Non-thermal Atmospheric Pressure Plasma Research Articles

Improvement of Cell Growth of Uterosacral Ligament Fibroblast Derived from Pelvic Organ Prolapse Patients by Cold Atmospheric Plasma Treated Liquid.

Pelvic organ prolapse (POP) is a chronic disorder that affects quality of life in women. Several POP treatments may be accompanied by abrasion, constant infection, and severe pain. Therefore, new treatment methods and improvements in current treatments for POP are required. Non-thermal atmospheric-pressure plasma is a rising biomedical therapy that generates a mixed cocktail of reactive species by different mechanisms. In this study, we applied a cylinder-type dielectric barrier discharge plasma device to create a plasma-treated liquid (PTL). The PTL was added to primary cultured human uterosacral ligament fibroblast (hUSLF) cells from POP patients at each stage. Surprisingly, treatment with diluted PTL increased hUSLF cell viability but decreased ovarian cancer cell viability. PTL also decreased cell apoptosis in hUSLF cells but increased it in SKOV3 cells. Our results suggest that PTL protects hUSLF cells from cell apoptosis by controlling the p53 pathway and improves cell viability, implying that PTL is a promising application for POP therapy.

In vivo study on the healing of bone defect treated with non-thermal atmospheric pressure gas discharge plasma.

Medical treatment using non-thermal atmospheric pressure plasma (NTAPP) is rapidly gaining recognition. NTAPP is thought to be a new therapeutic method because it could generate highly reactive species in an ambient atmosphere which could be exposed to biological targets (e.g., cells and tissues). If plasma-generated reactive species could stimulate bone regeneration, NTAPP can provide a new treatment opportunity in regenerative medicine. Here, we investigated the impact of NTAPP on bone regeneration using a large bone defect in New Zealand White rabbits and a simple atmospheric pressure plasma (helium microplasma jet). We observed the recovery progress of the large bone defects by X-ray imaging over eight weeks after surgery. The X-ray results showed a clear difference in the occupancy of the new bone of the large bone defect among groups with different plasma treatment times, whereas the new bone occupancy was not substantial in the untreated control group. According to the results of micro-computed tomography analysis at eight weeks, the most successful bone regeneration was achieved using a plasma treatment time of 10 min, wherein the new bone volume was 1.51 times larger than that in the plasma untreated control group. Using H&E and Masson trichrome stains, nucleated cells were uniformly observed, and no inclusion was confirmed, respectively, in the groups of plasma treatment. We concluded the critical large bone defect were filled with new bone. Overall, these results suggest that NTAPP is promising for fracture treatment.

Molecular Mechanisms Underlying Cellular Responses to the Loading of Non-thermal Atmospheric Pressure Plasma-activated Solutions

Plasma medicine is a rapidly expanding new field of interdisciplinary research that combines physics, chemistry, biology, and medicine. Non-thermal atmospheric pressure plasma (NTAPP) has recently been applied to living cells and tissues, and has emerged as a novel technology for medical applications, such as wound healing, blood coagulation, and cancer treatment. NTAPP was found to affect cells indirectly through the treatment of cells with previously prepared medium irradiated by NTAPP, termed plasma-activated medium (PAM). The treatment of culture media with NTAPP results in the generation of a large amount of reactive oxygen species and reactive nitrogen species, and their derived species. We found that PAM triggered a spiral apoptotic cascade in the mitochondrial-nuclear network in A549 cancer cells. This process induced the depletion of total cellular NAD+ and elevations in intracellular calcium ion, ultimately leading to cell death. We also detected the production of hydroxyl radical and elevations in intracellular ferrous ions in PAM-treated cells. The elevations observed in ferrous ions may have been due to their release from the intracellular iron store, ferritin. However, difficulties are associated with applying PAM to the clinical phase because culture media cannot be used for medical treatments. The anti-tumor activity of plasma-activated Ringer's solution was significantly stronger than that of PAM. At the end, we herein demonstrated the advantages of the combined application of plasma-activated acetate Ringer's solution and hyperthermia, a heat treatment at 42℃, for A549 cancer cell death and elucidated the underlying mechanisms.

Coupling of dielectric barrier discharge plasma with oxygen permeable membrane for highly efficient low-temperature permeation

Ceramic oxygen permeable membranes (OPMs) are widely considered the “next generation” technology for pure oxygen separation and catalytic membrane reactors. However, the main issue of OPM is high operating temperature (above 800 °C) and resulting implications for materials, cost, as well as operating complexities (e.g., sealing, creep deformation, and thermal shock during thermal cycling). A new design for coupling OPM La0.6Sr0.4Co0.2Fe0.8O3-δ with a dielectric barrier discharge plasma (a type of atmospheric pressure non-thermal plasma) is proposed for highly efficient low-temperature (600 °C) oxygen permeation. This study demonstrates that the plasma can activate the surface exchange reactions. Applying 15 W air-plasma can effectively reduce the apparent activation energy of the permeation process from 136.6 to 43.1 kJ mol−1. The oxygen flux is increased by a factor of nearly 30 at 600 °C with a plasma power of 15 W. The newly developed plasma-membrane micro-reactor design enables further performance enhancement at lower operating temperatures and integration with solid oxide fuel cells, catalytic membrane reactors, and oxygen permeable membranes.

Atmospheric Pressure and Ambient Temperature Plasma Jet Sintering of Aerosol Jet Printed Silver Nanoparticles.

Atmospheric pressure nonthermal plasmas hold great promise for applications in environmental control, energy conversion, and material processing. Even at room temperature, nonthermal plasmas produce energetic and reactive species that can initiate surface modifications at a plasma-surface interface, including thin-film nanoparticle assemblies, in a nondestructive and effective way. Here, we present the plasma-activated sintering of aerosol jet printed silver thin films on substrates ranging from glass to delicate materials including blotting paper, fruits, and flexible plastic. We characterize the microstructural evolutions and electrical properties of printed films along with the electrical, thermal, and optical properties of an argon plasma jet. We demonstrate an electrical conductivity as high as 1.4 × 106 S/m for printed films sintered under atmospheric conditions in which the surface temperature stays below 50 °C. These results highlight a future direction where additive manufacturing of electronic devices can be achieved on flexible and low-melting-point materials under ambient conditions without requiring additional thermal processing by utilizing nonthermal plasmas.

Tailoring the working gas flow to improve the surface modification of plasma-treated polymers

The paper aims to comparatively investigate the plasma-induced effects − under different discharge regimes: stationary and flowing gas (He and He + 0.5%O2) − on the surface properties of four types of polymers, with a distinct structure, degree of oxidation, and functionality. A pulsed dielectric barrier discharge is used to produce homogenous non-thermal atmospheric-pressure plasma for uniform, efficient, reproducible chemical surface processing. The discharge characteristics, specific to each mode of operation, were analyzed in correlation with the changes in the surface characteristics found following plasma exposure. The plasma treatment increases the surface hydrophilization of all tested polymers, regardless of the discharge mode of operation. Nevertheless, the optimum discharge regime for surface functionalization is correlated with the polymer structure and discharge characteristics. Thus, polypropylene and polystyrene present the maximum wettability in trapping gas mode, while poly(methyl methacrylate) and polysulfone, in the flowing gas mixture. The experimental results demonstrate that working in trapping gas mode is advantageous due to enhanced (>15÷40%) incorporation onto the surface of functional groups related to both oxygen and nitrogen species.

Optimal Power of Atmospheric Pressure Plasma Jet with a Simple DBD Configuration for Biological Application

The new strategy, non-thermal atmospheric pressure plasma (N-APP), as a ’physical’ method, could offer a simple, fast, effective, and economic way of disinfection of equipment, surfaces, a method that is unlikely to cause micro-organisms resistance, or allergic, and toxic reactions. Recently, cold physical plasma had been extensively studied by researchers as a possible therapy in dentistry and oncology, as well as the application of non-thermal plasma in biomedical researches such as wound healing. In clinical dermatology, cold plasmas are mainly used for the treatment of chronic wounds and pathogen-based skin diseases, in which stimulation of tissue repair and decontamination. In this research, the characterization of home-made Helium Non-Equilibrium atmospheric pressure plasma jet (He -NAPPJ), that had been generated using a dielectric barrier discharge (DBD) configuration for exceptional standardization protocol of this plasma source that meets medical requirements. The device equipped with two powered electrodes as well as a grounded electrode, driven by an (8 kVp-p) voltage, the frequency (12 kHz), and the distance between the nozzle of the plasma jet and the target were used as constant data. As a working gas, the Helium gas (He) was used in different flow rates (2, 4, 6, and 8) slm. The optical emission spectroscopy was used to measure the plasma parameters, of which the electronic excitation temperature and density of electrons were determined by the Boltzmann’s plot method and Stark broadening effect equation respectively. The result of the emission line spectrum showed the presence of nitrogen and oxygen between lines 300 nm until 700 nm. Nitrogen and oxygen are involved in the oxidation process which is known as Reactive Nitrogen species and reactive oxygen species. These species are the main key in bacteria inactivation and the wound healing process. Furthermore, the results had revealed, the optimal condition using the flow rate (6 slm) with 32 °C He gas temperature that had been stabilized for 20 min, plume length 40 mm, The distance is 15 mm from the distal end of the Pyrex tube (DBD) and the wound surface, the power density 44 mWatt/cm2, and plasma radiation energy dose: 76 J/cm2. These results were considered in this study as a safe operating condition for biomedical applications.

Investigation of a non-thermal atmospheric pressure plasma jet in contact with liquids using fast imaging

An experimental diagnostic based on a nanosecond-intensified charged coupled device camera and optical emission spectroscopy (OES) are proposed to observe the interfacial region between the plasma plume and liquid surfaces. The study is simulating the investigations of using non thermal atmospheric pressure plasma jets for the eradication of bacterial biofilms. The spatially and temporally resolved images are focused on the contact region in the open air between the nozzle of the reactor and liquid targets. The emission intensity from one discharge cycle is captured and accumulated over several cycles to investigate the formation and the kinetic evolution of the plasma during the interaction. Moreover, the emission intensity of the helium plasma jet and plasma behaviour with different samples are observed. It is found that some dynamic of the plasma discharge has changed during the interaction with different targets. The method can be used to improve the need of understanding of the physics and chemistry of plasma jet during the interaction with liquid surfaces. Different types of species that arrived to the samples were studied and compared with the free jet mode using OES.

UV Absorption Spectroscopy for the Diffusion of Plasma-Generated Reactive Species through a Skin Model

Skin applications of non-thermal atmospheric pressure plasma (NTAPP) have been at-tracting attention from medical and cosmetic aspects. The reactive species generated from plasma sources have been known to play important roles in the skin. For proper applications, it is essential to know how they diffuse into the skin. In this study, the penetration of active species from NTAPP through a skin model was analyzed by UV absorption spectroscopy. The diffusions of hydrogen peroxide, nitrite, and nitrate were quantified through curve fitting. We utilized an agarose gel to mimic epidermis and dermis layers, and we used a lipid film or a pig skin sample to mimic the stratum corneum (SC). The diffusion characteristics of reactive species through this skin model and the limitations of this method were discussed

Implementation of a Non-Thermal Atmospheric Pressure Plasma for Eradication of Plant Pathogens from a Surface of Economically Important Seeds.

Plant pathogenic bacteria cause significant economic losses in the global food production sector. To secure an adequate amount of high-quality nutrition for the growing human population, novel approaches need to be undertaken to combat plant disease-causing agents. As the currently available methods to eliminate bacterial phytopathogens are scarce, we evaluated the effectiveness and mechanism of action of a non-thermal atmospheric pressure plasma (NTAPP). It was ignited from a dielectric barrier discharge (DBD) operation in a plasma pencil, and applied for the first time for eradication of Dickeya and Pectobacterium spp., inoculated either on glass spheres or mung bean seeds. Furthermore, the impact of the DBD exposure on mung bean seeds germination and seedlings growth was estimated. The observed bacterial inactivation rates exceeded 3.07 logs. The two-minute DBD exposure stimulated by 3–4% the germination rate of mung bean seeds and by 13.4% subsequent early growth of the seedlings. On the contrary, a detrimental action of the four-minute DBD subjection on seed germination and early growth of the sprouts was noted shortly after the treatment. However, this effect was no longer observed or reduced to 9.7% after the 96 h incubation period. Due to the application of optical emission spectrometry (OES), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM), we found that the generated reactive oxygen and nitrogen species (RONS), i.e., N2, N2+, NO, OH, NH, and O, probably led to the denaturation and aggregation of DNA, proteins, and ribosomes. Furthermore, the cellular membrane disrupted, leading to an outflow of the cytoplasm from the DBD-exposed cells. This study suggests the potential applicability of NTAPPs as eco-friendly and innovative plant protection methods.

Effects of Pre-Treatment Using Plasma on the Antibacterial Activity of Mushroom Surfaces.

Although non-thermal atmospheric pressure plasma is an efficient tool for preventing post-harvest microbial contamination, many studies have focused on the post-treatment of infected or contaminated foods. In this study, we examined the antimicrobial quality of mushrooms pre-treated with a non-thermal atmospheric pressure plasma jet (NTAPPJ) or plasma-treated water (PTW). The CFU (Colony Forming Unit) number of Escherichia coli inoculated on surfaces of mushrooms pre-treated with NTAPPJ or PTW was significantly reduced (about 60–75% for NTAPPJ and about 35–85% for PTW), and the reduction rate was proportional to the treatment time. Bacterial attachment and viability of the attached bacteria were decreased on NTAPPJ-treated mushroom surfaces. This may be caused by the increased hydrophilicity and oxidizing capacity observed on NTAPPJ-treated mushroom surfaces. In PTW-treated mushrooms, bacterial attachment was not significantly changed, but death and lipid peroxidation of the attached bacteria were significantly increased. Analysis of mushroom quality showed that loss of water content was greater in mushrooms treated with NTAPPJ compared to that in those with no treatment (control) and PTW treatment during storage. Our results suggest that pre-treatment with NTAPPJ or PTW can improve the antibacterial quality of mushroom surfaces by decreasing bacterial attachment (for NTAPPJ) and increasing bacterial lipid peroxidation (for both NTAPPJ and PTW).

Combination of vaporized ethyl pyruvate and non-thermal atmospheric pressure plasma for the inactivation of bacteria on lettuce surfaces

The effect of vaporized ethyl pyruvate (EP) and atmospheric pressure plasma (APP) treatments on the inactivation of total viable counts of bacteria on fresh lettuce leaves samples after treatment and during storage (1 and 3 days) at 6 and 25 °C was studied. For this purpose, freshly grown B. cereus and Escherichia coli were inoculated on the lettuce leaves prior to treatments. Combination of EP (at a concentration of around 10 μL dm−3) with APP was more effective on inactivation of bacteria when compared to EP and APP treatments separately, reducing the total viable counts nearly 5 CFU cm−2 compared to control. The use of EP and APP together led to around 2.5 more log (CFU cm−2) reductions when compared to the sole use of EP and APP separately. B. cereus cells were almost three times more susceptible to APP treatment than E. coli. Growth inhibition increased after storing the treated samples at 25 °C by around 2.5 and 1.5 logs for E. coli and B. cereus, respectively, compared to 6 °C. APP treatment time (30 and 60 s) and storage time (1 and 3 days) did not significantly affect the inactivation levels. E. coli was more effectively inactivated after EP + O2 treatment followed by storage at 25 °C. The highest level of inactivation was noted as nearly 5 log reductions. Slight differences in the peak intensities of FTIR spectra of treated lettuce samples were observed compared to control, indicating slight modifications on the chemical structure on the lettuce leaves. Industrial relevanceThe microbial load influences the quality, safety, and shelf-life of fresh produce such as lettuce. Current decontamination techniques may cause some unwanted effects such as odor, discoloration, and decreased nutritional value. This study shows that the use of the APP-EP hurdle represents a promising strategy to improve the decontamination efficiency and hence, enhance the shelf-life of freshly cut vegetables. The data obtained contribute to a better understanding of APP-EP-induced effects on the quality and shelf-life of fresh-cut lettuce and provide a scientific basis for industrial implementation.

Non-thermal atmospheric pressure plasma activates Wnt/\u03b2-catenin signaling in dermal papilla cells

There is an unmet need for novel, non-pharmacological therapeutics to treat alopecia. Recent studies have shown the potential biological benefits of non-thermal atmospheric pressure plasma (NTAPP), including wound healing, angiogenesis, and the proliferation of stem cells. We hypothesized that NTAPP might have a stimulatory effect on hair growth or regeneration. We designed an NTAPP-generating apparatus which is applicable to in vitro and in vivo experiments. The human dermal papilla (DP) cells, isolated fresh hair follicles, and mouse back skin were exposed with the NTAPP. Biological outcomes were measured using RNA-sequencing, RT-PCR, Western blots, and immunostaining. The NTAPP treatment increased the expression levels of Wnt/β-catenin pathway-related genes (AMER3, CCND1, LEF1, and LRG1) and proteins (β-catenin, p-GSK3β, and cyclin D1) in human DP cells. In contrast, inhibitors of Wnt/β-catenin signaling, endo-IWR1 and IWP2, attenuated the levels of cyclin D1, p-GSK3β, and β-catenin proteins induced by NTAPP. Furthermore, we observed that NTAPP induced the activation of β-catenin in DP cells of hair follicles and the mRNA levels of target genes of the β-catenin signaling pathway (CCND1, LEF1, and TCF4). NTAPP-treated mice exhibited markedly increased anagen induction, hair growth, and the protein levels of β-catenin, p-GSK3β, p-AKT, and cyclin D1. NTAPP stimulates hair growth via activation of the Wnt/β-catenin signaling pathway in DP cells. These findings collectively suggest that NTAPP may be a potentially safe and non-pharmacological therapeutic intervention for alopecia.

Evaluation of cold atmospheric-pressure plasma against burn wound infections and gene silencing.

Background and Objectives:Non-thermal atmospheric-pressure plasma or cold plasma is defined as an ionized gas. This study aimed to investigate the effect of cold plasma on Pseudomonas aeruginosa strains. Also, the expression level of the alp virulence gene before and after treatment with cold plasma was compared with the Housekeeping gene gyrA.Materials and Methods:P. aeruginosa isolates recovered from hospitalized burn patients at Shahid Motahari Burns Hospital, Tehran, Iran. The Kirby Bauer disk diffusion method was used to determine the antimicrobial susceptibility test. Then, the antibacterial effect of atmospheric non-thermal plasma was evaluated on P. aeruginosa in as in vitro and in vivo studies at different times on Muller Hinton agar and in mouse model (treated by plasma every day/ 90 sec). The histopathological study was evaluated by Hematoxylin-Eosin staining. Data were analyzed using SPSS software by the Chi-square test and Pvalues less than 0.05 considered as statistically significant.Results:Results indicated that non-thermal atmospheric plasma inhibited the growth of P. aeruginosa. The non-thermal helium plasma accelerates wound healing for 6 days. Results showed that cold plasma decreased virulence gene expression alp after treatment. Therefore, cold plasma can be suggested as a complementary therapeutic protocol to reduce bacterial infection and accelerate wound healing and reduce the expression of virulence genes of pathogens.Conclusion:Cold plasma showed pathogen inhibitory properties of P. aeruginosa and virulence alkaline protease and wound healing properties in animal models, so this inexpensive and suitable method can be presented to the medical community to disinfect burn wounds and improve wound healing.

Non-Thermal Atmospheric Pressure Plasma-Conditioned Root Dentin Promotes Attraction and Attachment of Primary Human Dental Pulp Stem Cells in Real-Time Ex Vivo

This study investigated if non-thermal atmospheric pressure plasma (NTAPP) treatment of root dentin surfaces promotes human dental pulp stem cell (hDPSCs) adhesion. Freshly extracted human single-rooted teeth (n = 36) were decoronated and cut (first vertically, then horizontally) into root dentin slices (3 mm thick). Primary hDPSCs cultures were seeded onto slices randomly assigned to pretreatment groups (n = 9/group): NaOCl (1.5%), EDTA (17%) then NTAPP (Group I); NaOCl then NTAPP (Group II); NaOCl then EDTA (Group III); and NaOCl alone (Group IV). Cell viability and proliferation were measured using MTT assay with log-linear statistical analysis. Cell attachment and spreading morphologies on dentin slices (n = 3/group) were examined through scanning electron microscopy. Early cell adhesion events and subcellular activities were observed in real time by live-cell imaging through holotomographic microscopy. Cell viability and proliferation were significantly higher on NTAPP-treated dentin (p < 0.05), without interactions with EDTA (p > 0.05). The attachment, spreading, extensions and multiple layers of hDPSCs were heightened on NTAPP-treated dentin. Cell adhesion, spreading, and dentinal tubule penetration were hastened on NTAPP-treated dentin surfaces in real-time, with elevated subcellular activities and intracellular lipid droplet formation. NTAPP-treated root dentin surfaces support enhanced cellular responses, potentially promoting pulp-dentin regeneration.

THE EFFECTS OF DIMMER CONTROLLED ATMOSPHERIC PRESSURE PLASMA JET TO THE BIOPHYSICAL STRUCTURES OF HeLa CELLS

Non-thermal atmospheric pressure plasma jet (NTAPPJ) was shown as a promising tool for sterilization, treatment of chronic wounds & tumors. A portable and facile NTAPPJ system will broaden the application of plasma for many other biomedical applications. This paper demonstrates the feasibility of a customized dimmer controllable atmospheric pressure plasma jet (APPJ) in treating HeLa cells. A plasma torch was energized at 8 kVpp and 35 kHz from a neon transformer and discharged with argon gas-producing plasma plume of various gas species. The output intensity of the plasma discharge was adjusted by the voltage input from the dimmer controller circuit. Between 60 – 220 V, a different power output of the dimmer can be varied between 8.4 to 83.6 W, to generate different intensities of non-thermal APPJ (NTAPPJ). The NTAPPJ was then applied to HeLa cells for 20 sec & it was found that cells reduced their adhesion at a dimmer power < 20 W but stayed viable. This progressed to observations of damaged cell body when the power was increased beyond 20 W & the cell membranes shattered when the power was up to 83.6 W. This was due to the ultraviolet rays and reactive oxygen species (ROS), that induced detrimental effects to the cells. The controllable NTAPPJ system, based on dimmer control, induced different levels of effects on the biophysical structures of cells, ranging from reduced cell spread to apoptosis and eventually cell membrane disintegration.

Removal of Various Pollutants from Wastewater Using Plasma-Modified Lignocellulose-Derived as a Low-Cost Adsorbent: An Overview

In their search for an alternative to commercial adsorbents, much research is turned to the local biomass-based materials such as agricultural residues and assimilated derivatives. However, natural biomass due to its low specific surface area must first undergo several pre-treatments. Among the newly emerging electric techniques for environmental applications, those who operate at atmospheric pressure (Non-thermal plasma) have recently found many breakthrough applications arising from their easy use with no extra additional reagents and their high reactivity. The Non-thermal plasma treatment of biomass is one of the promising developed approaches mainly due to significant effects including the formation of micro and macrospores, the increase of surface roughness, and surface functionalization. The most used plasma is non-thermal, so as not to denature the biomass, likewise the hot plasma can burn and/or destroy high contains carbon biomaterials. Especially, the gliding arc plasma obtained using moisten air as feeding gas, which is known to induce acidifying and oxidizing effects in an aqueous target. The primary species HO• radicals [E° (HO•/H2O) = 2.85 V/SHE] mainly formed in the arc will be with the dimer H2O2 [E°(H2O2/H2O) = 1.76 V/SHE] the determining agents for the chemical reactions induced. Exposure of a target to this kind of environment is likely to promote great surface transformations. This approach has some advantages: (i) the merit of not using commercial chemical reagents, the reactive species being in situ generated; (ii) the risks related to the manipulation of the products, the plasma reactor is robust and can be modulated to treat large quantity; (iii) the efficiency of the bi-functionality of the plasma (acidifier and oxidative). In this review, we will highlight the main changes induced by exposure of biomass to plasma treatment and also make a comparative study between chemically and plasma-activated materials in the removal of various pollutants from aqueous solution; and finally, we summarize the findings in the existing literature.

The effect of TiO2 coatings on the formation of ozone and nitrogen oxides in non-thermal atmospheric pressure plasma

The use of photocatalytic materials in plasma systems has the potential to enhance the selectivity and yield of desired products. However, the surface interaction between the photocatalyst and plasma is a complex process that is not well understood. This work presents a comprehensive study of the effects of combining titanium dioxide (TiO2) photocatalysts with non-thermal atmospheric pressure nitrogen-oxygen plasmas, which increases the production of ozone and dinitrogen pentoxide (N2O5) while limiting the formation of harmful nitrogen dioxide (NO2) and nitrous oxide (N2O) by products. TiO2 coatings were deposited by magnetron sputtering onto barium titanate (BaTiO3) particulates for use within a packed bed dielectric barrier discharge reactor (DBD). The presence of titanium dioxide can affect the plasma chemistry in the DBD by acting as a sink for atomic oxygen, through photocatalytic formation of superoxide anion radical (O2-), and alteration of the dielectric constant of the BaTiO3 particulates. This work explains the complex interaction of these effects on oxygen and nitrogen plasma chemistry. The effect of the photocatalyst surface properties, gas composition and residence time on the reaction pathways for the formation of ozone and nitrogen oxides (NxOy) were investigated. The photocatalytic activity of titanium dioxide was improved by annealing the coated surface, and was subsequently found to enable the formation of ozone, increase the formation of N2O5 while significantly decreasing the formation of harmful NO2 and N2O with a residence time of 0.011 s

A surface dielectric barrier discharge non-thermal plasma to induce cell death in colorectal cancer cells

A novel coaxial surface dielectric barrier discharge (SDBD) non-thermal atmospheric pressure plasma device, driven by a 35.7-kHz DC pulse and adjustable by a pulse-width modulation, was developed in this study and preliminarily tested for its killing effects of a cancer cell type. This study was divided into three phases, namely, air phase, liquid phase, and cell phase. First, the electrical characteristics and emissions were examined. Two-beam UV-LED absorption spectroscopy was also newly developed to measure the absolute hydroxyl radical (OH⋅) density in the filamentary discharge. Then, the effects of energy doses and treatment durations on three types of liquids and on the colorectal adenocarcinoma cell, SW620, were examined. From Lissajous figures (Q–V plot), the developed SDBD possesses the maximum power density and energy dose of 0.33 ± 0.05 W/cm2 and 19.5 ± 3.00 J/cm2, respectively, when the voltage was set at 3.44 kV and the power at 115 mW. From two-beam UV-LED absorption spectroscopy results, the OH⋅ density increased by 0.32, 0.58, and 0.86 × 1019 m−3, with operational powers of 29, 58, and 115 mW, respectively, within 1-min treatment. In liquid phases, the plasma device can increase the concentrations of H2O2 and NO2− in a time-dependent manner. Finally, cell-phase studies, including the examination of the cell morphology, cell viability, and gene expression of the SW620 cell, show that the device can time-dependently induce the mortality of the SW620 cell, relevant to the up-regulation of the Bax/Bcl-2 expression ratio. Taken together, this novel SDBD plasma device shows potential as another alternative for cancer treatment, although further modification is required.

Anti-inflammatory effect of non-thermal atmospheric pressure plasma for periodontitis treatment: in vitro pilot study

Anti-inflammatory effect of non-thermal atmospheric pressure plasma for periodontitis treatment: <i>in vitro</i> pilot study