A comparison of two cold atmospheric helium plasma devices which utilise the same RF power generator

Cold atmospheric plasma (CAP) is a simple and inexpensive method to produce plasma in ambient air. In this study, CAP was generated by flowing helium gas through a glass tube with a copper electrode rounded externally around it to provide an electric field for gas excitation. The plasma extended for up to a few centimeters from the opening of the tube forming a plume. Optical emission spectroscopy (OES) was used to identify the composition of the plasma along the length of the plume. Four positions along the plume were investigated at flow rates of 1, 1.5, and 2.5 L min−1. Results revealed that the plume consisted of a varying composition of excited state species dependent on the location in the plume and gas flow rate. Identified in the emission spectra were the nitrogen second positive and first negative system along with OH* emissions at 282 and 308 nm. The OH* emissions, found at the opening of the tube, had a higher intensity as the flow rate increased and were attributed to impurities from the ambient air in the source tubing, while the N2 and N2 + emissions came from the nitrogen of the ambient air and dominated the rest of the measured spectra. Identifying the species and their intensities at different locations of the plume with different flow rates helped in determining the appropriate location and flow rate needed for a specific application of the surface treatment of ultra-high-molecular-weight-polyethylene (UHMWPE) to change its roughness. Additional spectra were taken in situ with an UHMWPE sample present to compare the reactive species of a free jet with those when a target was present. Finally, preliminary roughness tests showed increases of as low as three and as much as over ten times the pristine value depending on the position of the polymer in the plume and the source flow rate.

This article provides a concise methodology for the development of a cold atmospheric pressure plasma jet and its characterization. To optimize the plasma jet parameters for biological and industrial applications, it is highly necessary to thoroughly understand its characteristics. The major emphasis of this work is to utilize simple and advanced diagnostics systematically with low complexity in the post-data analysis and to obtain in situ information of plasma jet parameters. The detailed optimization methods and the effect of the applied voltage and gas flow rate to achieve the stable plasma jet of the desired dimensions are discussed. In addition, the effects of the gas flow rate on the discharge current profiles and filament behavior are provided. Moreover, optical techniques, such as optical emission spectroscopy and time-resolved fast imaging, are used for the characterization of plasma parameters, i.e., Texc and ne, in a simple way. The gas temperature along the length of the plasma jet is estimated using a K-type thermocouple. The discussed simple characterization techniques and range of parameters of our designed plasma source will be useful for the development and optimization of plasma jet sources for various biological and industrial applications. Furthermore, we have also discussed various applications where we can use the discoursed diagnostics for the system development as well as for characterization. As the characterization of cold atmospheric pressure plasma jets is a multiphysics study, this concise characterization report on the cold atmospheric pressure plasma aims to provide necessary information for early researchers.

In this work, we apply optical emission spectroscopy to investigate active plasma species to study that plasma nitrogen treatment affects polystyrene surfaces. Data concerning these active plasma species are crucial for exploring the polystyrene layer's functionality deposited on quartz crystal microbalance (QCM) surface. Wettability function in biosensors development is essential aspects for biomolecule immobilization. The surface of the polystyrene layer was modified by plasma nitrogen treatment. The process parameters affecting plasma species and characteristic, and hence the treatment results studied in this work were chamber pressure, flow rate, and DC bias. The plasma analysis was conducted by optical emission spectroscopy. The spectroscopy was utilized to predict the active species of plasma, the electron temperature Te and the electron density Ne. The dominant reactive species was N2+ which go through different plasma interactions and on the polystyrene surface depending on the DC bias voltage, the nitrogen- gas flow rate, and the chamber pressure. The plasma treatment results suggest that the ion bombardment was the dominant mechanism that changes the polystyrene's surface. The plasma behavior and surface interactions were found complex with the variation of the process parameter. Keywords: Electron density, Electron temperature, OES, Nitrogen-plasma treatment, Wettability

Study of a Cold Atmospheric Pressure Plasma jet device for indirect treatment of Squamous Cell Carcinoma

In recent years, research on cold atmospheric plasma has shown good application potential in the field of wastewater treatment. In this study, we designed a micro-porous plasma jet specifically for formaldehyde degradation in wastewater with air as the discharge gas. Electrical diagnosis and optical emission spectroscopy were performed to characterize plasma and identify plasma radicals/species. The mechanism of plasma degradation of formaldehyde was investigated by studying the physicochemical properties of plasma treated solution. The results indicated that the discharge intensity was positively correlated with the voltage. Additionally, the discharge intensity initially increased with the gas flow rate, and then gradually decreased with further increases in the gas flow rate. The spectral intensity was positively correlated with the voltage, and negatively correlated with gas flow. Under the discharge conditions of 8 kV voltage, 1 SLM gas flow, the degradation efficiency was the highest, and the formaldehyde degradation rate after 30 min treatment was 30.2%. Under the synergistic catalysis of plasma/FeSO4/TiO2, the degradation rate could reach 51.84%. Our research indicates that the micro-porous air plasma jet has the potential to be a green and efficient way to degrade formaldehyde in wastewater.

Background: Cold plasma is shown to inhibit the cancer cell growth. Manipulation of different plasma parameters might have influence on the production of major reactive species which leads to killing of the cancer cells. Antiproliferative activity of cold atmospheric pressure plasma jet was investigated on small-cell lung carcinoma BHY cell line (squamous cell carcinoma) under different in vitro conditions. Methods: A homemade plasma jet was designed and created using pure helium gas. To identify the species created by the plasma jet, optical emission spectroscopy (OES) was employed. Next, the effect of plasma jet was examined on lung cancer cell survival by MTT assay and the effects of main parameters were evaluated on plasma performance. In this favor, various treatment times including 60, 90, 120, 180, and 300 s in combination with different voltages of 5, 11, and 14 kV were investigated, and the results were analyzed at 2, 24, and 48 h after exposure to plasma. Results: Predominant species of OES spectra were O, OH, N2+, and N2. Results of MTT assay indicated a dramatic reduction in cell viabilities in both dose- and time-dependent manners, and more than 75% of cancer cells were died after 48 h at 180 s of plasma treatment. Conclusion: The homemade plasma jet can chiefly contribute to the production of reactive oxygen and nitrogen species (reactive oxygen species and reactive nitrogen species) and can induce apoptosis in small-cell lung carcinoma BHY cell line.

Introduction. Cold atmospheric plasma (CAP) has emerged as a promising technology for neutralizing microbes, including multidrug-resistant strains. This study investigates CAP's potential as an alternative to traditional antimicrobial drugs for microbial inactivation.Hypothesis/Gap Statement. In the era of increasing antimicrobial resistance, there is a persistent need for alternative antimicrobial strategies. CAP exerts its effects by generating reactive oxygen and nitrogen species (RONS), but its comparative efficacy against antimicrobial drugs requires further exploration.Aim. To evaluate the antimicrobial efficacy of CAP in inactivating multidrug-resistant Escherichia coli (ATCC BAA-2469), Staphylococcus aureus (MTCC 96) and Candida albicans (MTCC 227) and to compare its effectiveness with standard antimicrobial drugs.Methodology. CAP, produced by an indigenously developed dielectric barrier discharge (DBD) setup comprising a quartz-glass-covered high-voltage electrode and a grounded stainless steel mesh electrode, was used to treat three pathogenic samples with varying treatment times (0-60 s). The zone of inhibition (ZoI; zone where microbes cannot grow) induced by CAP was compared with the ZoI of selected antimicrobial drugs (5-300 mcg). Scanning electron microscopy (SEM) analysed morphological changes, while optical emission spectroscopy (OES) detected RONS generated during treatment. Growth curve analysis assessed CAP's impact on microbial growth, and statistical analysis compared CAP-induced ZoI with drug-induced ZoI.Results. CAP treatment produced substantial ZoI against E. coli, S. aureus and C. albicans, with the largest ZoI (1194±35.35 mm²) in C. albicans after 60 s. DBD-CAP showed equivalent or superior efficacy compared with selected antimicrobial drugs based on ZoI comparisons. SEM revealed extensive cellular damage in all three pathogens, with visible morphological disruption within 60 s. Growth curve analysis showed a significant delay in microbial proliferation with increasing CAP exposure, effectively inhibiting growth over 24 h. OES confirmed the presence of RONS-related molecular bands [N2(C-B), N2 +(B-X) and OH(A-X)] and atomic O lines in the CAP.Conclusion. CAP treatment exhibits equivalent or superior antimicrobial activity compared to selected antimicrobial drugs. CAP treatment exerts effects by inactivating pathogens, disintegrating cellular morphology and delaying microbial growth. These findings highlight CAP as a promising alternative to prolonged treatments, addressing antimicrobial resistance and advancing clinical strategies.

Summary Background The development of antibiotic resistance by microorganisms is an increasing problem in medicine. In chronic wounds, bacterial colonization is associated with impaired healing. Cold atmospheric plasma is an innovative promising tool to deal with these problems. Objectives The 5‐min argon plasma treatment has already demonstrated efficacy in reducing bacterial numbers in chronic infected wounds in vivo. In this study we investigated a 2‐min plasma treatment with the same device and the next‐generation device, to assess safety and reduction in bacterial load, regardless of the kind of bacteria and their resistance level in chronic wounds. Methods Twenty‐four patients with chronic infected wounds were treated in a prospective randomized controlled phase II study with 2 min of cold atmospheric argon plasma every day: 14 with MicroPlaSter alpha device, 10 with MicroPlaSter beta device (next‐generation device) in addition to standard wound care. The patient acted as his/her own control. Bacterial species were detected by standard bacterial swabs and bacterial load by semiquantitative count on nitrocellulose filters. The plasma settings were the same as in the previous phase II study in which wounds were exposed for 5 min to argon plasma. Results Analysis of 70 treatments in 14 patients with the MicroPlaSter alpha device revealed a significant (40%, P < 0·016) reduction in bacterial load in plasma‐treated wounds, regardless of the species of bacteria. Analysis of 137 treatments in 10 patients with the MicroPlaSter beta device showed a highly significant reduction (23·5%, P < 0·008) in bacterial load. No side‐effects occurred and the treatment was well tolerated. Conclusions A 2‐min treatment with either of two cold atmospheric argon plasma devices is a safe, painless and effective technique to decrease the bacterial load in chronic wounds.

Development and characterization of a spark plasma device designed for medical and aesthetic applications

Cold atmospheric plasma (CAP) treatment is a rapidly expanding and emerging technology for cancer treatment. Direct CAP jet irradiation is limited to the skin and it can also be invoked as a supplement therapy during surgery as it only causes cell death in the upper three to five cell layers. However, the current cannulas from which the plasma emanates are too large for intracranial applications. To enhance efficiency and expand the applicability of the CAP method for brain tumors and reduce the gas flow rate and size of the plasma jet, a novel micro-sized CAP device (µCAP) was developed and employed to target glioblastoma tumors in the murine brain. Various plasma diagnostic techniques were applied to evaluate the physics of helium µCAP such as electron density, discharge voltage, and optical emission spectroscopy (OES). The direct and indirect effects of µCAP on glioblastoma (U87MG-RedFluc) cancer cells were investigated in vitro. The results indicate that µCAP generates short- and long-lived species and radicals (i.e., hydroxyl radical (•OH), hydrogen peroxide (H2O2), and nitrite (NO2−), etc.) with increasing tumor cell death in a dose-dependent manner. Translation of these findings to an in vivo setting demonstrates that intracranial µCAP is effective at preventing glioblastoma tumor growth in the mouse brain. The µCAP device can be safely used in mice, resulting in suppression of tumor growth. These initial observations establish the µCAP device as a potentially useful ablative therapy tool in the treatment of glioblastoma.

An atmospheric-pressure plasma jet (APPJ) based on dielectric barrier discharge was manufactured to analyze its discharge characteristics. The APPJ was driven by 50 kHz sinusoidal waveform having peak-to-peak voltage 3–4 kV and He or Ar was used for working gases. In the APPJ system, the active species generated in the plasma such as electrons, ions, and radicals are transported along the flow channel. Thus, the density of these species has a strong spatial dependence because of admixture with air in plasma channel.1 In this study, discharge characteristics were investigated by using optical emission spectroscopy. Different optical emission distributions were observed according to plasma conditions such as working gas, gas flow rate, and input voltage. For Ar plasma, OH and N 2 related emission lines were detected higher than those in He plasma. On the other hand, relatively strong emission lines of N 2 + and O excited species were detected in He plasma case. These results are caused by difference of energy level to generate ions or metastable species in each plasmas. Especially, metastable He atom plays an important role in downstream plasma region. Also, the APPJ was investigated by using axis-symmetry 2D fluid simulation and compared with the experimental results. The effects of working gas-air mixture in the downstream region were modeled with binary diffusion and Navier-Stokes equation.

Summary form only given. The capability of cold atmospheric plasmas to inactivate microorganisms is well established. By comparison, their ability to destruct solid proteins from surgical instruments is much less understood with only a few studies reported. Yet surgical instruments are typically contaminated by both pathogenic microorganisms and infectious protein. In this contribution, we present a systematic study of protein destruction using cold atmospheric pressure helium discharge. Helium-oxygen mixture is preferred as the working gas, because it can reduce the gas temperature near room temperature and as such allow its application to polymer- based instruments. Our study has two components the first being plasma destruction of solid protein deposited on stainless-steel disks as a model of surgical instruments and the second being plasma destruction of three different sets of surgical forceps that have already been autoclaved. A number of characterization techniques are used, including laser- induced fluorescence, scanning-electron microscope, electron energy dispersion X-ray analysis and electrophoresis. The objective of our study is to demonstrate the intrinsic capability of cold atmospheric plasmas to destruct surface proteins and also the benefits and challenges of implementing this technique for medical sterilization. A supplementary study is also presented to study and differentiate possible protein destruction mechanisms using optical emission spectroscopy and protein destruction kinetics and through a series of experiments aimed to differentiate the production of different plasma species. The results from this study suggest that (1) intrinsically cold atmospheric plasmas are capable of both protein destruction and microbial inactivation; (2) the technology can be adapted for decontamination of real surgical instruments: and (3) atomic oxygen and excited nitride oxide are key decontaminating agents.

Progressive incidence and a pessimistic survival rate of breast cancer in women worldwide remains one of the most concerning topics. Progressing research indicates a potentially high effectiveness of use cold atmospheric plasma (CAP) systems. The undoubted advantage seems its simplicity in combination with other anti-cancer modalities. Following observed trend of studies, one inventory CAP system was applied to directly treat human breast cancer cell lines and culturing in two different Plasma Activated Media (PAM) for combined utilization. Proposed CAP treatments on MCF-10 A, MCF-7, and MDA-MB-231 cell lines were studied in terms of impact on cell viability by MTT assay. Disturbances in cell motility following direct and combined CAP application were assessed by scratch test. Finally, the induction of apoptosis and necrosis was verified with annexin V and propidium iodide staining. Reactive species generated during CAP treatment were determined based on optical emission spectrometry analysis along with colorimetric methods to qualitatively assess the NO2−, NO3−, H2O2, and total ROS with free radicals concentration. The most effective approach for CAP utilization was combined treatment, leading to significant disruption in cell viability, motility and mostly apoptosis induction in breast cancer cell lines. Determined CAP dose allows for mild outcome, showing insignificant harm for the non-cancerous MCF-10 A cell line, while the highly aggressive MDA-MB-231 cell line shows the highest sensitivity on proposed CAP treatment. Direct CAP treatment seems to drive the cells into the sensitive state in which the effectiveness of PAM is boosted. Observed anti-cancer response of CAP treatment was mostly triggered by RNS (mostly NO2− ions) and ROS along with free radicals (such as H2O2, OH•, O2-•, 1O2, HO2•). The combined application of one CAP source represent a promising alternative in the development of new and effective modalities for breast cancer treatment.

A helium cold atmospheric pressure plasma jet (HCAPPJ) driven by a commercial neon power supply was designed and utilized for inactivation bacteria. The generated reactive spices by HCAPPJ were investigated by optical emission spectroscopy. The reactive species of OH, OI, OI, N21+, N21+ and He were identified in the UV–Vis wavelength region. The reactive species was not detected between 200 nm and 300 nm, as the flow rate of helium gas increased that led to the plasma temperature reducing to a value near to the room temperature. In this work, we studied the impact of HCAPPJ on Gram-positive and Gram-negative bacteria. The survival amounts of the two types of bacteria were decreased vastly when the rate flow rate was equal to 10 L/min.

Cold atmospheric plasma (CAP) has become a topical research area due to its diverse applications in agriculture, medicine, environment, materials, energy, nanotechnology, and other fields. Plasmas in contact with liquids form marked sensitivity patterns at the interface depending on controlling parameters, including gas species, driving current, gas flow rate, gap length, and electrolyte conductivity. This review overviews basic aspects of plasmas inducing self-organization including computational and experimental studies and potential applications of such plasmas-treated liquids in agriculture and medicine. Representative experimental evidence of self-organized pattern (SOP) in diverse types of plasma discharges is reviewed. Generation and transport of reactive species in SOP plasma and SOP plasma interacting with liquids are introduced and discussed from their potential applications in agriculture and medicine.