Non-equilibrium Pressure Plasma Research Articles

Cytotoxic effects of plasma-irradiated fullerenol

Fullerenol dissolved in water was irradiated with a non-equilibrium atmospheric pressure plasma. Plasma irradiation altered the fullerenol solution by introducing carbonyl groups, ether bonds, and intercalated nitrate anions. The resulting plasma-irradiated fullerenol (PF) was added in cell culture medium. PF-supplemented medium exhibited a cytotoxic effect on HeLa cells. Notably, HeLa cells cultured in the PF-added cell culture medium generated intracellular reactive oxygen and nitrogen species, such that the endocytosis of PF induced the apoptotic cell death. The cytotoxic effect inducing apoptosis was found in the PF-supplemented medium.

Influence of space charge density on electron energy distribution function and on composition of atmospheric pressure He/O2/air plasmas

Atmospheric pressure non-equilibrium plasma represents an efficient source of reactive species for different kinds of applications. Rich chemistry of such plasmas develops on longer time scales and is difficult to handle by kinetic models so global models are often applied to study such processes. The Maxwell-Boltzmann (MB) distribution is often used in global modelling of these non-equilibrium systems, even for the calculation of electron rate coefficients. In order to test the sensitivity of plasma composition on the space charge density and consequently on the assumed electron energy distribution function (EEDF), the zero-dimensional global model is applied to the helium/oxygen mixture (0.5% of O2 with humid air impurities. To test the effect of the distribution function on global models we have included the data calculated based on the non-equilibrium EEDF for the processes where often exponential Arrhenius-like formulae as a function of the effective temperature are used. The initial calculation showed that the change in the form of distribution function mainly affects the processes with thresholds considerably higher than the mean electron energy while it does not change much the rates for the processes with the thresholds and peaks of the cross sections in the region of the mean energy. We have calculated variations of the EEDF with the charge density and the resulting changes in chemical kinetics.

Development of plasma-assisted inkjet printing and demonstration for direct printing of conductive silver line

Novel plasma-assisted inkjet printing, where inks during flight and after landing on a substrate are irradiated by atmospheric-pressure nonequilibrium plasma, is developed as a rapid one-step process without any pre-/post-treatments. A silver line with good electrical conductivity was fabricated on a polyimide. Compared with heat treatment, the line shows lower electrical resistivity and a narrower line width even with a much shorter treatment time.

Driving Force of Plasma Bullet in Atmospheric-Pressure Plasma

When plasma is generated by applying high-voltage alternating current (AC), the driving force of the temporally and spatially varying electric field is applied to the plasma. The strength of the driving force of the plasma at each spatial position is different because the electrons constituting the atmospheric-pressure nonequilibrium (cold) plasma move at a high speed in space. If the force applied to the plasma is accelerated only by the driving force, the plasma will be accelerated infinitely. The equilibrium between the driving force and the restricting force due to the collision between the plasma and neutral particles determines the inertial force and the drift velocity of the plasma. Consequently, the drift velocity depends on the strength of the time-averaged AC electric field. The pressure applied by the AC electric field equilibrates with the plasma pressure. From the law of conservation of energy, the pressure equilibrium is maintained by varying the drift velocity of the plasma.

Synergistic effects of plasma-activated medium and chemotherapeutic drugs in cancer treatment

Chemotherapy is an important treatment method for metastatic cancer, but the drug-uptake efficiency of cancer cells needs to be enhanced in order to diminish the side effects of chemotherapeutic drugs and improve survival. The use of a nonequilibrium low-temperature atmospheric-pressure plasma jet (APPJ) has been demonstrated to exert selective effects in cancer therapy and to be able to enhance the uptake of molecules by cells, which makes an APPJ a good candidate adjuvant in combination chemotherapy. This study estimated the effects of direct helium-based APPJ (He-APPJ) exposure (DE) and He-APPJ-activated RPMI medium (PAM) on cell viability and migration. Both of these treatments decreased cell viability and inhibited cell migration, but to different degrees in different cell types. The use of PAM as a culture medium resulted in the dialkylcarbocyanine (DiI) fluorescent dye entering the cells more efficiently. PAM was combined with the anticancer drug doxorubicin (Doxo) to treat human heptocellular carcinoma HepG2 cells and human adenocarcinomic alveolar basal epithelial A549 cells. The results showed that the synergistic effects of combined PAM and Doxo treatment resulted in stronger lethality in cancer cells than did PAM or Doxo treatment alone. To sum up, PAM has potential as an adjuvant in combination with other drugs to improve curative cancer therapies.

Nanosecond-Pulsed DBD Plasma For A Clinical Trial Of Actinic Keratosis

Actinic keratosis (AK) is a pre-cancerous skin lesion, the earliest clinical stage in a continuum of malignancy that may lead to squamous cell carcinoma (SCC), a skin cancer that accounts for significant morbidity (over 1 million cases in the US annually), and thousands of preventable deaths annually. This translates to a total direct cost for AK of about $1.2 billion and approximately 8.2 million office visits annually. Available treatments ablate lesions via cryotherapy, curettage or long-term application of chemotherapeutic or immune-modulator drugs. They are typically associated with pain, scarring and inflammation, undesirable side effects that reduce patient compliance. To address these, we studied the use of non-equilibrium, atmospheric pressure plasma (NEAPP) for the treatment of AK in a small clinical trial. [1] One month post NEAPP treatment, over 50% of the lesions achieved full clinical resolution or showed significant improvement. Abscopal effects were observed in some cases, possibly through immune stimulation. [2] Furthermore, no patient experienced adverse effects, immediate or delayed. One year follow-up showed no recurrence of any of the treated lesions. [unpublished data] 2-year follow-up results and further optimization of treatment under a new clinical trial will be presented. Our results demonstrate that NEAPP may serve as a potential, effective treatment for AKs. Download : Download high-res image (166KB) Download : Download full-size image Evaluation of nspDBD treatment of AK. 9 lesions fully resolved, 3 showed significant improvement

Plasma-Activated Medium Inhibites Metastatic Activities Of Ovarian Cancer Cells In Vitro Via Repressing Mapk Pathway

Ovarian cancer is among the most malignant gynecologic cancers since peritoneal dissemination often occurs at the diagnosis of these patients. The 5-year survival rate is less than 50%. Recently, non-equilibrium atmospheric pressure plasma (NEAPP) has been introduced in medical field. We have already demonstrated the cytotoxic effect of the direct plasma exposure to ovarian cancer cells. However, it is difficult to expose cancer cells to plasma gas intraperitoneally. Thus, we established the system of plasma-activated medium (PAM) to treat ovarian cancer indirectly instead of a direct exposure to plasma [1]. In our previous works, it was demonstrated that PAM significantly inhibited proliferation ability of ovarian cancer cells, with fibroblast cells remaining unaffected though. Both in vitro and in vivo study had confirmed the cytotoxic effect of PAM to ovarian cancer. However, it still remains unknown whether PAM can affect metastasis of ovarian cancer cells, which is the fatal problem of ovarian cancer patients [2]. In this study, we tried to investigate PAM’s anti-metastasis effect in vitro and the underneath mechanism. Firstly, we performed wound-healing and transwell assay on ES2, one of ovarian cancer cell lines. We found that the cell migration and invasion abilities were significantly inhibited by PAM. Secondly, we established a co-culture system by seeding ES2 cells onto monolayer of peritoneal mesothelial cells, which models the initial step of ovarian cancer cells metastasis in human peritoneal cavity, and it was found that PAM significantly repressed ES2 cells to implant onto mesothelial cells. Moreover, mechanism study showed both mRNA and protein levels of MMP-9 were inhibited by PAM. And PAM significantly inhibited the phosphorylation of JNK1/2 MAPK and p38 MAPK (figure 1), which indicated that inhibition of MMP-9 was dependent on MAPK pathway [3]. In summary, it is indicated in this work that PAM presents efficient inhibitory effect towards ovarian cancer cells metastasis in vitro. Moreover, PAM’s anti-metastasis effect is implemented by repressing the activation MAPK pathway, resulting in de-activation of downstream target MMP-9, thus leading to suppression of cell migration and invasion. In the near future, it might be a new clinical strategy for metastatic ovarian cancer patients to choose PAM therapy via intaperitoneal treatment. Download : Download high-res image (86KB) Download : Download full-size image Fig. 1

CN (B 2Σ+ → X 2Σ+) Violet System in a Cold Atmospheric-Pressure Argon Plasma Jet

$$ {\text{CN}} (B^{2}\Sigma ^{ + } \to X^{2}\Sigma ^{ + } ) $$ violet system was investigated using optical emission spectroscopy in a non-equilibrium microwave atmospheric-pressure plasma jet in argon expanding in air. From the analysis of the emission spectra of the discharge in the range of 380 and 400 nm, the violet system of CN was found to be overlapped with the $$ {\text{N}}_{2}^{ + } \left( {B^{2}\Sigma _{u}^{ + } , v = 1 \to X^{2}\Sigma _{g}^{ + } , v = 1} \right) $$ and $$ {\text{N}}_{2} \left( {C^{3}\Pi _{u} \to B^{3}\Pi _{g} } \right) $$ bands, sequence $$ \Delta \upsilon = - \;3 $$ . A numerical disentangle technique, developed in this work, permitted to obtain a well resolved violet system from the different systems observed, namely the nitrogen First Negative and the Second Positive systems. The $$ {\text{CN}} (B^{2}\Sigma ^{ + } \to X^{2}\Sigma ^{ + } ) $$ band head intensity was determined and analysed as function of discharge powers between 30 and 150 W and fluxes between 2.5 and 10.0 slm. With aid of this numerical approach it was also possible to obtain the rotational temperature, from (1600 ± 100) to (2300 ± 100) K and vibrational temperature between (9000 ± 800) and (14,000 ± 800) K along the plasma jet. The kinetics of $$ {\text{CN}} (B^{2}\Sigma ^{ + } ) $$ state was analysed as well.

Non-equilibrium atmospheric pressure plasma as innovative method to crosslink and enhance mucoadhesion of econazole-loaded gelatin films for buccal drug delivery

In this paper we developed an innovative, effective and rapid one-step approach to crosslink mucoadhesive gelatin films for buccal drug delivery. The method, which involves the application of non-equilibrium pressure plasma for 3 or 5 minutes/side, was compared with a classical approach based on the use of a chemical crosslinking agent, namely genipin. Econazole nitrate (ECN), an imidazole antifungal agent used for the treatment of skin infections and mucosal candidiasis, was selected as model drug. X-Ray Diffraction characterization performed on the drug-containing gelatin films revealed that ECN undergoes to a topotactic transformation into Econazole (EC) immediately after mixing with gelatin suggesting the occurrence of an acid-base reaction between drug and gelatin during film processing. Plasma treatment, as well as genipin crosslinking, did not provoke any further variation of EC structure. However, plasma exposure significantly improved films adhesiveness and allowed to reach mucoadhesive strength values more than double with respect to those obtained with genipin, ascribable to the presence of polar and hydrophilic groups on the plasma treated film’s surface. A residence time of at least 48 h was obtained by properly selecting the plasma exposure times. These results, together with the in-vitro data showing retention of antifungal efficacy against a strain of Candida albicans, demonstrated that plasma treatment was a valid and rapid alternative, easy to scale-up, to chemical crosslinking methods for the production of highly mucoadhesive gelatin-based films.

Estimation of Flow Channel Parameters for Flowing Gas Mixed with Air in Atmospheric-pressure Plasma Jets

When the working gas of an atmospheric-pressure non-equilibrium (cold) plasma flows into free space, the diameter of the resulting flow channel changes continuously. The shape of the channel is obs...

Dynamic analysis of reactive oxygen nitrogen species in plasma-activated culture medium by UV absorption spectroscopy

The liquid-phase chemical kinetics of a cell culture basal medium during treatment by an argon-fed, non-equilibrium atmospheric-pressure plasma source were investigated using real-time ultraviolet absorption spectroscopy and colorimetric assays. Depth- and time-resolved NO2− and NO3− concentrations were strongly inhomogeneous and primarily driven by convection during and after plasma–liquid interactions. H2O2 concentrations determined from deconvolved optical depth spectra were found to compensate for the optical depth spectra of excluded reactive species and changes in dissolved gas content. Plasma-activated media remained weakly basic due to NaHCO3 buffering, preventing the H+-catalyzed decomposition of NO2− seen in acidic plasma-activated water. An initial increase in pH may indicate CO2 sparging. Furthermore, the pH-dependency of UV optical depth spectra illustrated the need for pH compensation in the fitting of optical depth data.

Optical emission spectroscopy of atmospheric-pressure non-equilibrium plasma with mist injection

This paper describes optical emission spectroscopic diagnostics of atmospheric-pressure non-equilibrium plasma with mist injection. Electron number densities and gas temperatures are estimated from Hβ (486 nm) and OH (309 nm) spectra to be on the order of 1015 cm-3 and 440–540 K, respectively, for the conditions tested in this study. Comparison of the rotational temperatures of N2 and OH indicates that two-temperature analysis of OH rotational spectra provides gas temperature even with mist injection.

The Catalytic Effect of Electronegative Additives on Removal of Perchloroethylene Vapor from Air by Pulsed Corona Discharge

It is established that electronegative additives (CCl4, freon-113) produce a catalytic effect on the conversion of volatile organic compounds (VOCs) under the action of atmospheric-pressure nonequilibrium plasma generated in pulsed corona discharge. At concentrations below 0.1%, these additives significantly decrease the discharge current, but the energy efficiency of the process of VOC removal from air increases. The catalytic effect of electronegative additives on the VOC conversion in air and nitrogen is quantitatively demonstrated in the case of perchloroethylene C2Cl4 (PCE) vapor removal. The addition of 0.085% CCl4 to air reduces the energy consumption for PCE removal at initial concentration of 0.09% by half (from 12 to 6 eV per molecule) at a 63% degree of cleaning. Mechanisms explaining the active inf luence of electronegative additives on the discharge current and the process of impurity removal are suggested.

Effect of Plasma-Activated Lactated Ringer's Solution on Pancreatic Cancer Cells In Vitro and In Vivo.

The medical applications of nonequilibrium atmospheric pressure plasma in cancer therapy have attracted attention. We previously reported on the antitumor effect of plasma-activated medium. However, this approach requires plasma-activated liquids that are administrable to the human body. In this study, we produced plasma-activated lactated Ringer's solution (PAL) and evaluated its antitumor effect and mechanism. Furthermore, we evaluated the effect of the intraperitoneal administration of PAL using a peritoneal dissemination mouse tumor model. The antitumor effect of PAL on pancreatic cancer cell lines was evaluated using proliferation and apoptosis assays. In addition, cellular reactive oxygen species (ROS) generation was examined. The role of ROS was assessed using a proliferation assay with N-acetyl cysteine (NAC). An adhesion assay was performed to evaluate the effect of PAL on cell adhesion. Finally, pancreatic cancer cells stably expressing luciferase (AsPC-1/CMV-Luc) were injected intraperitoneally into mice, followed by intraperitoneal injection of PAL. Peritoneal dissemination was monitored using in vivo bioluminescent imaging. The antitumor effect of PAL was shown in all cell lines in vitro. The TUNEL assay showed that PAL induced apoptosis. ROS uptake was observed in PAL-treated cells, and the antitumor effect was inhibited by NAC. Cell adhesion also was suppressed by PAL. The intraperitoneal administration of PAL suppressed the formation of peritoneal nodules in vivo. Our study demonstrated the antitumor effects of PAL in vitro and in vivo. Intraperitoneal administration of PAL may be a novel therapeutic option for peritoneal metastases.

Comparison on the Absolute Concentrations of Hydroxyl and Atomic Oxygen Generated by Five Different Nonequilibrium Atmospheric-Pressure Plasma Jets

Nonequilibrium atmospheric pressure plasma jets (N-APPJs) generate near or at room temperature plasmas in open space, which is attractive for various applications such as plasma medicine. Because of this advantage, different types of N-APPJs have been reported. Reactive species, such as hydroxyl (OH) and atomic oxygen (O), generated by N-APPJs, are believed to play important roles for many applications. However, there is no report on the comparison of the reactive species concentrations generated by different types of N-APPJs. In this paper, the absolute concentrations of OH and O generated by five different configurations of widely used N-APPJs are compared. For this initial study, all five N-APPJS are driven by the same pulsed dc power supply. Besides, the effects of different operating parameters, including the amplitude of the applied voltage, frequency, the content of the working gas, and the gas flow rate, on their concentrations are investigated. It is found that the OH and O concentrations of the five N-APPJs could have up to one order and five-folder difference, respectively. On the other hand, for all five devices, their peak O concentrations are about two orders higher than their peak OH concentrations. Finally, from the energy point of view, the reactive species generation efficiency of these devices are discussed and future work is proposed.

Crystallization of calcium oxalate dihydrate in a buffered calcium-containing glucose solution by irradiation with non-equilibrium atmospheric pressure plasma

Oxalate was synthesized in the glucose solution by irradiation with non-equilibrium atmospheric pressure plasma (NEAPP), in which the NEAPP plume contacted the solution surface, via the generation of several intermediate organic products such as gluconic acid. A thermodynamically unstable phase of calcium oxalate dihydrate crystallized rapidly during incubation of a NEAPP-irradiated glucose solution that contained calcium ions and was buffered at neutral pH. Longer irradiation times increased the growth rate and the number of seed crystals.

A ReaxFF-based molecular dynamics study of the mechanisms of interactions between reactive oxygen plasma species and the Candida albicans cell wall

Atmospheric pressure non-equilibrium plasmas have attracted significant attention and have been widely used to inactivate pathogens, yet the mechanisms underlying the interactions between plasma-generated species and bio-organisms have not been elucidated clearly. In this paper, reactive molecular dynamics simulations are employed to investigate the mechanisms of interactions between reactive oxygen plasma species (O, OH, and O2) and β-1,6-glucan (a model for the C. albicans cell wall) from a microscopic point of view. Our simulations show that O and OH species can break structurally important C-C and C-O bonds, while O2 molecules exhibit only weak, non-bonded interactions with β-1,6-glucan. Hydrogen abstraction from hydroxyl or CH groups occurs first in all bond cleavage mechanisms. This is followed by a cascade of bond cleavage and double bond formation events. These lead to the destruction of the fungal cell wall. O and OH have similar effects related to their bond cleavage mechanisms. Our simulation results provide fundamental insights into the mechanisms underlying the interactions between reactive oxygen plasma species and the fungal cell wall of C. albicans at the atomic level.

Intracellular responses to reactive oxygen and nitrogen species, and lipid peroxidation in apoptotic cells cultivated in plasma-activated medium

A mechanism of the cytotoxicity of plasma-activated medium (PAM) is revealed by examining the intracellular effects of reactive oxygen nitrogen species (RONS) and lipid oxidation. PAM is cell culture medium activated by irradiation using non-equilibrium atmospheric-pressure plasma using pure Ar gas in ambient air. Extracellular RONS in PAM induced the apoptotic death of HeLa cells. Temporal changes in intracellular RONS, such as ONOO−, NO, and O2−, were analyzed. Intracellular RONS generation in HeLa cells following incubation in PAM triggered activation of the caspase cascade pathway and lipid peroxidation of intracellular membranes to induce apoptosis.

Numerical simulation of physicochemical interactions between oxygen atom and phosphatidylcholine due to direct irradiation of atmospheric pressure nonequilibrium plasma to biological membrane with quantum mechanical molecular dynamics

Plasma medicine is one of the most attractive applications using atmospheric pressure nonequilibrium plasma. With respect to direct contact of the discharge plasma with a biological membrane, reactive oxygen species play an important role in induction of medical effects. However, complicated interactions between the plasma radicals and membrane have not been understood well. In the present work, we simulated elemental processes at the first stage of physicochemical interactions between oxygen atom and phosphatidylcholine using the quantum mechanical molecular dynamics code in a general software AMBER. The change in the above processes was classified according to the incident energy of oxygen atom. At an energy of 1 eV, the abstraction of a hydrogen atom and recombination to phosphatidylcholine were simultaneously occurred in chemical attachment of incident oxygen atom. The exothermal energy of the reaction was about 80% of estimated one based on the bond energies of ethane. An oxygen atom over 10 eV separated phosphatidylcholine partially. The behaviour became increasingly similar to physical sputtering. The reaction probability of oxygen atom was remarkably high in comparison with that of hydrogen peroxide. These results suggest that we can uniformly estimate various physicochemical dynamics of reactive oxygen species against membrane lipids.

Plasma-induced flow instabilities in atmospheric pressure plasma jets

Pulsed plasma excitation of rare gases flowing into air has been shown to impact the stability of the flow in non-equilibrium atmospheric pressure plasma jets (APPJs). In this paper, the results from a numerical modeling investigation of the stability of a round He APPJ with a powered electrode exposed to the gas flow are discussed. Localized gas heating at the powered electrode occurs on the time scale of the voltage pulse, tens to 100 ns, which is short compared to the fluid timescales. An acoustic wave propagates from this heated, expanding gas and exits the jet. The wave disturbs the shear layer between the He and surrounding humid air, exciting a shear instability which grows downstream with the flow and increases the mixing of the humid air into the He. The effects of the eddy-dominated flow on ionization wave (IW) propagation in an APPJ were investigated. The IW followed the regions of the highest helium concentration, resulting in an increased production of NO, HO2, and NO2.