Non-thermal Plasma Device Research Articles

Inclusion of Biological Targets in the Analysis of Electrical Characteristics of Non-Thermal Plasma Discharge

In Plasma Medicine studies, the effect of non-thermal plasma (NTP) on biological targets is typically correlated with the amount of stable reactive oxygen and nitrogen species produced in a liquid medium. The effect of NTP and the response of the biological target on cellular redox mechanisms is overlooked in these investigations. Additionally, the influence of electrical properties of cells on the physical properties of NTP is neglected. Therefore, we used a floating electrode dielectric barrier discharge plasma to explore the impact of cell structure, size, and viability of the biological target on the physical properties of NTP. Lissajous figures were used to determine circuit capacitance and energy per cycle during NTP exposure of different cell suspensions. We show that both, structural integrity and active enzymic processes of cells change the electrical properties of NTP. Correlations were also drawn between NTP-produced hydrogen peroxide and nitrite with measured capacitance. Our studies indicate that the observed changes between different cell suspensions may be due to a feedback loop between the biological target and the NTP source. In future studies, a more detailed analysis is needed to improve the control of clinical NTP devices.

Applications in Biomedicine and Fabrication Using Plasma and Nanomaterials

A comprehensive analysis of the individual plasma characteristics and the physical processes involved in the organization of nanoscale solid-state systems throughout a wide spectrum of elemental composition, structural configuration, and dimensionality is presented here. As a result of these phenomena, it may be possible to localize and regulate matter and energy at the nanoscale and to create self-organized nanosolids with exceptional and unique properties. The introduction of a unified conceptual framework that is based on the regulation of the creation, transport, and self-organization of precursor species is followed by the explanation of a number of plasma-specific nonequilibrium and kinetics-driven phenomena that occur over a wide range of temporal and geographical scales. When the plasma is brought down to dimensions of micrometers and nanometers, new emergent phenomena come into play. Examples include chirality-controlled single-walled carbon nanotubes, semiconducting quantum dots and nanowires, ultra-fine manipulation of graphenes, nanodiamonds, and organic matter, as well as nanoplasma effects and nanoplasmas of various states of matter. Over the last several years, there has been intense research into the use of plasma medicine. Due to the vast range of cancer cell selectivity, treating every form of cancer is still a challenging endeavor for medical professionals. Plasma jets and dielectric barrier discharges are two examples of the many varieties of nonthermal plasma devices that have been developed as a result of research in more sophisticated forms of plasma physics. When nonthermal plasma is brought into contact with biological material, a great number of charged particles and reactive species are produced. The primary components consist of plasma ultra-violets, reactive nitrogen species, and reactive oxygen species. These species may be employed alone or in combination with nanomaterials in a variety of biomedical applications that aim to improve human health. They may also be used in the synthesis of nanomaterials with physiological significance. Several different biomedical applications are described in relation to the synergy that may be achieved between plasma and nanomaterials in this study, along with new developments in plasma-based synthesis of physiologically relevant nanomaterials.

Tetrachloroaurate (III)–induced oxidation increases nonthermal plasma-induced aldehydes

Research on nonthermal plasma (NTP) devices first began almost five decades ago. NTP devices discharge electrons, positive ions, ultraviolet light, reactive oxygen species (ROS) and reactive nitrogen species (RNS) at near-physiological temperatures. Advances in plasma science have enabled the manipulation of ROS/RNS irradiation for medical applications. During preclinical stages and in human clinical trials, NTP promotes blood coagulation, eradication of bacterial, viral, and biofilm-related infections, wound healing, and cancer therapy. Previously, tetrachloroaurate (III) increased NTP-induced oxidative stress that was attenuated by reduced and oxidized glutathione, indicating that the presence of interactions between metal ions and biomolecules may modulate biological effects. In this study, using 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) as a spin probe in electron paramagnetic resonance (EPR), we observed that the tetrachloroaurate-induced M4PO-X spin adduct was significantly suppressed by ascorbate and α-tocopherol, while dehydroascorbate (DHA) and Trolox were ineffective. Tetrachloroaurate-induced lipid peroxidation, which was measured by 2-thiobarbituric acid-reactive substances (TBARS) in combination with NTP exposure, was suppressed by ascorbate, α-tocopherol and Trolox, while DHA was ineffective. Furthermore, N-acetyl-l-cysteine and dithiothreitol efficiently suppressed tetrachloroaurate-induced M4PO-X spin adduct and lipid peroxidation. LC‒MS/MS analyzes identified hexanal that was significantly elevated by NTP exposure and/or tetrachloroaurate. However, 25 and 250 μM ascorbate did not significantly suppress the formation of aldehydes, such as acetaldehyde, hexanal, nonanal, nonenal, and 4‑hydroxy-2-nonenal. Further studies are warranted to elucidate the redox reactions between metal ions, including gold (III), and biomolecules to expand the possibility of NTP application in medicine and agriculture.

Nano-particle Characteristic Emitted from Gasoline Direct Injection Engine Equipped with Non-Thermal Plasma Device

The impact of non-thermal plasma (NTP) on particulate matter (PM) removal, nitrogen oxide (NOx) reduction, and hydrocarbon species in exhaust gases from gasoline direct injection (GDI) engines using gasoline E20 fuel and a mean effective pressure (IMEP) of 6 bar. The experiments were conducted with an exhaust gas flow rate of 20 L/min, applying high voltage in the range of 0 to 10 kV (2 kV per step) at a frequency of 500 Hz. The results show that NTP reduces PM concentrations, particularly in the nucleation mode (10 nm particles). Maximum PM removal of approximately 83% However, with experimental results, compared to 0 kV, the production of particulate matter Aitken mode increased up to 19 times for a voltage increase of 10 kV, and NOx removal has been at a maximum of about 9.5%, with an energy density of 5 J/L at 10 kV. The effects of NTP on hydrocarbon species such as ethylene, propylene, acetylene, 1.3 butadiene, methane, and ethane have been slightly affected by increased high voltages.

Osseointegration Properties of Titanium Implants Treated by Nonthermal Atmospheric-Pressure Nitrogen Plasma

Pure titanium is used in dental implants owing to its excellent biocompatibility and physical properties. However, the aging of the material during storage is detrimental to the long-term stability of the implant after implantation. Therefore, in this study, we attempted to improve the surface properties and circumvent the negative effects of material aging on titanium implants by using a portable handheld nonthermal plasma device capable of piezoelectric direct discharge to treat pure titanium discs with nitrogen gas. We evaluated the osteogenic properties of the treated samples by surface morphology and elemental analyses, as well as in vitro and in vivo experiments. The results showed that nonthermal atmospheric-pressure nitrogen plasma can improve the hydrophilicity of pure titanium without damaging its surface morphology while introducing nitrogen-containing functional groups, thereby promoting cell attachment, proliferation, and osseointegration to some extent. Therefore, nitrogen plasma treatment may be a promising method for the rapid surface treatment of titanium implants.

Perspectives and Advances of Nonthermal Plasma Technology in Cancers

Cancer is a devastating and life-threatening disease. It is the second leading cause of death worldwide after heart diseases. While science has significantly advanced to improve the treatment outcome and quality of life in cancer patients, there are still many issues with the current therapies, such as toxicity and the development of resistance to treatment. Among the novel tools to overcome these limitations is nonthermal plasma (NTP) and its treatment regimens. Recent progress in NTP devices with ion temperatures close to room temperature demonstrated significant potential in cancer therapy. NTP devices provide a unique combination of reactive oxygen species (ROS), reactive nitrogen species (RNS), photons, and electric fields that exhibit desirable properties of triggering cell death pathways, selectively for cancer cells. While in principle NTP is nonnecrotic and gentle to the tissue, but reactive oxygen and nitrogen species (RONS)-triggered tumor cell death exhibited to have pro-immunogenic properties. Many <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> experiments have demonstrated antitumor effects of direct NTP, synergistic applications of NTP with anticancer drugs/treatments, and plasma-conditioned medium (PCM) applications against a variety of cancer cells. The latest results and findings in this field are the subject of this review along with a brief lay-reader-explanation of cancer and immunology. In this review, initially, we give an overview of the literature that deals with studies on the use of NTP for cancer treatment. Subsequently, we present typical results from that literature to illustrate the advances of NTP in oncology. Finally, we discuss some challenges and future scopes offered by NTP for cancer treatment.

Nonthermal plasma‐generated ozone inhibits human coronavirus 229E infectivity on glass surface

AbstractOzone has been used for surface disinfection to contain bacterial, fungal, mold, and certain viral infections; however, the use of ozone generated from nonthermal plasma devices have not been thoroughly investigated for surface disinfection. Here, we aimed to determine the impact of nonthermal plasma‐generated ozone (PGO) on the coronavirus. Human coronavirus 229E was exposed to PGO and its infectivity was evaluated. PGO exposure of approximately 7 ppm reduced the viral titer after 4 h. Our results indicate that PGO exposure not only reduces the expression of the viral nucleocapsid gene and spike glycoprotein levels but may also stimulate the expression of the antiviral response gene in host cells. These findings can thus be useful to support existing surface disinfection methods.

Tetrachloroaurate (III)-induced oxidation increases non-thermal plasma-induced oxidative stress

Non-thermal plasma (NTP) devices have been explored for medical applications. NTP devices discharge electrons, positive ions, ultraviolet (UV), reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as the hydroxyl radical (•OH), singlet oxygen (1O2), superoxide (O2 •-), hydrogen peroxide (H2O2), ozone, and nitric oxide, at near-physiological temperature. At preclinical stages or in human clinical trials, NTP promotes blood coagulation, eradication of bacterial, viral, and biofilm-related infections, wound healing, and cancer cell death. Here, we observed that ferric, vanadium, and gold(III) ions significantly elevated lipid peroxidation, which was measured by 2-thiobarbituric acid-reactive substances (TBARS) in combination with NTP exposure. Using 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) as a spin probe in electron paramagnetic resonance (EPR), we observed that tetrachloroaurate (III) yielded an M4PO-X spin adduct. Tetrachloroaurate-induced oxidation was attenuated efficiently by reduced (GSH) and oxidized glutathione (GSSG), while glycine (Gly), and L-glutamate (Glu), components of GSH, were ineffective. Furthermore, GSH and GSSG efficiently suppressed tetrachloroaurate-induced lipid peroxidation, while Gly and Glu were ineffective in suppressing TBARS elevation. These results indicate that tetrachloroaurate-induced oxidation is attenuated by GSH as well as GSSG. Further studies are warranted to elucidate the redox reactions between metal ions and biomolecules to advance the clinical application of NTP.

The application of a novel non-thermal plasma device with double rotary plasma jets for inactivation of Salmonella Enteritidis on shell eggs and its effects on sensory properties

Consumer awareness and distaste towards both bacterial and chemical contaminations on food items have been increasing in recent years. Non-thermal plasma (NTP) is a cutting-edge technology which has been shown to effectively inactivate bacteria on the treated foods. Although the general NTP with a single plasma jet is appropriate for the continuous operation process, it suffers limitations due to its smaller scanning area. Here, a novel NTP device with a double rotary nozzle jet system was utilized, which could treat an area instead of a point. The shell eggs inoculated with Salmonella enterica serotype Enteritidis (SE) were placed on a moving platform under the double rotary nozzle jet system. The efficacy of the NTP treatment on microbial decontamination was evaluated by testing a total of 26 combinations of operating parameters consisting of various plasma power (150, 180, 210 W), argon flow rate (10, 15, 20 slm), repetition of the moving platform (4, 6, 8 times), and speed of the moving platform (5, 10 mm/s). Although significantly higher SE reduction (p < 0.05) was achieved with higher power, more repetitions, larger argon flow rates, and lower speed of the platform, these parameters induced significant alterations in the sensory properties of the treated eggs. By comprehensively considering the bacterial reductions, egg quality, and sensory properties, NTP treatment with combination T (180 W-15 slm-6 times-10 mm/s) was determined to be the optimal parameter, which achieved >4 log CFU/egg of SE reduction and significantly better sensory properties than commercially washed eggs (p < 0.05). Additionally, SEM analysis revealed that NTP treatment with combination T resulted in less damage to egg cuticles compared to commercially washed eggs. This novel NTP device offers an efficient antibacterial activity under shorter exposure time (30 s), smaller argon flow rate (15 slm), and lower power (180 W) without adversely affecting the overall quality of the treated eggs. Therefore, this NTP device equipped with the double rotary jet system possesses a potential solution for future industrial applications.

Quantification of Plasma-Produced Hydroxyl Radicals in Solution and their Dependence on the pH

HO radicals are the most important reactive species generated during water treatment by non-thermal plasma devices. In this letter, we report the first quantification of the steady-state concentration and lifetime of plasma-produced hydroxyl radicals in water solutions at pH 3 and 7, and we discuss the differences based on their reactivity with other plasma-generated species. Finally, we show to what extent the use of chemical probes to quantify short-lived reactive species has an influence on the results and that it should be taken into account.

Applying a large-scale device using non-thermal plasma for microbial decontamination on shell eggs and its effects on the sensory characteristics

Concerns related to foodborne pathogens such as Salmonella enterica serovar Enteritidis (SE) necessitate the decontamination of eggs. Multiple studies have successfully demonstrated the use of non-thermal plasma (NTP) technology in inactivating SE on artificially inoculated shell eggs. However, the NTP devices abovementioned were operated in the batch mode and small scale. The present study is the first attempt to evaluate the effectiveness of a large-scale device using NTP for egg decontamination. The designed NTP was operated at 400 W (power), 30 slm (Ar flow rate), 5 and 10 eggs/min (speed of conveyor belt), and 4 cm (distance between the plasma jets and egg samples). Conducting a two-round treatment for the egg samples at 400 W-30 slm-5 eggs/min-4 cm achieved the highest reduction of SE populations (3.57 log CFU/egg). SEM observation revealed less damage on the surface of the plasma-treated eggs than the commercial-washed eggs. Overall, NTP treatment can maintain the freshness quality and sensory characteristics until 15-day storage. This study demonstrated a large-scale NTP system was able to effectively achieve a significant reduction of pathogenic SE without adversely affecting egg quality properties. These results suggested the readiness of this NTP device for industrial applications.

Enhanced Osseointegration and Bio-Decontamination of Nanostructured Titanium Based on Non-Thermal Atmospheric Pressure Plasma

Alkali-treated titanate layer with nanonetwork structures (TNS) is a promising surface for improving osseointegration capacity in implants. Nevertheless, there is a risk of device failure as a result of insufficient resistance to biofilm contamination. This study tested whether treatment using a handheld non-thermal plasma device could efficiently eliminate biofilm contamination without destroying the surface nanostructure while re-establishing a surface that promoted new bone generation. TNS specimens were treated by a piezoelectric direct discharge (PDD) plasma generator. The effect of decontamination was performed utilizing Staphylococcus aureus. The evaluation of initial cell attachment with adhesion images, alkaline phosphatase activity, extracellular matrix mineralization, and expression of genes related to osteogenesis was performed using rat bone marrow mesenchymal stem cells, and the bone response were evaluated in vivo using a rat femur model. Nanotopography and surface roughness did not significantly differ before and after plasma treatments. Cell and bone formation activity were improved by TNS plasma treatment. Furthermore, plasma treatment effectively eliminated biofilm contamination from the surface. These results suggested that this plasma treatment may be a promising approach for the treatment of nanomaterials immediately before implantation and a therapeutic strategy for peri-implantitis.

Characterization of ozone production from multi-cylinder reactor in non-thermal plasma device using multivariable power least squares method

Other than usage for environmental remediation, ozone is also increasingly studied for its potential in combustion enhancement. In this study, the characterization of the ozone production at varied voltage, duty cycle and cylinder configuration for reactor was conducted using multivariable power least squares method (MPLSM). This alternative correlation method in the form of power function was applied in this study to determine the dominant factor affecting the ozone production using the multi-cylinder reactor. The regressed equation using MPLSM method indicated voltage as the dominant factor in the production of ozone compared to the effect of duty cycle. The correlations generated from MPLSM for both reactor configurations were able to predict most of the ozone concentration results within 25% deviation from the actual experimental data. As such, MPLSM could be considered as an alternative method to be used for correlations of non-polynomial results.

Reaction kinetic study of nonthermal plasma continuous degradation of acetone in a closed-loop reactor

Nonthermal plasma (NTP) degradation has been shown to be a promising method for volatile organic compounds (VOCs) removal from air. However, there have been few studies on the degradation of indoor VOCs using NTP, and even less on their reaction kinetics. In this study, NTP degradation of acetone, a representative of oxygenated VOCs, in a closed-loop reactor operating in recirculation mode was investigated. Acetone and organic by-products were characterized in real-time by proton transfer reaction time-of-flight mass spectrometry. The results showed that approximately 85.7% of the acetone degraded within 7.5 h with dielectric barrier discharge treatment at 4.3 W. Methanol, acetaldehyde, formic acid, and acetic acid were observed to be the main organic byproducts with concentrations time-dependent on the order of ppb/ppm. The concentrations of the inorganic by-products O3 and NO2 are also time-dependent and can decrease to nearly 0 after a sufficient degradation time. Based on the concentration measurement in real-time, several rate laws were used to fit the concentration variations of acetone and the organic by-products, and it was observed that they strictly followed the simple kinetic reaction rate laws: acetone followed the first-order rate law, and formic acid formation followed the one-half-order rate law, etc. This study provides a good example of characterizing NTP removal of VOCs in airtight spaces and has important theoretical and practical significance in designing a better NTP device, predicting NTP degradation reaction rate, and accelerating the practical application of NTP technology for indoor air treatment.

Effects of humidity on room disinfection by dielectric barrier discharge plasma

Atmospheric pressure plasma is one of the most promising low-temperature methods for room sterilization. In this study, we demonstrate that plasma with a circulation system can disinfect the entire space in a laboratory chamber with very high uniformity. We also prove that humidity can accelerate the disinfecting power of plasma by generating active species from water molecules as well as delivering them through water vapor. Compared to low humidity (20%–50%) conditions, at high humidities (70%–90%), the quantities of plasma generated reactive species, specifically OH radicals and hydrogen peroxide, are increased two-fold while the quantity of generated ozone is halved. Ultraviolet irradiation of the plasma further reduces the amount of environmentally harmful ozone. Using an atmospheric pressure non-thermal plasma device, room disinfection and the eradication drug resistant Staphylococcus aureus were successfully achieved.

Design of a portable, battery-powered non-thermal atmospheric plasma device and characterization of its antibacterial efficacies

Strong and broad-spectrum antimicrobial efficacy of non-thermal plasma is well known, and non-thermal plasma devices approved for clinical use has become a part of clinical practice. However, these devices require an external power input which limits their use only to a healthcare facility. In this study, a portable, battery-powered, non-thermal plasma device was designed; a prototype was manufactured and its antibacterial efficacies were evaluated on planktonic and biofilm forms of E. coli and S. aureus. The designed device was capable of efficiently inactivating tested bacteria in their planktonic and biofilm forms.

Plasma and Nanomaterials: Fabrication and Biomedical Applications.

Application of plasma medicine has been actively explored during last several years. Treating every type of cancer remains a difficult task for medical personnel due to the wide variety of cancer cell selectivity. Research in advanced plasma physics has led to the development of different types of non-thermal plasma devices, such as plasma jets, and dielectric barrier discharges. Non-thermal plasma generates many charged particles and reactive species when brought into contact with biological samples. The main constituents include reactive nitrogen species, reactive oxygen species, and plasma ultra-violets. These species can be applied to synthesize biologically important nanomaterials or can be used with nanomaterials for various kinds of biomedical applications to improve human health. This review reports recent updates on plasma-based synthesis of biologically important nanomaterials and synergy of plasma with nanomaterials for various kind of biological applications.

Chlorobenzene Degradation in Simultaneous Gas–Liquid Phases Assisted by DBD Plasma

Chlorobenzene (CB) is a toxic compound and is broadly used as a raw material for phenol, solvents, and agrochemical products, among other substances. CB being a very lightly soluble compound in water (~0.450 mL/L) is highly volatile, and it can be found in both liquid and gas phases. In this paper, the treatment of CB was carried out in an aqueous solution assisted by nonthermal plasma (NTP) generated by a dielectric barrier discharge. NTP was utilized as a generator, producing active species for the treatment of CB in both liquid and gas phases, attaining high degradation efficiencies >95% and using a low electric power consumption <20 W. Energy efficiencies of CB removal in kg/kWh were estimated, and relatively high values ~0.5 kg/kWh were obtained with a low-energy consumption. Attained degradation efficiencies were determined using gas chromatography and mass spectrometry. Optical emission spectroscopy study was conducted to determine the gas temperature during experimentations. Thus, the estimated magnitude was lower than 110 °C in overall cases. Meanwhile, the resulting excitation temperature was near to 0.2 eV. This magnitude is in the range of typical temperatures for similar NTP devices.

Application of Response Surface Methodology for characterization of ozone production from Multi-Cylinder Reactor in non-thermal plasma device

Ozone is a reactant which can be applied for various environmental treatment processes. It can be generated via atmospheric air non-thermal plasmas when sufficient voltages are applied through a combination of electrodes and dielectric materials. In this study, the concentration of ozone generated via two different configurations of multi-cylinder dielectric barrier discharge (DBD) reactor (3 x 40 mm and 10 x 10 mm) was investigated. The influence of the voltage and the duty cycle to the concentration of ozone generated by each configuration was analysed using response surface methodology. Voltage was identified as significant factor to the ozone production process. However, the regressed model was biased towards one of the configuration, leaving the predicted results of another configuration to be out of range.

Development of a dimensionless parameter for characterization of dielectric barrier discharge devices with respect to geometrical features

Non-thermal plasma (NTP) devices produce excited and radical species that have higher energy levels than their ground state and are utilized for various applications. There are various types of NTP devices, with dielectric barrier discharge (DBD) reactors being widely used. These DBD devices vary in geometrical configuration and operating parameters, making a comparison of their performance in terms of discharge power characteristics difficult. Therefore, this study proposes a dimensionless parameter that is related to the geometrical features, and is a function of the discharge power with respect to the frequency, voltage, and capacitance of a DBD. The dimensionless parameter, in the form of a ratio of the discharge energy per cycle to the gap capacitive energy, will be useful for engineers and designers to compare the energy characteristics of devices systematically, and could also be used for scaling up DBD devices. From the results in this experiment and from the literature, different DBD devices are categorized into three separate groups according to different levels of the energy ratio. The larger DBD devices have lower energy ratios due to their lower estimated surface discharge areas and capacitive reactance. Therefore, the devices can be categorized according to the energy ratio due to the effects of the geometrical features of the DBD devices, since it affects the surface discharge area and capacitance of the DBD. The DBD devices are also categorized into three separate groups using the Kriegseis factor, but the categorization is different from that of the energy ratio.