Use Of Cold Plasma Research Articles

The use of cold plasma technology in the surface disinfection system

The work is devoted to the presentation of the system analysis results of hierarchical processes of the viral pandemic and development, based on the use of cold plasma, of technical means to counteract viral threats. The main place is occupied by the description of the application of cold plasma technologies for the purpose of viral disinfection and countering the spread of viruses in various environments. The results of practical field experiments are presented

Synergistic effects of an atmospheric pressure plasma jet and pulsed electric field on cells and skin.

Nonthermal atmospheric pressure plasmas produce reactive plasma species including charged particles and reactive oxygen nitrogen species, which are known to induce oxidative stress in living cells in liquid or tissue. In the meantime, pulsed electric fields have been widely used in reversible or irreversible electropermeabilization for either the delivery of plasmid DNA or inactivation of cancer cells. This work discusses the synergistic effects of nanosecond pulsed plasma jets and pulsed electric field on inactivation of pancreatic cancer cells in vitro and enhancement of plasmid DNA delivery to guinea pig skin in vivo. Higher inactivation rates of the cancer cells in suspension were obtained with combined treatment of 300-ns 50 kV/cm pulsed electric field and a 1-min exposure of a nanosecond pulsed, 250-μm plasma jet. Increased efficiency of gene electrotransfer to skin was also observed after a 3-min treatment of a nanosecond pulsed, 1-mm plasma jet. Application of the plasma alone at the same dosage did not have significant effect on gene delivery. These findings signify the dosage-dependent cell-response to both the electric fields and plasma. Importantly, the use of cold plasma to increase the sensitization of the biological cells in response to pulsed electric fields could be an effective approach to enhance the desired effects in electroporation-based applications.

Electrochemical reduction of nitrogen to ammonia: Progress, challenges and future outlook

Ammonia is an important chemical used in the production of fertilizers. The electrochemical nitrogen reduction reaction (NRR) to synthesize ammonia has emerged to be a potential alternative approach. Here, we provide a short opinion of the current progress and challenges of nitrogen reduction reaction from the recent literature. Different types of electrocatalysts with their performances and design principles are briefly outlined. However, most of the electrocatalysts showed unsatisfactory catalytic performance for NRR because of various factors, such as the competing side reactions and the large thermodynamic energy barrier. Hence, the concept of conducting NRR should be re-evaluated. We provide our opinion on the future possible outlook on how to improve the NRR performance. Alternative external energy input should be coupled with the electrochemical reduction of nitrogen to help with the activation of nitrogen to ammonia. Some possible energy input could be the use of cold plasma and surface plasmon resonance.

Cold atmospheric pressure He-plasma jet and plasma ball interactions with the Venus flytrap: Electrophysiology and side effects

Cold atmospheric pressure radio frequency plasma (CAPP) can play an important role in agriculture, medicine, biophysical and bioelectrochemical applications, disinfection and sterilization, synthesis of different compounds, nitrogen fixation, and treatment of surfaces. Here we found that reactive oxygen and nitrogen species, UV–Vis photons, and high-frequency strong electromagnetic fields with an amplitude of a few kV produced by a cold plasma jet can interact with bio-tissue and damage it if the plasma treatment is long enough. The electrophysiological effects of CAPP treatment of bio-tissue and electrical signals transmission were measured in the Venus flytrap. The plasma ball does not produce any visible side effects on the Venus flytrap, but induces electrical signals in bio-tissue with very high amplitude. Plasma (Kirlian) photography shows the existence of a blue aura around the plasma ball due to a corona discharge. Understanding the mechanisms of interactions between CAPP and bio-tissue and preventing side effects can contribute to the application of plasma technology in medicine and agriculture. The use of cold plasma in medicine and agriculture should be monitored for side effects from strong high-frequency electro-magnetic fields, UV photons, and reactive oxygen and nitrogen species to protect against undesirable consequences.

Assessment of quality and safety of pork treated with low-temperature atmospheric-pressure plasma

It is known that processing methods ensuring partial or full microbial inactivation are quite limited. Therefore, it is of great interest to develop technique and technologies allowing the effective action on microorganisms without a significant influence on product properties. The use of cold plasma can be one of the promising methods of meat product treatment by cold sterilization. The present work examines a possibility of chilled meat treatment with low-temperature atmospheric-pressure plasma to increase its stability to microbial spoilage and extend shelf life. To obtain low temperature plasma, the equipment developed by the designing department “Plasmamed” was used. Chilled meat was treated with low-temperature atmospheric-pressure argon plasma for 5, 10, 20 and 30 min. Samples were stored at a temperature of 2–4 °C for 10 days. Organoleptic indices, moisture weight fraction, changes in pH and water activity were analyzed before treatment and during storage. Sanitary microbiological analyses were carried out by the following indicators: quantity of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM), the presence and quantity of coliforms, Salmonella, Escherichia coli, Listeria monocytogenes, Proteus. It was shown that meat cold treatment with argon plasma inhibited the development of mesophilic microorganisms. The colony forming units detected in the samples after ten days of storage were determined by the duration of exposure to plasma. It was proved that meat treatment for 15 and 30 min had the bactericidal effect and facilitated an improvement in meat color during storage. The organoleptic indices of the samples treated with plasma corresponded to the requirements of standards and approved consumer characteristics.

Effect of Cold Plasma on Quality Retention of Fresh-Cut Produce

In recent years, the consumption of the fresh-cut products has been increased due to the consumers’ lifestyle and awareness. However, maintaining the quality and nutritional value of these products during storage is being difficult in comparison to whole fruits and vegetables. In actual, the procedures used in the fresh-cut industry may intensify the deterioration caused by physical damage by minimal processing. Commonly, the quality degradation, discolouration, loss of moisture, loss of firmness, microbial load increase, and loss of nutrients and flavor occur in the fresh-cut product after minimal processing. To maintain the quality and increase the shelf-life of the fresh-cut product, it is necessary to use various techniques, including physical, chemical, and nondestructive processes. In this review, first, an introduction to minimal processing and its effect on fresh-cut product quality was expressed, and then, the methods used to maintain fresh-cut product quality after minimal processing were reviewed. Finally, the effect of cold plasma on the qualitative characteristics in some fresh-cut products was investigated. The review showed that cold plasma treatments can significantly inhibit microorganisms and extend the shelf-life of fresh-cut products. In addition, no or minimal impacts were observed on physicochemical and organoleptic quality attributes of the treated fresh-cut products. Therefore, the use of cold plasma is promising for the fresh-cut industry.

Qualitative changes in hyssop (Hyssopus officinalis L.) as affected by cold plasma, packaging method and storage duration

Certain post-harvest processes of medicinal and aromatic crops (MACs) such as washing, drying, cutting and milling, decontamination, packaging, and warehousing are widely applied in the industry. However, the effects of some of them on the active ingredients have been less thoroughly studied. Changes in the essential oil (EO) content and composition of hyssop leaves were studied under cold plasma treatments (voltage values of 17, 20 and 23 kV for 1, 5 and 10 min), using different packaging methods (packaged with air, nitrogen, and under vacuum) and storage duration (0, 3 and 6 months). All samples were hydro-distilled for EO content evaluation and EO composition was determined by gas chromatography and gas chromatography–mass spectrometry. In addition, color properties and structure of the glandular trichomes were studied. The results showed that cold plasma treatment significantly reduced EO content in comparison to the control, while higher intensities resulted in a greater reduction of EO. There were slight variations of a browning index between cold plasma treated samples, although no specific trend was observed. The trichomes were vulnerable to cold plasma intensity and prolongation. With increasing treatment duration at all intensities of cold plasma, important compounds such as cis-pinocamphone, trans-pinocamphone and β-pinene were reduced. The EO content was decreased with increasing storage time in all packaging methods, which was not significant in the samples packed with nitrogen gas. During the storage period, the amounts of cis and trans-pinocamphone were reduced, but β-pinene content increased. Overall, this study showed that the use of cold plasma as a new disinfection technique can cause changes in hyssop EO, while nitrogen packaging, compared to other methods, was able to preserve both EO content and components during storage.

Cold Plasma Treatment Accelerates Regeneration of the Skin after Mechanical Damage

The results of an experimental study of the cold plasma effect on skin regeneration after mechanical damage of various types are presented. It has been shown that the use of cold plasma accelerates wound healing and significantly reduces inflammatory processes.

Evaluation of DBD Plasma Effects on Barley Seed Germination and Seedling Growth

The experimental results of dielectric barrier discharge (DBD) plasma treatment on barley (Hordeum Valgare L cv. Yusef) seed germination and seedling growth are analyzed and presented. The seeds were exposed to DBD plasma with 40-, 80-, and 120-W powers for 15 s. All treatments showed positive effects on seed germination, seedling growth, and vigor index. The scanning electron microscope (SEM) images and water imbibition evaluations of plasma-treated seeds revealed that the treatments improved water absorption in the seeds. Similar positive improvements were observed for the plasma-treated seeds in the seedling stage. The best germination characteristics were obtained in 80-W DBD plasma, which included an 18.28% increment in total germination percentage, and 13.35%, 66.83%, 38.55%, and 31.93% increment on the seed germination potential, vigor index, shoot height, and root length, respectively. Moreover, the seed germination of the plasma-treated barley was studied after 2, 7, 14, and 30 days of storage, which indicated the desirable effect of plasma over the storage time. It is concluded that the use of cold plasma can significantly improve the germination and seedling growth of barley seeds.

Selective treatments of prostate tumor cells with a cold atmospheric plasma jet

Background: Low temperature plasma is an ionised gas generated at atmospheric pressure with the temperature of heavy particles (ions, molecules, atoms) close to room temperature. Recent progress highlighted the efficiency of plasma to induce cell death in many cancer cell lines. In the current context of the emergence of the use of cold plasma for medical purposes, this article aims to study the effect of a cold plasma of helium on ex-vivo prostate cells.Methods: A cold atmospheric plasma torch was developed to treat different tumor cells. Parameters like electric voltage, gas flow, cell/torch distance, and exposure time were studied to improve the effects of plasma onto two human prostate tumor cells lines, with different metastatic potential, LNCaP and PC3 and then, compared to human prostate epithelial cells P69. The plasma torch operated by a voltage up to 10 kV, without any risk of arcing, exhibited a visible plasma plume up to about 70 mm, with a temperature close to room temperature. The induced temperature rise due to the plasma treatment is measured to ensure that observed results are not thermal effects. After plasma treatment, microscopy and MTT analyses are achieved to measure cells viability. An ordinary one-way ANOVA test were used between two groups with p-value less than 0.05.Results: An optimized protocol leads to the tumor cells death with regard to cell viability. Cold plasma treatment exhibits differential effect, regarding tumor status of cells without any significant influence of thermal effect (temperature increases of only few degrees Celcius above room temperature). The results show that non-tumor cells P69 are less sensitive to cold plasma exposure with a cell viability of 67% after 120 s of treatment, compared to tumor cell lines LNCaP and PC3, respectively at cell viability of 29% and 23% for the same treatment time.Conclusion: The cold helium plasma treatment showed a selective effect on prostate cells, with an enhanced apoptosis way for tumor cells, whereas the healthy cells are more resistant to the treatment. Moreover, during the treatment, the surface temperature rises only few degrees Celcius. This result is very promising for future in-vivo treatments.

Application of non-heating methods for disinfecting vegetable raw materials in the production of food

Possible risks associated with the accumulation and migration of mycotoxins during germination of crops are presented. The presence of an acceptable level of surface microflora of grain can, during germination, intensify the accumulation of mycotoxins, which later migrate into the finished product, making it dangerous for the consumer. It is noted that the process of germination of grain crops cannot be carried out without the stage of disinfection. Promising methods of grain disinfection using non-thermal effects of exposure and the results of our own research are given. It is noted that the concept of food safety in world practice today is aimed at preserving the main food ingredients and their properties. Thermal effects lead to an effective reduction in the development of microorganisms, but at the same time cause significant losses of thermolabile compounds and adversely affect the organoleptic, physicochemical and functional properties of the final product. Ultrasonic exposure, nanosecond electromagnetic pulses and exposure to cold plasma are proposed as disinfecting methods. The methods presented today are widely used in world practice. They allow not only to deactivate molds, but also to destroy the already formed aflatoxins in food products (use of cold plasma). Based on the foregoing, it can be said that the danger of pathogenic microflora ingress and aflatoxin accumulation in food products (especially whole grains) is still present, since even a minimal amount of them can cause global harm to public health, therefore, the search and development of new disinfection methods is an urgent problem modern production.

Dielectric barrier atmospheric cold plasma applied on camu-camu juice processing: Effect of the excitation frequency

The aim of this paper was to evaluate the effect of cold plasma excitation frequency on camu-camu juice processing. Different levels of frequency (200, 420, 583, 698 and 960 Hz) were applied on camu-camu juice to measure the contents of ascorbic acid and anthocyanins, as well as to evaluate the antioxidant compounds (DPPH, ABTS, FRAP and phenolic compounds), peroxidase and polyphenol oxidase enzymatic activity and color. Furthermore, the juice bioaccessibility was evaluated after simulated digestion. The ascorbic acid concentration was increased when higher excitation frequencies were employed, increasing their bioavailability. Anthocyanins, peroxidase and polyphenol oxidase presented considerable degradation with increasing the plasma excitation frequency. For this reason, the juice processing proposed herein represents an alternative to enhance its nutritional quality. Moreover, the use of cold plasma reduced the activity concentration of endogenous enzymes, presenting considerable degradation for higher excitation frequency.

Cold plasma: exploring a new option for management of postharvest fungal pathogens, mycotoxins and insect pests in Australian stored cereal grain

Various strategies are used to reduce postharvest cereal grain contaminants such as insect pests and fungal pathogens. Chemical and physical treatments are common management practices but may leave harmful chemical residues on grains or alter their nutrient content (particularly temperature treatments) and have other limitations. This review explores the recent literature regarding cold plasma, with emphasis on its efficacy for decontamination of postharvest cereal grain from biological contaminants. Cold plasma is an ionised gas containing reactive oxygen and nitrogen species, electrons and free radicals that are lethal to microorganisms and has the potential to decontaminate food surfaces and to increase shelf life. Studies conducted on rice, wheat, corn, barley and oats have demonstrated that cold plasma significantly reduced the amount of fungi, bacteria and their spores on grain surfaces. Cold plasma may also detoxify mycotoxins, and control insect pests. Evidence from various global studies demonstrates the potential use of cold plasma to manage postharvest fungi, mycotoxins and insect pests in Australian stored cereal grain.

NON-THERMAL PLASMA AT ATMOSPHERIC PRESSURE AND ITS OPPORTUNITIES FOR APPLICATIONS

The subject of this review is the low-temperature (or "cold") weakly-ionized but strongly non-equilibrium plasma created at atmospheric pressure in gaseous mixtures or directly in atmospheric air. Cold plasma is rather new, but very perspective object. The strong non-equilibrium of the weakly-ionized plasma leads to that energetic electrons despite their small quantity very effectively excite and dissociate the neutral particles which are contained in surrounding gas, for example, of a molecule of oxygen and water. The pointed above property of cold plasma is valuable from the practical point of view because it allows creating in plasma-forming gas rather intensive ultra-violet radiation and high concentration of physically and biochemically reactive species (metastable atoms and molecules, radicals, ozone, and others) with rather small specific energy consumption. Now the usage of cold plasma at atmospheric pressure gives the opportunity to solve many practical problems which were earlier seeming unsolvable. It is possible even to claim that the approaches based on the use of cold plasma in dense gases define modern progress in many fields of science, biomedicine and, in particular, in the field of chemical technology. The review of modern experimental methods of creation of the cold plasma at atmospheric pressure is given. Physical and chemical features of cold plasma in dense gases have been considered. Special attention is paid to the kinetics of the charged particles in non-equilibrium plasma and the vibrationally excited molecules as well. Additionally, the kinetics of the electronic excited and metastable states is taken into account because they also influence a biochemical activity of low-temperature plasma. A lot of places is given to concrete examples of the modern practical use of such plasma in ecology for the destruction of the low-concentrated harmful organic and inorganic impurities in the exhausted airflows at atmospheric pressure.

Cold plasma as a novel treatment to reduce the in vitro growth and germination of Colletotrichum species

This study investigated the use of cold plasma to reduce the in vitro growth of two postharvest fungal plant pathogens, Colletotrichum alienum and C. fioriniae, isolated from avocados. Cold plasma (CP) was used to treat pure cultures and conidial suspensions of both pathogens, for 180 or 360 s, in either open or sealed environments from varying distances. In an open environment, the 360 s treatment at a distance of 5 cm reduced the colony growth of freshly inoculated cultures to less than 2 mm/day compared to the control of more than 8 mm/day, and treatment of conidial suspensions resulted in almost 100% reduction of conidial germination. In the same environment, the 180 s CP treatment did not significantly reduce the colony growth of fresh or actively growing cultures, but did suppress the germination of conidia by up to 80%. In a sealed environment, the 360 s CP treatment also effectively reduced the growth of freshly inoculated cultures, with no growth for some isolates. Production of reactive oxygen and nitrogen species was observed during treatment, and these may have contributed to the reduction in growth and germination. These results demonstrate the potential of CP for the control of two Colletotrichum species.

Plasma frio: una alternativa para reducir la viabilidad de los conidios de Aspergillus flavus presentes en granos de lenteja

Microbiological food safety is a major issue and the genus Aspergillus is of great interest given the frequency of its toxin contamination in grains. This paper describes the use of cold plasma generated with argon and a mixture of argonnitrogen as a method of sanitizing lentil beans. Lentil beans were sanitized and exposed to Aspergillus flavus conidia then four different experimental sets were prepared, using only argon and a mixture of argon-nitrogen to generate plasma at nitrogen flow rates of 1.2, 0.81 and 0.32 L/min. Each lentil bean was exposed for 5, 10 and 15 min to plasma. Assays were performed in triplicate. Beans not exposed to plasma were used as controls. All plasma treatments caused a lethal effect on A. flavus conidia within exposure periods of 5 to 15 min. The application of argon plasma showed a log10 reduction of 0.81 (84%) after 15 min. The mixture of argon: nitrogen at 0.81 and 0.32 L/min had a higher lethal effect than argon alone. Although lentil beans sterilization was not completely achieved, an important log10 reduction of 1.43 (96.44 %) and 5.53 (99.99 %) of A. flavus conidia was obtained after 15 min of exposure to the plasma generated by argon-nitrogen mixture using nitrogen at flow rates of 0.81 and 0.32 L/min, respectively. Nitrogen flow rate of 0.32 L/min showed a reduction above 3.0 logarithmic units, so this treatment showed a fungicidal activity. The lowest reduction, 0.3 logarithmic units (50.3 %) was observed at a nitrogen flow rate of 1.2 L/min. Additionally, as a consequence of plasma exposure, conidia of A. flavus showed a delay in germination process and also conidia formation was affected. It was concluded that cold plasma could be used as an alternative to sanitize grains and avoid contamination by microorganisms, which cause grain deterioration and affect its nutritional properties.

Cold Plasma Treatment as an Alternative for Ochratoxin a Detoxification and Inhibition of Mycotoxigenic Fungi in Roasted Coffee.

Ochratoxin A (OTA) produced by mycotoxigenic fungi (Aspergillus and Penicillium spp.) is an extremely toxic and carcinogenic metabolite. The use of cold plasma to inhibit toxin-producing microorganisms in coffee could be an important alternative to avoid proliferation of mycotoxigenic fungi. Roasted coffee samples were artificially inoculated with A. westerdijikiae, A. steynii, A. versicolor, and A. niger, and incubated at 27 °C over 21 days for OTA production. Samples were cold plasma treated at 30 W input power and 850 V output voltage with helium at 1.5 L/min flow. OTA production in coffee was analyzed by high performance liquid chromatography coupled to a mass spectrometer (HPLC-MS). After 6 min of treatment with cold plasma, fungi were completely inhibited (4 log reduction). Cold plasma reduces 50% of OTA content after 30 min of treatment. Toxicity was estimated for extracts of artificially contaminated roasted coffee samples using the brine shrimp (Artemia salina) lethality assay. Toxicity for untreated roasted coffee was shown to be “toxic”, while toxicity for cold plasma treated coffee was reduced to “slightly toxic”. These results suggested that cold plasma may be considered as an alternative method for the degradation and reduction of toxin production by mycotoxigenic fungi in the processing of foods and feedstuffs.

Short term atmospheric pressure cold plasma treatment: A novel strategy for enhancing the substrate utilization in a thermophile, Geobacillus sp. strain WSUCF1

The aim of this study was to investigate the effect of atmospheric pressure cold plasma on the microbial substrate utilization and biomass yield in a thermophilic strain. Geobacillus sp. strain WSUCF1, a thermophile capable of producing cellulolytic enzymes with higher activity was used for this investigation. Treatment with cold plasma for 4 min increased the rates of glucose utilization by 74% and biomass yield by 60% when compared with the control. WSUCF1 treated with plasma also displayed enhanced biofilm formation. This study for the first time, reports the use of cold plasma for enhancing the substrate utilization and biofilm formation in a thermophile.

Nrf2 signaling and inflammation are key events in physical plasma-spurred wound healing.

Wound healing is strongly associated with the presence of a balanced content of reactive species in which oxygen-dependent, redox-sensitive signaling represents an essential step in the healing cascade. Numerous studies have demonstrated that cold physical plasma supports wound healing due to its ability to deliver a beneficial mixture of reactive species directly to the cells.Methods: We described a preclinical proof-of-principle-concept of cold plasma use in a dermal, full-thickness wound model in immunocompetent SKH1 mice. Quantitative PCR, Western blot analysis, immunohistochemistry and immunofluorescence were perfomed to evaluate the expression and cellular translocation of essential targets of Nrf2 and p53 signaling as well as immunomodulatory and angiogenetic factors. Apoptosis and proliferation were detected using TUNEL assay and Ki67 staining, respectively. Cytokine levels in serum were measured using bead-based multiplex cytokine analysis. Epidermal keratinocytes and dermal fibroblasts were isolated from mouse skin to perform functional knockdown experiments. Intravital fluorescence analysis was used to illustrate and quantified microvascular features.Results: Plasma exerted significant effects on wound healing in mice, including the promotion of granulation and reepithelialization as a consequence of the migration of skin cells, the balance of antioxidant and inflammatory response, and the early induction of macrophage and neutrophil recruitment to the wound sites. Moreover, through an early and local plasma-induced p53 inhibition with a concomitant stimulation of proliferation, the upregulation of angiogenetic factors, and an increased outgrowth of new vessels, our findings explain why dermal skin repair is accelerated. The cellular redox homeostasis was maintained and cells were defended from damage by a strong modulation of the nuclear E2-related factor (Nrf2) pathway and redox-sensitive p53 signaling.Conclusions: Although acute wound healing is non-problematic, the pathways highlighted that mainly the activation of Nrf2 signaling is a promising strategy for the clinical use of cold plasma in chronic wound healing.

Perspective: The physics, diagnostics, and applications of atmospheric pressure low temperature plasma sources used in plasma medicine

Low temperature plasmas have been used in various plasma processing applications for several decades. But it is only in the last thirty years or so that sources generating such plasmas at atmospheric pressure in reliable and stable ways have become more prevalent. First, in the late 1980s, the dielectric barrier discharge was used to generate relatively large volume diffuse plasmas at atmospheric pressure. Then, in the early 2000s, plasma jets that can launch cold plasma plumes in ambient air were developed. Extensive experimental and modeling work was carried out on both methods and much of the physics governing such sources was elucidated. Starting in the mid-1990s, low temperature plasma discharges have been used as sources of chemically reactive species that can be transported to interact with biological media, cells, and tissues and induce impactful biological effects. However, many of the biochemical pathways whereby plasma affects cells remain not well understood. This situation is changing rather quickly because the field, known today as “plasma medicine,” has experienced exponential growth in the last few years thanks to a global research community that engaged in fundamental and applied research involving the use of cold plasma for the inactivation of bacteria, dental applications, wound healing, and the destruction of cancer cells/tumors. In this perspective, the authors first review the physics as well as the diagnostics of the principal plasma sources used in plasma medicine. Then, brief descriptions of their biomedical applications are presented. To conclude, the authors' personal assessment of the present status and future outlook of the field is given.