H. M. Thomas

Effects of cold atmospheric plasma on mucosal tissue culture

Thermal plasmas have been commonly used in medical applications such as plasma ablation and blood coagulation. Newer developments show that plasmas can be generated with ion temperatures close to room temperature: these non-thermal or so-called cold atmospheric plasmas (CAPs) therefore open up a wide range of further biomedical applications. Based on the understanding of the bactericidal, virucidal and fungicidal properties of CAPs, information about the effects of CAP on mucosal cells and tissue is still lacking. Therefore this study focuses on the interaction of CAP with healthy head and neck mucosal cells on a molecular level. To analyse this interaction in detail, fresh tissue samples from healthy nasal and pharyngeal mucosa were harvested during surgery, assembled to a three-dimensional tissue culture model (mini organ cultures) and treated with CAP for different treatment times. Effects on the viability, necrosis induction and mutagenic activity were evaluated with the trypan blue exclusion test, Annexin-V/PI staining and alkaline microgel electrophoresis (comet assay). Trypan blue exclusion test revealed that the CAP treatment significantly decreases the cell viability for all tested treatment times (5, 10, 30, 60 and 120s; p< 0.05), but only a treatment time of 120s showed a cytotoxic effect as the viability dropped below 90%. Annexin-V/PI staining revealed a significant increase in necrosis in CAP treated pharyngeal tissue cultures for treatment times of 60 and 120s ( p< 0.05). For nasal tissue this effect was already detected for a 30s treatment ( p< 0.05). Comet assay analysis showed no mutagenic effects after exposure to CAP. (Some figures may appear in colour only in the online journal)

Elementary physics of complex plasmas

1 Complex Plasma - Why It Is an Unusual State of Matter?.- 1.1 General Physical Differences Between Complex Plasma and Ordinary Matter.- 1.2 General Terminology in Complex Plasma and Ordinary Matter.- 1.3 History: Complex Plasmas in Space Physics.- 1.4 Problems of Strong Coupling in Plasmas.- 1.4.1 Phase Space for Strong Coupling in Ordinary Plasmas.- 1.4.2 Physics and Consequences of Large Grain Charges.- 1.4.3 Physics and Consequences of Dust Charge Screening.- 1.4.4 Phase Space for Strong Coupling in Complex Plasmas.- 1.5 Openness of Complex Plasma Systems and Long-range Collective Interactions.- 1.5.1 Variability of Grain Charges.- 1.5.2 Openness of Complex Plasma Systems.- 1.5.3 Long-range Unscreened Grain Interactions.- 1.6 Plasma Condensation.- 1.6.1 First Observations of Plasma Condensation.- 1.6.2 Grain Interactions.- 1.7 Special Aspects of Complex Plasma Investigations.- 1.7.1 Kinetic Level for Dust Investigation in Experiments.- 1.7.2 Obstacles in Complex Plasmas.- 1.7.3 Interactions of Grain Clouds and Fast Grains with Plasma Crystals.- 1.8 Structures and Self-organization in Complex Plasmas.- 1.8.1 Observations of Structures in Complex Plasmas.- 1.8.2 Self-organization in Complex Plasmas.- 1.9 Outlook of the Subsequent Presentation.- References.- 2 Why Complex Plasmas Have Many Applications in Future Technology?.- 2.1 Main Discoveries in Applications of Complex Plasmas.- 2.2 Computer Technology.- 2.2.1 Simple Principles Used in Computer Technology.- 2.2.2 Investigation of Dust Clouds in Etching Devices.- 2.3 First Steps to Using Complex Plasma Properties in Computer Industry.- 2.3.1 New Laboratory Experiments in Complex Plasmas Inspired by Computer Technology Problems.- 2.4 New Surfaces, New Materials.- 2.4.1 New Surfaces.- 2.4.2 New Materials.- 2.4.3 New Magnetic Materials.- 2.5 New Energy Production.- 2.5.1 Necessity of New Energy Sources.- 2.5.2 Controlled Fusion Devices.- 2.5.3 Table Size Fusion and Neutron Sources.- 2.5.4 Solar Cells.- 2.6 Environmental Problems.- 2.6.1 Dust is Found Everywhere.- 2.6.2 Global Warming.- 2.6.3 Noctilucent Clouds.- 2.6.4 The Ozone Layer.- 2.6.5 Industrial Emissions and Car Exhausts.- References.- 3 Elementary Processes in Complex Plasmas.- 3.1 Screening of Grain Field in a Plasma.- 3.1.1 Elementary Estimates.- 3.1.2 Linear Debye Screening.- 3.1.3 Non-linear Screening.- 3.1.4 Problems to Solve in Grain Screening.- 3.2 Charging of Grains in Partially Ionized Plasma.- 3.2.1 Introductory Remarks.- 3.2.2 Equation for Micro-particle Charging.- 3.2.3 Orbital Motion Limited Model.- 3.2.4 Extensions of OML Approach.- 3.2.5 Role of Potential Barriers in Non-linear Screening for Grain Charging.- 3.2.6 Radial Drift Limited Model.- 3.2.7 Diffusion Limited Model.- 3.2.8 Problems for Modeling of Grain Charging.- 3.3 Forces Acting on Ions.- 3.3.1 Absorption of Ions on Grains. The Charging Coefficient.- 3.3.2 Friction of Ions in Gas of Grains. The Drag Coefficient.- 3.3.3 Other Forces Acting on Ions.- 3.4 Forces Acting on Grains.- 3.4.1 Ion Drag and Electric Field Forces.- 3.4.2 Temperature Gradients and Thermophoretic Force.- 3.4.3 Neutral Gas Drag force, Gravity force, and Dust Inertia.- 3.5 Forces Acting on Electrons: Characteristic Electric Fields.- 3.5.1 Electron Friction in Absorbing Collisions with Grains and Electron Inertia.- 3.5.2 Balance of Forces for Electrons.- 3.5.3 Electric Fields and Condition for Quasi-neutrality.- References.- 4 Collective Effects in Complex Plasmas.- 4.1 Collective Linear Modes.- 4.1.1 Dispersion Relations for Low Frequency Modes.- 4.1.2 Basic State of Complex Plasmas.- 4.1.3 Dispersion Relation for DISW.- 4.1.4 Dispersion Relation for DAW.- 4.2 Universal Instability of a Complex Plasma.- 4.2.1 Instability in the Range of DISW.- 4.2.2 Instability in the Range of DAW.- 4.2.3 Instability Stabilization in the Range of DAW.- 4.2.4 Physics of the Instability.- 4.2.5 Instability Rates.- 4.2.6 Effects of Finite Size.- 4.2.7 Electrostatic Gravitational-like Instability and Modes in Plasma Clusters.- 4.2.8 Complex Plasma Structurization.- 4.3 Collective Modes Excited by Fast Particles.- 4.3.1 Mach Cones: General Remarks and the Cone Angle.- 4.3.2 Wave Intensity and Distribution of Wavelengths.- 4.3.3 Wave Excitation by Outside Particles Moving near Boundary.- 4.4 Observations of Collective Modes.- 4.4.1 Introductory Remarks.- 4.4.2 Experimental Observations of DISW.- 4.4.3 Experimental Observations of DAW.- 4.5 Problems to be Solved for Collective Modes.- 4.5.1 Structurization Instability and the Finite System Effects.- 4.5.2 Surface Waves.- 4.5.3 Induced Processes for Collective Modes.- 4.5.4 Collective Modes in the External Magnetic Field.- 4.5.5 Instabilities in Complex Plasmas.- 4.5.6 Non-linear Responses.- 4.5.7 Strong Non-linearities and Modulational Interactions.- 4.5.8 Kinetic Description of Collective Modes.- 4.6 Fluctuations, Collective Pair Interactions, and Pair Correlation Functions.- 4.6.1 Relations between Various Fluctuations.- 4.6.2 Correlation Functions.- 4.6.3 Zero Fluctuations and Collective Pair Interactions of Grains.- 4.6.4 Dust Non-collective Charge Fluctuations.- 4.6.5 Charge Fluctuations Induced by Dust Fluctuations.- References.- 5 Micro-particle Collective and Non-collective Pair Interactions.- 5.1 General Properties of Micro-particle Pair Interactions.- 5.1.1 Grain Pair Interactions in Crystals and Clusters.- 5.1.2 Two Grains: Electrostatic Energy and Interaction Forces.- 5.1.3 Role of Openness of Complex Plasma Systems.- 5.1.4 Pair Interaction and Non-linearity in Screening.- 5.2 Shadow Non-collective Attraction Forces.- 5.2.1 Shadow Attraction Created by Ion Flux.- 5.2.2 Shadow Attraction Created by Neutral Flux.- 5.2.3 Agglomeration of Grains.- 5.2.4 Problems of Non-collective Grain Attraction.- 5.3 Collective Attraction for Linear Screening.- 5.3.1 Collective Attraction in the Limit ? ? 1.- 5.3.2 Physics of Collective Attraction.- 5.3.3 Attraction of Finite Size Grains.- 5.3.4 Natural Boundary Conditions.- 5.3.5 Limiting Expressions for Collective Attraction.- 5.3.6 Attraction in an Ion Flow for ? ? 1.- 5.3.7 Attraction in a Magnetic Field for ? ? 1.- 5.4 Collective Interactions for Non-linear Screening.- 5.4.1 Collision-dominated Case ? ? 1.- 5.4.2 Ionization Proportional to Electron Density.- 5.4.3 General Properties of Non-linear Collective Attraction.- 5.5 Measurements of Screened Potential in Grain-grain Collisions.- 5.5.1 Experimental Technique.- 5.5.2 Collision Experiments.- 5.5.3 Problems for Future Experiments.- References.- 6 Experiments on Plasma Crystals and Long-range Correlations.- 6.1 Plasma Crystals.- 6.1.1 Crystal Structures Observed.- 6.1.2 Observational Techniques.- 6.1.3 Structure of Crystals.- 6.1.4 Dislocations and Defects.- 6.2 Melting and Phase Transitions.- 6.2.1 General Description of Phase Transitions.- 6.2.2 Phenomenological Description.- 6.2.3 Translational and Orientational Order.- 6.2.4 Dust Grain Temperatures.- 6.3 Paradigms for Plasma Crystal Formation.- 6.3.1 Applicability of New Paradigms.- 6.3.2 Paradigms for Crystal Formation.- 6.3.3 Van der Waals Equations and Collective Interactions.- 6.4 Inspiration from Experiments.- References.- 7 Mono-layer Plasma Crystals and Clusters.- 7.1 Mono-layer Plasma Crystals.- 7.1.1 Specific Properties of Mono-layers.- 7.1.2 Theory of 2D Dust-lattice Waves.- 7.1.3 Experiments on 2D Dust-lattice Waves.- 7.1.4 Stimulated Plasma Crystal Sublimation.- 7.1.5 Theory of Dust Bending Waves.- 7.1.6 2D Dust Shear Waves.- 7.1.7 2D Dust-lattice Wave Mach Cones.- 7.2 2D Plasma Clusters.- 7.2.1 Introductory remarks.- 7.2.2 Experiments on Small and 2D Clusters.- 7.2.3 Observations and Ordering Rules.- 7.2.4 Theory of 2D Clusters.- 7.2.5 Boundary-free 2D Clusters.- 7.2.6 Numerical Simulations of Boundary-free Clusters.- References.- 8 Comments on Other Dust Structures: Concluding Remarks.- 8.1 Dust Helical Clusters.- 8.1.1 General Remarks.- 8.1.2 MD Simulations and Analytical Results.- 8.1.3 Problems to Solve.- 8.2 Disordered Grain Structures.- 8.2.1 Role of Plasma Fluxes.- 8.2.2 Structures in Disordered States.- 8.2.3 General Features of Disordered Structures.- 8.2.4 Dust Void Problems.- 8.2.5 Problems for Future Investigations.- 8.3 Dust Wall Sheaths.- 8.3.1 General Remarks.- 8.3.2 Collisionless Dust Wall Sheaths.- 8.3.3 Further Problems of Dust Wall Sheath Studies.- 8.4 Dust Structures between Walls.- 8.4.1 Collision-Dominated Single Flat Layer.- 8.4.2 Other Structures between Electrodes.- 8.4.3 Problems for Future Research.- 8.5 Dust Convection in Structures.- 8.5.1 General Remarks.- 8.5.2 Problems to Solve.- 8.6 Hybrid Dust Structures.- 8.7 Micro-gravity Experiments.- 8.8 Future Research: Outlook for Complex Plasmas.- 8.9 Conclusion.- References.

Cold atmospheric plasma (CAP) changes gene expression of key molecules of the wound healing machinery and improves wound healing in vitro and in vivo.

Cold atmospheric plasma (CAP) has the potential to interact with tissue or cells leading to fast, painless and efficient disinfection and furthermore has positive effects on wound healing and tissue regeneration. For clinical implementation it is necessary to examine how CAP improves wound healing and which molecular changes occur after the CAP treatment. In the present study we used the second generation MicroPlaSter ß® in analogy to the current clinical standard (2 min treatment time) in order to determine molecular changes induced by CAP using in vitro cell culture studies with human fibroblasts and an in vivo mouse skin wound healing model. Our in vitro analysis revealed that the CAP treatment induces the expression of important key genes crucial for the wound healing response like IL-6, IL-8, MCP-1, TGF-ß1, TGF-ß2, and promotes the production of collagen type I and alpha-SMA. Scratch wound healing assays showed improved cell migration, whereas cell proliferation analyzed by XTT method, and the apoptotic machinery analyzed by protein array technology, was not altered by CAP in dermal fibroblasts. An in vivo wound healing model confirmed that the CAP treatment affects above mentioned genes involved in wound healing, tissue injury and repair. Additionally, we observed that the CAP treatment improves wound healing in mice, no relevant side effects were detected. We suggest that improved wound healing might be due to the activation of a specified panel of cytokines and growth factors by CAP. In summary, our in vitro human and in vivo animal data suggest that the 2 min treatment with the MicroPlaSter ß® is an effective technique for activating wound healing relevant molecules in dermal fibroblasts leading to improved wound healing, whereas the mechanisms which contribute to these observed effects have to be further investigated.

The plasma condensation: Liquid and crystalline plasmas

Colloidal plasmas may “condense” under certain conditions into liquid and crystalline states, while retaining their essential plasma properties. This “plasma condensation” therefore leads to new states of matter: “liquid plasmas” and “plasma crystals.” The experimental discovery was first reported in 1994, and since then many researchers have begun to investigate the properties of condensed plasma states. In this paper we describe some of the basic physics required to understand colloidal plasmas and discuss experiments conducted to investigate the details of the interaction between the plasma particles (in particular, the interaction potential), the melting phase transition, and the thermodynamics of this new state of matter.

Study of the 3D plasma cluster environment by emission spectroscopy

Three-dimensional (3D) plasma clusters were formed inside a quasi-neutral plasma of very small size (38?mm3) obtained by applying a radio frequency (rf) to a small electrode at the edge of a main plasma. In order to find the density of such a plasma, spectroscopic analysis at three wavelengths was performed. The emission structure of the small plasma as well as of the whole discharge was obtained with a resolution of 0.5?mm. The optical thickness of the plasma allowed us to apply the steady-state corona model for the calculation of the plasma density. The density was estimated to be 2.8?1016?m?3 in the small plasma, one order higher than in the main plasma volume.

DEVELOPMENT OF A DUST MANTLE ON THE SURFACE OF AN INSOLATED ICE-DUST MIXTURE : RESULTS FROM THE KOSI-9 EXPERIMENT

Astronomical observations indicate that formation and destruction of dust mantles on cometary nuclei may be the cause for erratic and systematic variations of cometary activity, i.e. emission of dust. A laboratory experiment (KOSI-9) has been performed to study the evolution of a dust mantle on top of a sublimating ice-dust mixture in vacuum. A sample consisting of water ice with a 10% (by weight) admixture of olivine grains has been insolated in three periods at variable intensities from 200 to 1900 W/m2. Both increasing surface temperature of the sample and decreasing gas and particle emissions indicated the formation of a dust mantle during the first period. During the second insolation period after the gas flux had reached a critical value of a few 1021 water molecules m−2 s−1, avalanches of mantle material occurred on the inclined sample surface, broke up the mantle locally, and opened up a fresh icy surface. Enhanced ice and dust particle emission resumed for some time from these spots. A large number of the emitted dust particles were of a fluffy aggregate structure, i.e., they had large cross section to mass ratios compared to compact particles. During the third period the critical gas flux was not reached and no enhanced dust and ice emission was observed. A dry dust mantle of a few millimeters thickness developed during the course of the experiment. Consequences of these findings for cometary scenarios are discussed.

Complex plasmas: I. Complex plasmas as unusual state of matter

This paper opens a series of review papers devoted to the physics of the so-called complex plasmas. The review contains a description of new physical phenomena met in dusty plasmas and complex plasmas. The term complex plasma is used for a state where some components (dust) are in crystal or liquid state, while the others (electron, ions, and neutral atoms) are in gaseous state. Experimental and the theoretical investigations of such a complex state of matter are presented. It is emphasized that (i) complex plasma represents quite an unusual state of matter, (ii) the system of dust grain cannot be considered as a Coulomb system, because it always has long-range and nonscreened interactions between the grains both of repulsive and attractive type and because the shielding of the grains is always nonlinear, (iii) the interactions between the particles in complex plasmas and in usual matter differ substantially due to strong plasma absorption on grains and the necessity to support the plasma density by an external source of ionization, (iv) the usual concept of free energy is not applicable to complex plasmas, because it is actually an open system, and (v) the collective nature of pair dust interaction is one of the most important new features of complex plasmas. The theory of elementary processes in complex plasmas, including these new phenomena, can be used to explain existing experiments on dust-plasma crystals, dust clusters, and waves and instabilities in complex plasmas.

Gravity compensation in complex plasmas by application of a temperature gradient

Micron-sized particles are suspended or lifted up in a gas by thermophoresis. This allows the study of many processes occurring in strongly coupled complex plasmas at the kinetic level in a relatively stress-free environment. First results of this study are presented. The technique is also of interest for technological applications.

Cold atmospheric plasma, a new strategy to induce senescence in melanoma cells.

Over the past few years, the application of cold atmospheric plasma (CAP) in medicine has developed into an innovative field of research of rapidly growing importance. One promising new medical application of CAP is cancer treatment. Different studies revealed that CAP may potentially affect the cell cycle and cause cell apoptosis or necrosis in tumor cells dependent on the CAP device and doses. In this study, we used a novel hand‐held and battery‐operated CAP device utilizing the Surface Micro Discharge (SMD) technology for plasma production in air and consequently analysed dose‐dependent CAP treatment effects on melanoma cells. After 2 min of CAP treatment, we observed irreversible cell inactivation. Phospho‐H2AX immunofluorescence staining and Flow cytometric analysis demonstrated that 2 min of CAP treatment induces DNA damage, promotes induction of Sub‐G1 phase and strongly increases apoptosis. Further, protein array technology revealed induction of pro‐apoptotic events like p53 and Rad17 phosphorylation of Cytochrome c release and activation of Caspase‐3. Interestingly, using lower CAP doses with 1 min of treatment, almost no apoptosis was observed but long‐term inhibition of proliferation. H3K9 immunofluorescence, SA‐ß‐Gal staining and p21 expression revealed that especially these low CAP doses induce senescence in melanoma cells. In summary, we observed differences in induction of apoptosis or senescence of tumor cells in respond to different CAP doses using a new CAP device. The mechanism of senescence with regard to plasma therapy was so far not described previously and is of great importance for therapeutic application of CAP.

Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament

The first successful growth of diamond layers on levitated seed particles in CH4/H2 plasma is presented. The particles were grown in a rf CH4/H2 plasma chamber equipped with a tungsten hot filament. The seed diamond particles injected in a plasma are negatively charged and levitated under the balance of several forces, and diamond chemical vapor deposition takes place on them. The SEM images show that the crystalline structures are formed after the coagulation of islands. The micro-Raman spectroscopy of the particle grown after several hours shows the clear peak assigned to diamond.