Plasma Needle Research Articles

Gas flow dependence for plasma-needle disinfection of S. mutans bacteria

The role of gas flow and transport mechanisms are studied for a small low-power impinging jet of weakly-ionized helium at atmospheric pressure. This plasma needle produces a non-thermal glow discharge plasma that kills bacteria. A culture of Streptococcus mutans (S. mutans) was plated onto the surface of agar, and spots on this surface were then treated with plasma. Afterwards, the sample was incubated and then imaged. These images, which serve as a biological diagnostic for characterizing the plasma, show a distinctive spatial pattern for killing that depends on the gas flow rate. As the flow is increased, the killing pattern varies from a solid circle to a ring. Images of the glow reveal that the spatial distribution of energetic electrons corresponds to the observed killing pattern. This suggests that a bactericidal species is generated in the gas phase by energetic electrons less than a millimetre from the sample surface. Mixing of air into the helium plasma is required to generate the observed O and OH radicals in the flowing plasma. Hydrodynamic processes involved in this mixing are buoyancy, diffusion and turbulence.

Corona-glow transition in the atmospheric pressure RF-excited plasma needle

We present clear evidence of two different discharge modes of the atmospheric pressure RF-excited plasma needle and the transition mechanism by the finite element method. The gas used is helium with 0.1% nitrogen addition. The needle has a point-to-plane geometry with a radius of 30 µm at the tip, 150 µm at the base and an inter-electrode gap of 1 mm. We employ the one-moment fluid model with the local field approximation. Our simulation results indicate that the plasma needle operates as a corona discharge at low power and that the discharge mode transitions to a glow discharge at a critical power. The discharge power increases but the discharge voltage drops abruptly by a factor of about 2 in the corona-glow transition. The plasma density and ionization is confined near the needle tip in corona-mode while it spreads back along the needle surface in glow-mode. The corona-glow transition is also characterized by a dramatic decrease in sheath thickness and an order of magnitude increase in plasma density and volume-averaged ionization. The transition is observed whether or not secondary electron emission is included in the model, and therefore we suggest that this is not an α –γ transition.

Measurements of voltage–current characteristics of a plasma needle and its effect on plant cells

In this paper we present voltage–current–power characteristics of a plasma needle operating in the flow of helium at atmospheric pressure. In addition, we show some examples of how such a plasma affects plant tissues. In the characterization of the plasma needle, current and voltage waveforms were recorded by two derivative probes. These two probes are similar to the probes previously used by Puač et al for measuring transmitted power in low pressure CCP rf discharge. The instantaneous power was calculated from current and voltage waveforms and U–I characteristics of the discharge were determined. Regimes of operation with and without the grounding ring at the tip of the needle were considered. We have chosen two model systems to study the effect of the plasma needle on plant cells and tissues: sweet fern gametophyte (prothallus) and calli produced in vitro. Since the prothallus consists of a single layer of cells, the cytological effects could be easily examined. In addition, calli and prothallus are easy to manipulate and in vitro culture provides a possibility to work under constant and controlled conditions.

Reattachment and Apoptosis After Plasma-Needle Treatment of Cultured Cells

Nonthermal plasmas can be used to locally influence cell adhesion: cells can be removed from their surroundings without causing necrosis. In fact, cells remain alive and can reattach within hours. This phenomenon may, in the future, be used for microsurgical procedures. Another method to remove cells is to induce apoptosis or programmed cell death. This type of cell death is preferred above necrosis, which may cause inflammation reactions. When the detached cells are allowed to reattach and grow, it is important to know their condition. Therefore, long-term effects of plasma-needle treatment were assessed, with special focus on reattachment and apoptosis. The cells were treated using a plasma needle. This device generates a small (1-mm diameter) plasma at atmospheric pressure. To avoid any heat effects, it is important that the plasma temperature is at or below physiological temperature. This is the case for the plasma needle.

Plasma-Needle Treatment of Substrates With Respect to Wettability and Growth of Escherichia coli and Streptococcus mutans

In this paper, surface modification of various materials exposed to a nonthermal atmospheric plasma is investigated. The used source is the plasma needle: a radio-frequency-driven nonthermal atmospheric microplasma. A number of substrates (Perspex and polystyrene) were treated with the plasma needle. The modification of materials was subsequently identified as hydrophilization of the surface and was experimentally validated by water-contact-angle measurements. Furthermore, the effect of this modification on the growth of two bacterial species, which are the Escherichia coli and Streptococcus mutans, is studied. The bacteria were cultured on treated and nontreated polystyrene 96-well plates; the growth of E. coli on the treated substrates was enhanced, while for S. mutans, it was reduced. An explanation of these effects is provided

Killing of S. mutans Bacteria Using a Plasma Needle at Atmospheric Pressure

Streptococcus mutans (S. mutans) bacteria were killed using a low-power millimeter-size atmospheric-pressure glow-discharge plasma or plasma needle. The plasma was applied to a culture of S. mutans that was plated onto the surface of an agar nutrient in a Petri dish. S. mutans is the most important microorganism for causing dental caries. A spatially resolved biological diagnostic of the plasma is introduced, where the spatial pattern of bacterial colonies in the sample was imaged after plasma treatment and incubation. For low-power conditions that would be attractive for dentistry, images from this biological diagnostic reveal that S. mutans was killed within a solid circle with a 5-mm diameter, demonstrating that site-specific treatment is possible. For other conditions, which are of interest for understanding plasma transport, images show that bacteria were killed with a ring-shaped spatial pattern. This ring pattern coincides with a similar ring in the spatial distribution of energetic electrons, as revealed by Abel-inverted images of the glow. The presence of the radicals OH and O was verified using optical-emission spectroscopy

Development of a smart positioning sensor for the plasma needle

In the study of plasma–surface interactions, a well-defined distance from the surface is desired. In this paper, an innovative method is proposed for using the intrinsic properties of a low-power atmospheric plasma to control this distance. It is proposed that the vicinity of a (even poorly) conducting surface imposes a change in the plasma impedance. This effects the reflection of electrical power, which can easily be measured, and provides a non-contact sensor for the distance between the plasma source and the substrate. For this sensor to work, a low-loss and efficient matching network is designed, such that changes in the reflected power are relatively high. With this high-quality matching network at hand, a characterization of the plasma needle is performed in terms of impedance and related parameters. Although characterization is not essential for the development of the sensor, it contributes to fundamental knowledge about the plasma source. Finally, coherence measurements are performed to determine the performance of the above described sensor in different experimental settings.

A plasma needle generates nitric oxide**This paper was submitted as part of the special section featuring papers from the 27th International Conference on Phenomena in Ionized Gases. To view the special section go to stacks.iop.org/PSST/15/i=2.

Generation of nitric oxide (NO) by a plasma needle is studied by means of mass spectrometry. The plasma needle is an atmospheric glow generated by a radio-frequency excitation in a mixture of helium and air. This source is used for the treatment of living tissues, and nitric oxide may be one of the most important active agents in plasma therapy. Efficient NO generation is of particular importance in the treatment of cardiovascular diseases.Mass spectrometric measurements have been performed under various plasma conditions; gas composition in the plasma and conversion of feed gases (nitrogen and oxygen) into other species has been studied. Up to 30% of the N2 and O2 input is consumed in the discharge, and NO has been identified as the main conversion product.

Numerical description of discharge characteristics of the plasma needle

The plasma needle is a small atmospheric, nonthermal, radio-frequency discharge, generated at the tip of a needle, which can be used for localized disinfection of biological tissues. Although several experiments have characterized various qualities of the plasma needle, discharge characteristics and electrical properties are still not well known. In order to provide initial estimates on electrical properties and quantities such as particle densities, we employed a two-dimensional, time-dependent fluid model to describe the plasma needle. In this model the balance equation is solved in the drift-diffusion approach for various species and the electron energy, as well as Poisson’s equation. We found that the plasma production occurs in the sheath region and results in a steady flux of reactive species outwards. Even at small (<0.1%) admixtures of N2 to the He background, N2+ is the dominant ion. The electron density is typically 1011cm−3 and the dissipated power is in the order of 10mW. These results are consistent with the experimental data available and can give direction to the practical development of the plasma needle.

Deactivation of Escherichia coli by the plasma needle

In this paper we present a parameter study on deactivation of Escherichia coli (E. coli) by means of a non-thermal plasma (plasma needle). The plasma needle is a small-sized (1 mm) atmospheric glow sustained by radio-frequency excitation. This plasma will be used to disinfect heat-sensitive objects; one of the intended applications is in vivo deactivation of dental bacteria: destruction of plaque and treatment of caries. We use E. coli films plated on agar dishes as a model system to optimize the conditions for bacterial destruction. Plasma power, treatment time and needle-to-sample distance are varied. Plasma treatment of E. coli films results in formation of a bacteria-free void with a size up to 12 mm. 104–105 colony forming units are already destroyed after 10 s of treatment. Prolongation of treatment time and usage of high powers do not significantly improve the destruction efficiency: short exposure at low plasma power is sufficient. Furthermore, we study the effects of temperature increase on the survival of E. coli and compare it with thermal effects of the plasma. The population of E. coli heated in a warm water bath starts to decrease at temperatures above 40°C. Sample temperature during plasma treatment has been monitored. The temperature can reach up to 60°C at high plasma powers and short needle-to-sample distances. However, thermal effects cannot account for bacterial destruction at low power conditions. For safe and efficient in vivo disinfection, the sample temperature should be kept low. Thus, plasma power and treatment time should not exceed 150 mW and 60 s, respectively.

Plasma treatment of mammalian vascular cells: a quantitative description

For the first time, quantitative data was obtained on plasma treatment of living mammalian cells. The nonthermal atmospheric discharge produced by the plasma needle was used for treatment of mammalian endothelial and smooth muscle cells. The influence of several experimental parameters on cell detachment and necrosis was tested using cell viability assays. Interruption of cell adhesion (detachment) was the most important cell reaction to plasma treatment. Treatment times of 10 s were enough to detach cells in the cultured cell sheet. Under extreme conditions, cell necrosis occurred. Cell detachment without necrosis could be achieved at low voltages. It was shown that the thickness of the liquid layer covering the cells was the most important factor, which had more influence than treatment time or applied voltage. The results show no remarkable differences between the responses of the two cell types.

Power outflux from the plasma: an important parameter in surface processing

In this work we characterize a low-power radio-frequency atmospheric plasma (plasma needle) in terms of dissipated (input) and emitted power per unit surface (power outflux). The plasma is a non-thermal source, used for treatment of biological tissues and other vulnerable surfaces. A calibrated thermal probe is used to determine the power emitted from the plasma towards treated surfaces. Transmission of the emitted plasma power through various media (solid layers, fluids and physiological media) is studied for a broad range of plasma conditions. These data give insight into various contributions to the power outflux (thermal conduction, radiation and energetic species), as well as the penetration depth of the plasma into treated objects. The power outflux is shown to be a very important parameter, which determines the performance of the plasma tool. For the effectiveness and reproducibility of the process the power outflux is much more important than the nominal power setting. Thus, a thermal probe should become a standard control unit in surface processing reactors.

Electrical and optical characterization of the plasma needle

The plasma needle is a source to create a non-thermal radiofrequency plasma at atmospheric pressure. To improve the ease of working on biological samples, a flexible plasma probe was designed. In the new configuration, the needle was confined in a plastic tube through which helium flow was supplied. The new set-up was characterized by impedance measurements and emission spectroscopy. Impedance measurements were performed by means of an adjustable matching network; the results were modelled. The discharge was found to be entirely resistive; the measured voltage was in the range 140–270 Vrms and it was in excellent agreement with model results. From the resistance, the electron density was estimated to be 1017 m−3.Optical measurements showed substantial UV emission in the range 300–400 nm. Active oxygen radicals ( and ) were detected. Furthermore, the influence of helium flow speed was investigated. At low flow speeds, the density of molecular species in the plasma increased.UV emission and density of active species are important factors that determine the performance of plasma in the treatment of biological materials. Therefore, the new characterization will help us to understand and optimize the interactions of atmospheric plasma with cells and tissues.

The Effects of UV Irradiation and Gas Plasma Treatment on Living Mammalian Cells and Bacteria: A Comparative Approach

Living mammalian cells and bacteria were exposed to irradiation from narrow-band UV lamps and treated with a nonthermal gas plasma (plasma needle). The model systems were: Chinese Hamster Ovary (CHO-K1) cells (fibroblasts) and Escherichia Coli bacteria. UV irradiation can lead to cell death (necrosis) in fibroblasts, but the doses that cause such damage are much higher than those needed to destroy Escherichia Coli. The usage of UV radiation in combination with active oxygen radicals lowers the UV dose sufficient to kill the cells. However, in any case the fibroblasts seem to be fairly resistant to UV radiation and/or radicals. Possibly, the lamps may be used for decontamination of infected wounds. The most important active species in an atmospheric plasma are the radicals; the role of UV is less pronounced. Treatment of CHO-K1 cells with the plasma needle can lead to cell necrosis under extreme conditions, but moderate doses cause only a temporary interruption of cell adhesion. Plasma needle may be used for fine tissue treatment (e.g., controlled cell removal without inflammation) and also for bacterial decontamination.

Plasma Treatment of Dental Cavities: A Feasibility Study

Much effort is invested in the development of tissue-saving methods in dentistry. Cleaning and sterilization of infected tissue in a dental cavity or in a root channel can be accomplished using mechanical or laser techniques. However, with both approaches, heating and destruction of healthy tissue can occur. Recently, a nonthermal atmospheric plasma (plasma needle) has been developed. In this work, the interactions of this plasma with dental tissue is studied, and its capability of bacterial inactivation is tested. A plasma needle is an efficient source of various radicals, which are capable of bacterial decontamination; however, it operates at room temperature and thus, does not cause bulk destruction of the tissue. Plasma treatment is potentially a novel tissue-saving technique, allowing irregular structures and narrow channels within the diseased tooth to be cleaned.

Electric discharge plasmas influence attachment of cultured CHO K1 cells.

Non-thermal plasmas can be generated by electric discharges in gases. These plasmas are reactive media, capable of superficial treatment of various materials. A novel non-thermal atmospheric plasma source (plasma needle) has been developed and tested. Plasma appears at the end of a metal pin as a submillimetre glow. We investigate the possibility of applying the plasma needle directly to living tissues; the final goal is controlled cell treatment in microsurgery. To resolve plasma effects on cells, we study cultured Chinese hamster ovarian cells (CHO-K1) as a model system. When these are exposed to the plasma, instantaneous detachment of cells from the surface and loss of cell-cell interaction is observed. This occurs in the power range 0.1-0.2 W. Cell viability is assessed using propidium iodide (PI) and cell tracker green (CTG) fluorescent staining utilizing confocal laser scanning microscopy (CLSM). Detached cells remain alive. Use of higher doses (plasma power >0.2 W) results in cell necrosis. In all cases, plasma-influenced cells are strictly localized in submillimetre areas, while no reaction in surrounding cells is observed. Due to its extreme precision, plasma treatment may be applicable in refined tissue modification.

Gas Plasma Effects on Living Cells

This paper surveys the research activities at the Eindhoven University of Technology (The Netherlands) in the area of biomedical applications of gas discharge plasmas. A non-thermal atmospheric plasma source (the plasma needle) has been developed, and its interactions with living mammalian cells and bacteria are studied. It is concluded that plasma can efficiently kill bacteria without harming the cells, and also influence the cells without causing cell death (necrosis). In future it will lead to applications like skin (wound) and caries treatment.

Superficial treatment of mammalian cells using plasma needle

Interactions of a small-size, non-thermal plasma (plasma needle) with living cells in culture are studied. We have demonstrated the non-destructive character of the plasma needle: under moderate conditions (low-power and low concentration of molecular species) the plasma needle does not heat biological samples and does not induce cell death. Treatment of living cells is restricted to the cell exterior (membrane). As a result of the interactions of plasma radicals with cell adhesion molecules, cell attachment is temporarily interrupted; the loose cells can be removed, reattached or transferred. This effect may prove very useful in fine surgery, where a part of the tissue must be removed with high-precision, without damage to the adjacent cells and without inflammatory reaction.

Plasma needle: a non-destructive atmospheric plasma source for fine surface treatment of (bio)materials

A non-thermal plasma source (`plasma needle') generated under atmospheric pressure by means of radio-frequency excitation has been characterized. Plasma appears as a small (sub-mm) glow at the tip of a metal pin. It operates in helium, argon, nitrogen and mixtures of He with air. Electrical measurements show that plasma needle operates at relatively low voltages (200–500 V peak-to-peak) and the power consumption ranges from tens of milliwatts to at most a few watts. Electron-excitation, vibrational and rotational temperatures have been determined using optical emission spectroscopy. Excitation and vibration temperatures are close to each other, in the range 0.2–0.3 eV, rotational gas temperature is at most a few hundred K. At lowest power input the source has the highest excitation temperature while the gas remains at room temperature. We have demonstrated the non-aggressive nature of the plasma: it can be applied on organic materials, also in watery environment, without causing thermal/electric damage to the surface. Plasma needle will be used in the study of plasma interactions with living cells and tissues. At later stages, this research aims at performing fine, high-precision plasma surgery, like removal of (cancer) cells or cleaning of dental cavities.

血しょう確保の立場からみたニプロ血しょう採取装置（ＮＤＰ‐１００）の評価

Plasmapheresis using the automated membrane device (NDP-100) for plasma collection was carried out on 219 normal donors. The aim of this study was the evaluation of donor safety, the recovery rates of proteins and coagulation factors, and the efficiency of the plasma collection in Red Cross Blood Centers.As to donor safety, there were no significant changes in the donor's physical and biochemical test results. Complement activation, as already indicated, was noticed to be slightly elevated. The obtained plasma showed good protein recovery such as total protein, albumin, IgG, fibrinogen and factor VIII and IX levels. However, this procedure required around 60 minutes to collect 400ml of plasma (needle to needle time), plus 15 minutes for set-up and priming the device. As a result, an operator can only carry out four plasmaphereses a day. Furthermore, because of the long needle to needle time, many donors who experienced the centrifuge system using Haemonetics PCS did not agree to the use of NDP 100 device for the following donation.In conclusion, this system is required to shorten the time of the procedure.