Applications of Plasma-Activated Liquid in the Medical Field

Atmospheric cold plasma alters plant traits and negatively affects the growth and development of fall armyworm in rice

Plasma is considered as the fourth state of matter, and atmospheric cold plasma (cold plasma) is a type of plasma consisting of ionized gases containing excited species of atoms, molecules, ions, and free radicals at near room temperature. Cold plasma is generated by applying high voltage to gases, causing it to ionize thus forming plasma. Although cold plasma has been found to break seed dormancy and improve germination rate, only a few studies have explored the potential of cold plasma against insect herbivory. Given that cold plasma produces reactive oxygen and nitrogen species that can activate plant signalling molecules, it is plausible that cold plasma can have differential effects against insect herbivores. To test this, we evaluated the effectiveness of cold plasma on a polyphagous lepidopteran pest, Fall armyworm (FAW) [Spodoptera frugiperda (Lepidoptera: Noctuidae)] on rice (Oryza sativa L.) using an atmospheric plasma jet reactor that generated cold plasma using ambient air as the source gas. We treated rice seeds from two commonly grown Arkansas cultivars (Jewel and Diamond) with cold plasma, followed by irrigation with Cold Plasma-Activated Water (PAW). We then independently tested FAW growth on an artificial diet partially made with PAW. Our results show that cold plasma significantly affected the feeding, growth, and development of FAW, irrespective of the rice varieties. The effects of cold plasma treatment resulted in reduced damage by FAW, lower mass gain and longer pupation period on FAW compared to the untreated control. However, the effects of cold plasma on rice growth and development were dependent on the rice varieties. Cold plasma treatment also induced detrimental effects on FAW leading to ~ 25% mortality on cold plasma-treated plants when compared to untreated controls. Collectively, these findings offer significant evidence of the potential of cold plasma as a novel component for sustainable pest management.

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

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

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

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

Cold atmospheric plasma-activated saline alleviates secondary injury post-SCI by inhibiting extracellular matrix remodeling and infiltration of proinflammatory macrophages

BACKGROUND

Cold atmospheric plasma (CAP) has been shown to improve the recovery of transected peripheral nerves. We determined the protective role of CAP-activated saline (CAP-AS) treatment in the acute and subacute stages of spinal cord injury (SCI) in mice.

METHODS

C57BL/6 SCI mice were treated with CAP-AS for 14 days. Injury recovery was assessed weekly for four weeks by conducting motor function tests, including the Basso Mouse Scale (BMS) and footprint test. Transcriptome analysis was conducted on day 14 to elucidate potential mechanisms, which were further validated through immunofluorescence examinations of the injured spinal cord tissues on day 28 and the levels of proinflammatory cytokines produced by macrophages in vitro.

RESULTS

Compared to the SCI group, the CAP-AS-treated groups presented significantly better hindlimb motor function after four weeks. The downregulated (SCI vs. SCI + CAP-AS, with CAP-AS activated for 20 min) differentially expressed genes (DEGs) were enriched in the extracellular region, extracellular matrix (ECM), and ECM-receptor interaction. In contrast, the upregulated DEGs were enriched in immune response-associated pathways. Histological changes in the CAP-AS-treated groups were observed to further validate the predicted mechanisms 28 days post-injury. The alleviation of secondary injury was confirmed by an increase in GFAP-positive and NFH-positive areas, and enhanced outgrowth of 5-HT-positive fibers. Inhibited ECM remodeling was confirmed by a decrease in the areas positive for PDGFRβ, fibronectin, and laminin. A decrease in the infiltration of macrophages and activation of microglia was determined by a decrease in CD68-positive and F4/80-positive areas. The inhibitory effect of CAP-AS on inflammation was further supported by a decrease in the levels of the proinflammatory cytokines IL-1β, IL-6, and TNF-α in CAP-AS-treated M1 macrophages.

CONCLUSION

CAP-AS can alleviate secondary injury in SCI model mice by inhibiting ECM remodeling in injured tissues and reducing the infiltration or activation of proinflammatory macrophages/microglia.

Non-thermal atmospheric pressure plasma induces selective cancer cell apoptosis by modulating redox homeostasis

BACKGROUND

Anticancer treatments aim to selectively target cancer cells without harming normal cells. While non-thermal atmospheric pressure plasma (NTAPP) has shown anticancer potential across various studies, the mechanisms behind its selective action on cancer cells remain inadequately understood. This study explores the mechanism of NTAPP-induced selective cell death and assesses its application in cancer therapy.

METHODS

We treated HT1080 fibrosarcoma cells with NTAPP and assessed the intracellular levels of mitochondria-derived reactive oxygen species (ROS), mitochondrial function, and cell death mechanisms. We employed N-acetylcysteine to investigate ROS's role in NTAPP-induced cell death. Additionally, single-cell RNA sequencing was used to compare gene expression in NTAPP-treated HT1080 cells and human normal fibroblasts (NF). Western blotting and immunofluorescence staining examined the expression and nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2), a key antioxidant gene transcription factor. We also evaluated autophagy activity through fluorescence staining and transmission electron microscopy.

RESULTS

NTAPP treatment increased ROS levels and induced mitochondrial dysfunction, leading to apoptosis in HT1080 cells. The involvement of ROS in selective cancer cell death was confirmed by N-acetylcysteine treatment. Distinct gene expression patterns were observed between NTAPP-treated NF and HT1080 cells, with NF showing upregulated antioxidant gene expression. Notably, NRF2 expression and nuclear translocation increased in NF but not in HT1080 cells. Furthermore, autophagy activity was significantly higher in normal cells compared to cancer cells.

CONCLUSIONS

Our study demonstrates that NTAPP induces selective cell death in fibrosarcoma cells through the downregulation of the NRF2-induced ROS scavenger system and inhibition of autophagy. These findings suggest NTAPP's potential as a cancer therapy that minimizes damage to normal cells while effectively targeting cancer cells.

A novel liquid plasma derivative inhibits melanogenesis through upregulation of Nrf2

Non-thermal plasma (NTP) is an emerging technology with extensive applications in biomedicine, including treatment of abnormal pigmentation. However, very few studies have investigated how plasma induces anti-melanogenesis. Here, liquid plasma was prepared by treating an NTP jet with helium and oxygen (as carrier gases) for 15 min in serum-free culture media. In the zebrafish model, pigmentation ratio was observed with or without liquid plasma. The anti-melanogenic effect of liquid plasma was evaluated in human melanocytes by assessing the expression of melanogenesis-related genes using western blotting, RT-PCR, and immunohistochemistry. Liquid plasma reduced pigmentation in the zebrafish model and inhibited melanin synthesis in primary human melanocytes. Intracellular reactive oxygen species levels decreased and Nrf2 expression increased in liquid plasma-treated melanocytes. Liquid plasma affected microphthalmia-associated transcription factor (MITF) and tyrosinase mRNA and protein levels, tyrosinase activity, and melanin content. Considering the role of Wnt/β-catenin and PI3K/Akt pathways in melanogenesis, the effect of liquid plasma on this pathway was determined; liquid plasma decreased active β-catenin, LEF1/TCF4, MITF, and tyrosinase levels in a time-dependent manner and inhibited the nuclear translocation of β-catenin. This inhibition subsequently suppressed melanogenesis by downregulating MITF and tyrosinase. These results suggest that liquid plasma may be used for treating pigmentary disorders.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

TRIAL REGISTRATION

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

Machine learning-aided evaluation of oxidative strength of cold atmospheric plasma-treated water

Plasma medicine is gaining attraction in the medical field, particularly the use of cold atmospheric plasma (CAP) in biomedicine. The chemistry of the plasma is complex, and the reactive oxygen species (ROS) within it are the basis for the biological effect of CAP on the target. Understanding how the oxidative power of ROS responds to diverse plasma parameters is vital for standardizing the effective application of CAP. The proven applicability of machine learning (ML) in the field of medicine is encouraging, as it can also be applied in the field of plasma medicine to correlate the oxidative strength of plasma-treated water (PTW) according to different parameters. In this study, plasma-treated water was mixed with potassium iodide-starch reagent for color formation that could be linked to the oxidative capacity of PTW. Corresponding images were captured resulting from the exposure of the color-forming agent to water treated with plasma for different time points. Several ML models were trained to distinguish the color changes sourced by the oxidative strength of ROS. The AdaBoost Classifier (ABC) algorithm demonstrated better performance among the classification models used by extracting color-based features from the images. Our results, with a test accuracy of 63.5%, might carry a potential for future standardization in the field of plasma medicine with an automated system that can be created to interpret the oxidative properties of ROS in different plasma treatment parameters via ML.

Plasma-activated liquid as a potential decontaminant in healthcare: assessment of antibacterial activity and use with cleaning cloths

BACKGROUND

Cold air plasma (CAP) can generate plasma-activated liquids (PALs) with high concentrations of reactive oxygen (ROS) and nitrogen species (RNS), e.g., nitrites, with antimicrobial properties.

AIM

We investigated the concentrations of ROS and RNS in saline PAL. We assessed planktonic bacterial inactivation by PAL and the decontamination of contaminated cleaning cloths.

METHODS

Phosphate-buffered saline (PBS) was treated with an air-driven CAP jet for 90 or 300 s to generate PAL. The ROS and RNS were measured using quantitative fluorescent (2,7-dichlorofluorescin diacetate) and colourimetric (Greiss) assays. Isolates of MRSA and Escherichia coli were incubated in PAL overnight and inactivation measured through colony forming unit (cfu) assays. Sections of cleaning cloths were incubated with MRSA and E. coli, and treated with PAL for 1 h. Bacterial inactivation was measured through resazurin reduction assays.

RESULTS

Nitrites increased from 0.1 μM in untreated PBS to 49.1 μM and to 94.0 μM in 90- and 300-s CAP-treated PAL, respectively. ROS increased from 30 μM in untreated PBS to 75 μM and to 103 μM in 90- and 300-s CAP-treated PAL, respectively. 90-s PAL reduced MRSA and E. coli viability (P<0.05) and 300-s PAL resulted in more than a 7-log reduction of both. One-hour treatment of contaminated cleaning cloths in PAL resulted in a 55% and 73% reduction in viable MRSA and E. coli, respectively (P<0.05).

CONCLUSION

Inactivation of planktonic bacteria correlated with ROS and RNS concentrations. PAL reduced bacteria contaminated cleaning cloths. PAL has potential as a hospital disinfectant, including cleaning cloths.

Delivery Systems for Plasma-reactive Species and their Applications in the Field of Biomedicine

Cold atmospheric plasma (CAP) is an ionized matter with potential applications in various medical fields, ranging from wound healing and disinfection to cancer treatment. CAP's clinical usefulness stems from its ability to act as an adjustable source of reactive oxygen and nitrogen species (RONS), which are known to function as pleiotropic signaling agents within cells. Plasma-activated species, such as RONS, have the potential to be consistently and precisely released by carriers, enabling their utilization in a wide array of biomedical applications. Furthermore, understanding the behavior of CAP in different environments, including water, salt solutions, culture medium, hydrogels, and nanoparticles, may lead to new opportunities for maximizing its therapeutic potential. This review article sought to provide a comprehensive and critical analysis of current biomaterial approaches for the targeted delivery of plasma-activated species in the hope to boost therapeutic response and clinical applicability.

Chemical decontamination of foods using non-thermal plasma-activated water

The presence of chemical contaminants in foods and agricultural products is one of the major safety issues worldwide, posing a serious concern to human health. Nonthermal plasma (NTP) containing richly reactive oxygen and nitrogen species (RONS) has been trialed as a potential decontamination method. Yet, this technology comes with multiple downsides, including adverse effects on the quality of treated foods and limited exposure to entire surfaces on samples with hard-to-reach spots, further hindering real-life applications. Therefore, plasma-activated water (PAW) has been recently developed to facilitate the interactions between RONS and contaminant molecules in the liquid phase, allowing a whole surface treatment with efficient chemical degradation. Here, we review the recent advances in PAW utilized as a chemical decontamination agent in foods. The reaction mechanisms and the main RONS contributors involved in the PAW-assisted removal of chemical contaminants are briefly outlined. Also, the comprehensive effects of these treatments on food qualities (chemical and physical characteristics) and toxicological evaluation of PAW (in vitro and in vivo) are thoroughly discussed. Ultimately, we identified some current challenges and provided relevant suggestions, which can further promote PAW research for real-life applications in the future.

Efficient inactivation of the contamination with pathogenic microorganisms by a combination of water spray and plasma-activated air

The global pandemic caused by SARS-CoV-2 has lasted two and a half years and the infections caused by the viral contamination are still occurring. Developing efficient disinfection technology is crucial for the current epidemic or infectious diseases caused by other pathogenic microorganisms. Gas plasma can efficiently inactivate different microorganisms, therefore, in this study, a combination of water spray and plasma-activated air was established for the disinfection of pathogenic microorganisms. The combined treatment efficiently inactivated the Omicron-pseudovirus through caused the nitration modification of the spike proteins and also the pathogenic bacteria. The combined treatment was improved with a funnel-shaped nozzle to form a temporary relatively sealed environment for the treatment of the contaminated area. The improved device could efficiently inactivate the Omicron-pseudovirus and bacteria on the surface of different materials including quartz, metal, leather, plastic, and cardboard and the particle size of the water spray did not affect the inactivation effects. This study supplied a disinfection strategy based on plasma-activated air for the inactivation of contaminated pathogenic microorganisms.

Liquid plasma as a treatment for cutaneous wound healing through regulation of redox metabolism

The skin functions as the outermost protective barrier to the internal organs and major vessels; thus, delayed regeneration from acute injury could induce serious clinical complications. For rapid recovery of skin wounds, promoting re-epithelialization of the epidermis at the initial stage of injury is essential, wherein epithelial keratinocytes act as leading cells via migration. This study applied plasma technology, which has been known to enable wound healing in the medical field. Through in vitro and in vivo experiments, the study elucidated the effect and molecular mechanism of the liquid plasma (LP) manufactured by our microwave plasma system, which was found to improve the applicability of existing gas-type plasma on skin cell migration for re-epithelialization. LP treatment promoted the cytoskeletal transformation of keratinocytes and migration owing to changes in the expression of integrin-dependent focal adhesion molecules and matrix metalloproteinases (MMPs). This study also identified the role of increased levels of intracellular reactive oxygen species (ROS) as a driving force for cell migration activation, which was regulated by changes in NADPH oxidases and mitochondrial membrane potential. In an in vivo experiment using a murine dorsal full-thickness acute skin wound model, LP treatment helped improve the re-epithelialization rate, reaffirming the activation of the underlying intracellular ROS-dependent integrin-dependent signaling molecules. These findings indicate that LP could be a valuable wound management material that can improve the regeneration potential of the skin via the activation of migration-related molecular signaling within the epithelial cell itself with plasma-driven oxidative eustress.

Enhancement of Wheat Seed Germination, Seedling Growth and Nutritional Properties of Wheat Plantlet Juice by Plasma Activated Water

Previous studies have shown the great potential of using plasma-activated water (PAW) on improving agriculture seed germination, however, information on the influence of PAW on crop plantlet juice remains scanty. In this research, the effect of PAW generated by atmosphere pressure Ar-O₂ plasma jet for 1-5 min on wheat seed germination, seedling growth and nutritional properties of wheat plantlet juice was investigated. Results revealed that all PAWs could enhance wheat seed germination and seedling growth in 7 days by improving the germination rate, germination index, fresh weight, dry weight and vigour index, and especially that PAW activated for 3 min (PAW-3) showed the best overall performance. In addition, the application of PAWs enhanced the nutritional properties of wheat plantlet juice from those grown for 14 days by improving total soluble solids, protein content, photosynthetic pigments, total phenolic content, antioxidant activity, enzyme activity, free amino acids and minerals content, and the best enhancement was also observed in PAW-3. It was concluded that PAWs would be an effective technique to enhance the growth and nutritional properties of crop sprouts, which could be served as functional foods in many forms.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00344-022-10677-3.

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.

Editorials for ‘Advances in Cold Plasma in Biomedicines’

Research in the field of plasma medicine has provided many explanations for various phenomena, as well as the involvement of the chemical elements of plasma; however, it still lacks in biological mechanism analyses [...]

Liquid-type plasma-controlled in situ crosslinking of silk-alginate injectable gel displayed better bioactivities and mechanical properties

Silk is a promising biomaterial for injectable hydrogel, but its long-gelation time and cytotoxic crosslinking methods are the main obstacles for clinical application. Here, we purpose a new in situ crosslinking technique of silk-alginate (S-A) injectable hydrogel using liquid-type non-thermal atmospheric plasma (LTP) in vocal fold (VF) wound healing. We confirmed that LTP induces the secondary structure of silk in a dose-dependent manner, resulting in improved mechanical properties. Significantly increased crosslinking of silk was observed with reduced gelation time. Moreover, controlled release of nitrate, an LTP effectors, from LTP-treated S-A hydrogel was detected over 7 days. In vitro experiments regarding biocompatibility showed activation of fibroblasts beyond the non-cytotoxicity of LTP-treated S-A hydrogels. An in vivo animal model of VF injury was established in New Zealand White rabbits. Full-thickness injury was created on the VF followed by hydrogel injection. In histologic analyses, LTP-treated S-A hydrogels significantly reduced a scar formation and promoted favorable wound healing. Functional analysis using videokymography showed eventual viscoelastic recovery. The LTP not only changes the mechanical structures of a hydrogel, but also has sustained biochemical effects on the damaged tissue due to controlled release of LTP effectors, and that LTP-treated S-A hydrogel can be used to enhance wound healing after VF injury.

Degradation of Bacterial Antibiotic Resistance Genes during Exposure to Non-Thermal Atmospheric Pressure Plasma

Bacterial resistance to antibiotics has become a major public health problem in recent years. The occurrence of antibiotics in the environment, especially in wastewater treatment plants, has contributed to the development of antibiotic-resistant bacteria (ARB) and the spread of antibiotic resistance genes (ARGs). Despite the potential of some conventional processes used in wastewater treatment plants, the removal of ARB and ARGs remains a challenge that requires further research and development of new technologies to avoid the release of emerging contaminants into aquatic environments. Non-thermal atmospheric pressure plasmas (NTAPPs) have gained a significant amount of interest for wastewater treatment due to their oxidizing potential. They have shown their effectiveness in the inactivation of a wide range of bacteria in several fields. In this review, we discuss the application of NTAPPs for the degradation of antibiotic resistance genes in wastewater treatment.