Composition Of Reactive Species Research Articles

Plasma-Functionalized Liquids for Decontamination of Viable Tissues: A Comparative Approach

Plasma-functionalized liquids (PFLs) are rich in chemical species, such as ozone, hydrogen peroxide, singlet oxygen, hydroxyl radical and nitrogen oxides, commonly referred to as reactive oxygen and nitrogen species (RONS). Therefore, manifold applications are being investigated for their use in medicine, agriculture, and the environment. Depending on the goal, a suitable plasma source concept for the generation of PFLs has to be determined because the plasma generation setup determines the composition of reactive species. This study investigates three PFL-generating plasma sources—two spark discharges and a flow dielectric barrier discharge (DBD) system—for their efficacy in eliminating microbial contaminants from tissue samples aiming to replace antibiotics in the rinsing process. The final goal is to use these tissues as a cell source for cell-based meat production in bioreactors and thereby completely avoid antibiotics. Initially, a physicochemical characterization was conducted to better understand the decontamination capabilities of PFLs and their potential impact on tissue viability. The results indicate that the flow DBD system demonstrated the highest antimicrobial efficacy due to its elevated reactive species output and the possibility of direct treatment of tissues while tissue integrity remained. Achieving a balance between effective large-scale decontamination and the biocompatibility of PFLs remains a critical challenge.

Reactive species variation in cold atmospheric pressure plasma jet discharge under the influence of intrinsic parameters and its effect on E. coli inactivation.

Cold atmospheric pressure plasma jet (CAPJ) has piqued the interest of researchers for various antimicrobial applications such as disinfection, wound decontamination, etc. In the current context, a deeper understanding of the correlation between CAPJ's intrinsic parameters, discharge characteristics, species composition, and antimicrobial activity is required for any successful application. This research evaluated the effect of intrinsic operational parameters such as voltage, frequency, gas flow rate, and operating gas on the reactive species composition of an in-house-developed CAPJ discharge along with the antimicrobial activity. It was observed that the identified excited atoms (Ar I, He I, N2, and O I), ions (Ar+, N2+, N+, H2O+, H3O+, etc.), radical reactive oxygen and nitrogen species (RONS) (OH•), and nonradical RONS (O I, O+, OH+, NO+, O2+, O2-, NO2-, N2O2-, NO3-, N2O3-, etc.) might play a synergistic role in bacterial inactivation via oxidative and electrostatic stress. The variation in voltage, frequency, gas flow rate, and operating gas influenced the discharge chemistry, leading to variation in bacterial inactivation. The reactive species in the discharge responsible for such variation was evaluated extensively. This investigation into various operational parameters would aid in determining the most effective settings for a developed CAPJ to achieve high productivity.

Gas plasma-induced platelet activation corresponds to reactive species profiles and lipid oxidation

Surgical-induced hemostasis is a critical step in the closure of incisions, which is frequently achieved via electrocauterization and subsequent tissue necrotization. The latter is associated with postoperative complications. Recent in vivo work suggested reactive species-producing gas plasma technology as a pro-homeostatic agent acting via platelet activation. However, it remained elusive how platelet activation is linked to lipid and protein oxidation and the reactive species compositions. A direct relation between the reactive species composition and platelet activation was revealed by assessing the production of several reactive species and by using antioxidants. In addition, platelet lipidome and proteome analysis identified significantly regulated key lipids in the platelet activation pathway, such as diacylglycerols and phosphatidylinositol as well as oxylipins like thromboxanes. Lipid oxidation products mainly derived from phosphatidylethanolamine and phosphatidylserine species were observed at modest levels. In addition, oxidative post-translational modifications were identified on key proteins of the hemostasis machinery. This study provides new insights into oxidation-induced platelet activation in general and suggests a potential role of those processes in gas plasma-mediated hemostasis in particular.

The localised density of H2O2 in the effluent of a cold atmospheric pressure plasma jet determined by continuous-wave cavity ring-down spectroscopy

Although the research on cold atmospheric pressure plasma jets and their applications is steadily growing, several questions remain open regarding fundamental aspects of how reactive species, such as hydrogen peroxide (H2O2), are generated in cold atmospheric pressure plasma jets, and how the composition of reactive species can be tailored for a specific purpose. Accordingly, absolute and spatially resolved distributions of the densities of reactive species in the effluent of cold atmospheric pressure plasma jets are required. In this work, a time efficient way to determine the local distribution of gas phase H2O2 in the effluent of a cold atmospheric-pressure plasma jet using continuous-wave cavity ring-down spectroscopy at a wavelength of 8.12 μm is presented. By a combination of an axial scan and of several radial distributions, the localised density distribution of H2O2 in the effluent of the kINPen-sci plasma jet was obtained. Therefore, the effective absorption length was determined from the evolution of the radial distributions as a function of the distance from the nozzle, which was 1.6 mm close to the nozzle of the plasma jet, and increased to approximately 5 mm at a distance of 10 mm from the nozzle. The maximum density of approximately 2 ⋅ 1014 cm−3 was found in the centre of the effluent close to the nozzle. From the presented localised density distribution, it can be concluded that H2O2 is significantly generated within the plasma zone of the plasma jet. This work presents an important step towards the understanding of formation and consumption mechanisms of biomedically relevant species in the plasma zone and the effluent of a cold atmospheric pressure plasma jet.

Comparing efficiencies of polypropylene treatment by atmospheric pressure plasma jets

AbstractPlasma treatment of polypropylene (PP) is a well‐established method of improving its surface properties. However, the efficiencies of different plasma discharges are seldom compared. Herein, we discuss the differences in PP treated by three arc‐based commercial plasma jets working in dry air, Plasmatreat rotating plasma jet (PT‐RPJ), AFS PlasmaJet® (AFS‐PJ), and SurfaceTreat gliding arc jet (ST‐GA), and by the low‐temperature RF plasma slit jet (RF‐PSJ) working in argon. The AFS‐PJ has a significantly different reactive species composition dominated by nitrogen oxides. It induced higher thermal loads leading to surface damage. The other arc‐based jets (PT‐RPJ and ST‐GA) created the PP surface with higher oxygen and nitrogen concentration than the low‐temperature RF‐PSJ. It induced a higher adhesion strength measured on PP‐aluminum joints.

Formation and transformation of reactive species in the Fe2+/peroxydisulfate/Cl− system

The influence of Cl− on the formation mechanism of active components is often neglected in the Fe2+/peroxydisulfate (PDS) system containing a large amount of ferryl ion reactive specie (Fe(Ⅳ)). In the current investigation, the effects of Cl− concentration on the removal of methyl phenyl sulfoxide (PMSO), the formation of methyl phenyl sulfone (PMSO2), the transformation of reactive species and oxidation products were investigated under different reaction conditions that included Fe2+ dosage, PDS dosage, and pH0. The results showed that Cl− complexing Fe2+ increased the formation path of sulfate radical (SO4·−) in the Fe2+/PDS system. Fe2+ dosage and pH0 value affected the content and morphology of Fe2+-Cl− complex, thus affecting the composition of reactive species. According to the experiment of free radical steady-state concentration, it was found that low concentration of Cl− reacted with SO4·− and increased the steady-state concentration of chlorine radicals (8.09 × 10−13 M [·Cl]ss at 1.41 mM Cl−), while at high concentration of Cl−, the contents of SO4·−, hydroxyl radical (·OH) and dichloride anion radicals (Cl2·−) increased and the contents of Fe(Ⅳ) and ·Cl decreased. ·Cl had strong reactivity with PMSO, and PMSO and its oxidation products were chlorinated under the combined action of ·Cl and Cl2·−. This work reveals the reaction mechanism and environmental application risks of Fe2+/PDS technology and lays the groundwork for subsequent industrial application of Fe2+/PDS system.

Deep investigation on different effects of Cl− in transformation of reactive species in Fe(II)/NH2OH/PDS and Fe(II)/NH2OH/H2O2 systems

Hydroxylamine (NH2OH) has been verified to efficiently strengthen pollutants oxidation in Fe(II)/peroxydisulfate (PDS) and Fe(II)/H2O2 systems. However, the different effects of hydroxylamine salts types were rarely recognized. Herein, the effects of two commonly used hydroxylamine salts (i.e. NH2OH·HCl and (NH2OH)2·H2SO4) on oxidation kinetics and reactive species composition were compared in Fe(II)/PDS and Fe(II)/H2O2 systems for the first time. Pseudo first order kinetics could only describe benzoic acid (BA) oxidation well in Fe(II)/NH2OH/H2O2 system, which was related to the different concentration changes of Fe(III) determined by[Oxidant][NH3OH+]2. Hydroxylamine salts types influenced not kinetic rules, but reaction rates of target compounds. The empirical reaction rate constant of BA in Fe(II)/NH2OH·HCl/PDS system was 141.5% of that in Fe(II)/(NH2OH)2·H2SO4/PDS system under the same concentration of NH2OH (1.4 mM), while the apparent reaction rate constant in Fe(II)/NH2OH·HCl/H2O2 system was 68% of that in Fe(II)/(NH2OH)2·H2SO4/H2O2 system. This opposite effect resulted from the differences in primary reactive species compositions and their interactions with Cl−. Reactive species identification indicated that Cl− would decrease the contribution of ferryl ion (Fe(IV)) and transform sulfate radical (SO4·−) to hydroxyl radical (·OH) in Fe(II)/NH2OH/PDS system, while it competitively consumed the only reactive species ·OH in Fe(II)/NH2OH/H2O2 system. This study highlights the importance of reductants types on strengthening Fenton oxidation and offers a reference for reasonable construction of the relevant systems.

Response of reactive species generation and biological inactivation to electromagnetically assisted cold plasma jets

External static electric and magnetic fields aligned parallel to the propagation direction of a plasma jet affect its dynamic characteristics and the response of reactive species present. A positive electric field was shown to enhance the intensity of ionization waves and the number of positive ions, thereby promoting the generation of aqueous OH and the inactivation of tumor cells subjected to the plasma jet. Correspondingly, the concentration of aqueous O2− and sterilization by the plasma jet gradually increase with increasing negative electric field intensity. The application of an external magnetic field induces a deformation of the plasma plume, manifesting specifically as a radial contraction/expansion of the plasma plume inside/outside the quartz tube because of the influence of magnetic pressure. In addition, with the external magnetic field, the generation of reactive species and the biological inactivation within the plasma jet are improved and can be attributed to the enhanced discharge arising mainly from electrons confined by the axial magnetic field and the radial magnetic pressure. Our work shows that external magnetic fields are well suited to improving the energy efficiency with regard to plasma jet applications, whereas external electric fields provide a means to manipulate the flux and composition of reactive species over the substrate downstream.

Ar metastable densities (3P2) in the effluent of a filamentary atmospheric pressure plasma jet with humidified feed gas

The Ar(3P2) metastable density in the effluent of the cold atmospheric pressure plasma jet kINPen was investigated as a function of the feed gas humidity, the gas curtain composition, and the distance from the nozzle by means of laser atomic absorption spectroscopy. The filamentary character of the plasma jet was considered as the absorption signals are from single individual events. From the effective lifetime, the quenching coefficient for Ar(3P2) by water was determined. A maximum Ar(3P2) density of (6.0±0.7)×1013 cm−3 was obtained close to the nozzle for a feed gas humidity of 20 ppm. The densities near the nozzle decreased inversely proportional to the water content in the feed gas leveling off at approximately 1×1013 cm−3, independently from the gas curtain composition. With the addition of water to the feed gas, the excitation dynamics changed, and the production and lifetime of Ar(3P2) was reduced. The impact of Ar(3P2) on the reactive species composition in the effluent was found to be smaller than within the plasma zone inside the plasma jet device.

Optical spectrum of the coaxial DBD forming the plasma jet in fast air flow at atmospheric pressure

The non-thermal plasma source based on the high-frequency (100 kHz) sinusoidal dielectric barrier discharge (DBD) generating the plasma jet in air at atmospheric pressure is described. This source uses the electrode system of a coaxial geometry and able to work at the low- and high-power regimes. A narrow plasma jet was generated in airflow at the velocities in the range of 20-80 m/s. The emissive UV-Visual spectra of the discharge zone and plasma jet are presented. The change of the emissive spectrum along the length of plasma jet and on the surface of the quartz substrate to be treated is studied as well. The spectrum reflects the composition of reactive species generated by DBD. The presented experimental results give insight into the properties of the gas discharge plasma inside the coaxial DBD and the spatial characteristics of plasma jet outside the discharge zone as well.

On the composition of reactive species in air plasma jets and their influence on the adhesion of polyurethane foam to low-pressure polyethylene

In this paper, non-thermal plasma sources based on the high-frequency sinusoidal coaxial dielectric barrier discharge (DBD) using fast flowing ambient air as feedstock gas at atmospheric pressure are described. These single- and multi-tube sources are able to generate low- and high-power turbulent plasma jets. Experimental results on both the spatio-temporal behavior of plasma inside the DBD and parameters of plasma jet(s) outside the discharge zone are presented. These results are complemented by information on the composition of reactive species generated by high-power airflow DBD. This information has been obtained from analysis of the emissive spectra of the discharge zone and plasma jet in the UV–visual region. The basic set of elementary plasma-chemical processes responsible for the generation of reactive species in the discharge zone and their further changes in hot air plasma jet is also presented. Although the oxygen concentration in the working gas is high, the concentration of reactive species in the plasma jet is enough for effective surface treatment. This is proved by the essential improvement in the adhesion of polyurethane foam (PF) to low-pressure polyethylene (PE) after treatment by the hot air plasma jet. The changes in the spatial microstructure of the scaffolds on PE surfaces taking place after plasma treatment have been established. The reasons for the adhesion improvement are discussed. The results obtained are of both scientific and practical interest, since PE pipes covered with PF are used in the housing and community sectors, the oil and gas industry, etc.

Kinetic Description of Heterogeneous Catalytic Processes Using Adsorption Substitution Reactions

Complex heterogeneous catalytic processes involving strongly chemisorbed particles (SCPs) are considered: syntheses of methanol, pyrocatechol, and diphenylamine and hydrogenation of CO and benzene. Nonstationary transformations of SCPs (CO and benzene) during continuous analysis of the gas phase are studied with mass spectrometric, flame ionization and thermal conductivity detectors. It is shown that the adsorption substitution reaction (ASR) proceeds before catalysis under typical conditions of these processes; in other words, the substitution reaction, rather than Langmuir adsorption equilibrium, determines the composition of reactive species on the catalyst surface. Consequently, ASRs and chemical transformations of SCPs must be considered for kinetic description of heterogeneous catalytic processes. It is shown that the ASRs allow us to describe these catalytic processes simply and adequately, and the obtained models can be used for the regulation and optimization of processes.

Analysis of Plasma-activated Medium (PAM) in aqueous solution by an Atmospheric Pressure Plasma Jet (APPJ)

Plasma-activated medium (PAM) has been produced by exposing a liquid media to Argon plasma jet. The jet plasma exposure to liquid media has produced reactive Oxygen species (ROS) in liquid phase. This study aims to determine the number of reactive species in plasma-activated medium. An atmospheric pressure plasma jet (APPJ) was generated with a dielectric barrier discharge (DBD) column by AC high voltage. Some parameters varied including exposure time; i.e. 5, 10, 15, 20, 25, and 30 min; and the distance between reactor and active media; i.e. 1, 2 and 3 cm. Some analysis conducted including variation of exposure times, the distances of reactor to PAM which affect produced concentration, and the reactive species composition in plasma-activated medium. In addition, temperature characteristics, pH levels, dissolved ozone and dissolved hydrogen peroxide concentrations were also observed in this study. The results showed that increased exposure time resulted in decreased pH, increased temperature and increased concentrations of ozone and hydrogen peroxide. The maximum reactive species composition was obtained at the distance between reactor and plasma-activated medium of 2 cm. Maximum reactive species composition obtained in this study has temperature of 29-30 Celsius degrees; pH 3.5; dissolved ozone 2.97 ppm; and Hydrogen Peroxide 215 ppm.

Environmental Control of an Argon Plasma Effluent and Its Role in THP-1 Monocyte Function

Plasma medicine is a rapidly advancing field. As one promising application, cold plasma has been ascribed a beneficial role in wound healing in which monocytes/macrophages play an important part. Wound healing and many other physiological and pathological processes are subject to redox control. Cold plasma expels reactive species of many kinds, thereby altering the redox state and mediating cell and tissue responses. Controlling this species efflux could be a valuable asset to control biological effects. We, therefore, investigated the biological response of a plasma treatment regimen that was gas shielded from the ambient environment. In this gas curtain, several N2:O2 ratios were investigated, and we discovered a modulation within the composition of active compounds ( ${\text {NO}}_{2}^{-}$ , ${\text {NO}}_{3}^{-}$ , and H2O2) in physiological solutions. Using a human monocyte cell line, the cell’s scavenging activity toward these molecules was assessed. With regard to cellular processes important in wound healing, such as cytokines release, O2 shielding provided stronger stimulation compared to N2 shielding. Altogether, the results support the idea that tuning the plasma-derived reactive species composition may be an interesting approach to improve plasma medical applications.

Controlled cytotoxicity of plasma treated water formulated by open-air hybrid mode discharge

Plasma treated liquids (PTLs) provide a means to convey a broad range of effects of relevance for food, environmental, or clinical decontamination, plant growth promotion, and therapeutic applications. Devising the reactive species ingredients and controlling the biological response of PTLs are of great interest. We demonstrate an approach by using an open-air hybrid mode discharge (HMD) to control the principal reactive species composition within plasma treated water (PTW), which is then demonstrated to regulate the cytotoxicity of PTW. The cytotoxicity of HMD produced PTW demonstrates a non-monotonic change over the discharge time. Although hydrogen peroxide and nitrite are not the sole effectors for cell death caused by PTW, using them as principal reactive species indicators, cytotoxicity can be removed and/or enhanced by formulating their concentrations and composition through adjusting the discharge mode and time on-line during PTW generation without the addition of additional working gas or chemical scavengers. This work demonstrates that a hybrid mode discharge can be employed to generate a PTW formulation to control a biological response such as cytotoxicity. This provides insights into how plasma treated liquids may be harnessed for biological applications in a specific and controllable manner.

The study of creation of polymerizable species in radio frequency hydrocarbon plasma polymerization in a closed reactor system

The study of radio frequency glow discharge of saturated hydrocarbon monomer indicated that the glow forms distinctive glow in plasma polymerization systems. The radio-frequency ethane plasma polymerization in a closed reactor system was studied. The composition of reactive species in the luminous gas phase was monitored during the deposition process by optical emission spectroscopy. Optical emission analysis indicates that polymerizable species are mainly formed in the glow region. It was found that, in such a closed plasma system, the deposition of ethane plasma polymers could be visualized as the batch processes. In the early stage of radio-frequency plasma initiation, the deposition of plasma polymers was dominated by the hydrocarbon-based species because the hydrocarbon-based species polymerized much quicker than hydrogen-based species. In the final stage, because of the exhaustion of all polymerizable species in the system, the deposition terminated and the deposited plasma polymer surface was endlessly treated by nonpolymer forming gas plasma. The growth of radio frequency plasma polymerized hydrocarbon film clearly showed the dominating effects of luminous gas phases on the polymerizable tendency in plasma polymerization system.

Plasma jet's shielding gas impact on bacterial inactivation.

One of the most desired aims in plasma medicine is to inactivate prokaryotic cells and leave eukaryotic cells unharmed or even stimulate proliferation to promote wound healing. The method of choice is to precisely control the plasma component composition. Here the authors investigate the inactivation of bacteria (Escherichia coli) by a plasma jet treatment. The reactive species composition created by the plasma in liquids is tuned by the use of a shielding gas device to achieve a reactive nitrogen species dominated condition or a reactive oxygen species dominated condition. A strong correlation between composition of the reactive components and the inactivation of the bacteria is observed. The authors compare the results to earlier investigations on eukaryotic cells and show that it is possible to find a plasma composition where bacterial inactivation is strongest and adverse effects on eukaryotic cells are minimized.

Long Plasma Jet Generated by DC Discharge in N<sub>2</sub> at Atmospheric Pressure: Impact of Trace Admixtures on Composition of Reactive Species in Far Afterglow

The object under study is a long plasma jet (up to 15 cm) generated by a steady-state dc discharge in N2 at atmospheric pressure. Successful usage of long afterglow plasma jet for distant treatment of 3-D object of a complicated shape with deep slots was demonstrated. This paper focuses on a role of trace impurities in plasma-forming gas on chemical composition of reactive species in far afterglow plasma. This role was studied numerically by example of the additives in high-purity nitrogen contained in high-pressure N2 tank. It is shown that small oxygen admixtures (at 10 ppm level) to N2 can be more effective in production of atomic oxygen than ambient air. Besides, trace admixtures of water vapor and hydrocarbons (at parts per million level) lead to full change in a composition of reactive species in far afterglow in comparison with the set of primary species generated by plasma source.

Nitrogen Shielding of an Argon Plasma Jet and Its Effects on Human Immune Cells

Atmospheric pressure plasmas are widely used in research for biomedical or clinical applications. Reactive oxygen species and reactive nitrogen species (RNS) produced by plasmas are thought to be of major significance in plasma-cell interactions. Different applications, however, may demand for different plasma properties. Tailoring plasma devices by modulating the supply gas or the surrounding is a suitable way to alter reactive species composition, vacuum ultra violet emission, or temperature. Treatment regimens involving availability of oxygen or humidity may lead to increased hydrogen peroxide deposition in liquids and thus will be toxic to cells. Using an atmospheric pressure argon plasma jet, we applied a nitrogen gas curtain to its visible effluent during treatment of human immune cells. The curtain deprived the plasma of molecular oxygen. This excluded gas-phase oxygen plasma chemistry and led to generation of highly energetic metastables. Planar laser-induced fluorescence spectroscopy verified laminar gas flow and complete elimination of surrounding air by the gas curtain. We used human immune cells to monitor cytotoxic effects as they are highly relevant in potential clinical plasma applications, e.g., treatment of chronic wounds. Air curtain plasma treatment led to significantly higher cytotoxicity compared with nitrogen curtain plasma treatment. Scavenging of hydrogen peroxide abrogated cell death in both gas curtain conditions. This indicated a negligible contribution of highly energetic metastables or increased gas temperature to cytotoxicity. Finally, the results suggested an oxygen-independent generation of hydrogen peroxide pointing to an indirect role of UV or RNS in plasma-mediated cytotoxicity.

The effect of tuning cold plasma composition on glioblastoma cell viability.

Previous research in cold atmospheric plasma (CAP) and cancer cell interaction has repeatedly proven that the cold plasma induced cell death. It is postulated that the reactive oxygen species (ROS) and reactive nitrogen species (RNS) play a major role in the CAP cancer therapy. In this paper, we seek to determine a mechanism of CAP therapy on glioblastoma cells (U87) through an understanding of the composition of the plasma, including treatment time, voltage, flow-rate and plasma-gas composition. In order to determine the threshold of plasma treatment on U87, normal human astrocytes (E6/E7) were used as the comparison cell line. Our data showed that the 30 sec plasma treatment caused 3-fold cell death in the U87 cells compared to the E6/E7 cells. All the other compositions of cold plasma were performed based on this result: plasma treatment time was maintained at 30 s per well while other plasma characteristics such as voltage, flow rate of source gas, and composition of source gas were changed one at a time to vary the intensity of the reactive species composition in the plasma jet, which may finally have various effect on cells reflected by cell viability. We defined a term “plasma dosage” to summarize the relationship of all the characteristics and cell viability.