Bacterial inactivation by plasma treated water enhanced by reactive nitrogen species

Enhanced oxidation of parabens in an aqueous solution by air-assisted cold plasma

Various contaminants of emerging concern (CECs) including pharmaceuticals and personal care products (PPCPs) have been known to threaten the aquatic ecosystem and human health even at low levels in surface water. Among them, the wide variety use of parabens as preservatives may pose potential threat to human because parabens may present estrogenic activity. Various advanced oxidation processes have been attempted to reduce parabens, but challenges using cold plasma (CP) are very rare. CP is worth paying attention to in reducing parabens because it has the advantage of generating radical ions, including reactive oxygen/nitrogen species and various ions. Accordingly, this study demonstrates how CP can be utilized and how CP competes with other advanced oxidation processes in energy requirements. Quantified ethyl-, propyl-, and butyl-paraben indicate that CP can effectively degrade them up to 99.1% within 3 h. Regression reveals that the kinetic coefficients of degradation can be increased to as high as 0.0328 min-1, comparable to other advanced oxidation processes. Many by-products generated from the oxidation of parabens provide evidence of the potential degradation pathway through CP treatment. In addition, we found that the electrical energy consumption per order of CP (39-95 kWh/m3/order) is superior to other advanced oxidation processes (69∼31,716 kWh/m3/order). Overall, these results suggest that CP may be a viable option to prevent adverse health-related consequences associated with parabens in receiving water.

Antimicrobial efficacy of direct air gas soft jet plasma for the in vitro reduction of oral bacterial biofilms

The aim of this study was to evaluate the antimicrobial efficacy of an air gas soft jet CAP for its potential use in removing oral biofilms, given that plasma-based technologies have emerged as promising methods in periodontology. Two types of biofilms were developed, one by Streptococcus mutans UA 159 bacterial strain and the other by a complex mixture of saliva microorganisms isolated from a patient with periodontitis. This latter biofilm was characterized via Next Generation Sequencing to determine the main bacterial phyla. The CAP source was applied at a distance of 6 mm for different time points. A statistically significant reduction of both CFU count and XTT was already detected after 60 s of CAP treatment. CLSM analysis supported CAP effectiveness in killing the microorganisms inside the biofilm and in reducing the thickness of the biofilm matrix. Cytotoxicity tests demonstrated the possible use of CAP without important side effects towards human gingival fibroblasts cell line. The current study showed that CAP treatment was able to significantly reduce preformed biofilms developed by both S. mutans and microorganisms isolated by a saliva sample. Further studies should be conducted on biofilms developed by additional saliva donors to support the potential of this innovative strategy to counteract oral pathogens responsible for periodontal diseases.

Collaborative Optimization Design of Self-Powered Sterilizer with Highly Efficient Synergistic Antibacterial Effect

The development of self-powered sterilizers has garnered significant attention in the scientific and engineering fields. However, there remains an urgent need to improve their sterilization efficiency. In this study, we present a self-powered sterilizer with superior antibacterial capability by maximizing the utilization of breakdown discharge generated by a soft-contact freestanding rotary triboelectric nanogenerator (FR-TENG). To achieve this, a collaborative optimization strategy is proposed, encompassing the structural design of the FR-TENG, the implementation of double voltage rectification, and manipulation of the gaseous phase. Through a comprehensive analysis of antibacterial rates and microscopic images, the effectiveness of the self-powered sterilizer against various types of bacteria, including Gram-positive and Gram-negative species, as well as mixed bacteria in natural seawater, is demonstrated. Further investigations into bacterial morphologies and solution compositions reveal that the synergistic effect between electroporation and the generation of reactive oxygen/nitrogen species contributes to efficient sterilization. Additionally, controlled trials and molecular dynamics simulations are conducted to quantitatively elucidate the synergistic antibacterial effect between electroporation and reactive oxygen/nitrogen species. This study highlights the effectiveness of the collaborative optimization strategy in enhancing the sterilization efficiency of self-powered sterilizers while providing valuable insights into the synergistic antibacterial mechanisms of physical and chemical sterilization.

Probing time-resolved plasma-driven solution electrochemistry in a falling liquid film plasma reactor: Identification of HO2- as a plasma-derived reducing agent

Many applications involving plasma-liquid interactions depend on the reactive processes occurring at the plasma-liquid interface. We report on a falling liquid film plasma reactor allowing for in situ optical absorption measurements of the time-dependence of the ferricyanide/ferrocyanide redox reactivity, complemented with ex situ measurement of the decomposition of formate. We found excellent agreement between the measured decomposition percentages and the diffusion-limited decomposition of formate by interfacial plasma-enabled reactions, except at high pH in thin liquid films, indicating the involvement of previously unexplored plasma-induced liquid phase chemistry enabled by long-lived reactive species. We also determined that high pH facilitates a reduction-favoring environment in ferricyanide/ferrocyanide redox solutions. In situ conversion measurements of a 1:1 ferricyanide/ferrocyanide redox mixture exceed the measured ex situ conversion and show that conversion of a 1:1 ferricyanide/ferrocyanide mixture is strongly dependent on film thickness. We identified three dominant processes: reduction faster than ms time scales for film thicknesses >100 µm, •OH-driven oxidation on time scales of <10 ms, and reduction on 15 ms time scales for film thickness <100 µm. We attribute the slow reduction and larger formate decomposition at high pH to HO2- formed from plasma-produced H2O2 enabled by the high pH at the plasma-liquid interface as confirmed experimentally and by computed reaction rates of HO2- with ferricyanide. Overall, this work demonstrates the utility of liquid film reactors in enabling the discovery of new plasma-interfacial chemistry and the utility of atmospheric plasmas for electrodeless electrochemistry.

Mitigation of T3SS-mediated virulence in waterborne pathogenic bacteria by multi-electrode cylindrical-DBD plasma-generated nitric oxide water

S. enterica, S. flexneri, and V. parahaemolyticus bacteria are globally recognized to cause severe diarrheal diseases, consisting of Type III Secretion System (T3SS) effectors that help in bacterial infection and virulence in host cells. This study investigates the properties of multi-electrode cylindrical DBD plasma-generated nitric oxide water (MCDBD-PG-NOW) treatment on the survival and virulence of S. enterica, S. flexneri, and V. parahaemolyticus bacteria. The Colony Forming Unit (CFU) assay, live/dead cell staining, lipid peroxidation assay, and bacteria morphological analysis showed substantial growth inhibition of bacteria. Moreover, to confirm the interaction of reactive nitrogen species (RNS) with bacterial membrane biotin switch assay, DAF-FM, and FTIR analysis were carried out, which established the formation of S-nitrosothiols in the cell membrane, intracellular accumulation of RNS, and changes in the cell composition post-PG-NOW treatment. Furthermore, the conventional culture-based method and a quantitative PCR using propidium monoazide showed minimal VBNC induction under similar condition. The efficiency of bacteria to adhere to mammalian colon cells was significantly reduced. In addition, the infection rate was also controlled by disrupting the virulent genes, leading to the collapse of the infection mechanism. This study provides insights into whether RNS generated from PG-NOW might be beneficial for preventing diarrheal infections.

Atmospheric non-thermal plasma inactivation of Ascosphaera apis, the causative agent of chalkbrood disease in honeybee

Ascosphaera apis is a worldwide pathogenic fungi of honeybees that can cause a decline in bee populations. In this study, we investigated the antifungal activity of non-thermal plasma on fungal growth. Spore inactivation after exposure to gas plasma by liquid phase and plasma activated water (PAW) and pathogenicity of A. apis in vivo were also examined. The results demonstrated that the mycelial growth of fungi was completely inhibited after argon plasma treatment. Both gas plasma and PAW exposures resulted in a significant decrease of A. apis spore numbers, maximum reduction of 1.71 and 3.18-fold, respectively. Germinated fungal spores on potato dextrose agar were also reduced after plasma treatment. SEM analysis revealed a disruption in the morphological structure of the fungal spores. The pathogenicity of A. apis on honeybee larvae was decreased after spores treated by gas plasma and PAW with a disease inhibition of 63.61 ± 7.28% and 58.27 ± 5.87%, respectively after 7 days of cultivation. Chalkbrood in honey bees have limited control options and our findings are encouraging. Here, we demonstrate a possible alternative control method using non-thermal plasma for chalkbrood disease in honeybees.

Plasma-generated nitric oxide water: A promising strategy to combat bacterial dormancy (VBNC state) in environmental contaminant Micrococcus luteus

The viable but non-culturable (VBNC) is an inactive state, and certain bacteria can enter under adverse conditions. The VBNC state challenges the environment, food safety, and public health since VBNCs may resuscitate and pose a risk to human health. The aim of this study was to investigate the effect of plasma-generated nitric oxide water (PG-NOW) on airborne contaminant Micrococcus luteus (M. luteus) and examine its potential to induce the VBNC state. The essential conditions for bacteria to enter VBNC state are low metabolic activity and rare or no culturable counts. The results indicated that PG-NOW effectively eliminates M. luteus, and the remaining bacteria are in culturable condition. Moreover, the conventional cultured-based method combined with a propidium iodide monoazide quantitative PCR (PMAxxTM-qPCR) showed no significant VBNC induction and moderate culturable counts. Results from the qPCR revealed that gene levels in PG-NOW treated bacteria related to resuscitation-promoting factors, amino acid biosynthesis, and fatty acid metabolism were notably upregulated. PG-NOW inactivated M. luteus showed negligible VBNC formation and alleviated infection ability in lung cells. This study provides new insights into the potential use of PG-NOW reactive species for the prevention and control of the VBNC state of M. luteus.

Visible light-driven NH2Cl activation by g-C3N4 photocatalysis producing reactive nitrogen species to degrade bisphenol A

The photolysis of monochloramine (NH₂Cl), a widely used disinfectant, under UVC irradiation produces different radicals for the micropollutant degradation. For the first time, this study demonstrates the degradation of bisphenol A (BPA) via the NH₂Cl activation by graphitic carbon nitride (g-C₃N₄) photocatalysis using visible light-LEDs at 420 nm, termed as the Vis₄₂₀/g-C₃N₄/NH₂Cl process. The process produces •NH₂, •NH₂OO, •NO and •NO₂ via the e_CB^-- and O₂^•--induced activation pathways and •NHCl and NHClOO• via the h_VB⁺-induced activation pathway. The produced reactive nitrogen species (RNS) enhanced 100% of the BPA degradation compared with the Vis₄₂₀/g-C₃N₄. Density functional theory calculations confirmed the proposed NH₂Cl activation pathways and further demonstrated that e_CB^-/O₂^•- and h_VB⁺ induced the cleavage of N-Cl and N-H bonds in NH₂Cl, respectively. The process converted 73.5% of the decomposed NH₂Cl to nitrogen-containing gas, compared with that of approximately 20% in the UVC/NH₂Cl process, leaving much less ammonia, nitrite and nitrate in water. Among different operating conditions and water matrices tested, of particular significance is natural organic matter of 5 mgDOC/L only reduced 13.1% of the BPA degradation compared against that of at least 46% reduction in the UVC/NH₂Cl process. Only 0.017-0.161 µg/L of disinfection byproducts were produced, two orders of magnitudes lower than that in the UVC/chlorine and UVC/NH₂Cl processes. The combined use of visible light-LEDs, g-C₃N₄ and NH₂Cl significantly improves the micropollutant degradation and reduces the energy consumption and byproduct formation of the NH₂Cl-based AOP.

Comparison of Physicochemical Properties of Silver and Gold Nanocomposites Based on Potato Starch in Distilled and Cold Plasma-Treated Water

Nanometal-containing biocomposites find wide use in many industries and fields of science. The physicochemical properties of these materials depend on the character of the polymer, the size and shape of the metallic nanoparticles, and the interactions between the biopolymer and the nanoparticles. The aim of the work was to synthesise and study the effect of plasma-treated water on the properties of the obtained metallic nanoparticles as well as the physicochemical and functional properties of nanocomposites based on potato starch. The metallic nanoparticles were synthesised within a starch paste made in distilled water and in distilled water exposed to low-temperature, low-pressure plasma. The materials produced were characterised in terms of their physicochemical properties. Studies have shown that gold and silver nanoparticles were successfully obtained in a matrix of potato starch in distilled water and plasma water. SEM (Scanning Electron Microscopy) images and UV-Vis spectra confirmed the presence of nanosilver and nanosilver in the obtained composites. On the basis of microscopic images, the size of nanoparticles was estimated in the range from 5 to 20 nm for nanoAg and from 15 to 40 nm for nanoAu. The analysis of FTIR-ATR spectra showed that the type of water used and the synthesis of gold and silver nanoparticles did not lead to changes in the chemical structure of potato starch. DLS analysis showed that the nanoAg obtained in the plasma water-based starch matrix were smaller than the Ag particles obtained using distilled water. Colour analysis showed that the nanocomposites without nanometals were colourless, while those containing nanoAg were yellow, while those with nanoAu were dark purple. This work shows the possibility of using plasma water in the synthesis of nanometals using potato starch, which is a very promising polysaccharide in terms of many potential applications.

A, Boopathy B, Chatterjee R, M. H, Chakravortty D, Rao L. Generation of neutral pH high‐strength plasma‐activated water from a pin to water discharge and its bactericidal activity on multidrug‐resistant pathogens

Plasma‐activated water (PAW) is emerging as a green alternative technology in biomedicine due to its rich and diverse aqueous reactive nitrogen and oxygen species (RONS). This study explores how to configure a pin to water (P2W) discharge to generate neutral pH high‐strength plasma‐activated water (hs‐PAW) and its bactericidal activity on hypervirulent multidrug resistance (MDR) pathogens. The factors affecting the strength of PAW, namely: water type, PAW temperature, plasma enclosure, and activation time, were studied and optimized to generate hs‐PAW having 650 ± 40 mg/l of and 215 ± 15 mg/l of H2O2 at a pH of 7. This study demonstrates a simple P2W discharge set up to handle the MDR pathogens and can be easily scalable for real‐world medical applications.

Optimization of Plasma-activated Water and Validation of a Potential Surrogate for Salmonella for Future Egg Washing Processes

Plasma-activated water (PAW) is considered a novel sanitizer for the food industry due to the antimicrobial mechanisms exhibited by reactive oxygen and nitrogen species. The plasma operation parameters can affect the chemistry of PAW and can therefore influence its microbial inactivation efficacy. This study statistically optimized the operating conditions of PAW (activation time, distance from nozzle, and volume of water) using response surface methodology. Two optimized conditions of PAW were identified for the inactivation of planktonic cells of the avirulent strain of Salmonella Typhimurium MHM112 providing a minimum reduction of 6.3 log. All three operating parameters significantly affected the physicochemical characteristics (pH, ORP, EC, nitrite, and nitrate) and microbial inactivation efficacy of PAW. Mixing of small batches using the two optimized conditions to obtain larger volumes did not significantly change the microbial inactivation. However, there were significant reductions in nitrite and nitrate concentrations in PAW due to the mixing of batches while the pH and ORP values remained unaffected. The storage of large volumes of PAW for 25 min at 40-46°C, which is the commercial egg washing temperature in the United States, did not significantly impact S. Typhimurium MHM112 inactivation or the physicochemical characteristics of PAW. A validation study using a cocktail of six pathogenic strains of Salmonella revealed no significant differences in inactivation between the avirulent S. Typhimurium MHM112 and the pathogenic strains, suggesting that the avirulent S. Typhimurium MHM112 may serve as a surrogate for sanitation of S. enterica at the optimized conditions of PAW. The results obtained from this study are useful for our long-term goal of evaluating PAW efficacy in surface egg washing to inactivate Salmonella.

Effect of the pH on the Antibacterial Potential and Cytotoxicity of Different Plasma-Activated Liquids

In this study, different plasma-activated liquids were evaluated for their antimicrobial effects against Escherichia coli, as well as for their cytotoxicity on mammalian cells. The PALs were prepared from distilled (DIS), deionized (DI), filtered (FIL), and tap (TAP) water. Additionally, 0.9% NaCl saline solution (SAL) was plasma-activated. These PALs were prepared using 5 L/min air gliding arc plasma jet for up to 60.0 min of exposure. Subsequently, the physicochemical properties, such as, the oxidation-reduction potential (ORP), the pH, the conductivity, and the total dissolved solids (TDS) were characterized by a water multiparameter. The PALs obtained showed a drastic decrease in the pH with increasing plasma exposure time, in contrast, the conductivity and TDS increased. In a general trend, the UV-vis analyses identified a higher production of the following reactive species of nitrogen and oxygen (RONS), HNO₂, H₂O₂, NO₃^-, and NO₂^-. Except for the plasma-activated filtered water (PAW-FIL), where there was a change in the position of NO₂^- and NO₃^- at some pHs, The higher production of HNO₂ and H₂O₂-reactive species was observed at a low pH. Finally, the standardized suspensions of Escherichia coli were exposed to PAL for up to 60.0 min. The plasma-activated deionized water (PAW-DI pH 2.5), plasma-activated distilled water (PAW-DIS pH 2.5 and 3), and plasma-activated tap water (PAW-TAP 3.5) showed the best antimicrobial effects at exposure times of 3.0, 10.0, and 30.0 min, respectively. The MTT analysis demonstrated low toxicity of all of the PAL samples. Our results indicate that the plasma activation of different liquids using the gliding arc system can generate specific physicochemical conditions that produce excellent antibacterial effects for E. coli with a safe application, thus bringing future contributions to creating new antimicrobial protocols.

Possible Synergies of Nanomaterial-Assisted Tissue Regeneration in Plasma Medicine: Mechanisms and Safety Concerns

Cold atmospheric plasma and nanomedicine originally emerged as individual domains, but are increasingly applied in combination with each other. Most research is performed in the context of cancer treatment, with only little focus yet on the possible synergies. Many questions remain on the potential of this promising hybrid technology, particularly regarding regenerative medicine and tissue engineering. In this perspective article, we therefore start from the fundamental mechanisms in the individual technologies, in order to envision possible synergies for wound healing and tissue recovery, as well as research strategies to discover and optimize them. Among these strategies, we demonstrate how cold plasmas and nanomaterials can enhance each other's strengths and overcome each other's limitations. The parallels with cancer research, biotechnology and plasma surface modification further serve as inspiration for the envisioned synergies in tissue regeneration. The discovery and optimization of synergies may also be realized based on a profound understanding of the underlying redox- and field-related biological processes. Finally, we emphasize the toxicity concerns in plasma and nanomedicine, which may be partly remediated by their combination, but also partly amplified. A widespread use of standardized protocols and materials is therefore strongly recommended, to ensure both a fast and safe clinical implementation.

Mechanistic Insight into Permeation of Plasma-Generated Species from Vacuum into Water Bulk

Due to their potential benefits, cold atmospheric plasmas (CAPs), as biotechnological tools, have been used for various purposes, especially in medical and agricultural applications. The main effect of CAP is associated with reactive oxygen and nitrogen species (RONS). In order to deliver these RONS to the target, direct or indirect treatment approaches have been employed. The indirect method is put into practice via plasma-activated water (PAW). Despite many studies being available in the field, the permeation mechanisms of RONS into water at the molecular level still remain elusive. Here, we performed molecular dynamics simulations to study the permeation of RONS from vacuum into the water interface and bulk. The calculated free energy profiles unravel the most favourable accumulation positions of RONS. Our results, therefore, provide fundamental insights into PAW and RONS chemistry to increase the efficiency of PAW in biological applications.

Energy-Efficient Small-Scale Ammonia Synthesis Process with Plasma-Enabled Nitrogen Oxidation and Catalytic Reduction of Adsorbed NOx

Industrial ammonia production without CO₂ emission and with low energy consumption is one of the technological grand challenges of this age. Current Haber-Bosch ammonia mass production processes work with a thermally activated iron catalyst needing high pressure. The need for large volumes of hydrogen gas and the continuous operation mode render electrification of Haber-Bosch plants difficult to achieve. Electrochemical solutions at low pressure and temperature are faced with the problematic inertness of the nitrogen molecule on electrodes. Direct reduction of N₂ to ammonia is only possible with very reactive chemicals such as lithium metal, the regeneration of which is energy intensive. Here, the attractiveness of an oxidative route for N₂ activation was presented. N₂ conversion to NO_x in a plasma reactor followed by reduction with H₂ on a heterogeneous catalyst at low pressure could be an energy-efficient option for small-scale distributed ammonia production with renewable electricity and without intrinsic CO₂ footprint.

Current Advancements in the Molecular Mechanism of Plasma Treatment for Seed Germination and Plant Growth

Low-temperature atmospheric pressure plasma has been used in various fields such as plasma medicine, agriculture, food safety and storage, and food manufacturing. In the field of plasma agriculture, plasma treatment improves seed germination, plant growth, and resistance to abiotic and biotic stresses, allows pesticide removal, and enhances biomass and yield. Currently, the complex molecular mechanisms of plasma treatment in plasma agriculture are fully unexplored, especially those related to seed germination and plant growth. Therefore, in this review, we have summarized the current progress in the application of the plasma treatment technique in plants, including plasma treatment methods, physical and chemical effects, and the molecular mechanism underlying the effects of low-temperature plasma treatment. Additionally, we have discussed the interactions between plasma and seed germination that occur through seed coat modification, reactive species, seed sterilization, heat, and UV radiation in correlation with molecular phenomena, including transcriptional and epigenetic regulation. This review aims to present the mechanisms underlying the effects of plasma treatment and to discuss the potential applications of plasma as a powerful tool, priming agent, elicitor or inducer, and disinfectant in the future.

Antimicrobial effects of microwave plasma-activated water with skin protective effect for novel disinfectants in pandemic era

Skin antiseptics have important implications for public health and medicine. Although conventional antiseptics have considerable antimicrobial activity, skin toxicity and the development of resistance are common problems. Plasma-treated water has sterilization and tissue-regenerative effects. Therefore, the aim of this study was to identify whether plasma-activated water (PAW) manufactured by our microwave plasma system can be used as a novel antiseptic solution for skin protection. PAW was produced by dissolving reactive nitrogen oxide gas using microwave plasma in deionized water. The antibacterial effects of PAW against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and Salmonella typhimurium and effective concentrations were investigated by a solid agar plate assay. The factors mediating the effects of PAW were evaluated by the addition of reactive species scavengers. Cytotoxicity and cell viability assays were performed to examine the protective effect of PAW on normal skin cells. PAW exhibited excellent sterilization and no toxicity in normal skin cells. Experiments also confirmed the potential of PAW as a sanitizer for SARS-CoV-2. Our findings support the use of PAW as an effective skin disinfectant with good safety in the current situation of a global pandemic.

Modulating the Antioxidant Response for Better Oxidative Stress-Inducing Therapies: How to Take Advantage of Two Sides of the Same Medal?

Oxidative stress-inducing therapies are characterized as a specific treatment that involves the production of reactive oxygen and nitrogen species (RONS) by external or internal sources. To protect cells against oxidative stress, cells have evolved a strong antioxidant defense system to either prevent RONS formation or scavenge them. The maintenance of the redox balance ensures signal transduction, development, cell proliferation, regulation of the mechanisms of cell death, among others. Oxidative stress can beneficially be used to treat several diseases such as neurodegenerative disorders, heart disease, cancer, and other diseases by regulating the antioxidant system. Understanding the mechanisms of various endogenous antioxidant systems can increase the therapeutic efficacy of oxidative stress-based therapies, leading to clinical success in medical treatment. This review deals with the recent novel findings of various cellular endogenous antioxidant responses behind oxidative stress, highlighting their implication in various human diseases, such as ulcers, skin pathologies, oncology, and viral infections such as SARS-CoV-2.

The Improvement of Reserve Polysaccharide Glycogen Level and Other Quality Parameters of S. cerevisiae Brewing Dry Yeasts by Their Rehydration in Water, Treated with Low-Temperature, Low-Pressure Glow Plasma (LPGP)

The increasing popularity of active dry yeast arises from its properties, such as ease of storage, and simplicity of preparation and dosing. Herein, we elaborate on the effect of plasma-treated water (PTW) under air atmosphere (PTWAir) and nitrogen (PTWN) on the improvement of the reserve polysaccharide glycogen level and other quality parameters of S. cerevisiae brewing dry yeast in comparison with the non plasma-treated water (CW). For this purpose, strains of top-fermenting (S. cerevisiae T58 (poor quality), S33 (poor quality)) and bottom-fermenting (S. pastorianus W30/70 (poor quality)) yeast stored one year after opening and S. cerevisiae US-05 (fresh strain) were selected to examine the influence of PTWs toward the quality parameters of yeast biomass after the rehydration and fermentation process. The obtained results showed that in the case of poor quality yeast strains, PTWAir increased glycogen content after the rehydration and fermentation process, which was a favorable trend. A similar increase was observed for the trehalose content. Results showed that PTWN significantly reduced the number of yeast cells in ale strains and the viability of all analyzed samples. The lowest viability was observed in Sc S33 strain for PTWAir (41.99%), PTWN (18.6%) and CW (22.86%). PTWAir did not contribute to reducing the analyzed parameter; in particular, the results of Sc T58 yeast strain’s viability are shown: PTWAir (58.83%), PTWN (32.28%) and CW (43.56%). The obtained results suggest that rehydration by PTWN of dry yeast with a weakened condition is not recommended for both qualitative and cost-related reasons, while PTWAir significantly contributed to the improvement of some yeast parameters after rehydration and fermentation (higher glycogen and trehalose content).

Plasma bioscience for medicine, agriculture and hygiene applications

Nonthermal biocompatible plasma (NBP) sources operating in atmospheric pressure environments and their characteristics can be used for plasma bioscience, medicine, and hygiene applications, especially for COVID-19 and citizen. This review surveyed the various NBP sources, including a plasma jet, micro-DBD (dielectric barrier discharge) and nanosecond discharged plasma. The electron temperatures and the plasma densities, which are produced using dielectric barrier discharged electrode systems, can be characterized as 0.7 ~ 1.8 eV and (3-5) × 1014-15 cm-3, respectively. Herein, we introduce a general schematic view of the plasma ultraviolet photolysis of water molecules for reactive oxygen and nitrogen species (RONS) generation inside biological cells or living tissues, which would be synergistically important with RONS diffusive propagation into cells or tissues. Of the RONS, the hydroxyl radical [OH] and hydrogen peroxide H2O2 species would mainly result in apoptotic cell death with other RONS in plasma bioscience and medicines. The diseased biological protein, cancer, and mutated cells could be treated by using a NBP or plasma activated water (PAW) resulting in their apoptosis for a new paradigm of plasma medicine.

Application of Water Treated with Low-Temperature Low-Pressure Glow Plasma (LPGP) in Various Industries

Plasma processing is now a key technology across the world, and nonthermal low-temperature plasmas are being increasingly used. This situation can be explained by a rapidly growing interest in the optimization of existing methods, as well as the development of new ones. Over the last few years, the production of plasma-treated water (PTW) by low-temperature low-pressure glow plasma (LPGP) under an atmosphere of various gases has been increasingly gaining in popularity. Research has been conducted on producing plasma-treated water in the presence of air, nitrogen, ammonia, carbon dioxide, and methane. All the obtained results show that the changed physicochemical properties of the water depend on the type of gas used and the duration of the plasma treatment. New research is emerging on the possibility of using this water in plant breeding, animal husbandry, cosmetology, medicine, and food. For the first time, plasma-treated water has also been tested for use in the brewing industry at the raw material preparation stage. The results obtained in all branches of science are very promising, contributing to the growing interest in plasma-treated water within the scientific community.

Inactivation efficacy and mechanism of pulsed corona discharge plasma on virus in water

The presence of viruses in water is a major risk for human and animal health due to their high resistance to disinfection. Pulsed corona discharge plasma (PCDP) efficiently inactivates bacteria by causing damage to biological macromolecules, but its effect on waterborne virus has not been reported. This study evaluated the inactivation efficacy of PCDP to viruses using spring viremia of carp virus (SVCV) as a model. The results showed that 4-log₁₀ reduction of SVCV infectivity in cells was reached after 120 s treatment, and there was no significant difference in survival of fish infected with SVCV inactivated by PCDP for 240 s or more longer compared to the control fish without virus challenge, thus confirming the feasibility of PCDP to waterborne virus inactivation. Moreover, the high input energy density caused by voltage significantly improved the inactivation efficiency. The further research indicated that reactive species (RS) generated by pulsed corona discharge firstly reacted with phosphoprotein (P) and polymerase complex proteins (L) through penetration into the SVCV virions, and then caused the loss of viral infectivity by damage to genome and other structural proteins. This study has significant implications for waterborne virus removal and development of novel disinfection technologies.

Vulnerability of SARS-CoV-2 and PR8 H1N1 virus to cold atmospheric plasma activated media

Cold Atmospheric Plasma (CAP) and Plasma Activated Media (PAM) are effective against bacteria, fungi, cancer cells, and viruses because they can deliver Reactive Oxygen and Nitrogen Species (RONS) on a living tissue with negligible damage on health cells. The antiviral activity of CAP against SARS-CoV-2 is being investigated, however, the same but of PAM has not been explored despite its potential. In the present study, the capability of Plasma Activated Media (PAM) to inactivate SARS-CoV-2 and PR8 H1N1 influenza virus with negligible damage on healthy cells is demonstrated. PAM acted by both virus detaching and diminished replication. Furthermore, the treatment of A549 lung cells at different times with buffered PAM did not induce interleukin 8 expression, showing that PAM did not induce inflammation. These results open a new research field by using PAM to the development novel treatments for COVID-19, influenza, and other respiratory diseases.

Interactions between pH, reactive species, and cells in plasma-activated water can remove algae

Lightning strikes cause nitrogen to dissolve in water and form reactive nitrogen and oxygen species, which form natural fertilizers that can be absorbed through plant roots. Such processes during rainstorm events can be simulated by applying plasma to a solution. Plasma-activated water (PAW) has great potential as a source of various dissolved reactive chemical species. Different mixtures of species are produced using different solution compositions. Here, basil seeds were grown in PAW to prevent blooms of Chlorella vulgaris and ion chromatography and UV-vis spectroscopy were used to quantify reactive ions. NO₂⁻, NO₃⁻, and H₂O₂ were found to be key to the antialgal effect. Secondary reactive ions such as peroxynitrite (ONOO⁻, ONOOH) were also involved. The antialgal effect was strongly related to the pH around the algal cells. Acidification was predominantly caused by the generation of NO₂⁻ and H₂O₂. After two weeks monitoring basil growth, the antifungal properties were preserved, few reactive oxygen species formed in the plasma zone, and only reactive nitrogen species were transformed into reactive peroxynitrite ions. The pH around the cells was determined using an iridium oxide microelectrode. The PAW antialgal mechanism depended on acidic conditions (pH 2.2, at which peroxynitrite can be generated) under which ONOOH penetrated the algal cell membranes, destroying the cells and preventing growth. This practical and sustainable PAW process allows a surprising amount of fertilizer to be generated with an antialgal effect that could be used in various eco-friendly agricultural processes under ambient conditions.

PAW is effective in inactivating microorganisms. We have measured a local pH to reveal the mechanism of algicidal effect in PAW. This is because protons pumped from the cell generate peroxynitrite around the cell to generate an acidic region.

High removal efficiency of industrial toxic compounds through stable catalytic reactivity in water treatment system

We identified optimal conditions for the disposal of high concentration of organic contaminants within a short time using a hybrid advanced oxidation process (AOP) combining various oxidizing agents. Plasma-treated water (PTW) containing many active species, that play dominant roles in the degradation of organic substances like hydroxyl radicals, atomic oxygen, ozone, and hydrogen peroxide, was used in this study as a strategy to improve degradation performance without the use of expensive chemical reagents like hydrogen peroxide. In particular, the optimal decomposition conditions using PTW, which were combined with 10 mg/h ozone, 2 g/L iron oxide, and 4 W UV light, demonstrated excellent removal abilities of a high concentration of reactive black 5 (RB5; 100 mg/L, >99%, [k] = 4.15 h^-1) and tetracycline (TC; 10 mg/L, >96.5%, [k] = 3.35 h^-1) for 25 min, approximately 1.5 times higher than that without PTW (RB5; 100 mg/L, 94%, [k] = 2.80 h^-1). These results confirmed that the production of strong reactive hydroxyl radicals from the decomposition process, as well as various reactive species included in PTW efficiently attacked pollutant substances, resulting in a higher removal rate. This suggests that a water treatment system with this optimal condition based on complex AOP systems using PTW could be useful in critical environmental and biomedical applications.

New Trends in Photodynamic Inactivation (PDI) Combating Biofilms in the Food Industry-A Review

Biofilms cause problems in the food industry due to their persistence and incompetent hygiene processing technologies. Interest in photodynamic inactivation (PDI) for combating biofilms has increased in recent years. This technique can induce microbial cell death, reduce cell attachment, ruin biofilm biomolecules and eradicate structured biofilms without inducing microbial resistance. This review addresses microbial challenges posed by biofilms in food environments and highlights the advantages of PDI in preventing and eradicating microbial biofilm communities. Current findings of the antibiofilm efficiencies of this technique are summarized. Additionally, emphasis is given to its potential mechanisms and factors capable of influencing biofilm communities, as well as promising hurdle strategies.

Role of polystyrene microplastics in sunlight-mediated transformation of silver in aquatic environments: Mechanisms, kinetics and toxicity

Sunlight-oxidative ageing is a common and critical process for microplastics (MPs) in aquatic environments. O₂^•-, ¹O₂, and •OH generation has been widely proven in this process, which can alter metal speciation based on its reduction and oxidation potential. Herein, chemical speciation of Ag mediated by polystyrene (PS) MPs was determined under simulated sunlight irradiation. The O₂^•- generation on the PS MPs surfaces is the vital factor for Ag⁺ reduction, regardless of acid or base conditions. The ¹O₂ and •OH are dominant factors, and ¹O₂ played a more important role than •OH for its higher formation amount, causing oxidative dissolution of newly formed Ag⁰ nanoparticles (NPs). The Ag NPs can hetero-aggregate with PS MPs through electrostatic interactions with O-containing groups (C-O, C-OH and CO), and co-precipitate from the water phase. This hetero-aggregation can stabilize Ag NPs by inhibiting Ag NPs surface photooxidation and suppressing Ag⁺ release. Transformation of Ag species (from Ag⁺ to Ag⁰ NPs) mediated by sunlight with PS MPs significantly suppressed acute toxicity of Ag⁺ to Escherichia coli, Selenastrum capricornutum, Daphnia magna and zebrafish. This study emphasized that PS MPs play an important role in the speciation, migration and toxicity of Ag⁺ in freshwater environments.

Non-thermal plasma-based inactivation of bacteria in water using a microfluidic reactor

Failure of conventional water treatment systems may lead to the contamination of water sources, which can cause outbreaks of waterborne healthcare associated infections. Advanced oxidation processing by non-thermal plasma has the potential to treat water without the addition of chemicals. Antibiotic resistant Pseudomonas aeruginosa and Escherichia coli were chosen to investigate the use of non-thermal plasma generated in a microfluidic reactor to disinfect bacteria contaminated water. The microfluidic reactor used in this study utilized a dielectric barrier discharge, in a gas-liquid phase annular flow regime. Microbiological analysis of water inoculated with P. aeruginosa and E. coli was carried out before and after plasma treatment. Using air as the carrier gas, effective disinfection of water was achieved. At the lowest flow rate (35 µL/min), P. aeruginosa and E. coli viability were drastically reduced, with an approximate 8 log maximum decrease in viability following an estimated residence time of 5 s of plasma treatment. Scanning electron microscopy indicated changes in cell morphology due to the plasma treatment. Live/Dead assays revealed that the membranes of the cells had been damaged after plasma treatment. This work demonstrated that non-thermal plasma has the potential to disinfect against microbial contamination in water.

Evaluation of non-thermal effect of microwave radiation and its mode of action in bacterial cell inactivation

A growing body of literature has recognized the non-thermal effect of pulsed microwave radiation (PMR) on bacterial systems. However, its mode of action in deactivating bacteria has not yet been extensively investigated. Nevertheless, it is highly important to advance the applications of PMR from simple to complex biological systems. In this study, we first optimized the conditions of the PMR device and we assessed the results by simulations, using ANSYS HFSS (High Frequency Structure Simulator) and a 3D particle-in-cell code for the electron behavior, to provide a better overview of the bacterial cell exposure to microwave radiation. To determine the sensitivity of PMR, Escherichia coli and Staphylococcus aureus cultures were exposed to PMR (pulse duration: 60 ns, peak frequency: 3.5 GHz) with power density of 17 kW/cm² at the free space of sample position, which would induce electric field of 8.0 kV/cm inside the PBS solution of falcon tube in this experiment at 25 °C. At various discharges (D) of microwaves, the colony forming unit curves were analyzed. The highest ratios of viable count reductions were observed when the doses were increased from 20D to 80D, which resulted in an approximate 6 log reduction in E. coli and 4 log reduction in S. aureus. Moreover, scanning electron microscopy also revealed surface damage in both bacterial strains after PMR exposure. The bacterial inactivation was attributed to the deactivation of oxidation-regulating genes and DNA damage.

Characterizations of a Plasma-Water System Generated by Repetitive Microsecond Pulsed Discharge with Air, Nitrogen, Oxygen, and Argon Gases Species

A non-thermal plasma-water system using a microsecond pulsed high-voltage power supply was investigated with air, nitrogen, oxygen, and argon gas feedings individually. Optical emission spectroscopy (OES) was utilized to characterize the primary active species inside the plasmas generated by different gas feedings. The OES method was also employed to estimate the neutral gas and electron temperatures. The pH and the oxidation-reduction potential (ORP) of plasma-activated water (PAW) were measured in the liquid phase. An ion chromatography system (ICS) was employed to present the PAW activity, such as nitrite and nitrate species. Moreover, hydrogen peroxide as a secondary active species inside the activated water, generated by the gases mentioned above, was measured by potassium permanganate titration. It was found that the gas species have a noticeable effect on the pH level as well as the ORP of PAW. In the cases of argon and oxygen plasmas, the pH level of PAW does not change significantly. In contrast, the pH values of PAW generated by air and nitrogen plasmas decline sharply during the treatment time. Moreover, the gas species have a significant impact on the concentrations of nitrite, nitrate, and hydrogen peroxide generated in PAW. The activated water generated by oxygen plasma provides the highest level of hydrogen peroxide. Although the consumed power of argon plasmas was half of the other plasma sources, it provides relatively high hydrogen peroxide contents compared to the nitrogen and air plasmas.

Molecular design and preparation of 2-aminothiazole sulfanilamide oximes as membrane active antibacterial agents for drug resistant Acinetobacter baumannii

A series of 2-aminothiazole sulfanilamide oximes were developed as new membrane active antibacterial agents to conquer the microbial infection. Benzoyl derivative 10c was preponderant for the treatment of drug-resistant A. baumannii infection in contrast to norfloxacin and exerted excellent biocompatibility against mammalian cells including erythrocyte and LO2 cell line. Meanwhile, it had ability to eradicate established biofilm to alleviate the resistance burden. Mechanism investigation elucidated that compound 10c was able to disturb the membrane effectively and inhibit lactic dehydrogenase, which led to cytoplasmic content leakage. The cellular redox homeostasis was interfered via the production of reactive oxygen and nitrogen species (RONS), which further contributed to respiratory pathway inactivation and reduction of GSH activity. This work indicated that 2-aminothiazole sulfanilamide oximes could be a promising start for the exploitation of novel antibacterial agents against pathogens.

The Effect of Using Micro-Clustered Water as a Polymer Medium

The aim of the study was to investigate the changes within the physicochemical properties of gelatin, carrageenan, and sodium alginate hydrosols prepared on the basis of micro-clustered (MC) water. The rheological parameters, contact angle and antioxidant activity of hydrosols were investigated. Moreover, the pH, oxidation–reduction potential (ORP) and electrical conductivity (EC) were measured. The hydrosols with MC water were characterized by a lower pH, decreased viscosity, a lower contact angle, and only slightly lower antioxidant activity than control samples. The results showed that hydrosol’s properties are significantly changed by MC water, which can lead to enhancement of its applicability but requires further investigation.

Plasma bioscience and its application to medicine

Nonthermal atmospheric pressure biocompatible plasma (NBP), alternatively called bio-cold plasma, is a partially ionized gas that consists of charged particles, neutral atoms and molecules, photons, an electric field, and heat. Recently, nonthermal plasma-based technology has been applied to bioscience, medicine, agriculture, food processing, and safety. Various plasma device configurations and electrode layouts has fast-tracked plasma applications in the treatment of biological and material surfaces. The NBP action mechanism may be related to the synergy of plasma constituents, such as ultraviolet radiation or a reactive species. Recently, plasma has been used in the inactivation of viruses and resistant microbes, such as fungal cells, bacteria, spores, and biofilms made by microbes. It has also been used to heal wounds, coagulate blood, degrade pollutants, functionalize material surfaces, kill cancers, and for dental applications. This review provides an outline of NBP devices and their applications in bioscience and medicine. We also discuss the role of plasma-activated liquids in biological applications, such as cancer treatments and agriculture. The individual adaptation of plasma to meet specific medical requirements necessitates real-time monitoring of both the plasma performance and the target that is treated and will provide a new paradigm of plasma-based therapeutic clinical systems.

Physical plasma-derived oxidants sensitize pancreatic cancer cells to ferroptotic cell death

Despite modern therapeutic advances, the survival prospects of pancreatic cancer patients remain poor, due to chemoresistance and dysregulated oncogenic kinase signaling networks. We applied a novel kinome activity-mapping approach using biological peptide targets as phospho-sensors to identify vulnerable kinase dependencies for therapy sensitization by physical plasma. Ser/Thr-kinome specific activity changes were mapped upon induction of ferroptotic cell death in pancreatic tumor cells exposed to reactive oxygen and nitrogen species of plasma-treated water (PTW). This revealed a broad kinome activity response involving the CAMK, the AGC and CMGC family of kinases. This systems-level kinome network response supports stress adaptive switches between chemoresistant anti-oxidant responses of Kelch-like ECH-associated protein 1 (KEAP1)/Heme Oxygenase 1 (HMOX1) and ferroptotic cell death sensitization upon suppression of Nuclear factor (erythroid derived 2)-like 2 (NRF2) and Glutathione peroxidase 4 (GPX4). This is further supported by ex vivo experiments in the chicken chorioallantoic membrane assay, showing decreased GPX4 and Glutathione (GSH) expression as well as increased lipid peroxidation, along with suppressed BxPC-3 tumor growth in response to PTW. Taken all together, we demonstrate that plasma treated water-derived oxidants sensitize pancreatic cancer cells to ferroptotic cell death by targeting a NRF2-HMOX1-GPX4 specific kinase signaling network.

Distinct Chemistries Define the Diverse Biological Effects of Plasma Activated Water Generated with Spark and Glow Plasma Discharges

The spread of multidrug-resistant bacteria poses a significant threat to human health. Plasma activated liquids (PAL) could be a promising alternative for microbial decontamination, where different PAL can possess diverse antimicrobial efficacies and cytotoxic profiles, depending on the range and concentration of their reactive chemical species. In this research, the biological activity of plasma activated water (PAW) on different biological targets including both microbiological and mammalian cells was investigated in vitro. The aim was to further an understanding of the specific role of distinct plasma reactive species, which is required to tailor plasma activated liquids for use in applications where high antimicrobial activity is required without adversely affecting the biology of eukaryotic cells. PAW was generated by glow and spark discharges, which provide selective generation of hydrogen peroxide, nitrite and nitrate in the liquid. The PAW made by either spark or glow discharges showed similar antimicrobial efficacy and stability of activity, despite the very different reactive oxygen species (ROS) and reactive nitrogen species profiles (RNS). However, different trends were observed for cytotoxic activities and effects on enzyme function, which were translated through the selective chemical species generation. These findings indicate very distinct mechanisms of action which may be exploited when tailoring plasma activated liquids to various applications. A remarkable stability to heat and pressure was noted for PAW generated with this set up, which broadens the application potential. These features also suggest that post plasma modifications and post generation stability can be harnessed as a further means of modulating the chemistry, activity and mode of delivery of plasma functionalised liquids. Overall, these results further understanding on how PAL generation may be tuned to provide candidate disinfectant agents for biomedical application or for bio-decontamination in diverse areas.

New developments in anti-biofilm intervention towards effective management of orthopedic device related infections (ODRI's)

Orthopedic device related infections (ODRI's) represent a difficult to treat situation owing to their biofilm based nature. Biofilm infections once established are difficult to eradicate even with an aggressive treatment regimen due to their recalcitrance towards antibiotics and immune attack. The involvement of antibiotic resistant pathogens as the etiological agent further worsens the overall clinical picture, pressing on the need to look into alternative treatment strategies. The present review highlightes the microbiological challenges associated with treatment of ODRI's due to biofilm formation on the implant surface. Further, it details the newer anti-infective modalities that work either by preventing biofilm formation and/or through effective disruption of the mature biofilms formed on the medical implant. The study, therefore aims to provide a comprehensive insight into the newer anti-biofilm interventions (non-antibiotic approaches) and a better understanding of their mechanism of action essential for improved management of orthopedic implant infections.

The Feasibility Study of Plasma-activated Water as a Physical Therapy to Induce Apoptosis in Melanoma Cancer Cells In-vitro

Low-temperature plasma (LTP) has demonstrated great potential in biomedicine, especially in cancer therapy in-vivo and in-vitro. Plasma activated water (PAW) as an indirect plasma therapy is a significant source of reactive oxygen and nitrogen species (RONS) which play an important role in apoptosis induction in cancer cells. In this study, Helium (He) plasma jet operating in 0.75 W and 20 kHz as dissipated power and frequency, respectively, is used as the cold plasma source. The electrical, thermal, and spectroscopic properties of (He) plasma jet and pH as well as the conductivity and temperature of PAW samples, are investigated. The concentration of hydrogen peroxide (H2O2), nitrite (NO2 -) and nitrate (NO- 3), which are produced in water as long-lived anticancer RONS, was measured 471.6, 7.9 and 93.5 μM, respectively after 6 min of plasma treatment. Alamar Blue and flow cytometry assays were employed to investigate the B16F10 cancer metabolic activity and apoptosis. These data support that cold atmospheric plasma (CAP) can produce a certain concentration of anti-cancer agents in water and induce apoptosis in melanoma cancer cells due to RONSs via activating the caspase 3 pathway.

Effect of plasma-induced oxidative stress on the glycolysis pathway of Escherichia coli

Antibiotic resistance is one of the world's most urgent public health problems. Due to its antibacterial properties, cold atmospheric plasma (CAP) may serve as an alternative method to antibiotics. It is claimed that oxidative stress caused by CAP is the main reason of bacteria inactivation. In this work, we computationally investigated the effect of plasma-induced oxidation on various glycolysis metabolites, by monitoring the production of the biomass. We observed that in addition to the significant reduction in biomass production, the rate of some reactions has increased. These reactions produce anti-oxidant products, showing the bacterial defense mechanism to escape the oxidative damage. Nevertheless, the simulations show that the plasma-induced oxidation effect is much stronger than the defense mechanism, causing killing of the bacteria.

Plasma Agriculture from Laboratory to Farm: A Review

In recent years, non-thermal plasma (NTP) application in agriculture is rapidly increasing. Many published articles and reviews in the literature are focus on the post-harvest use of plasma in agriculture. However, the pre-harvest application of plasma still in its early stage. Therefore, in this review, we covered the effect of NTP and plasma-treated water (PTW) on seed germination and growth enhancement. Further, we will discuss the change in biochemical analysis, e.g., the variation in phytohormones, phytochemicals, and antioxidant levels of seeds after treatment with NTP and PTW. Lastly, we will address the possibility of using plasma in the actual agriculture field and prospects of this technology.

Anticancer Effects of Plasma-Activated Medium Produced by a Microwave-Excited Atmospheric Pressure Argon Plasma Jet

Cold atmospheric plasma (CAP) has been reported to have strong anticancer effects in vitro and in vivo. CAP has been known to induce apoptosis in most cancer cells by treatment to cells using direct and indirect treatment methods. There are many reports of apoptosis pathways induced by CAP, but for indirect treatment, there is still a lack of fundamental research on how CAP can cause apoptosis in cancer cells. In this study, we applied an indirect treatment method to determine how CAP can induce cancer cell death. First, plasma-activated medium (PAM) was produced by a 2.45 GHz microwave-excited atmospheric pressure plasma jet (ME-APPJ). Next, the amounts of various reactive species in the PAM were estimated using colorimetric methods. The concentration of NO₂^– and H₂O₂ in PAM cultured with cancer cells was measured, and intracellular reactive oxidative stress (ROS) changes were observed using flow cytometry. When PAM was incubated with A549 lung cancer cells, there was little change in NO₂^– concentration, but the concentration of H₂O₂ gradually decreased after 30 min. While the intracellular ROS of A549 cells was rapidly increased at 2 hours, there was no significant change in that of PAM-treated normal cells. Furthermore, PAM had a significant cytotoxic effect on A549 cells but had little effect on normal cell viability. In addition, using flow cytometry, we confirmed that apoptosis of A549 cells occurred following flow cytometry and western blot analysis. These results suggest that among various reactive species produced by PAM, hydrogen peroxide plays a key role in inducing cancer cell apoptosis.

Plasma-Functionalized Water: from Bench to Prototype for Fresh-Cut Lettuce

Fresh-cut produce like lettuce may contain a very high microbial load, including human pathogens. Therefore, the need for antimicrobial agents at post-harvest stages to mitigate microbial cross-contamination and growth is evident. Sanitation based on non-thermal plasma (NTP) reveals innovative food processing possibilities by application at different points along the food chain, for production, modification, and preservation, as well as in packaging of plant- and animal-based food. The aim of the present study was to evaluate the applicability of plasma-treated water (PTW) as antimicrobial process water additives for washing in fresh-cut lettuce processing. Antibacterial activities of PTW the natural occurring microflora of lettuce were examined. Different process variants of PTW application inside the washing process were investigated. Fresh-cut lettuce were investigated regarding microbiological safety and food quality. Samples were analyzed for antimicrobial and metabolic activity as well as metabolic vitality to prove food safety. The investigations for food quality included color and texture analyses and nitrate concentration detection in fresh tissue as well as microscopic measurements by scanning electron microscopy (SEM) and atomic force microscopy (AFM) for tissue surface structure and transmission electron microscopy (TEM) for cell organelle investigations. The application of PTW allowed up to 5 log10 cycle reduction, depending on the process variant and scale (lab and pilot scale). The increase of antimicrobial activity was accompanied by a reduction of metabolic activity, but not consequently by a decrease in metabolic vitality. Food quality was not affected by the use of PTW in the washing process of the fresh-cut lettuce. The promising results in color and texture were supported by the results of the microscopic assays. These promising results may lead to an industrial application of PTW as process water additive in fresh-cut produce processing to reduce the microbial load on the food surface and in addition in the process water or on food processing surfaces.

Inactivation of foodborne pathogens by the synergistic combinations of food processing technologies and food-grade compounds

There is a need to develop food processing technologies with enhanced antimicrobial capacity against foodborne pathogens. While considering the challenges of adequate inactivation of pathogenic microorganisms in different food matrices, the emerging technologies are also expected to be sustainable and have a minimum impact on food quality and nutrients. Synergistic combinations of food processing technologies and food-grade compounds have a great potential to address these needs. During these combined treatments, food processes directly or indirectly interact with added chemicals, intensifying the overall antimicrobial effect. This review provides an overview of the combinations of different thermal or nonthermal processes with a variety of food-grade compounds that show synergistic antimicrobial effect against pathogenic microorganisms in foods and model systems. Further, we summarize the underlying mechanisms for representative combined treatments that are responsible for the enhanced microbial inactivation. Finally, regulatory issues and challenges for further development and technical transfer of these new approaches at the industrial level are also discussed.

A Biomimetic Nanogenerator of Reactive Nitrogen Species Based on Battlefield Transfer Strategy for Enhanced Immunotherapy

Currently, cell membrane is always utilized for the construction of biomimetic nanoparticles. By contrast, mimicking the intracellular activity seems more meaningful. Inspired by the specific killing mechanism of deoxy-hemoglobin (Hb) dependent drug (RRx-001) in hypoxic red blood cells (RBC), this work aims to develop an inner and outer RBC-biomimetic antitumor nanoplatform that replicates both membrane surface properties and intracellularly certain therapeutic mechanisms of RRx-001 in hypoxic RBC. Herein, RRx-001 and Hb are introduced into RBC membrane camouflaged TiO₂ nanoparticles. Upon arrival at hypoxic tumor microenvironment (TME), the biomimetic nanoplatform (R@HTR) is activated and triggers a series of reactions to generate reactive nitrogen species (RNS). More importantly, the potent antitumor immunity and immunomodulatory function of RNS in TME are demonstrated. Such an idea would transfer the battlefield of RRx-001 from hypoxic RBC to hypoxic TME, enhancing its combat capability. As a proof of concept, this biomimetic nanoreactor of RNS exhibits efficient tumor regression and metastasis prevention. The battlefield transfer strategy would not only present meaningful insights for immunotherapy, but also realize substantial breakthroughs in biomimetic nanotechnology.

In situ generation of plasma-activated aerosols via surface acoustic wave nebulization for portable spray-based surface bacterial inactivation

The presence of reactive species in plasma-activated water is known to induce oxidative stresses in bacterial species, which can result in their inactivation. By integrating a microfludic chipscale nebulizer driven by surface acoustic waves (SAWs) with a low-temperature atmospheric plasma source, we demonstrate an efficient technique for in situ production and application of plasma-activated aerosols for surface disinfection. Unlike bulk conventional systems wherein the water is separately batch-treated within a container, we show in this work the first demonstration of continuous plasma-treatment of water as it is transported through a paper strip from a reservoir onto the chipscale SAW device. The significantly larger surface area to volume ratio of the water within the paper strip leads to a significant reduction in the duration of the plasma-treatment, while maintaining the concentration of the reactive species. The subsequent nebulization of the plasma-activated water by the SAW then allows the generation of plasma-activated aerosols, which can be directly sprayed onto the contaminated surface, therefore eliminating the storage of the plasma-activated water and hence circumventing the typical limitation in conventional systems wherein the concentration of the reactive species diminishes over time during storage, resulting in a reduction in the efficacy of bacterial inactivation. In particular, we show up to 96% reduction in Escherichia coli colonies through direct spraying with the plasma-activated aerosols. This novel, low-cost, portable and energy-efficient hybrid system necessitates only minimal maintenance as it only requires the supply of tap water and battery power for operation, and is thus suitable for decontamination in home environments.