Fluorescence measurements of peroxynitrite/peroxynitrous acid in cold air plasma treated aqueous solutions

Innovative Method for Water-in-Oil Emulsion Treatment Using Atmospheric Nonthermal-Plasma Technology

The field of plasma-liquid interactions is rapidly growing, with increasing publications across applications. While plasma's interactions with water and oil have been researched, there is a notable gap in the study of plasma-emulsion interactions and their practical applications. Investigating plasma-emulsion interactions offers a dual advantage, as demonstrated in this study, as it is applicable to both water/oil separation and emulsion stabilization processes. This study introduces a groundbreaking approach utilizing the fountain dielectric barrier discharge (FDBD) plasma reactor. The reactor exposes a model emulsion to different plasma gases, such as air, nitrogen, argon, and ammonia, along with varying parameters of plasma input voltage and treatment time. Consequently, due to demulsification, the emulsion segregates into distinct water and oil phases. Remarkably, the results demonstrate that short-term plasma treatment leads to the separation of over 99% of emulsified water. However, prolonged exposure to plasma for around 7 min reveals a decrease in the volume of free-separated water, implying the occurrence of stable emulsion formation instead of further demulsification. To optimize experimental conditions for compliance with regulatory requirements, the study employs the response surface methodology (RSM). Adapting pH and separation contours in three-dimensional (3D) RSM plots shows that achieving higher separation is likely associated with higher pH levels in air, nitrogen, and argon plasmas. Notably, the plasma treatment involving ammonia gas elevates the pH level and yields the highest degree of separation compared with air, nitrogen, or argon plasmas.

Inhibition of Fungal Growth and Aflatoxin B1 Synthesis in Aspergillus flavus by Plasma-Activated Water

The gaseous reactive oxygen/nitrogen species (RONS) generated by cold atmospheric plasma (CAP) can effectively inactivate Aspergillus flavus (A. flavus) and prolong the shelf-life of food. Plasma-activated water (PAW) is the extension of cold plasma sterilization technology. Without the limitation of a plasma device, PAW can be applied to more scenarios of food decontamination. However, the efficacy of PAW as a carrier of RONS for eradicating A. flavus or inhibiting its growth remains unclear. In this study, the immediate fungicidal effect and long-term inhibitory effect of PAW on A. flavus were investigated. The results demonstrated that 60-min instant-prepared PAW could achieve a 3.22 log reduction CFU/mL of A. flavus and the fungicidal efficacy of PAW gradually declined with the extension of storage time. Peroxynitrite (ONOO^-/ONOOH) played a crucial role in this inactivation process, which could damage the cell wall and membrane structure, disrupt intracellular redox homeostasis, and impair mitochondrial function, ultimately leading to fungal inactivation. In addition to the fungicidal effect, PAW also exhibited fungistatic properties and inhibited the synthesis of aflatoxin B₁ (AFB₁) in A. flavus. By analyzing the cellular antioxidant capacity, energy metabolism, and key gene expression in the AFB₁ synthesis pathway, it was discovered that PAW can significantly reduce ATP levels, while increasing SOD and CAT activity during 5-d cultivation. Meanwhile, PAW effectively suppressed the expression of genes related to AFB₁ synthesis.

Effects of Plasma-Activated Water Treatment on the Inactivation of Microorganisms Present on Cherry Tomatoes and in Used Wash Solution

Herein, we investigated the potential of plasma-activated water (PAW) as a wash solution for the microbial decontamination of cherry tomatoes. We analyzed the efficacy of PAW as a bactericidal agent based on reactive species and pH. Immersion for 5 min in PAW15 (generated via plasma activation for 15 min) was determined as optimal for microbial decontamination of fresh produce. The decontamination efficacy of PAW15 exceeded those of mimic solutions with equivalent reactive species concentrations and pH (3.0 vs. 1.7 log reduction), suggesting that the entire range of plasma-derived reactive species participates in decontamination rather than a few reactive species. PAW15-washing treatment achieved reductions of 6.89 ± 0.36, 7.49 ± 0.40, and 5.60 ± 0.05 log₁₀ CFU/g in the counts of Bacillus cereus, Salmonella sp., and Escherichia coli O157:H7, respectively, inoculated on the surface of cherry tomatoes, with none of these strains detected in the wash solution. During 6 days of 25 °C storage post-washing, the counts of aerobic bacteria, yeasts, and molds were below the detection limit. However, PAW15 did not significantly affect the viability of RAW264.7 cells. These results demonstrate that PAW effectively inactivates microbes and foodborne pathogens on the surface of cherry tomatoes and in the wash solution. Thus, PAW could be used as an alternative wash solution in the fresh produce industry without cross-contamination during washing and environmental contamination by foodborne pathogens or potential risks to human health.

Simultaneous removal of norfloxacin and chloramphenicol using cold atmospheric plasma jet (CAPJ): Enhanced performance, synergistic effect, plasma-activated water (PAW) contribution, mechanism and toxicity evaluation

The extensive abuse and inadvertent discharge of various antibiotics into the environment has become a serious problem for posing a big threat to human health. In order to deal with this problem, we utilized cold atmospheric plasma jet (CAPJ) to treat two different antibiotics, namely, norfloxacin and chloramphenicol, and investigated the efficiencies and corresponding mechanisms for removing the mixed antibiotics. In the application of the CAPJ technique, we made use of not only the direct plasma processing, but also the indirect plasma-activated water (PAW) treatment. The efficiency for mixed antibiotics treatment was considerably enhanced as compared to the efficiency for treatment of single antibiotics. The contributions from the CAPJ-induced reactive oxygen/nitrogen species (RONS) were examined, showing that ·OH and ¹O₂ played a major role in the degradation of norfloxacin and chloramphenicol in the direct plasma treatment, while ¹O₂ played a major role in the PAW treatment. The bio-toxicity evaluation was also provided to verify the ecological safety of the CAPJ treatment. As such, this work has not only showed the effectiveness of CAPJ treatment of mixed antibiotics, but also elucidated the mechanisms for the enhanced treatment efficiency, which may provide a new solution for treatment of antibiotics in the environment.

Defects in Mitochondrial Functions Affect the Survival of Yeast Cells Treated with Non-Thermal Plasma

Exposure of living cells to non-thermal plasma produced in various electrical discharges affects cell physiology and often results in cell death. Even though plasma-based techniques have started finding practical applications in biotechnology and medicine, the molecular mechanisms of interaction of cells with plasma remain poorly understood. In this study, the involvement of selected cellular components or pathways in plasma-induced cell killing was studied employing yeast deletion mutants. The changes in yeast sensitivity to plasma-activated water were observed in mutants with the defect in mitochondrial functions, including transport across the outer mitochondrial membrane (∆por1), cardiolipin biosynthesis (∆crd1, ∆pgs1), respiration (ρ⁰) and assumed signaling to the nucleus (∆mdl1, ∆yme1). Together these results indicate that mitochondria play an important role in plasma-activated water cell killing, both as the target of the damage and the participant in the damage signaling, which may lead to the induction of cell protection. On the other hand, our results show that neither mitochondria-ER contact sites, UPR, autophagy, nor proteasome play a major role in the protection of yeast cells from plasma-induced damage.

Combined effect of atmospheric gas plasma and UVA light: A sustainable and green alternative for chemical decontamination and microbial inactivation of fish processing water

The simultaneous use of UVA light irradiation coupled with low energy cold plasma generated by a dielectric barrier discharge prototype, results in significant enhancement of efficiency of the integrated process with respect to the sole plasma treatment. This effect has been demonstrated both on microbial inactivation of a food-borne pathogen, i.e. Listeria monocytogenes, and on the degradation of a compound of biological origin such as phenylalanine. In the latter case, the analysis of its reaction intermediates and the spectroscopic identification and quantification of peroxynitrites, allowed to propose mechanistic hypotheses on the nature of the observed synergistic effects. Moreover, it has been demonstrated that the process does not affect the quality of trout fillets, indicating its suitability as a chlorine-free, green, and sustainable tool for the decontamination of fish processing water.

The inactivation efficacy of plasma-activated acetic acid against Salmonella Typhimurium cells and biofilm

AIM

This study aimed to examine the inactivation efficacy of plasma-activated acetic acid (PAAA) against Salmonella Typhimurium cells and biofilm and elucidate the underlying the chemical inactivation pathway.

METHODS AND RESULTS

PAAA was prepared by discharging plasma to 20 ml of 0.2% (v/v) acetic acid (AA) for 20 min (2.2 kHz and 8.4 kVpp). The count of cells and biofilms decreased by 5.71 log CFU ml^-1 and 4 log CFU/cm² after 10 min of treatment with 0.2% PAAA and 0.4% PAAA compared with control group (without any treatment), respectively. In 0.2% PAAA, the concentrations of hydrogen peroxide (H₂ O₂ ) and nitrate anions were directly proportional to the plasma discharge time, while nitrite anions (NO₂ ^- ) was not detected. However, the pH values of both 0.2% PAAA and plasma-activated water were inversely proportional to the plasma discharge time. Treatment with catalase, L-histidine, D-mannitol, and sodium azide inhibited the antibacterial activity of PAAA.

CONCLUSION

H₂ O₂ , Singlet oxygen, Hydroxyl radical, and NO₂ ^- are involved in the generation and decomposition of peroxynitrous acid generated from PAAA functioned as intermediate agent, which could diffuse through cell membranes of bacteria and induce cell injury.

SIGNIFICANCE AND IMPACT OF STUDY

This study provides the understanding of efficacy and selectivity of PAAA which could be a novel decontamination agent.

Efficient disinfection of SARS-CoV-2-like coronavirus, pseudotyped SARS-CoV-2 and other coronaviruses using cold plasma induces spike protein damage

Coronavirus disease 2019 (COVID-19) has become a worldwide public health emergency, and the high transmission of SARS-CoV-2 variants has raised serious concerns. Efficient disinfection methods are crucial for the prevention of viral transmission. Herein, pulse power-driven cold atmospheric plasma (CAP), a novel sterilization strategy, was found to potently inactivate SARS-CoV-2-like coronavirus GX_P2V, six strains of major epidemic SARS-CoV-2 variants and even swine coronavirus PEDV and SADS-CoV within 300 s (with inhibition rate more than 99%). We identified four dominant short-lived reactive species, ONOO^-, ¹O₂, O₂^- and·OH, generated in response to CAP and distinguished their roles in the inactivation of GX_P2V and SARS-CoV-2 spike protein receptor binding domain (RBD), which is responsible for recognition and binding to human angiotensin-converting enzyme 2 (hACE2). Our study provides detailed evidence of a novel surface disinfection strategy for SARS-CoV-2 and other coronaviruses.

Low Temperature Plasma Strategies for Xylella fastidiosa Inactivation

The quarantine bacterium Xylella fastidiosa was first detected in Salento (Apulia, Italy) in 2013 and caused severe symptoms in olives, leading to plant death. The disease, named Olive Quick Decline Syndrome (OQDS), is caused by the strain “De Donno” ST53 of the subspecies pauca of this bacterium (XfDD), which is spread by the insect Philaenus spumarius. The epidemic poses a serious threat to the agricultural economy and the landscape, as X. fastidiosa infects several plant species and there is yet no recognized solution. Research on OQDS is focused on finding strategies to control its spread or mitigate its symptoms. As a perspective solution, we investigated the efficacy of the low-temperature plasma and plasma-activated water to kill bacterial cells. Experiments were conducted in vitro to test the biocidal effect of the direct application of a Surface Dielectric Barrier Discharge (SDBD) plasma on bacteria cells and Plasma Activated Water (PAW). PAW activity was tested as a possible biocidal agent that can move freely in the xylem network paving the way to test the strategy on infected plants. The results showed a high decontamination rate even for cells of XfDD embedded in biofilms grown on solid media and complete inactivation in liquid culture medium.

Inactivation of E. coli, S. aureus, and Bacteriophages in Biofilms by Humidified Air Plasma

In this study, humidified air dielectric barrier discharge (DBD) plasma was used to inactivate Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and bacteriophages in biofilms containing DNA, NaCl, carbohydrates, and proteins. The humidified DBD plasma was very effective in the inactivation of microbes in the (≤1.0 μm) biofilms. The number of surviving E. coli, S. aureus, and bacteriophages in the biofilms was strongly dependent on the constituent and thickness of the biofilms and was greatly reduced when the plasma treatment time increased from 5 s to 150 s. Our analysis shows that the UV irradiation was not responsible for the inactivation of microbes in biofilms. The short-lived RONS generated in the humidified air DBD plasma were not directly involved in the inactivation process; however, they recombined or reacted with other species to generate the long-lived RONS. Long-lived RONS diffused into the biofilms to generate very active species, such as ONOOH and OH. This study indicates that the geminated NO₂ and OH pair formed due to the homolysis of ONOOH can cause the synergistic oxidation of various organic molecules in the aqueous solution. Proteins in the biofilm were highly resistant to the inactivation of microbes in biofilms, which is presumably due to the existence of the unstable functional groups in the proteins. The unsaturated fatty acids, cysteine-rich proteins, and sulfur–methyl thioether groups in the proteins were easily oxidized by the geminated NO₂ and OH pair.

Cold Atmospheric Plasma, Platelet-Rich Plasma, and Nitric Oxide Synthesis Inhibitor: Effects Investigation on an Experimental Model on Rats

The evolution of reconstructive methods for defects of the human body cannot yet replace the use of flap surgery. Research is still preoccupied with the ideal techniques for offering the best chances of survival of the flaps. In our study, we investigated the effects of cold atmospheric plasma (CAP), N-nitro-L-arginine methyl ester (L-NAME), and platelet-rich plasma (PRP) injectable solutions on flap survival using an in vivo model. Twenty-four Wistar rats (four groups) had the McFarlane flap raised and CAP, L-NAME, and PRP substances tested through a single dose subcutaneous injection. The control group had only a saline solution injected. To the best of our knowledge, this is the first study that evaluated a CAP activated solution through injection on flaps. The flap survival rate was determined by clinical examination (photography documented), hematology, thermography, and anatomopathological tests. The image digital analysis performed on the flaps showed that the necrosis area (control—49.64%) was significantly lower for the groups with the three investigated solutions: CAP (14.47%), L-NAME (18.2%), and PRP (23.85%). Thermography exploration revealed less ischemia than the control group on the CAP, L-NAME, and PRP groups as well. Anatomopathological data noted the best degree of angiogenesis on the CAP group, with similar findings on the L-NAME and PRP treated flaps. The blood work did not indicate infection or a strong inflammatory process in any of the subjects. Overall, the study shows that the CAP activated solution has a similar (better) impact on the necrosis rate (compared with other solutions with known effects) when injected on the modified dorsal rat skin flap, and on top of that it can be obtained fast, in unlimited quantities, non-invasively, and through a standardized process.

Reactive Nitrogen Species Generated by Gas-Liquid Dielectric Barrier Discharge for Efficient Degradation of Perfluorooctanoic Acid from Water

Perfluorooctanoic acid (PFOA) poses a serious threat to the ecological environment and biological health because of its ubiquitous distribution, extreme persistence, and high toxicity. In this study, we designed a novel gas-liquid dielectric barrier discharge (GLDBD) reactor which could efficiently destruct PFOA. PFOA removal efficiencies can be obtained in various water matrices, which were higher than 98.0% within 50 min, with energy yields higher than 114.5 mg·kWh^-1. It was confirmed that the reactive species including e^-, ONOOH, •NO₂, and hydroxyl radicals (•OH) were responsible for PFOA removal. Especially, this study first revealed the crucial role of reactive nitrogen species (RNS) for PFOA degradation in the plasma system. Due to the generation of a large amount of RNS, the designed GLDBD reactor proved to be less sensitive to various water matrices, which meant a broader promising practical application. Moreover, influential factors including high concentration of various ions and humic acid (HA), were investigated. The possible PFOA degradation pathways were proposed based on liquid chromatograph-mass spectrometer (LC-MS) results and density functional theory (DFT) calculation, which further confirmed the feasibility of PFOA removal with RNS. This research, therefore, provides an effective and versatile alternative for PFOA removal from various water matrices.

Toxicity Assessment of Long-Term Exposure to Non-Thermal Plasma Activated Water in Mice

Non-thermal plasma activated water (PAW) has recently emerged as a powerful antimicrobial agent. Despite numerous potential bio-medical applications, studies concerning toxicity in live animals, especially after long-term exposure, are scarce. Our study aimed to assess the effects of long-term watering with PAW on the health of CD1 mice. PAW was prepared from distilled water with a GlidArc reactor according to a previously published protocol. The pH was 2.78. The mice received PAW (experimental group) or tap water (control group) daily for 90 days as the sole water source. After 90 days, the following investigations were performed on the euthanatized animals: gross necropsy, teeth mineral composition, histopathology, immunohistochemistry, hematology, blood biochemistry, methemoglobin level and cytokine profile. Mice tolerated PAW very well and no adverse effects were observed during the entire period of the experiment. Histopathological examination of the organs and tissues did not reveal any structural changes. Moreover, the expression of proliferation markers PCNA and Ki67 has not been identified in the epithelium of the upper digestive tract, indicating the absence of any pre- or neoplastic transformations. The results of our study demonstrated that long-term exposure to PAW caused no toxic effects and could be used as oral antiseptic solution in dental medicine.

Graphene-Based Flexible Sensors for Simultaneous Detection of Ascorbic Acid, Dopamine, and Uric Acid

Many diseases are closely related to abnormal concentrations of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Therefore, the detection of these small molecules is significant for monitoring life metabolism and healthy states. Electrochemical detection has been widely used to detect small molecules due to its good selectivity, high sensitivity, and good economics. Fabrication and application are two sides of the coin, and we cannot give up one for the other. Graphene (GN) is a very suitable material for electrochemical sensing due to its excellent catalytic performance and large specific surface area. It possesses many excellent properties but cannot hold itself alone due to its nanoscale thickness. Herein, we have fabricated three-dimensional (3D) GN nanosheets (GNSs) on flexible carbon cloth (CC) by thermal chemical vapor deposition (CVD). The GNSs/CC can successfully detect AA, DA, and UA simultaneously. We find that these GNSs/CC sensors show good performance with 7 h CVD modification. The linear ranges of AA, DA, and UA are 0.02-0.1, 0.0005-0.02, and 0.0005-0.02 mM, respectively. The detection sensitivity rates of AA, DA, and UA are 5,470, 60,500, and 64,000 μA mM-1 cm-2, respectively. Our GNSs/CC flexible sensors can be successfully applied in the human serum for UA detection. The result matches with commercial sensors very well.

Plasma-activated water production and its application in agriculture

The use of plasma-activated water (PAW) treatment is a promising technology that has many advantages, such as high efficiency, flexibility, environmental safety, and no residue. Thus, PAW has been applied in the agriculture industry to increase agricultural production. The application of PAW technology in agricultural production should emphasize its systematic nature, controllability, and operability, making it practical. This review systematically illustrates the production of PAW and the factors influencing it. The application of PAW in agriculture and its mechanism are discussed, including the effect on seed germination, the promotion of plant growth, and the control of plant diseases and pests. The implications of PAW for agriculture production and some of the related challenges are discussed. This review provides a deeper understanding of the viability of PAW technology in agriculture production. © 2021 Society of Chemical Industry.

Peroxynitrous Acid Generated In Situ from Acidified H2O2 and NaNO2. A Suitable Novel Antimicrobial Agent?

Peroxynitrite (ONOO-) and peroxynitrous acid (ONOOH) are known as short acting reactive species with nitrating and oxidative properties, which are associated with their antimicrobial effect. However, to the best of our knowledge, ONOOH/ONOO- are not yet used as antimicrobial actives in practical applications. The aim is to elucidate if ONOOH generated in situ from acidified hydrogen peroxide (H2O2) and sodium nitrite (NaNO2) may serve as an antimicrobial active in disinfectants. Therefore, the dose-response relationship and mutagenicity are investigated. Antimicrobial efficacy was investigated by suspension tests and mutagenicity by the Ames test. Tests were conducted with E. coli. For investigating the dose-response relationship, pH values and concentrations of H2O2 and NaNO2 were varied. The antimicrobial efficacy is correlated to the dose of ONOOH, which is determined by numerical computations. The relationship can be described by the efficacy parameter W, corresponding to the amount of educts consumed during exposure time. Sufficient inactivation was observed whenever W ≥ 1 mM, yielding a criterion for inactivation of E. coli by acidified H2O2 and NaNO2. No mutagenicity of ONOOH was noticed. While further investigations are necessary, results indicate that safe and effective usage of ONOOH generated from acidified H2O2 and NaNO2 as a novel active in disinfectants is conceivable.

Plasma Treated Water Solutions in Cancer Treatments: The Contrasting Role of RNS

Plasma Treated Water Solutions (PTWS) recently emerged as a novel tool for the generation of Reactive Oxygen and Nitrogen Species (ROS and RNS) in liquids. The presence of ROS with a strong oxidative power, like hydrogen peroxide (H₂O₂), has been proposed as the main effector for the cancer-killing properties of PTWS. A protective role has been postulated for RNS, with nitric oxide (NO) being involved in the activation of antioxidant responses and cell survival. However, recent evidences proved that NO-derivatives in proper mixtures with ROS in PTWS could enhance rather than reduce the selectivity of PTWS-induced cancer cell death through the inhibition of specific antioxidant cancer defenses. In this paper we discuss the formation of RNS in different liquids with a Dielectric Barrier Discharge (DBD), to show that NO is absent in PTWS of complex composition like plasma treated (PT)-cell culture media used for in vitro experiments, as well as its supposed protective role. Nitrite anions (NO₂^-) instead, present in our PTWS, were found to improve the selective death of Saos2 cancer cells compared to EA.hy926 cells by decreasing the cytotoxic threshold of H₂O₂ to non-toxic values for the endothelial cell line.

Acidified Nitrite Contributes to the Antitumor Effect of Cold Atmospheric Plasma on Melanoma Cells

Cold atmospheric plasma (CAP) is partially ionized gas near room temperature with previously reported antitumor effects. Despite extensive research and growing interest in this technology, active components and molecular mechanisms of CAP are not fully understood to date. We used Raman spectroscopy and colorimetric assays to determine elevated nitrite and nitrate levels after treatment with a MiniFlatPlaster CAP device. Previously, we demonstrated CAP-induced acidification. Cellular effects of nitrite and strong extracellular acidification were assessed using live-cell imaging of intracellular Ca²⁺ levels, cell viability analysis as well as quantification of p21 and DNA damage. We further characterized these observations by analyzing established molecular effects of CAP treatment. A synergistic effect of nitrite and acidification was found, leading to strong cytotoxicity in melanoma cells. Interestingly, protein nitration and membrane damage were absent after treatment with acidified nitrite, thereby challenging their contribution to CAP-induced cytotoxicity. Further, phosphorylation of ERK1/2 was increased after treatment with both acidified nitrite and indirect CAP. This study characterizes the impact of acidified nitrite on melanoma cells and supports the importance of RNS during CAP treatment. Further, it defines and evaluates important molecular mechanisms that are involved in the cancer cell response to CAP.

Interactions of plasma-activated water with biofilms: inactivation, dispersal effects and mechanisms of action

Biofilms have several characteristics that ensure their survival in a range of adverse environmental conditions, including high cell numbers, close cell proximity to allow easy genetic exchange (e.g., for resistance genes), cell communication and protection through the production of an exopolysaccharide matrix. Together, these characteristics make it difficult to kill undesirable biofilms, despite the many studies aimed at improving the removal of biofilms. An elimination method that is safe, easy to deliver in physically complex environments and not prone to microbial resistance is highly desired. Cold atmospheric plasma, a lightning-like state generated from air or other gases with a high voltage can be used to make plasma-activated water (PAW) that contains many active species and radicals that have antimicrobial activity. Recent studies have shown the potential for PAW to be used for biofilm elimination without causing the bacteria to develop significant resistance. However, the precise mode of action is still the subject of debate. This review discusses the formation of PAW generated species and their impacts on biofilms. A focus is placed on the diffusion of reactive species into biofilms, the formation of gradients and the resulting interaction with the biofilm matrix and specific biofilm components. Such an understanding will provide significant benefits for tackling the ubiquitous problem of biofilm contamination in food, water and medical areas.

Features and application of coupled cold plasma and photocatalysis processes for decontamination of water

Dielectric barrier discharge plasma and photocatalysis have been proposed as tools for decontamination of process water, especially in food industry. The present investigation aims to redefine and identify the features of coupling the two technologies in terms of degradation efficiency of a model compound. Results show that, when the process is carried out in plasma activated water in the presence of irradiated TiO₂, the efficiency of the integrated process is lower than the sum of the two processes acting separately. It is proposed that afterglow species, e.g. hydrogen peroxide and/or peroxynitrites could be activated by UVA light irradiation producing hydroxyl radicals in the liquid phase. Even if TiO₂ limits this additional effect by acting as UVA screen barrier material, its decontamination efficiency under certain conditions results higher than that obtained with plasma systems. These results open the route to chlorine-free decontamination processes and redefine the application framework of this integrated approach.

Plasma-activated water: Physicochemical properties, microbial inactivation mechanisms, factors influencing antimicrobial effectiveness, and applications in the food industry

Novel nonthermal inactivation technologies have been increasingly popular over the traditional thermal food processing methods due to their capacity in maintaining microbial safety and other quality parameters. Plasma-activated water (PAW) is a cutting-edge technology developed around a decade ago, and it has attracted considerable attention as a potential washing disinfectant. This review aims to offer an overview of the fundamentals and potential applications of PAW in the agri-food sector. A detailed description of the interactions between plasma and water can help to have a better understanding of PAW, hence the physicochemical properties of PAW are discussed. Further, this review elucidates the complex inactivation mechanisms of PAW, including oxidative stress and physical effect. In particular, the influencing factors on inactivation efficacy of PAW, including processing factors, characteristics of microorganisms, and background environment of water are extensively described. Finally, the potential applications of PAW in the food industry, such as surface decontamination for various food products, including fruits and vegetables, meat and seafood, and also the treatment on quality parameters are presented. Apart from decontamination, the applications of PAW for seed germination and plant growth, as well as meat curing are also summarized. In the end, the challenges and limitations of PAW for scale-up implementation, and future research efforts are also discussed. This review demonstrates that PAW has the potential to be successfully used in the food industry.

A Synergistic Effect of Reactive Oxygen and Reactive Nitrogen Species in Plasma Activated Liquid Media Triggers Astrocyte Wound Healing

Astrocyte proliferation and migration toward injured Central Nervous System (CNS) areas are key features of astrogliosis and glial scar formation. Even though it is known that intracellular and environmental Reactive Oxygen and Nitrogen Species (RONS) affect astrocyte behaviour in physiological and pathophysiological conditions, their effects on the migration and growth of astrocytes are still unclear. Plasma-technologies are emerging in medicine as a tool to generate RONS for treating cells directly or through Plasma Activated Liquid Media (PALM). In this paper, we show for the first time how the use of PALM can modulate both astrocyte growth and migration as a function of active species produced by plasma in liquids. Our results show that PALM, generated by means of cold atmospheric pressure plasmas fed with N_2, air or O₂, can modulate astrocyte behaviour depending on the content of hydrogen peroxide and nitrite in the liquid. In particular, H₂O₂ enriched PALM induced a negative effect on cell growth associated with the mild wound healing improvement of primary astrocytes, in a scratch assay. Nitrite enriched PALM induced a selective effect on the wound healing without affecting cell growth. PALM containing a more balanced level of H₂O₂ and NO₂^- were able to affect cell growth, as well as significantly ameliorate wound healing. None of the PALM investigated induced upregulation of the gliotic inflammatory marker glial fibrillary acidic protein (GFAP), or of the astrocyte markers Aquaporin-4 (AQP4) and Connexin-43 (Cx-43) analysed by Western blot. Finally, immunofluorescence analysis revealed the presence of NO₂^- able to induce elongated protrusions at the front end of wounded astrocytes in the direction of cell migration. With our study we believe to have shown that PALM offer a novel tool to modulate astrocyte behaviour and that they are promising candidates for controlling astrogliosis in the case of CNS injuries.

Time-resolved luminescence detection of peroxynitrite using a reactivity-based lanthanide probe

Peroxynitrite (ONOO-) is a powerful and short-lived oxidant formed in vivo, which can react with most biomolecules directly. To fully understand the roles of ONOO- in cell biology, improved methods for the selective detection and real-time analysis of ONOO- are needed. We present a water-soluble, luminescent europium(iii) probe for the rapid and sensitive detection of peroxynitrite in human serum, living cells and biological matrices. We have utilised the long luminescence lifetime of the probe to measure ONOO- in a time-resolved manner, effectively avoiding the influence of autofluorescence in biological samples. To demonstrate the utility of the Eu(iii) probe, we monitored the production of ONOO- in different cell lines, following treatment with a cold atmospheric plasma device commonly used in the clinic for skin wound treatment.