. A ring-shaped profile was observed for these species in samples treated close to the nozzle with helium APPJ, while no ring-shaped profile was observed with O2 addition. Addition of O2 increased O3 levels, and was detected up to 3 cm in the radial direction. [Preview Abstract] |
Tuesday, October 13, 2015 10:45AM - 11:00AM |
ET1.00003: Controlling Fluences of Reactive Species Produced by Multipulse DBDs onto Wet Tissue: Frequency and Liquid Thickness Wei Tian, Mark J. Kushner Tissue covered by a thin liquid layer treated by atmospheric pressure plasmas for biomedical applications ultimately requires a reproducible protocol for human healthcare. The outcomes of wet tissue treatment by dielectric barrier discharges (DBDs) depend on the plasma dose which determines the integral fluences of radicals and ions onto the tissue. These fluences are controlled in part by frequency and liquid thickness. In this paper, we report on results from a computational investigation of multipulse DBDs interacting with wet tissue. The DBDs were simulated for 100 stationary or random streamers at different repetition rates and liquid thicknesses followed by 10 s to 2 min of afterglow. At 100 Hz, NO$_{\mathrm{aq}}$ and OH$_{\mathrm{aq}}$ are mixed by randomly striking streamers, although they have different rates of solvation. NO$_{\mathrm{aq}}$ is nearly completely consumed by reactions with OH$_{\mathrm{aq}}$ at the liquid surface. Only H$_{2}$O$_{\mathrm{2aq}}$, produced through OH$_{\mathrm{aq}}$ mutual reactions, survives to reach the tissue. After 100 pulses, the liquid becomes ozone-rich, in which the nitrous ion, NO${_{2}^{-}}_{\mathrm{aq}}$, is converted to the nitric ion, NO${_{3}^{-}}_{\mathrm{aq}}$. Reducing the pulse frequency to 10 Hz results in significant fluence of NO$_{\mathrm{aq}}$ to the tissue as NO$_{\mathrm{aq}}$ can escape during the interpulse period from the liquid surface where OH$_{\mathrm{aq}}$ is formed. For the same reason, NO${_{2}^{-}}_{\mathrm{aq}}$ can also reach deeper into the liquid at lower frequency. Frequency and thickness of the liquid are methods to control the plasma produced aqueous species to the underlying tissue. [Preview Abstract] |
Tuesday, October 13, 2015 11:00AM - 11:15AM |
ET1.00004: Effect of active species on animal cells in culture media induced by DBD Plasma irradiation using air Tetsuya Ohtsubo, Reoto Ono, Nobuya Hayashi Little has been reported on action mechanism of active species produced by plasmas affecting living cells. In this study, active species in culture medium generated by torch type DBD and variations of animal cells are attempted to be clarified. Animal cells are irradiated by DBD plasma through various media such as DMEM, PBS and distilled water. Irradiation period is 1 to 15 min. The distance between the lower tip of plasma touch and the surface of the medium is 10 mm. Concentrations of NO2-, O3 in liquid are measured. After the irradiation, the cells were cultivated in culture medium and their modifications are observed by microscope and some chemical reagents. Concentration of NO2-and H2O2 in all media increased with discharge period. Increase rate of NO2- concentration is much higher than that of hydrogen peroxide. After plasma irradiation for 15 min, concentrations of NO2 were 80mg/L in DMEM, 30 mg/L in PBS and 15mg/L in distilled water. Also, the concentration of H2O2 became 3mg/L in DMEM, 6.5 mg/L in PBS and 6.5mg/L in distilled water. The significant inactivation of cells was observed in the PBS. Above results indicate that, in this experiment, H2O2 or OH radicals would affect animal cells in culture media. [Preview Abstract] |
Tuesday, October 13, 2015 11:15AM - 11:30AM |
ET1.00005: Characterization of Wet Air Plasma Jet Powered by Sinusoidal High Voltage and Nanosecond Pulses for Plasma Agricultural Application Keisuke Takashima, Keisuke Shimada, Hideaki Konishi, Toshiro Kaneko Not only for the plasma sterilization but also for many of plasma life-science applications, atmospheric pressure plasma devices that allowed us to control its state and reactive species production are deserved to resolve the roles of the chemical species. Influence of the hydroxyl radical and ozone on germination of conidia of a strawberry pathogen is presented. Water addition to air plasma jet significantly improves germination suppression performance, while measured reactive oxygen species (ROS) are reduced. Although the results show a negative correlation between ROS and the germination suppression, this infers the importance of chemical composition generated by plasma. For further control of the plasma product, a plasma jet powered by sinusoidal high voltage and nanosecond pulses is developed and characterized with the voltage--charge Lissajous. Control of breakdown phase and discharge power by pulse-imposed phase is presented. [Preview Abstract] |
Tuesday, October 13, 2015 11:30AM - 12:00PM |
ET1.00006: Measurement of reactive species for plasma medicine Invited Speaker: Ryo Ono Plasma medicine has been intensively studied over the last decade. Reactive oxygen and nitrogen species are responsible for the therapeutic effects in plasma medicine. To examine the therapeutic effects of reactive species, the densities of OH, O, and NO were measured using laser-induced fluorescence (LIF). A helium atmospheric-pressure plasma jet (10 kV, 10 kHz of 40 $\mu$s pulses) and a nanosecond streamer discharge (24 kV, 8 ns, 30 Hz) were utilized to treat mouse melanoma cells in a culture medium. Correlation between the dose of reactive species and deactivation rate of melanoma cells was measured with the aid of LIF. The results showed that the rate of cell death correlates with OH density, but not with O and NO densities. Next, a method to supply a specific reactive species to living organisms was developed. It utilizes photolysis of helium-buffered H$_{2}$O and O$_{2}$ by vacuum ultraviolet (VUV) light to produce reactive species. The VUV method was utilized to sterilize \textit{Bacillus atrophaeus} on agar plate. With the VUV method, it was succeeded to show sterilization only by OH radicals. A 30 s treatment with approximately 0.1 ppm OH radicals caused visible sterilization. [Preview Abstract] |
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