Plasma-activated water: generation, origin of reactive species and biological applications

Protein fractions in cow milk inhibit decontamination by cold atmospheric plasma

There is a growing body of research on the infection of cow milk by Prototheca algae, a potential human pathogen. This study presents investigations on plasma treatment to inactivate Prototheca directly in milk. However, microbiological tests revealed a surprisingly high survival rate of Prototheca in milk compared to saline solution treated under the same conditions. This phenomenon appears to be due to presence of proteins that act as scavengers of plasma reactive species, with OH• radicals playing a major role. Studies using MALDI-TOF MS, FTIR, XPS and UV-VIS on a model solution of peptone K (simulating the molecular structure of milk protein fractions) confirmed the high reactivity of peptides with OH• radicals, leading primarily to the substitution of hydrogen atoms with hydroxyl groups and cleavage of peptide chains. The obtained results encourage a broader consideration of proteins' role in plasma treatment processes, including applications in food products and plasma medicine.

Efficacy of oxidative disinfectants, quaternary ammonium compounds and dry heat on the inactivation of Salmonella Enteritidis in different cellular states

The investigation of disinfection methods with different antimicrobial mechanisms is of utmost importance in determining inactivation kinetics pertaining to various cellular states of Salmonella. The present study evaluated the effectiveness of different conventional and novel disinfectants against the inactivation of suspended and desiccated Salmonella enterica Enteritidis FUA1946. A comparative study was conducted to evaluate the efficacy of various disinfection methods, including dry heat, membrane-acting benzalkonium chloride (BAC), conventional oxidizing agents such as peracetic acid (PAA) and hydrogen peroxide (H2O2) in the inactivation of S. Enteritidis. Further, the efficacy of novel oxidizers such as plasma-activated water bubbles (PAWB) and plasma-activated hydrogen peroxide water bubbles (PAHP-WB) was evaluated against the suspended and desiccated S. Enteritidis. The results showed that the disinfectant concentration, treatment temperature, and treatment time significantly affected the susceptibility of the S. Enteritidis to disinfection methods. Compared to the surface-dried cells, the S. Enteritidis suspensions displayed a higher lethality to the tested disinfectants. The results revealed a greater resistance of the air-dried and equilibrated S. Enteritidis on the stainless steel to dry heat, BAC, H2O2, and PAWB. The PAA treatment 40 °C displayed high efficacy against the S. Enteritidis on the stainless steel. This emphasizes the need to incorporate effective disinfection programmes to prevent the spread of S. Enteritidis in dry processing environments. Moreover, conducting a comparative analysis of the diverse cellular states of bacteria is crucial in the context of disinfection of the low-aw food processing industry.

Biological solutions activated by cold plasma at atmospheric pressure: A new therapeutic approach for skin wound healing

Chronic wounds are a major public health problem, and nearly 35 % of them do not heal with conventional treatments. The direct application of cold plasmas at atmospheric pressure, partially ionized gases, is an emerging technology with a range of potential biomedical applications, including the improvement of wound healing. A new method that is easier to implement has been developed: the use of biological solutions exposed to cold plasmas at atmospheric pressure, known as plasma-activated media (PAM). Numerous preclinical studies and in vitro models indicate that PAM treatments facilitate wound healing by promoting the migration of cell types such as keratinocytes, fibroblasts and mesenchymal stem/stromal cells, stimulating angiogenesis, and inhibiting bacterial proliferation, all of which are critical to this vital process. PAM treatments modulate the inflammatory response, induce the expression of growth factors and matrix metalloproteinases, reduce cellular adhesion, promote cytoskeletal modifications and activate several biochemical pathways involved in the wound healing process, possibly through the action of plasma-generated reactive oxygen and nitrogen species. Some studies have shown that PAM may have applications in the treatment of other skin conditions either by reducing the production of pro-inflammatory cytokines or by inducing apoptosis of tumor cells. PAM treatments therefore represent a promising new therapy for the management of dermatological conditions, particularly for chronic skin and mucosal wounds.

FlexiPlasma Microcatheter-Embolic Material (FPM-EM) Platform: A Non-Inflammatory Pyroptosis Strategy for Precision Hepatocellular Carcinoma Therapy

Hepatocellular carcinoma (HCC) remains a global challenge, with conventional locoregional therapies like transarterial chemoembolization (TACE) lacking tumor specificity and promoting metastasis and inflammation. Cold atmospheric plasma (CAP) offers a tumor-selective ablation strategy but suffers from limited tissue penetration. To overcome this, the FlexiPlasma microcatheter (FPM) is developed, integrating flexible non-metallic microtubes and ring-shaped electrodes for precise CAP delivery to deep tumors. The optimized FPM-generated CAP eliminates cytotoxic UV and ozone while inducing tumor-specific pyroptosis via a ROS/Caspase-8/GSDMC pathway. Gasdermin-C (GSDMC) is highly expressed in liver tumors but absent in normal tissues, ensuring selective targeting with minimal inflammation. FPM is combined with embolic material (EM), PPP@CD hydrogel, enhancing injectability, tumor embolization, and sustained drug release. This FPM-EM strategy potentiates antitumor immunity, particularly CD4+ and CD8+ T-cell responses. These findings establish FPM-EM as a safe, effective, and minimally invasive therapy for HCC, revealing a non-inflammatory pyroptosis mechanism and broadening the potential of CAP-based cancer treatments. The FPM-EM combination offers promising new therapeutic options for HCC, addressing the limitations of TACE. Furthermore, the FPM-EM platform can be extended to the interventional therapy of other tumors and adapted to incorporate various drugs and nano-/micro-materials, highlighting the strong potential for future clinical translation.

Plasma-activated water promotes and finely tunes arbuscular mycorrhizal symbiosis in Lotus japonicus

BACKGROUND

Plasma-activated water (PAW) is a recently developed cutting-edge technology that is increasingly gaining interest for its applications in medicine, food industry and agriculture. In plant biology, PAW has been shown to enhance seed germination, plant growth, and plant resilience against biotic and abiotic stresses. Despite increasing knowledge of the beneficial effects exerted by PAW on plants, little information is currently available about how this emerging technology may affect mutualistic plant-microbe interactions in the rhizosphere.

RESULTS

In this work we investigated the impact of irrigation with PAW, generated by a plasma torch, on arbuscular mycorrhizal (AM) symbiosis. Roots of the model legume Lotus japonicus expressing the bioluminescent Ca2+ reporter aequorin responded to treatment with PAW 5' (obtained by 5 min water exposure to plasma) with the immediate induction of cytosolic and nuclear Ca2+ signals, indicating that Ca2+-mediated signalling is one of the earliest cellular responses to PAW. The long-lasting elevations in intracellular Ca2+ levels were not found to alter cell viability. Quantitative analyses of AM fungal accommodation in the host plant roots along with phosphate accumulation in leaves, as well as chemical analysis of N, C, S in shoots, showed that treatments with PAW play a modulatory role on plant AM symbiotic performance, in a manner dependent on the time interval of water exposure to the plasma and on the duration of plant treatment with PAW. In particular, irrigation with PAW 5' increased fungal colonization after 4 weeks, leading to a significant increase in leaf phosphate content after 7 weeks.

CONCLUSIONS

Our findings reveal that PAW enhances AM symbiosis by facilitating early fungal accommodation in roots and subsequently increasing phosphate content in leaves at later stages. A better understanding of the mechanisms underlying the effects of PAW on the plant microbiome may drive research towards a fine-tuning of this novel green technology to maximize its beneficial effects in the context of a more sustainable agriculture.

Mechanism of plasma-activated water on the regulation of storage quality of fresh-cut carrots and activation of its antioxidant defence system

This study investigated the impact of plasma-activated water (PAW) on the storage quality of fresh-cut carrots (FCC). The findings revealed that PAW treatment, particularly the 3-min immersion method, led to a substantial enhancement in the quality of the stored carrots. Specifically, the PAW-3 min group decreased by 20.08 %, 55.34 %, and 52.66 % in L*, a*, and b* values respectively (comparing storage days 7 d to 0 d). Notably, the PAW-3 min group demonstrated the least decrease in brightness and exhibited superior yellow color retention compared to the other treatment groups. Concerning weight, a 4.86 % decrease was observed in the PW group from day 0 to day 7 of storage, while the PAW-5 min group exhibited a 2.06 % decrease, suggesting that prolonging the PAW treatment time enhances the retention of sample weight. With regard to hardness, the PAW-3 min group exhibited the least weight loss of 4.62 % among all the treatment groups. The H2O2, a reactive oxygen content, increased from 6.22 ± 0.26 μmol/g to 10.55 ± 0.13 μmol/g with the extension of PAW treatment time, achieving an enzyme inhibition of browning, thus controlling water evaporation and microbial activity. The study demonstrated that PAW ensured uniform water distribution, activated the antioxidant system, and promoted phenolic compound synthesis. It was determined that extended treatment times resulted in cellular damage, and that shorter PAW treatment times (1 to 3 min) were optimal. The findings of this study suggest that this non-chemical method is effective in extending the shelf-life of FCC.

Characteristics of chemical products under the NOx mode of dielectric barrier discharge: comprehensive effects of specific energy input and magnetic field

The reactive nitrogen species generated under the NOx mode of dielectric barrier discharge have attracted widespread attention in biomedical applications, with the crucial factor for their utilization being the regulation of the species proportion. In this work, we investigated the variation of NOx mode products in an AC-driven coaxial dielectric barrier discharge system under different specific energy inputs (SEIs) controlled by voltages and gas flow rates in the presence and absence of a magnetic field as a method for combinatorial multiparameter regulation. Our findings demonstrated that the effect of SEIs on products was closely related to the discharge conditions. Under constant conditions, increasing the SEI led to the promotion of NO and N2O, suppression of NO2, and stabilization of ONOO-. When the SEI was varied by adjusting the voltage, the product trend followed the same pattern as described above. However, when the SEI was varied by adjusting the gas flow rate, the product trend appeared to differ. As the gas flow rate increased, the discharge power remained almost unchanged, while the SEI decreased significantly, leading to the suppression of NO, N2O, NO2, and ONOO- production. The magnetic field did not significantly alter the SEI, but it affected the products. Introducing a 0.2 T magnetic field under constant conditions promoted the production of NO while suppressing N2O, NO2 and ONOO- formation. To understand the microscopic physicochemical mechanisms of product variations under multiple discharge parameters, we analyzed the chemical reaction network, presenting an overview of the effects of multiparameters on the generation of reactive nitrogen species. These insights hold significant value for plasma applications within the realm of biomedicine, where the regulated generation of reactive nitrogen species is pivotal in attaining the desired plasma performance.

Microbial decontamination of fresh-cut celery using simultaneous ultrasound and plasma-activated water treatment

This study investigated an ultrasound (US) treatment strategy in plasma-activated water (PAW) (UP treatment) to inactivate indigenous aerobic bacteria, Escherichia coli O157:H7, and Listeria monocytogenes in fresh-cut celery. Both plasma discharge and US treatment times contributed to the inactivation of indigenous bacteria in celery. The predicted optimal UP treatment conditions included a discharge time of 61.5 min and treatment time of 338 s, resulting in the inactivation of indigenous bacteria, E. coli O157:H7, and L. monocytogenes by 2.7, 1.7, and 3.2 log CFU/g, respectively. With an increase in plasma discharge time or US treatment time, the oxidation-reduction potential and electrical conductivity values of PAW increased, while the pH decreased. UP treatment effectively inactivated bacteria non-thermally, without altering the color of celery. Furthermore, UP treatment led to an increase in cell lipid peroxidation, reactive oxygen species production, and the number of non-viable E. coli O157:H7 and L. monocytogenes cells with membrane damage. This study highlights the potential of UP treatment for bacterial decontamination of fresh-cut celery.

Cold Plasma-A Sustainable Energy-Efficient Low-Carbon Food Processing Technology: Physicochemical Characteristics, Microbial Inactivation, and Industrial Applications

Nonthermal technologies, mostly utilized for microbial inactivation and quality preservation in food, are attracting increased interest, particularly in nonthermal plasma. Cold plasma (CP) demonstrates favorable results, such as increased germination, enhanced functional and rheological characteristics, and the eradication of microorganisms. Consequently, CP is a novel technology in food processing that has significantly contributed to the prevention of food spoilage. This study highlights contemporary research on CP technology in food processing. This includes its use in microbial decontamination, shelf life extension, mycotoxin degradation, enzyme inactivation, and surface modification of food products. The CP generation techniques under low pressure, including glow discharge, radio frequency and microwave techniques, and atmospheric pressure, including dielectric barrier discharge (DBD), plasma jet, and corona discharge, are discussed. Additionally, the source for the generation of plasma-activated water (PAW) with its significant role in food processing is critically discussed. The CP is an effective method for the decontamination of several food materials like fruits, vegetables, meat, and low-moisture food products. Also, the review addressed the effects of CP on the physicochemical properties of foods and CP for pretreatment in various aspects of food processing, including drying of food, extraction of bioactive compounds, and oil hydrogenation. CP improved the drying kinetics of food, resulting in reduced processing time and improved product quality. Similarly, CP is effective in maintaining food safety and quality, removing the formation of biofilm, and also in reducing protein allergenicity. The review also underscored the importance of CP as a sterilizing agent for food packaging materials, emphasizing its role in enhancing the barrier characteristics of biopolymer-based food packaging materials. Therefore, it is concluded that CP is effective in the reduction of pathogenic microorganisms from food products. Moreover, it is effective in maintaining the nutritional and sensory properties of food products. Overall, it is effective for application in all aspects of food processing. There is a critical need for ongoing research on upscaling for commercial purposes.

Plasma-activated saline hyperthermic perfusion-induced pyroptosis boosts peritoneal carcinomatosis immunotherapy

Peritoneal carcinomatosis (PC) is a common metastatic cancer with limited treatment options. Herein, we present a novel strategy for the combined treatment of PC involving plasma-activated saline (PAS) and hyperthermic intraperitoneal perfusion. PAS revealed a strong cytotoxic effect because of reactive oxygen species (ROS) in two-dimensional cultures and three-dimensional tumor spheroids of PC-related cell lines. Notably, PAS induced Gasdermin E (GSDME)-dependent pyroptosis and immunogenic cell death in vitro. PAS-enhanced hyperthermic intraperitoneal perfusion (PE-HIP) increased the number of CD3+, CD4+ and CD8+ T cells, while decreased the number of regulatory T cells, indicating that PAS stimulated T cell-based immune responses in vivo. Moreover, PE-HIP significantly inhibited tumor growth and improved survival in a PC-mice model, with no significant toxic side effects. Meanwhile, vaccination with PAS-induced cell pyroptosis activated systemic antitumor immunity to prevent subcutaneous tumor growth. Overall, PE-HIP can serve as a new approach for PC treatment by ROS-assisted cancer immunotherapy.

Process Technologies for Disinfection of Food-Contact Surfaces in the Dry Food Industry: A Review

The survival characteristics of bacterial pathogens, including Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, and Escherichia coli, in foods with a low water activity (aw) have been extensively examined and reported. Microbial attachment on the food-contact surfaces can result in cross-contamination and compromise the safety of low-aw foods. The bactericidal potential of various conventional and novel disinfection technologies has been explored in the dry food industry. However, the attachment behavior of bacterial pathogens to food-contact surfaces in low-aw conditions and their subsequent response to the cleaning and disinfection practices requires further elucidation. The review summarizes the elements that influence disinfection, such as the presence of organic residues, persistent strains, and the possibility of microbial biotransfer. This review explores in detail the selected dry disinfection technologies, including superheated steam, fumigation, alcohol-based disinfectants, UV radiation, and cold plasma, that can be used in the dry food industry. The review also highlights the use of several wet disinfection technologies employing chemical antimicrobial agents against surface-dried microorganisms on food-contact surfaces. In addition, the disinfection efficacy of conventional and novel technologies against surface-dried microorganisms on food-contact surfaces, as well as their advantages and disadvantages and underlying mechanisms, are discussed. Dry food processing facilities should implement stringent disinfection procedures to ensure food safety. Environmental monitoring procedures and management techniques are essential to prevent adhesion and allow the subsequent inactivation of microorganisms.

Using plasma-activated water for decontamination of Salmonella spp. on common building surfaces in poultry houses

Plasma-activated water (PAW) has been shown to have antimicrobial properties, making it a promising tool for surface decontamination. This study evaluated the ability of PAW generated from high voltage atmospheric cold plasma to remove Salmonella from common surfaces (stainless steel (SS), polyvinyl chloride (PVC), concrete, and wood) found in poultry houses. PAW was generated by exposing distilled water to atmospheric cold plasma in 80% humid air at 90 kV and 60 Hz for 30 min. The resulting PAW contained 1120 ppm of nitrate and 1370 ppm of hydrogen peroxide, with a pH of 1.83. PAW was then applied to coupons of SS, PVC, wood, and concrete surfaces inoculated with 7-8 log10 CFU of cocktail of Salmonella spp. (S. Typhimurium, S. Newport, S. Montevideo, and S. Enteritidis). PAW effectively reduced Salmonella levels on SS and PVC surfaces to below the detection limit within 30 s. On wood surfaces, a longer treatment time of 7.5 min was required to achieve a maximum reduction of 2.63 log10 CFU, likely due to the porosity of the wood limiting PAW contact with the bacteria. On concrete surfaces, the reduction in Salmonella levels was only 0.98 log10 CFU. This was likely due to the greater surface roughness and high alkalinity, which neutralized the PAW species.

Elucidating the synergistic effects of aeration and non-thermal plasma on the degradation pathways of specific pollutants in wastewater

Organic pollutants originating from industrial discharges pose significant threats to human health and ecological balance. Conventional pretreatment methods face challenges due to high costs, limited efficiency, and the generation of residual sludge. Non-thermal plasma (NTP) technology, a promising advanced oxidation process, has attracted substantial research interest for its potential to rapidly and effectively treat industrial wastewater. This study employed a dielectric barrier discharge (DBD) reactor to investigate the feasibility of low-cost, efficient industrial wastewater treatment through NTP-mediated pollutant degradation. NTP generates reactive oxygen and nitrogen species (RONS), capable of complete organic pollutant oxidation. Wastewater samples from Kaveh Industrial City underwent treatment in a DBD reactor to induce the formation of reactive agents. Water quality parameters, including turbidity, total dissolved solids (TDS), total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), dissolved oxygen (DO), electrical conductivity (EC), and pH, were measured before and after synergetic plasma treatment. The combination of aeration/filtration and 90 min of plasma treatment significantly reduced turbidity compared to untreated wastewater. A 30-min NTP treatment coupled with aeration/filtration demonstrated superior efficiency in removing TDS and TSS, attributed to NTP-generated active species. Optimal COD and BOD5 removal was achieved through a 24-h aeration, adsorbent filtration, and 30-min NTP process. While standalone 30-min NTP treatment exhibited lower efficiency, the combined aeration/filtration system reduced EC and increased pH with extended plasma exposure. A comparative study of advanced oxidation processes showed that plasma treatment effectively reduced COD by 65 %. Plasma offers a cost-effective and efficient solution for wastewater treatment, despite slightly higher energy consumption. These findings underscore the potential of NTP as a viable strategy for industrial wastewater treatment. The integration of NTP with conventional pretreatment methods offers promising prospects for enhancing wastewater quality and environmental protection.

Physicochemical properties of plasma-activated water and associated antimicrobial activity against fungi and bacteria

Plasma-activated water (PAW), generated through Surface Dielectric Barrier Discharge, was tested against microbial contaminants. We assessed how the time of exposure to plasma treatment and the gas flow rate impact the chemical composition of PAW, and, in turn, how it influences these factors influence its efficacy against microorganisms. The effectiveness of PAW treatments was evaluated against the fungal phytopathogen Botrytis cinerea and both pathogenic (Xanthomonas campestris pv. vesicatoria) and beneficial (Bacillus amyloliquefaciens) bacteria. The physicochemical properties of PAW were assessed as the concentration of reactive species, namely, NO3- and NO2- and H2O2, pH, and oxidation-reduction potential. Higher levels of reactive species and lower pH during longer treatments were associated with greater antimicrobial efficacy. A correlation study and Principal Component Analysis demonstrated that the RONS content in PAW affected antimicrobial activity, with stronger correlations between NO2-, H2O2, and fungal inhibition, as well as between NO2- and bacterial inhibition. Almost complete inhibition was reached after 1 min of treatment for bacteria (log reduction of 4.5 for B. amyloliquefaciens and 5.1 for X. campestris) and after 3 min of treatment for B. cinerea (approximately 90% inhibition of conidial germination). The obtained results contribute to defining optimized treatment conditions using PAW for antimicrobial decontamination of plant products.

Antibacterial mechanism of atmospheric cold plasma against Pseudomonas fluorescens and Pseudomonas putida and its preservation application on in-packaged red shrimp paste

This study aimed to investigate the antibacterial mechanism of atmospheric cold plasma (ACP) against Pseudomonas fluorescens and Pseudomonas putida and its preservation effect on red shrimp paste. A reactive species (RS) assay showed that O3, H2O2, and total nitric oxide were generated after ACP treatment, which possessed great potential for antibacterial and food preservation. In vitro antibacterial results showed that excess RS inhibited bacterial activity through cell membrane damage. Molecular docking predictions and enzyme activity assays indicated that ACP-induced RS might deactivate dehydrogenases (such as malic dehydrogenase) by oxidatively modifying the active sites. Fluorescence quantification experiments validated the damage of RS to dsDNA. Further preservation tests on shrimp paste demonstrated that ACP treatment significantly delayed the increase in total viable count, Pseudomonas count, and total volatile basic‑nitrogen during refrigeration. This study deepened the understanding of the antibacterial mechanism of ACP and highlighted its potential application as a new preservation method.

Vacuum ultraviolet radiation from gaseous plasma for destruction of water contaminants

Innovative technological solutions are needed for water decontamination to combat the diverse pollutants present in water systems, as no single optimal decontamination technique is appropriate for all circumstances. Vacuum-ultraviolet (V-UV) radiation is a source of energetic photons that break molecular bonds, producing a plethora of chemically reactive agents, most notably OH● radicals, which can cause the degradation of harmful pollutants. Low-pressure gaseous plasma is a good source of V-UV radiation; however, its application to liquid water poses challenges. We constructed an inductively coupled radiofrequency plasma to produce high-intensity V-UV radiation, which was applied to contaminated water via a V-UV-transparent window. Plasma was sustained in hydrogen, as it produces the highest V-UV intensity among all gases at selected discharge parameters. Bacteriophage MS2 was used as an indicator of microbial decontamination efficiency. Reactive oxygen and nitrogen species were measured at various treatment setups to quantify their effect on MS2 inactivation and elucidate the primary inactivation factors. At optimal conditions, the concentration of active virus dropped by 9 log10 PFU/mL in 60 s. The optimal experimental setup was then used to treat bacteria E. coli, S. aureus, antibiotic tetracycline, and synthetic dye methylene blue as representatives of other types of pollutants, all of which were effectively removed/degraded within 10 min of treatment. A comparison of energy efficiency (EEO) to other disinfection setups was made for bacteriophage inactivation. With a low EEO value, we showcase the potential of this technique for further work in this field.

Plasma-Activated Water Improve Wound Healing in Diabetic Rats by Influencing the Inflammatory and Remodelling Phase

Diabetic foot ulcers have an enormous impact on patients' quality of life and represent a major economic burden. The cause is delayed and incomplete wound healing due to hyperglycemia, reduced blood flow, infections, oxidative stress and chronic inflammation. Plasma-activated water (PAW) is emerging as a new therapeutic approach in wound treatment, as it has many of the advantages of cold atmospheric plasma but is easier to apply, thus allowing for widespread use. The aim of this study was to investigate the potential of PAW to improve wound healing in diabetic rats, with a focus on uncovering the underlying mechanisms. Two full-thickness wounds in control and diabetic animals were treated with PAW, and healing was monitored for 15 days at five time points. PAW improved wound healing in diabetic rats and mainly affected the inflammatory phase of wound healing. Application of PAW decreased the number of inflammatory cells, myeloperoxidase (MPO) and N-acetyl-b-D-glycosaminidase (NAG) activity, as well as the mRNA expression of proinflammatory genes in diabetic rats. Ten days after injury, PAW treatment increased collagen deposition in the diabetic animals by almost 10% without affecting collagen mRNA expression, and this is in correlation with a decrease in the Mmp-9/Timp-1 ratio. In conclusion, PAW treatment affects wound healing by reducing the inflammatory response and influencing extracellular matrix turnover, suggesting that it has great potential to accelerate the healing of diabetic wounds.

Kinetic processes of interfacial transport of reactive species across plasma-water interfaces: the effect of temperature

This work quantifies, through use of molecular dynamics (MD) simulations, the kinetic rates of physical surface processes occurring at a plasma-water interface. The probabilities of adsorption, absorption, desorption and scattering were computed for O3, N2O, NO2, NO, OH, H2O2, HNO2, HNO3, and N2O5 as they interact with the interface at three water temperatures: 298 K, 323 K, and 348 K. Species are categorised into the short-residence group (O3, N2O, NO2, and NO) and the long-residence group (OH, H2O2, HNO2, HNO3, and N2O5) based on their mean surface residence time. It is reported that the most probable process for the short-residence group is desorption, which limits their characteristic residence time at the interface to less than 100 ps, while the long-residence species experience a mixture of absorption and desorption, with a characteristic residence time exceeding 200 ps for many species in this group. With increasing water temperature, a universal decline in characteristic surface residence time is observed. It is found that the short-residence group experience a reduction in probability of desorption in favour of scattering, whereas the long-residence group experience a reduction in probability of adsorption in favour of absorption and desorption. The data reported in this work facilitate the development of a basic surface kinetic model, which was used to find that tuning the plasma toward the production of HNO3 will result in an increase in the rate of uptake of reactive nitrogen species by a factor of 250%.

Enhanced Anticancer Efficacy of Alkaline Plasma-Activated Water through Augmented RONS Production

Despite notable advances in anticancer drug development, their manufacture and use pose environmental and health risks due to toxic byproducts, drug residue contamination, and cytotoxicity to normal cells. Therefore, developing cost-effective anticancer treatments with fewer toxic side effects and higher selectivity is essential to the advancement of highly effective anticancer therapies. Plasma-activated water (PAW) offers a green alternative to conventional chemical treatments as it reverts to water within days. However, the limited duration and dose of reactive oxygen and nitrogen species (RONS) in acidified PAW restrict its clinical deployment and the full understanding of their mechanism. In this study, we propose alkaline PAW as an innovative enhancement of the RONS technology. The alkaline PAW generated markedly superior RONS, with about 10 times higher levels of NO2-, H2O2, and ONOO-/O2•- than acidic PAW. The possible RONS generation pathways in alkaline PAW are analyzed by scavengers. In conventional acidic PAW, 70% of the H2O2 concentration is contributed by •OH but only about 20% in alkaline PAW. ONOO- is mainly formed through the reaction of O2•- with NO in alkaline pH, while in acidic PAW, it mainly forms from NO2- and H2O2. The results unveiled the synergistic and formidable anticancer effects of alkaline PAW against cancer cells, typified by an increase in intracellular ROS/RNS levels. Furthermore, alkaline PAW injection also effectively prevented xenograft tumor growth in mice. We systematically investigated this high-dose anticancer solution without using noble gases, toxic reagents, or extra energy consumption and successfully demonstrated the possibility of alkaline PAW being an effective and environmentally friendly therapeutic technology. The activity is closely linked to the RONS dose, and the generation pathway provides much-needed insight into the fundamental aspects of PAW chemistry required for the optimization of the biochemical activity of PAW.

Enhancing the efficacy of low doses of N-acetyl-L-cysteine in mitigating CCl4-induced hepatotoxicity in animal model using physical cold plasma

Liver diseases have become widespread especially due to various factors of modern life. Although the effect of N-acetyl-L-cysteine (NAC) is investigated in the recovery of liver damage, gas plasma therapy can be identified as a promising candidate. Our study aimed to enhance the effectiveness of ineffective doses of NAC in stopping CCl4-induced hepatotoxicity in rats by physical cold plasma. The plasma-treated NAC (PTN) structural changes were investigated through FTIR and LCMS/MS analysis. It was observed that the PTN consists of various chemical bioproducts with different molecular weights. We investigated an ineffective dose of NAC and its parallel effect through the administration of PTN on liver and kidney morphology and several biochemical factors including ALT, AST, and ALP. Additionally, we examined oxidative stress, antioxidant parameters, and glutathione (GSH) levels. Results showed that PTN exhibited greater antioxidant properties and increased GSH levels, contributing to its therapeutic effects. Also, the antioxidant enzymes and oxidative stress activities improved after receiving PTN. It also enhanced histological parameters, although various damages were detected in both liver and kidney tissues after CCl4 injection, PTN remarkably prevented the tissue changes caused by CCl4. PTN could protect against liver damage even at a very low dose of NAC, acting as a prophylactic drug with a high margin of safety for hepatotoxicity.

“Production and Chemical Composition of Plasma Activated Water: A Systematic Review and Meta‐Analysis”

The physio‐chemical interplay between cold atmospheric plasma (CAP) and water confers unique chemical and biological properties to the liquid, producing plasma‐activated water (PAW). This review systematically examines various methodologies for PAW production, focusing on the effects of process parameters on reactive oxygen and nitrogen species (RONS) concentration and pH levels in PAW. It presents detailed analyses of CAP sources, working gases, and treatment conditions, showcasing their impact on PAW processes. The extracted data are reprocessed to derive parameters such as mean energy density and RONS production efficiency. Specific plasma‐water configurations exhibit notably higher production rates, indicating promising opportunities for advancing PAW generation techniques and enhancing its applicability in various fields.

Secondary activation on plasma-activated water by plasma-treated cotton for restoring and enhancing disinfection effect

Plasma-activated water (PAW) is a novel antimicrobial agent with negligible toxicity and environmental burden, holding promise as an alternative to chemical disinfectants and antibiotics. In practice, liquid disinfectants are often soaked with cotton materials before further use. Rich in reducing functional groups on the surface, cotton will inevitably react with PAW, leading to the deterioration of PAW's functions. To resolve this issue, this work proposes a new concept of "secondary activation" for retaining and enhancing PAW's bioactivity, i.e., pre-treating cotton with air plasma before soaking PAW. For the first time, we find that the PAW absorbed by raw cotton completely loses its bactericidal effect, while plasma-treated cotton (PTC) restores the disinfection capacity and prolongs its effective duration. This restoration is attributed to the absorption of plasma-generated reactive species by cotton with oxidizing and nitrifying modifications on the fiber surface. Consequently, the concentrations of aqueous species in PAW increase rather than decrease after absorption by PTC. In addition, the PTC after 28-day storage can still enable PAW to achieve a bacterial reduction of ∼3 logs. This work identifies and addresses a crucial limitation in the disinfection application of PAW and elucidates the mechanism underlying PTC production and secondary activation of PAW.

Neurobehavioral toxicity of Cold plasma activated water following oral gavage in mice

Cold plasma-activated water (PAW) is a novel technology that was recently used in biomedical research; Despite its potential, PAW's safety remains inadequately assessed. The study explores the impact of PAW on behavioral responses and brain tissue histopathology in mice. Ten-week-old female albino mice were divided into three groups each containing 10 mice (5 replicates, 2 mice/cage) and received either distilled water (DW), or distilled water exposed to cold atmospheric plasma (CAP) for 3 min (PAW-3), or 15 min (PAW-15) by oral gavage in a dose of 200 μL/mice (3 times/week) for four weeks. PAW exhibited altered physicochemical properties compared to DW. Mice exposed to PAW demonstrated reduced burrowing activity, marble burying ability, and novel object recognition compared to controls, indicating potential neurobehavioral alterations. PAW-treated groups displayed notable histological lesions in brain tissues, including nerve cell necrosis, vascular congestion, and Purkinje cell degeneration, confirming neurotoxic effects. Positive reactions for NF-κB and iNOS in brain tissues of PAW-treated mice corroborated the histopathological findings, suggesting neuroinflammation and oxidative stress. The study highlights the need for further investigation into PAW's safety profile and optimal treatment protocols to mitigate potential neurobehavioral toxicity in biomedical research.

Effect of Plasma-Activated Water (PAW) Generated Using Non-Thermal Atmospheric Plasma on Phytopathogenic Bacteria

Plasma-activated water (PAW) exhibits potent antimicrobial properties attributed to the generation of diverse reactive oxygen and nitrogen species. This study assessed the effectiveness of PAW in vitro against phytopathogenic Xanthomonas arboricola and Pseudomonas syringae pv. syringae, which cause diseases on ornamental plants. Extending the plasma activation time of water and the incubation time of bacterial suspension in PAW increased the effectiveness of PAW. Treatments consisting of PAW activation using a power output of 200 W and a frequency of 50 Hz at different activation times and target population incubation times revealed significantly different effectiveness against P. syringae pv. syringae and X. arboricola. X. arboricola (reduction of 4.946 ± 0.20 log10 CFU/ml) was more sensitive to PAW inactivation than P. syringae pv. syringae (reduction of 3 ± 0.15 log10 CFU/ml). The plasma activation of water for 20 min followed by incubation of bacterial population for 180 min was proven to be the most effective treatment combination. The plasma activation time dose required to reduce the population by 90% was 7.47 ± 1.09 min for P. syringae pv. syringae and 4.45 ± 1.81 min for X. arboricola incubated for 180 min in PAW. The results of this study have the potential to further contribute to assessment of the effects of PAW on pathogen-infected plant tissues. In addition, the findings of this study could aid in further characterization of the reactive species formed during the plasma activation of water.

Essentials and Pertinence of Cold Plasma in Essential Oils, Metal-Organic Frameworks and Agriculture

Cold atmospheric pressure plasma (CAPP) comprises an ensemble of ionized gas, neutral particles, and/or reactive species. Electricity is frequently used to produce CAPP via a variety of techniques, including plasma jets, corona discharges, dielectric barrier discharges, and glow discharges. The type and flow rates of the carrier gas(es), temperature, pressure, and vacuum can all be altered to control the desired properties of the CAPP. Since a few decades ago, CAPP has become a widely used technology with applications in every walk of life. The plasma activated liquid mediums like water, ethanol, and methanol have been merged as novel sterilizers. With recent advancements in material science, particularly work on metal-organic frameworks (MOFs), essential oils, and agricultural technologies, CAPP has become a vital component of these advancements. Likewise, CAPP has been found as a green and benign technology to induce early seed germination and plant development. This review covers the critical components of CAPP, the production of reactive oxygen and nitrogen species, and mechanisms by which CAPP-based technologies are applied to agricultural products, MOFs, and essential oils.

Off-site production of plasma-activated water for efficient disinfection: The crucial role of high valence NOx and new chemical pathways

Efficient disinfection of pathogens is a critical concern for environmental disinfection and clinical anti-infective treatment. Plasma-activated water (PAW) is a promising alternative to chemical disinfectants and antibiotics for its strong disinfection ability and not inducing any acute toxicity. Previous plasma sources are commonly placed near or fully in contact with water as possible for more efficient activation, but the risk of electrode corrosion and metal particle contamination of water threatens the safety and stability of PAW. In this work, plasma-activated gas (PAG) rich in high-valence NOx is generated by a hybrid plasma configuration and introduced into water for off-site PAW production. It is found that plasma-generated O3 dominates the gas-phase reactions for the formation of high-valence NOx. With the time-evolution of O3 concentration, the gaseous NO3 radicals are produced behind N2O5 formation, but will be decomposed before N2O5 quenching. By decoupling the roles of gaseous NO3, N2O5, and O3 in the water activation, results show that short-lived aqueous species induced by gaseous NO3 radicals play the most crucial role in PAW disinfection, and the acidic environment induced by N2O5 is also beneficial for microbial inactivation. Moreover, SEM photographs and biomacromolecule leakage assays demonstrate that PAW disrupts the cell membranes of bacteria and thus achieves inactivation. In real-life applications, an integrated device for off-site PAW production with a yield of 2 L/h and a bactericidal efficiency of >99.9 % is developed. The PAW of 50 mL produced in 3 min using this device is more effective in disinfection than 0.5 % NaClO and 3 % H2O2 with the same bacterial contact time. Overall, this work provides new avenues for efficient PAW production and deepens insights into the fundamental chemical processes that govern the reactive chemistry in PAW for environmental and biomedical applications.

Therapeutic potential of plasma-treated solutions in atopic dermatitis

Atopic Dermatitis (AD) is a prevalent inflammatory skin disease that is currently incurable. Plasma-treated solutions (PTS) (e.g., culture media, water, or normal saline, previously exposed to plasma) are being studied as novel therapy. Recently, PTS is gaining attention due to its advantages over non-thermal plasma (also known as cold atmospheric plasma). Thus, we explore the application of PTS in treating AD. In vivo experiments demonstrated that PTS significantly alleviated AD-like symptoms. It reduced mast cell and macrophage infiltration, decreased scratching times and serum IgE levels. These therapeutic effects of PTS on AD mice were associated with the activation of the antioxidant molecule Nrf2. In vitro experiments revealed that PTS could decrease ROS level and regulate cytokine expression (such as IL-6, IL-10, IL-13 and CCL17) in TNF-α/IFN-γ-stimulated keratinocytes and LPS-stimulated M1 macrophages. Additionally, PTS could upregulate the expression of antioxidant stress molecules such as Nrf2, HO-1, NQO1 and PPAR-γ in both cell types. Overall, PTS demonstrated potent therapeutic potential for AD without notable side effects. Our research provided a promising approach to AD treatment and may serve as a potential therapeutic strategy in other inflammatory skin diseases.

Evaluation of plasma activated liquids for the elimination of mixed species biofilms within endoscopic working channels

The use of reusable flexible endoscopes has increased dramatically over the past decade, however despite improvements in endoscope reprocessing, the continued emergence of endoscopy-associated outbreaks as a result of multi-drug resistant bacteria has highlighted the need for a new approach to disinfection. Here, the use of plasma activated liquids (PALs) for the elimination of mixed species biofilm contamination within the working channels of endoscopes was evaluated. Cold atmospheric pressure plasma was used to chemically activate water and a commercially available pH buffered peracetic acid to create PALs. Polytetrafluoroethylene endoscope surrogate test pieces were contaminated with clinically relevant mixed species biofilms. The efficacy of PALs for the decontamination of narrow lumens was compared against the commercial disinfectant. Plasma activation was found to increase the antibiofilm capabilities of pH buffered peracetic acid by introducing reactive chemical species into the solution. Disinfection of endoscopic test pieces with plasma activated disinfectant (PAD) resulted in a 7.30 log10 reduction of biofilm contamination in 5 min, surpassing the 4.39 log10 reduction observed with the currently used endoscope disinfection method. PAD also resulted in reduced regrowth and recolonization of the surface of the endoscopic test pieces. Minimal changes to the surface morphology and composition were observed following exposure to PAD in comparison to the commercial disinfectant, suggesting the developed approach is no more aggressive than current disinfection approaches.

In Situ Uranium Extraction through the Synthesis of the Uranyl Peroxide Studtite Using a Nonthermal Plasma

Extraction of uranium from water is an essential step in in situ leach (ISL) mining and environmental decontamination. This is often done by precipitating uranium in solution as the uranyl peroxide studtite, [(UO2)(O2)(H2O)2](H2O)2, by adding hydrogen peroxide, which is energy-intensive to produce and hazardous to transport. Here, we present a method for synthesizing studtite, by generating reactive oxygen species in solution using a nonthermal plasma. Precipitation of studtite is observed within 5 min of the onset of plasma treatment as confirmed by X-ray diffraction and Raman spectral analysis. The faradaic efficiency of studtite formation is analyzed to estimate the values of hydrogen peroxide yield, 1.23 molecules per incident ion, and the rate constant of the studtite-forming reaction, 4.44 × 107 M-1 s-1. This work is a proof of concept and identifies significant parameters for the future development of a larger scale, higher throughput system.

Exploring non-thermal plasma technology for microalgae removal

The global population and economic development surge has substantially increased water demand, resulting in heightened sewage and pollutant generation, posing environmental hazards. Addressing this challenge necessitates the implementation of efficient and cost-effective water reclamation methods. Non-thermal plasma technology (NTP) has emerged as a promising solution, garnering attention for its superior efficiency compared to alternatives. While existing studies have predominantly focused on energy efficiency and pollutant removal, limited research has delved into the biological removal aspect, particularly concerning algae. This study utilized a dielectric barrier plasma diffuser to eliminate Spirulina microalgae (Spirulina platensis) from wastewater solutions, demonstrating higher algae removal and superior mass transfer compared to alternative plasma methods. The effect of sample volume, input voltage and power, flow rate, and initial solution concentration on the algae removal was investigated. Investigation of operational parameters revealed the best condition resulting in a 98 % removal rate and 20 g/kWh energy efficiency. The best conditions for the removal of Spirulina microalgae were considered in a sample volume of 50 mL, a voltage of 7.6 kV, a flow rate of 700 mL/min, and an initial solution concentration of 1280 mg/liter. Scanning Electron Microscope (SEM) images illustrated the impact of active species on cell structure, leading to the destruction of spiral form and loss of reproductive ability. The study underscores the potential of NTP for efficient algae removal and identifies key active species involved in the process. The removal of Spirulina microalgae was attributed to a combination of singlet oxygen (1O2), hydroxyl radicals, and ozone.

Effect of plasma-activated water on the supramolecular structure and techno-functional properties of starch: A review

This review discusses the changes in the multi-scale structure and functionality of starch after its hydrothermal modification using plasma-activated water (PAW). PAW contains reactive species that decrease the pH of the water and increase the oxidation-reduction potential, which promotes the oxidation and degradation of the surface of the starch granules to varying extents, depending on the botanical source and treatment conditions. In this article, we compile the information published so far on the effects of using PAW during heat-moisture and annealing treatments and discuss the results of the substitution of water with PAW on the long and short-range crystallinity, helical order, thermal behavior, functional properties, and digestibility. Additionally, we highlighted the possible application of PAW-modified starches. Finally, we provided an overview of future challenges, suggesting several potential directions to understand the mechanisms behind PAW use for developing sustainable modified starches for the food industry.

Plasma-Functionalized Liquids for Decontamination of Viable Tissues: A Comparative Approach

Plasma-functionalized liquids (PFLs) are rich in chemical species, such as ozone, hydrogen peroxide, singlet oxygen, hydroxyl radical and nitrogen oxides, commonly referred to as reactive oxygen and nitrogen species (RONS). Therefore, manifold applications are being investigated for their use in medicine, agriculture, and the environment. Depending on the goal, a suitable plasma source concept for the generation of PFLs has to be determined because the plasma generation setup determines the composition of reactive species. This study investigates three PFL-generating plasma sources-two spark discharges and a flow dielectric barrier discharge (DBD) system-for their efficacy in eliminating microbial contaminants from tissue samples aiming to replace antibiotics in the rinsing process. The final goal is to use these tissues as a cell source for cell-based meat production in bioreactors and thereby completely avoid antibiotics. Initially, a physicochemical characterization was conducted to better understand the decontamination capabilities of PFLs and their potential impact on tissue viability. The results indicate that the flow DBD system demonstrated the highest antimicrobial efficacy due to its elevated reactive species output and the possibility of direct treatment of tissues while tissue integrity remained. Achieving a balance between effective large-scale decontamination and the biocompatibility of PFLs remains a critical challenge.

Reactive species of plasma-activated water for murine norovirus 1 inactivation

Human norovirus (HuNoV), the leading cause of foodborne acute gastroenteritis, poses a serious threat to public health. Traditional disinfection methods lead to destructions of food properties and functions, and/or environmental contaminations. Green and efficient approaches are urgently needed to disinfect HuNoV. Plasma-activated water (PAW) containing amounts of reactive species is an emerging nonthermal and eco-friendly disinfectant towards the pathogenic microorganisms. However, the disinfection efficacy and mechanism of PAW on HuNoV has not yet been studied. Murine norovirus 1 (MNV-1) is one of the most commonly used HuNoV surrogates to evaluate the efficacy of disinfectants. In the current study, the inactivation efficacy of MNV-1 by PAW was investigated. The results demonstrated that PAW significantly inactivated MNV-1, reducing the viral titer from approximately 6 log10 TCID50/mL to non-detectable level. The decreased pH, increased oxidation-reduction potential (ORP) and conductivity of PAW were observed compared with that of deionized water. Compositional analysis revealed that hydrogen peroxide (H2O2), nitrate (NO3-) and hydroxyl radical (OH) were the functional reactive species in MNV-1 inactivation. L-histidine could scavenge most of the inactivation effect in a concentration-dependent manner. Moreover, PAW could induce damage to viral proteins. Part of MNV-1 particles was destroyed, while others were structurally intact without infectiousness. After 45 days of storage at 4 °C, PAW generated with 80 % O2 and 100 % O2 could still reduce over 4 log10 TCID50/mL of the viral titer. In addition, PAW prepared using hard water induced approximately 6 log10 TCID50/mL reduction of MNV-1. PAW treatment of MNV-1-inoculated blueberries reduced the viral titer from 3.79 log10 TCID50/mL to non-detectable level. Together, findings of the current study uncovered the crucial reactive species in PAW inactivate MNV-1 and provided a potential disinfection strategy to combat HuNoV in foods, water, and environment.

Cold plasma for enhancing covalent conjugation of ovalbumin-gallic acid and its functional properties

The utilization of cold plasma (CP) treatment to promote covalent conjugation of ovalbumin (OVA) and gallic acid (GA), as well as its functionality, were investigated. Results demonstrated that CP significantly enhanced the covalent grafting of OVA and GA. The maximum conjugation of GA, 24.33 ± 2.24 mg/g, was achieved following 45 s of CP treatment. Covalent conjugation between GA and OVA were confirmed through analyses of total sulfhydryl (-SH) group, Fourier transform infrared (FTIR) spectroscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Unfolding of the OVA molecule occurred upon conjugation with GA, as evidenced by multiple spectroscopy analyses. Additionally, conjugation with GA resulted in significant improvements in the antioxidant activity and emulsifying properties of OVA. This study demonstrated that CP is a robust and sustainable technique for promoting the covalent conjugate of polyphenols and proteins, offering a novel approach to enhance the functional properties of proteins.

Non-thermal plasma enhances growth and salinity tolerance of bok choy (Brassica rapa subsp. chinensis) in hydroponic culture

In this study, we aimed to examine the growth, physiological and biochemical status, and responses to salinity stress of bok choy (Brassica rapa subsp. chinensis) cultivated in a hydroponic system with a plasma-treated solution. Plasma gas generated using a cylindrical dielectric barrier discharge or air (control) was injected into Hoagland nutrient solution once a week for different durations (0, 5, and 10 min). After 4 weeks, the length of the shoots and roots, number of leaves, and dry weight of bok choy plants significantly increased in individuals grown with Hoagland solution treated with plasma gas for 10 min. An increase in dry weight of individual plants of approximately 80.5% was observed in plants in the plasma-treated group compared to those in a control group. The levels of chlorophyll, total soluble proteins, and nitrogen uptake, and transcription of genes related to salinity stress tolerance-WRKY2, HHP3, and ABI1- were also significantly elevated in bok choy grown with plasma treated Hoagland solution. Moreover, when exposed to 20 mM NaCl, plant length and leaf number were significantly increased, in the group grown with Hoagland solution treated with plasma gas for 10 min. Level of H2O2 was significantly elevated in the treated nutrient solutions. In plants grown with the treated nutrient solution, intracellular NO was highly detected in the cell division and elongation zone of roots. Our findings suggest that plasma treatment of nutrient solutions in hydroponic culture systems may improve the growth, physiological and biochemical status, and tolerance to salinity stress in plants, and a crucial role of H2O2 generated in the treated nutrient solutions may play in this improvement.

Inactivation effects of plasma-activated saline prepared by the mixed gases of discharged air and different gases

Plasma-activated water can efficiently inactivate pathogenic microorganisms and is considered to be a potent disinfectant in the medical, food, and agricultural industries. In this study, the air discharged by the gliding arc was mixed with different gases including O2, ambient air, synthetic air, and N2 at different flow rates to produce the activated gases, which were then activated gases were inducted into saline to prepare plasma-activated saline (PAS). The gaseous reactive species in the activated gases were composed of NO, NO2, and N2O5 and the aqueous reactive species in the PAS included H2O2, NO2 −, NO3 –, ⋅ OH , and 1O2 with different intensities, while the inactivation effects of the PAS also varied with the type and the flow rates of the mixed gases in the activated gases. The inactivation effects of the PAS treated by the discharged air mixed with O2, ambient air, and synthetic air started to become weak after 3 h placement. Scavenger analysis demonstrated that the 1O2 played a critical role in the inactivation process. This study indicated that air discharged by the gliding arc mixed with different gases could regulate the reactive species and the biological effects of PAS, providing insight into the preparation of PAS applied for disinfection.

Nebulized inhalation of plasma-activated water in the treatment of progressive moderate COVID-19 patients with antiviral treatment failure: a randomized controlled pilot trial

BACKGROUND

Antiviral drugs show significant efficacy in non-severe COVID-19 cases, yet there remains a subset of moderate COVID-19 patients whose pneumonia continues to progress post a complete course of treatment. Plasma-activated water (PAW) possesses anti-SARS-CoV-2 properties. To explore the potential of PAW in improving pneumonia in COVID-19 patients following antiviral treatment failure, we conducted this study.

METHODS

This was a randomized, controlled trial. Moderate COVID-19 patients with antiviral treatment failure were randomly assigned to the experimental group or the control group. They inhaled nebulized PAW or saline respectively. This was done twice daily for four consecutive days. We assessed improvement in chest CT on day 5, the rate of symptom resolution within 10 days, and safety.

RESULTS

A total of 23 participants were included, with 11 receiving PAW and 12 receiving saline. The baseline characteristics of both groups were comparable. The experimental group showed a higher improvement rate in chest CT on day 5 (81.8% vs. 33.3%, p = 0.036). The cumulative disappearance rate of cough within 10 days was higher in the experimental group. Within 28 days, 4 patients in each group progressed to severe illness, and no patients died. No adverse reactions were reported from inhaling nebulized PAW.

CONCLUSION

This pilot trial preliminarily confirmed that nebulized inhalation of PAW can alleviate pneumonia in moderate COVID-19 patients with antiviral treatment failure, with no adverse reactions observed. This still needs to be verified by large-scale studies.

TRIAL REGISTRATION

Chinese Clinical Trial Registry; No.: ChiCTR2300078706 (retrospectively registered, 12/15/2023); URL: www.chictr.org.cn .

Plasma activated water effects on behavior, performance, carcass quality, biochemical changes, and histopathological alterations in quail

BACKGROUND

Plasma-activated water (PAW) is an innovative promising technology which could be applied to improve poultry health. The current study investigated the effects of drinking water supply with PAW on quail behaviour, performance, biochemical parameters, carcass quality, intestinal microbial populations, and internal organs histopathology. A total of 54 twenty-one-day-old Japanese quail chicks were randomly allotted to three treatments provided with PAW at doses 0, 1 ml (PAW-1), and 2 ml (PAW-2) per one litter drinking water. Each treatment contained 6 replicates (3 birds/ cage; one male and two females).

RESULTS

The results clarified that there were no significant (P > 0.05) changes in behaviour, and performance. For the biochemical indicators, the PAW-1 group showed significantly higher serum H2O2, total protein and globulin levels compared with the other groups (P = 0.015, < 0.001, and 0.019; respectively). PAW groups had significantly lower serum creatinine and urea levels than the control (P = 0.003). For the carcass quality, the internal organs relative weight between different treatments was not changed. In contrast, there was a significant increase in the meat colour, taste, and overall acceptance scores in PAW groups compared with the control one (P = 0.013, 0.001, and < 0.001; respectively). For the intestinal microbial population, lactobacilli count was significantly higher in PAW-2 compared with the control group (P = 0.014), while there were no changes in the total bacterial count between different treatment groups. Moreover, mild histological changes were recorded in the intestine, liver, and spleen of PAW groups especially PAW-2 compared with the control one.

CONCLUSIONS

PAW offered benefits, such as reducing creatine and urea levels, improving meat characteristics, and increasing lactobacilli count, all of which are crucial for sustainable quail farming. Therefore, further research is needed.

Plasma-activated medium exerts tumor-specific inhibitory effect on hepatocellular carcinoma via disruption of the salvage pathway

Hepatocellular carcinoma has high fatality and poor prognosis. For curing hepatocellular carcinoma, the demand for effective therapeutic reagents with low toxicity is urgent. Herein, we investigated plasma-activated medium, an emerging reagent obtained via irradiation of cell-free medium with cold atmospheric plasma. Plasma-activated medium exerts inhibitory effect on many types of tumor cells with little toxicity to non-cancerous cells. In present study, we verified the tumor-specific inhibition of plasma-activated medium on hepatocellular carcinoma cell lines. Under the effect of plasma-activated medium, oxidative stress, mitochondrial dysfunction, and loss of intracellular NAD+ and ATP were detected inside cells, suggesting an energy depletion. Through investigating the salvage pathway which synthesizes NAD+ and maintains the respiratory chain in hepatocellular carcinoma, we found that the energy failure was resulted by the blockage of the salvage pathway. Moreover, nicotinamide phosphoribosyltransferase, the rate-limiting enzyme in the salvage pathway, was determined as an important target to be inactivated by the effect of plasma-activated medium. Additionally, the blockage of the salvage pathway activates AMPKα and suppresses mTOR pathway, which reinforces the cell growth inhibition. Overall, our findings demonstrated that the disruption of functions of nicotinamide phosphoribosyltransferase and the salvage pathway contribute to the tumor-specific cytotoxicity of plasma-activated medium.

Plasma-generated RONS in liquid transferred into cryo-microneedles patch for skin treatment of melanoma

Malignant melanoma is the most lethal form of skin cancer. As a promising anti-cancer agent, plasma-activated water (PAW) rich in reactive oxygen and nitrogen species (RONS) has shown significant potential for melanoma treatment. However, rapid decay of RONS and inefficient delivery of PAW in conventional injection methods limit its practical applications. To address this issue, here we report a new approach for the production of plasma-activated cryo-microneedles (PA-CMNs) patches using custom-designed plasma devices and processes. Our innovation is to incorporate PAW into the PA-CMNs that are fabricated using a fast cryogenic micro-molding method. It is demonstrated that PA-CMNs can be easily inserted into skin to release RONS and slow the decay of RONS thereby prolonging their bioactivity and effectiveness. The new insights into the effective melanoma treatment suggest that the rich mixture of RONS within PA-CMNs prepared by custom-developed hybrid plasma-assisted configuration induces both ferroptosis and apoptosis to selectively kill tumor cells. A significant inhibition of subcutaneous A375 melanoma growth was observed in PA-CMNs-treated tumor-bearing nude mice without any signs of systemic toxicity. The new approach based on PA-CMNs may potentially open new avenues for a broader range of disease treatments.

Nitric and nitrous acid formation in plasma-treated water: Decisive role of nitrogen oxides (NOx=1-3)

Nitrogen fixation using low-temperature plasma, particularly in relation to plasma-treated water (PTW) and its chemical and physical properties, has received a renewed research focus. Dissolving highly concentrated nitrogen oxides (NOx = 1-3) generated by air discharge into water results in the formation of two aqueous oxiacids (nitrous and nitric acids; HNOy = 2,3) and their conjugates (nitrate and nitrite ions; NOy-). Nonlinear formation of these species in PTW with respect to plasma conditions has been observed; however, the significance of the time-varying NOx on this nonlinearity has not yet been thoroughly investigated. Here, we demonstrate real-time observations of HNOy/NOy- as well as NOx production in a surface dielectric barrier discharge reactor containing distilled water. Synchronized two optical absorption spectroscopy systems were employed to simultaneously measure gas-phase NOx and liquid-phase HNOy/NOy- in the plasma reactor operated under different oxygen contents of 5, 20, and 50%. Our results showed that reducing the oxygen content in the reactor accelerated the chemical transition from O3 and NO3 to NO1,2, leading to a predominance of nitrite in PTW. Specifically, the NO3-rich period was extended with increasing O2 content, resulting in the production of nitrate-dominant PTW at low pH levels. Our findings highlight the potential for the selective generation of HNOy/NOy- in PTW through the active and passive control of NOx in a plasma reactor. The direct, real-time observation of NOx-HNOy/NOy- conversion presented here has potential for improving the control and optimization of PTW, thereby enhancing its applicability.

Plasma-activated water: Candidate hand disinfectant for SARS-CoV-2 transmission disruption

The global epidemic caused by SARS-CoV-2 has brought about worldwide burden and a sense of danger for more than two years, leading to a wide range of social, public health, economic and environmental issues. Self-inoculation through hands has been the primary way for environmental transmission of SARS-CoV-2. Plasma-activated water (PAW) has been reported as an effective, safe and environmentally friendly disinfectant against SARS-CoV-2. However, the inactivating effect of PAW on SARS-CoV-2 located on skin surface and its underlying mechanism of action have not been elucidated. In this study, PAW was prepared using an air-pressure plasma jet device. The antiviral efficiency of PAW1, PAW3, and PAW5 on the SARS-CoV-2 pseudovirus was 8.20 % (±2.88 %), 46.24 % (±1.79 %), and 91.71 % (±0.47 %), respectively. Additionally, determination of PAW's physicochemical properties, identification of major sterile effector in PAW, transmission electron microscopy analysis, malondialdehyde (MDA) assessment, SDS-PAGE, ELISA, and qPCR were conducted to reveal the virucidal mechanism of PAW. Our experimental results suggested that peroxynitrite, which was generated by the synergism of acidic environment and reactive species, was the major sterile effector of PAW. Furthermore, we found that PAW treatment significantly inactivated SARS-CoV-2 pseudovirus through the destruction of its structure of and the degradation of the viral RNA. Therefore, the possible mechanism for the structural destruction of SARS-COV-2 by PAW is through the action of peroxynitrite generated by the synergism of acidic environment and reactive species, which might react with and destroy the lipid envelope of SARS-CoV-2 pseudovirus. Nevertheless, further studies are required to shed light on the interaction mechanism of PAW-inherent RONS and viral components, and to confirm the determinant factors for virus inactivation of SARS-COV-2 by PAW. Therefore, PAW may be a candidate hand disinfectant used to disrupt the transmission of SARS-CoV-2.

Effect of plasma-activated water on planktonic and biofilm cells of Vibrio parahaemolyticus strains isolated from cutting board surfaces in retail seafood markets

AIMS

This research aimed to analyze cutting board surfaces in seafood markets to find Vibrio parahaemolyticus, assess the isolates' ability to form biofilms, generate and evaluate characteristics of plasma-activated water (PAW), and compare the effect of PAW on planktonic and biofilm cells of the isolated V. parahaemolyticus strains.

METHODS AND RESULTS

A total of 11 V. parahaemolyticus strains were isolated from 8.87% of the examined cutting boards. Biofilm-forming ability was evaluated for these isolates at temperatures of 10°C, 20°C, and 30°C using crystal violet staining. Four strains with the highest biofilm potential were selected for further analysis. The pH of the PAW used in the study was 3.41 ± 0.04, and the initial concentrations of hydrogen peroxide, nitrate, and nitrite were 108 ± 9.6, 742 ± 61, and 36.3 ± 2.9 µM, respectively. However, these concentrations decreased significantly within 3-4 days during storage at room temperature. PAW exhibited significant antimicrobial effects on V. parahaemolyticus planktonic cells, reducing viable bacteria up to 4.54 log CFU/ml within 20 min. PAW also reduced the number of biofilm cells on stainless steel (up to 3.55 log CFU/cm2) and high-density polyethylene (up to 3.06 log CFU/cm2) surfaces, although to a lesser extent than planktonic cells.

CONCLUSIONS

PAW exhibited significant antibacterial activity against V. parahaemolyticus cells, although its antibacterial properties diminished over time. Furthermore, the antibacterial activity of PAW against biofilm cells of V. parahaemolyticus was less pronounced compared to the planktonic cells. Therefore, the actual effectiveness of PAW in seafood processing environments can be affected by biofilms that may form on various surfaces such as cutting boards if they are not cleaned properly.

Electrical properties determine the liquid flow direction in plasma-liquid interactions

During atmospheric pressure plasma impingement, plasma induced liquid flow will influence the transport and distribution of plasma generated charged and reactive species in liquids. We use particle image velocimetry and supplementary pH, conductivity and temperature measurements to investigate electrical properties of an AC kHz plasma jet interacting with water and electrolytes. We observe that the dominant driving mechanism in low conductive solutions are surface forces such as shear stresses and stagnation-pressure induced dimpling. These give upwards flows beneath the plasma-liquid interaction point. In highly conductive solutions, such as water with dissolved salts, the dominant driving mechanism is electro-hydrodynamic forces, with flows directed downwards underneath the plasma jet in our system. We therefore demonstrate that the direction of initial plasma induced liquid flows can be controlled through the addition of salt ions. In electrically grounded salt solutions, we also observe time resolved flow direction switching, possibly due to modification of salt solutions via electrolytic and plasma induced reactions changing the dominant flow mechanism over time.

Cold atmospheric plasma-activated medium for potential ovarian cancer therapy

Cold atmospheric plasma (CAP) has emerged as an innovative tool with broad medical applications, including ovarian cancer (OC) treatment. By bringing CAP in close proximity to liquids such as water or cell culture media, solutions containing reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated, called plasma-activated media (PAM). In this systematic review, we conduct an in-depth analysis of studies focusing on PAM interactions with biological substrates. We elucidate the diverse mechanisms involved in the activation of different media and the complex network of chemical reactions underlying the generation and consumption of the prominent reactive species. Furthermore, we highlight the promises of PAM in advancing biomedical applications, such as its stability for extended periods under appropriate storage conditions. We also examine the application of PAM as an anti-cancer and anti-metastatic treatment for OC, with a particular emphasis on its ability to induce apoptosis via distinct signaling pathways, inhibit cell growth, suppress cell motility, and enhance the therapeutic effects of chemotherapy. Finally, the future outlook of PAM therapy in biomedical applications is speculated, with emphasis on the safety issues relevant to clinical translation.

Optical and Chemical Measurements of Solvated Electrons Produced in Plasma Electrolysis with a Water Cathode

It is known that glow discharges with a water anode inject and form solvated electrons at the plasma-liquid interface, driving a wide variety of reduction reactions. However, in systems with a water cathode, the production and role of solvated electrons are less clear. Here, we present evidence for the direct detection of solvated electrons produced at the interface of an argon plasma and a water cathode via absorption spectroscopy. We further quantify their yield using the dissociative electron attachment of chloroacetate, measuring a yield of 1.04 ± 0.59 electrons per incident ion, corresponding to approximately 100% faradaic efficiency. Additionally, we estimate a yield of 2.09 ± 0.93 hydroxyl radicals per incident ion. Comparison of this yield with other findings in the literature supports that these hydroxyl radicals are likely formed directly in the liquid phase rather than by diffusion from the vapor phase.

Evidence for Superoxide-Initiated Oxidation of Aniline in Water by Pulsed, Atmospheric Pressure Plasma

Plasma-driven solution electrochemistry (PDSE) uses plasma-generated reactive species to drive redox reactions in solution. Nonthermal, atmospheric pressure plasmas, when irradiating water, produce many redox species. While PDSE is a promising chemical tool, there is limited insight into the mechanisms of the reactions due to the variety of short-lived reagents produced. In this study, we use aniline as a model system for studying redox mechanisms of PDSE. We show that the plasma irradiation of aqueous aniline solutions drives the formation of polyaniline oligomer, which is suppressed under acidic starting conditions. The addition of (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO), a radical scavenger, decreases the formation of oligomer by 80%, and the addition of superoxide dismutase fully hinders oligomerization. These results lead us to conclude that the oligomerization of aniline by plasma irradiation is initiated by superoxide. This discovery provides novel insights into PDSE mechanisms and illustrates a potential method of harnessing superoxide for chemical reactions.

Portable and affordable cold air plasma source with optimized bactericidal effect

The paper reports a low-cost handheld source of a cold air plasma intended for biomedical applications that can be made by anyone (detailed technical information and a step-by-step guide for creating the NTP source are provided). The plasma source employs a 1.4 W corona discharge in the needle-to-cone electrode configuration and is an extremely simple device, consisting basically of two electrodes and a cheap power supply. To achieve the best bactericidal effect, the plasma source has been optimized on Escherichia coli. The bactericidal ability of the plasma source was further tested on a wide range of microorganisms: Staphylococcus aureus as a representative of gram-positive bacteria, Pseudomonas aeruginosa as gram-negative bacteria, Candida albicans as yeasts, Trichophyton interdigitale as microfungi, and Deinococcus radiodurans as a representative of extremophilic bacteria resistant to many DNA-damaging agents, including ultraviolet and ionizing radiation. The testing showed that the plasma source inactivates all the microorganisms tested in several minutes (up to 105-107 CFU depending on a microorganism), proving its effectiveness against a wide spectrum of pathogens, in particular microfungi, yeasts, gram-positive and gram-negative bacteria. Studies of long-lived reactive species such as ozone, nitrogen oxides, hydrogen peroxide, nitrite, and nitrate revealed a strong correlation between ozone and the bactericidal effect, indicating that the bactericidal effect should generally be attributed to reactive oxygen species. This is the first comprehensive study of the bactericidal effect of a corona discharge in air and the formation of long-lived reactive species by the discharge, depending on both the interelectrode distance and the discharge current.

Insights into the mechanisms of plasma physicochemical characteristics on ultralong-lasting plasma-activated water: the influence of DC power polarity on RONS generation

In our recent work, we successfully developed an innovative method based on pin-water discharge for preparing ultralong-lasting plasma-activated water (PAW) with a lifetime of up to 720 hours at room temperature. However, the impact of power polarity on the preparation method for ultralong-lasting PAW remains unclear. In this study, we discovered that ultralong-lasting PAW could only be achieved with positive polarity. Further analysis of the liquid reactive oxygen and nitrogen species (RONS) revealed that the absence of H2O2 in the discharge chamber was crucial for the failure of ultralong-lasting PAW preparation at negative polarity. To elucidate the mechanism underlying the generation of RONS at different polarities, we conducted plasma feature diagnosis, compared discharge morphologies, and performed theoretical analyses based on chemical reactions. Our results indicated that the introduction of water vapor molecules through intense spraying at positive polarity led to an increase in the generation of H2O2-related source particles, while also interfering with N2-related electron collision reactions and chemical reaction coefficients, ultimately affecting the production of NO2-. Consequently, there was relatively less liquid NO2- and more abundant H2O2 in the discharge chamber at positive polarity, whereas the opposite trend was observed for these two key RONS at negative polarity. Furthermore, the minimal amount of NO2- at positive polarity and the tiny amount of H2O2 at negative polarity in the discharge chamber would be respectively consumed by the relatively abundant H2O2 at positive polarity and NO2- at negative polarity.

The pH acidity and nitrate accumulation by plasma discharge enhanced the growth and phytochemicals of soybean sprouts grown in reused water

This study investigated the effect of plasma treatment on reused water and evaluated the interactions of the plasma-treated water (PTW) with plants or microbes to determine the optimal PTW for reuse. The repeated treatment gradually accumulated nitrate (NO3-) in the PTW and lowered its pH; afterward, it led to the sprouted soybeans accumulating other inorganic ions in the PTW. The biomass of soybean sprouts was enhanced by the accumulated NO3- but decreased due to the pH effect. Meanwhile, the acidic pH reduced the microbial counts, but they increased after sprinkling the PTW over the sprouts. The optimal PTW in our study, which had a gradual increase of NO3- (≤321.8 mg·L-1) with an acceptable pH (≥pH 3), significantly enhanced the biomass by 4.2% compared to the untreated control. Additionally, it increased the total content of amino acids and isoflavones by 9% and 18% in the growing part, respectively.