Low-temperature Helium Plasma Research Articles

Treatment of Fungal-Infected Diabetic Wounds with Low Temperature Plasma.

Diabetes mellitus renders patients susceptible to chronic wounds and various infections. Regarding the latter, fungal infections are of particular concern since, although they are the source of significant morbidity and mortality in immunocompromised patients, they are generally resistant to conventional treatment and a definite treatment strategy has not yet been established. Herein, we report the treatment of skin wounds in a diabetic rat model, infected by Candida albicans, with low temperature helium plasma generated in a hand-held atmospheric jet device. A fungal infection was induced on two dorsal skin wounds of the diabetic rats, and one wound was treated with the plasma jet whereas the other served as a control. Histological analysis revealed accelerated skin wound healing and decreased evidence of fungal infection in the plasma-treated group, as compared to the control group. Regeneration of the epidermis and dermis, collagen deposition, and neovascularization were all observed as a result of plasma treatment, but without wound contraction, scar formation or any evidence of thermal damage to the tissue. These findings demonstrate that the He plasma jet is remarkably effective in diabetic skin wounds infected by Candida albicans, thereby providing a promising medical treatment option for diabetes mellitus patients with skin wound and fungal infections.

Optical emission spectroscopy and collisional-radiative modeling for non-equilibrium, low temperature helium plasma

An optical emission spectroscopy (OES) technique combined with a collisional-radiative (CR) model is developed for measuring the electron temperature and density of low temperature helium (He) plasma. The CR modeling self-consistently solves the steady state population balance equation, including nonlinear radiation trapping and heavy particle collisional ionization as well as linear electron-impact processes and metastable diffusion. The CR modeling considers both Maxwellian and non-Maxwellian electron energy distributions, and the gas temperature parameter needed in the CR modeling is measured by adding a small amount of nitrogen gas and analyzing the rotational spectra of N2+ species. The electron temperature and density determined by the CR modeling and OES in He inductively-coupled plasma are compared with the values measured by a Langmuir probe for the RF power and the gas pressure variations. The considered plasmas are in the ranges of electron temperature 2–5eV and density 108–1010cm−3, and the gas pressure 200–800mTorr and temperature 500K. The trend and absolute values by the two methods are in overall agreement within the uncertainty range for the various RF powers and the gas pressures. The underlying population kinetics for the OES spectra is analyzed in detail.

水中で発生させたHe とO2 の混合ガスの大気圧低温プラズマによるホルムアルデヒド水溶液の分解

水中で発生させたHe とO2 の混合ガスの大気圧低温プラズマによるホルムアルデヒド水溶液の分解

Exposure of Indian RAFM under variation of He+ flux and target temperature in the CIMPLE-PSI linear device

The paper reports first investigations of the effect of low-temperature helium (He) plasma exposure on the India specific reduced activation ferritic martensitic (IN-RAFM) steel. Experiments are performed in the CIMPLE-PSI device, over the variation of ion-flux (∼3 × 1022−23 m−2s−1) and target temperature (316 K−830 K), for ion-fluence up to 1.6 × 1026 m−2. Strong morphology changes have been observed, in particular, fiber-form surface structures with nanometer-sized grain structures, pinholes, and hollow fibers. Surface enrichment of tungsten up to 2.3 at.% was measured by energy dispersive x-ray spectroscopy (EDX), which was supported by Rutherford backscattering spectrometry (RBS) measurements. This had happened because iron and chromium were preferentially sputtered out by the He ions. It is demonstrated that the porous, micrometer-sized surface inhomogeneities, produced under high ion-flux (≥8.0 × 1022 m−2s−1) and high target temperature (≥518 K), critically influence the shape of the RBS spectrum, which necessitates a revision of the data analysis procedure. Through optical emission spectroscopic observations, we demonstrate that the sputtering yield of the steel decreases with exposure time, primarily because of the formation of the porous surface microstructures and also due to the surface enrichment of the exposed samples with tungsten atoms. It is concluded that the formation of bubbles underneath the surface of RAFM, and their subsequent distortion and rupturing leads to the formation of fiber-form structures under the relatively high target temperature, high ion-flux irradiation conditions.

Influence of the Ion Mass in the Radial to Orbital Transition in Weakly Collisional Low-Pressure Plasmas Using Cylindrical Langmuir Probes

This paper presents an experimentally observed transition from the validity of the radial theories to the validity of the orbital theories that model the ion current collected by a cylindrical Langmuir probe immersed in low-pressure, low-temperature helium plasma when it is negatively biased with respect to the plasma potential, as a function of the positive ion-neutral collision mean free path to the Debye length ratio Λ=λ+/λD. The study has been also conducted on argon and neon plasmas, which allows a comparison based on the mass of the ions, although no transition has been observed for these gases. As the radial or orbital behavior of the ions is essential to establish the validity of the different sheath theories, a theoretical analysis of such a transition not only as a function of the parameters Λ and β=T+/Te, T+ and Te being the positive ion and electron temperature, respectively, but also as a function of the ion mass is provided. This study allows us to recognize the importance of the mass of the ion as the parameter that explains the transition in helium plasmas. Motivated by these theoretical arguments, a novel set of measurements has been performed to study the relationship between the Λ and β parameters in the transition that demonstrate that the effect of the ion mean free path cannot be completely ignored and also that its influence on the ion current collected by the probe is less important than the effect of the ion temperature.

Setting of helium plasma device (J-Plasma) in flap elevation

Abstract We have found a lot of interest in an your recently published article entitled “Utilization of low-temperature helium plasma (J-Plasma) for dissection and hemostasis during carotid endarterectomy”. In our opinion, our letter can amplify this recent article by extending the original manuscript content.

Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

The plasma-surface interaction is studied for a low temperature helium plasma jet generated at atmospheric pressure using Mueller polarimetry on an electro-optic target. The influence of the AC kHz operating frequency is examined by simultaneously obtaining images of the induced electric field and temperature of the target. The technique offers high sensitivity in the determination of the temperature variation on the level of single degrees. Simultaneously, the evolution of the electric field in the target caused by plasma-driven charge accumulation can be measured with the threshold of the order of 105 V/m. Even though a specific electro-optic crystal is used to obtain the results, they are generally applicable to dielectric targets under exposure of a plasma jet when they are of 0.5 mm thickness, have a dielectric constant greater than 4 and are at floating potential. Other techniques to examine the induced electric field in a target do not exist to the best of our knowledge, making this technique unique and necessary. The influence of the AC kHz operating frequency is important because many plasma jet designs used throughout the world operate at different frequency which changes the time between the ionization waves and hence the leftover species densities and stability of the plasma. Results for our jet show a linear operating regime between 20 and 50 kHz where the ionization waves are stable and the temperature increases linearly by 25 K. The charge deposition and induced electric fields do not increase significantly but the surface area does increase due to an extended surface propagation. Additionally, temperature mapping using a 100 μm GaAs probe of the plasma plume area has revealed a mild heat exchange causing a heating of several degrees of the helium core while the surrounding air slightly cools. This peculiarity is also observed without plasma in the gas plume.

Time-resolved studies of low-temperature, EUV-induced plasmas: EUV emission in selected spectral ranges

AbstractInteraction of extreme ultraviolet (EUV) pulses of high intensity with gases results in the creation of non-thermalized plasmas. Energies of the driving photons and photoelectrons are sufficient for creation of excited states, followed by emission of the EUV photons. In most cases, decay times of these states are short comparing to the driving EUV pulse. It means that just after stopping of the driving pulse, the EUV emission corresponding to the excited states should also stop. From our earlier measurements in the optical range, however, it can be concluded that lifetimes of such plasmas exceed a time duration of the driving pulse even two orders of magnitude. Hence, it can be expected that the time duration of the EUV emission can be also significantly longer than the irradiation time. In this work, EUV-induced, low-temperature helium (He), krypton, and xenon plasmas were investigated. EUV emission from these plasmas was studied, using a specially prepared detection system, allowing for time-resolved measurements, in selected spectral ranges. The detection system was based on a paraboloidal collector and a semiconductor photodiode, sensitive for the EUV photons. For spectral selection, the corresponding filters or multilayer mirrors were employed. In most cases, the time duration of the EUV emission was significantly longer than the driving EUV pulse. In case of He plasmas, the emission corresponding to excited atoms was detected even hundreds of nanoseconds after the irradiation. It was also shown that the corresponding time profiles depended on densities of gases to be ionized.

Elucidation of in vitro cellular steps induced by antitumor treatment with plasma-activated medium

Numerous studies have reported cold atmospheric plasma cytotoxic activities in various cancer cell lines, either by direct exposure to non-thermal plasma or indirectly by activating a medium (plasma-activated medium, PAM) prior to cell treatment. We suggested the use of in vitro 3D tumor model spheroids to determine the potential of PAM for cancer therapy at the tissue scale, especially in human tumor tissue. This work aimed to better understand the effect of PAM on human colorectal tumor spheroids by describing the in vitro-induced-cell death kinetics and associated mechanisms to further improve its therapeutic potential. Tumor spheroid growth was delayed depending on contact time with PAM. Medium osmolarity was increased by activation with low temperature Helium plasma jet but it did not fully explain the observed growth delay. PAM impaired tumor cell viability through intracellular ATP depletion, leading within hours to both cell apoptosis and necrosis as well as mitochondrial oxidative stress. When successive treatments were spaced over time, cumulative effects on the growth delay of spheroids were observed. Taken together, these results demonstrated that plasma-activated liquids may represent a novel and efficient therapeutic method for the treatment of tumors, especially when successive treatments are applied.

Resolution of Methylene Blue Aqueous Solution by Atmospheric Pressure Low Temperature Helium and Oxygen Mixture Gas Plasma Generated in Water

Resolution of Methylene Blue Aqueous Solution by Atmospheric Pressure Low Temperature Helium and Oxygen Mixture Gas Plasma Generated in Water

Low-temperature helium plasma generated at atmospheric pressures by non-standard field applicator

Low-temperature helium plasmas were sustained using radio frequency excitation waveforms in a cylindrical glass tube, both in steady state and flowing conditions.

Evaluation of the J-Plasma Electrosurgical Device Combined with Nebulized Collagen for Burn Healing in Rodents

Plasma medicine has developed dramatically in recent years and offers benefits in numerous areas. Much of the work has been carried out using innovative devices, but there remains a paucity of approved medical instruments that can be effectively translated into patient care in markets such as the United States. Although a wide variety of argon plasma coagulators are approved for medical use, these devices have not been considered to be viable for plasma medicine applications due to the high thermal energy of argon discharges. We explore the potential of a commercial helium plasma device to deliver low-energy, nonthermal plasma discharges to wound sites. The recently launched J-Plasma device (Apyx Medical; Clearwater, FL, USA) uses low-temperature helium plasma and delivers precise plasma power with minimal depth of thermal spread. We investigate the impact of J-Plasma on nebulized biologic materials and its minimal impact on protein chemical structure. We discuss the potential to deliver biologic materials and control modification of wound surfaces, and we present preliminary in vivo data from a rodent burn model.

Analysis of reactive oxygen and nitrogen species generated in three liquid media by low temperature helium plasma jet

In order to identify aqueous species formed in Plasma activated media (PAM), quantitative investigations of reactive oxygen and nitrogen species (ROS, RNS) were performed and compared to Milli-Q water and culture media without and with Fetal Calf Serum. Electron paramagnetic resonance, fluorometric and colorimetric analysis were used to identify and quantify free radicals generated by helium plasma jet in these liquids. Results clearly show the formation of ROS such as hydroxyl radical, superoxide anion radical and singlet oxygen in order of the micromolar range of concentrations. Nitric oxide, hydrogen peroxide and nitrite-nitrate anions (in range of several hundred micromolars) are the major species observed in PAM. The composition of the medium has a major impact on the pH of the solution during plasma treatment, on the stability of the different RONS that are produced and on their reactivity with biomolecules. To emphasize the interactions of plasma with a complex medium, amino acid degradation by means of mass spectrometry was also investigated using methionine, tyrosine, tryptophan and arginine. All of these components such as long lifetime RONS and oxidized biological compounds may contribute to the cytotoxic effect of PAM. This study provides mechanistic insights into the mechanisms involved in cell death after treatment with PAM.

Determination of Peroxide Explosive TATP and Related Compounds by Dielectric Barrier Discharge Ionization-Mass Spectrometry (DBDI-MS).

Dielectric barrier discharge ionization-mass spectrometry (DBDI-MS), which is based on the use of a low temperature helium plasma as ionization source, is used for the determination of trace amounts of triacetone triperoxide (TATP) and its homologue diacetone diperoxide (DADP) from surfaces. TATP is observed as [M+NH4]+ adduct, whereas DADP is observed as [M+O+NH4]+. Measurement of DADP with varying deuteration degrees (DADP, DADP-d6, and DADP-d12) indicates that DADP undergoes oxidation when ionized by DBDI. If acetonitrile is used as deposition solvent, TATP tends to show fragmentation and is not only detected as [M+NH4]+ but as [M-CH4+NH4]+ and [M-C2H4+NH4]+ as well. Quantification of TATP solutions from glass surfaces by DBDI-MS, using TATP-3,6,9-13C as internal standard, was done and validated using an LC/APCI-MS method. Achievable limits of detection (LOD) for TATP are equivalent to the deposition of 15 ng TATP and are comparable with other ambient desorption/ionization mass spectrometric techniques like desorption electrospray ionization (DESI).

Optical diagnostics with radiation trapping effect in low density and low temperature helium plasma

Low density (ne < 1011 cm−3) and low temperature (Te < 10 eV) helium plasma was generated by hot filament discharge. Electron temperature and density of neutral helium plasma were measured by Langmuir probe and were determined by line intensity ratio method using optical emission spectroscopy with population modelings. Simple corona model and collisional-radiative (CR) model without consideration for radiation trapping effect are applied. In addition, CR model taking into account the radiation trapping effect (RTE) is adopted. The change of single line intensity ratio as a function of electron temperature and density were investigated when the RTE is included and excluded. The changes of multi line intensity ratios as a function of electron temperature were scanned for various radiative-excitation rate coefficients from the ground state and the helium gas pressures related with the RTE. Our CR modeling with RTE results in fairly better agreement of the spectroscopic diagnostics for the plasma temperature or density with the Langmuir probe measurements for various helium gas pressures than corona modeling and CR modeling without RTE.

The Selective Characterization of Nonthermal Atmospheric Pressure Plasma Jet on Treatment of Human Breast Cancer and Normal Cells

The aim of this paper is to investigate the effect of nonthermal atmospheric pressure plasma jet on human breast cancer and normal cells. High voltage, dc-pulsed power supply was used to generate low temperature helium plasma in atmospheric pressure. In this paper, cancer and normal cells were exposed to plasma during four time steps. For further exploration, Doxorubicin as common chemotherapy drug was employed to compare the efficacy of plasma treatment with convectional cancer therapy. Also, the Caspase-Glo 3/7 assay was obtained to reveal the death process of cancer and normal cells. The results of MTT and apoptosis assay showed that the plasma treatment has drastically reduced the viability of breast cancer cells, while it has no significant damage to the normal cells. In addition, after plasma treatment three different zones were formed in the plate, which will represent the detachment of cells from plate surface. Moreover, adding 5% oxygen to the helium plasma will lead to enhancement of cancer cells viability reduction. In addition, the outcome of this paper has verified that the plasma treatment successfully overcomes drug treatment in inhibition of the cancer cells viability, while decreases the adverse effect of drug treatment.

Comparison of measured and simulated electron energy distribution functions in low-pressure helium plasmas

Knowledge of the electron energy distribution function (EEDF) is of great interest in different branches of plasma physics ranging from laboratory to fusion plasmas. In the frame of this work systematic measurements of the EEDF in low temperature helium plasmas (Te ≈ 2 eV) at different working gas pressures and discharge currents (Idis between 1 and 2 A) will be presented and compared with numerical particle-in-cell (PIC) code simulations. The experiments were conducted in the Innsbruck double plasma machine and in the Ljubljana linear magnetic plasma device with helium as the working gas. The EEDF was obtained by the second derivative of the characteristic of a Langmuir probe. The PIC code was used to simulate the EEDF by taking into account most of the physical parameters in the plasma vessel.

Simultaneous testing of multiclass organic contaminants in food and environment by liquid chromatography/dielectric barrier discharge ionization-mass spectrometry

A Dielectric Barrier Discharge Ionization (DBDI) LC/MS interface is based on the use of a low-temperature helium plasma, which features the possibility of simultaneous ionization of species with a wide variety of physicochemical properties. In this work, the performance of LC/DBDI-MS for trace analysis of highly relevant species in food and environment has been examined. Over 75 relevant species including multiclass priority organic contaminants and residues such as pesticides, polycyclic aromatic hydrocarbons, organochlorine species, pharmaceuticals, personal care products, and drugs of abuse were tested. LC/DBDI-MS performance for this application was assessed and compared with standard LC/MS sources (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)). The used benchtop Orbitrap mass spectrometer features a 10 Hz polarity switching mode, so that both positive and negative ion mode acquisitions are possible with acquisition cycles matching the requirements of fast liquid chromatography. Both polar and nonpolar species (including those typically analyzed by GC/electron ionization-MS) can be tested in a single run using polarity switching mode. The methodology was found to be effective in detecting a wide array of organic compounds at concentration levels in the low ng L(-1) to μg kg(-1) range in wastewater and food matrices, respectively. The linearity was evaluated in an olive oil extract, obtaining good correlation coefficients in the studied range. Additionally, minor matrix effects (≤15% of signal suppression or enhancement) were observed for most of the studied analytes in this complex fatty matrix. The results obtained were compared with data from both ESI and APCI sources, obtaining a merged coverage between ESI and APCI in terms of analyte ionization and higher overall sensitivity for the proposed ion source based on the DBD principle. The use of this approach further extends the coverage of current LC/MS methods towards an even larger variety of chemical species including both polar and nonpolar (non-ESI amenable) species and may find several applications in fields such as food and environment testing or metabolomics where GC/MS and LC/MS are combined to cover as many different species as possible.

Plasma Induced Oxidative Cleavage of Disulfide Bonds in Polypeptides during Nanoelectrospray Ionization

Cleavage of the disulfide bond within a polypeptide was observed when the nanoelectrospray (nanoESI) plume of a peptide solution interacted with a low-temperature helium plasma in air. Online mass spectrometric analysis revealed that chain separation accompanied by a mass increase of 1 or 16 Da for each chain was common to peptides having an interchain disulfide bond, while for peptides having intrachain disulfide bonds, the reaction products typically showed mass increases of 17 Da. Experimental results suggested that hydroxyl radicals initiated from the plasma were likely to be responsible via dissociative addition to the disulfide bond (RSSR'), giving rise to RSH and R'SO*. When the hydroxyl radical addition product ions ([M + nH + OH](n*+), n is the charge state) generated from peptides having intrachain peptides were subjected to collision-induced dissociation (CID) in an ion trap, a-, b-, and y-type sequence ions within the cyclic structure defined by the disulfide bond were observed in addition to the exocyclic cleavages typically seen from CID of [M + nH](n+) peptide ions. Rich structural information could thus be obtained. These findings were demonstrated in 14 peptides containing disulfide bonds and further by bovine insulin, which has three disulfide bonds. Collisional activation of the [M + 5H + OH](5*+) insulin ions provided 76% of the possible backbone cleavages as compared to 26% acquired from CID of the [M + 5H](5+) ions.

Birch Reduction of Benzene in a Low‐Temperature Plasma

Selective and specific dihydrogenation of benzene and other arenes has been observed in a low-temperature helium plasma. A surface Birch reduction mechanism has been proposed in which benzene molecules adsorbed on the discharge surface capture low-energy surface-adsorbed electrons and subsequently undergo protonation (see picture). Gas-phase oxidation processes accompany the reduction reaction.