Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session HW3: Plasma Interactions with Biological Surfaces |
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Chair: Masafumi Ito, Meijo University Room: State D |
Wednesday, November 5, 2014 8:00AM - 8:30AM |
HW3.00001: Cold flame on Biofilm - Transport of Plasma Chemistry from Gas to Liquid Phase Invited Speaker: Michael Kong One of the most active and fastest growing fields in low-temperature plasma science today is biological effects of gas plasmas and their translation in many challenges of societal importance such as healthcare, environment, agriculture, and nanoscale fabrication and synthesis. Using medicine as an example, there are already three FDA-approved plasma-based surgical procedures for tissue ablation and blood coagulation and at least five phase-II clinical trials on plasma-assisted wound healing therapies. A key driver for realizing the immense application potential of near room-temperature ambient pressure gas plasmas, commonly known as cold atmospheric plasmas or CAP, is to build a sizeable interdisciplinary knowledge base with which to unravel, optimize, and indeed design how reactive plasma species interact with cells and their key components such as protein and DNA. Whilst a logical objective, it is a formidable challenge not least since existing knowledge of gas discharges is largely in the gas-phase and therefore not directly applicable to cell-containing matters that are covered by or embedded in liquid (e.g. biofluid). Here, we study plasma inactivation of biofilms, a jelly-like structure that bacteria use to protect themselves and a major source of antimicrobial resistance. As 60-90\% of biofilm is made of water, we develop a holistic model incorporating physics and chemistry in the upstream CAP-generating region, a plasma-exit region as a buffer for as-phase transport, and a downstream liquid region bordering the gas buffer region. A special model is developed to account for rapid chemical reactions accompanied the transport of gas-phase plasma species through the gas-liquid interface and for liquid-phase chemical reactions. Numerical simulation is used to illustrate how key reactive oxygen species (ROS) are transported into the liquid, and this is supported with experimental data of both biofilm inactivation using plasmas and electron spin spectroscopy (ESR) measurement of liquid-phase ROS. [Preview Abstract] |
Wednesday, November 5, 2014 8:30AM - 8:45AM |
HW3.00002: Evaluation of the Efficacy of the Plasma Pencil Against Cancer Cells Soheila Mohades, Nazir Barekzi, Hamid Razavi, Mounir Laroussi The plasma pencil generates low temperature and atmospheric pressure plasma. To generate the plasma, high voltage pulses with short width (from nanosecond to microsecond) are applied to a noble gas. The working gas can be helium, argon or a mixture of these with air or oxygen. Generating plasma with helium provides a tolerable temperature for biological cells and tissues. Diagnostic measurements on the plasma plume has revealed the presence of active agents such as reactive oxygen species (ROS) and nitrogen reactive species (RNS), which are known to have biological implications. Recently, low temperature plasma has drawn attention to its potential in cancer therapy. In our lab, the plasma pencil has been used to treat leukemia, prostate and epithelial cancer cells [1]. The cancer cell line used here is the SCaBER (ATCC\textregistered HTB3\texttrademark ) cell line originating from a human bladder cancer. The results indicate that specific species induce the molecular mechanisms associated with cell death. The death of cells after plasma treatment will be studied using assays, such as DNA laddering and Caspase-3 activation, to elucidate the mechanism of the apoptotic or necrotic pathways. \\[4pt] [1] N. Barekzi and M. Laroussi, \textit{Plasma Process. Polym.} \textbf{10}, 1039 (2013). [Preview Abstract] |
Wednesday, November 5, 2014 8:45AM - 9:00AM |
HW3.00003: Multiple Pulses from Plasma Jets onto Liquid Covered Tissue Seth Norberg, Wei Tian, Eric Johnsen, Mark J. Kushner Atmospheric pressure plasma jets are being studied in the treatment of biological surfaces that are often covered by a thin layer of liquid. The plume of the plasma jet contains neutral radicals and charged species that solvate into the liquid and eventually form terminal species that reach the tissue below. The contribution of neutral and charged species to reactivity in the liquid is sensitive to whether the active plasma plume touches the liquid. In this paper, we discuss results from modeling the production of the aqueous species formed from the interaction of the plume of plasma jets over multiple pulses with the water layer, and the fluences of the species to the underlying tissue. The model used in this study, \textit{nonPDPSIM}, solves transport equations for charged and neutral species and electron energy, Poisson's equation for the electric potential, and Navier-Stokes equations for the neutral gas flow. Radiation transport includes photoionization of O$_{\mathrm{2}}$ and H$_{\mathrm{2}}$O in the gas and liquid phases and photodissocation of H$_{\mathrm{2}}$O$_{\mathrm{aq}}$ in the liquid. Multiple pulses when the plasma plume touches and does not touch the liquid will be examined. Two regimes of hydrodynamics will be discussed -- low repetition rates where the neutral radicals are blown away before the next discharge pulse, and high repetition rate when the plasma plume interacts with neutral radicals from previous pulses. The density of aqueous ions produced in the liquid layer is strongly dependent on whether the plasma effluent touches or does not touch the water surface. [Preview Abstract] |
Wednesday, November 5, 2014 9:00AM - 9:15AM |
HW3.00004: Atomic oxygen characteristics in a dielectric barrier discharge developed for wound treatment Sabrina Baldus, Daniel Schroeder, Volker Schulz-von der Gathen, Nikita Bibinov, Peter Awakowicz Nowadays, infected chronic wounds are a major problem of society. Atmospheric pressure plasmas like dielectric barrier discharges (DBDs) have already shown their ability of improving the wound healing process of chronic wounds in clinical trials. Yet, the mechanism of action is poorly understood. A DBD comprising a single driven electrode is a beneficial configuration for wound treatment. The patient itself functions as the counter electrode. Hence, reactive oxygen species (ROS) like ozone or atomic oxygen produced in the plasma reach the wound directly. Some ROS, including superoxide or nitric oxide, are produced by skin cells to repulse invading bacteria. Nevertheless, a very high amount of ROS leads to oxidative stress and can cause cell damage or even cell death. Therefore it is crucial to have a well characterized plasma for effective wound treatment. Plasma parameters are determined using absolutely calibrated optical emission spectroscopy. Density of atomic oxygen is measured applying xenon-calibrated two photon absorption laser induced fluorescence spectroscopy. A simulation of the afterglow chemistry, developed to gain insight in the characteristics of the atomic oxygen and its flux towards the treated surface, is cross-checked with measurement results. [Preview Abstract] |
Wednesday, November 5, 2014 9:15AM - 9:30AM |
HW3.00005: Long Term Effects of Multiple DBD Pulses on Thin Liquid Layers Over Tissue: Reactive Fluences and Electric Fields Wei Tian, Mark J. Kushner Atmospheric dielectric barrier discharges (DBDs) are used in treatment of tissue, often covered by thin liquid layers. The reactivity reaching the tissue depends on the plasma dose, composition and acidification of the liquid, and the cumulative delivery of electric fields through the liquid. In this paper, we report on a computational investigation of the interaction of DBDs with a thin liquid layer covering tissue over many minutes. We used \textit{nonPDPSIM,} a 2-d model in which Poisson's equation, the electron temperature equation, transport equations for charged and neutral species and radiation transport are solved in both the gas and liquid. The liquid layer, 100's $\mu $m thick, is water with dissolved gases [O$_{\mathrm{2aq}}$ (aq is aqueous), CO$_{\mathrm{2aq}}$], metal ions (Fe$^{\mathrm{2+}}_{\mathrm{aq}}$, Fe$^{\mathrm{3+}}_{\mathrm{aq}})$, and organics (RH$_{\mathrm{aq}})$. Hundreds of pulses at 100 Hz are computed, followed by minutes of afterglow. In the liquid, transient radicals (OH$_{\mathrm{aq}}$, H$_{\mathrm{aq}})$ are produced during the discharge pulse and are consumed during the interpulse period. Terminal species (H$_{\mathrm{2}}$O$_{\mathrm{2aq}}$, O$_{\mathrm{3aq}})$ accumulate and diffuse to the tissue. Ions are dominated by NO$_{{\mathrm{3}}^{\mathrm{-}}\mathrm{aq}}$, O$_{{\mathrm{2}}^{\mathrm{-}}\mathrm{aq}}$ and H$_{\mathrm{3}}$O$^{\mathrm{+}}_{\mathrm{aq}}$. Production of HNO$_{\mathrm{3aq}}$ and HOONO$_{\mathrm{aq}}$ is assisted by O$_{\mathrm{2aq}}$ for the first pulses and then O$_{\mathrm{3aq}}$. Accumulating nitric acid lowers the pH. RH$_{\mathrm{aq}}$ consumes most reactive oxygen species in the early plasma treatment leaving R\textbullet $_{\mathrm{aq}}$. With longer exposure, RH$_{\mathrm{aq}}$ can be consumed, enabling more ROS to reach the tissue. The cumulative exposure of electric fields to the tissue depends on the increasing conductivity of the liquid. [Preview Abstract] |
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