Plasma bioscience for medicine, agriculture and hygiene applications

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

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

Direct Applications of Non-Thermal Atmospheric Pressure Plasma: An Emerging Therapeutic Era in Ophthalmology

This article explores the burgeoning role of cold atmospheric plasma (CAP) in ophthalmology. The versatile nature of CAP has transformed various facets of eye care, offering novel possibilities across different clinical domains. From sterilizing surgical instruments without compromising their integrity to effectively managing challenging corneal diseases like microbial keratitis and fungal infections, CAP has shown promising results. Moreover, its potential role in promoting corneal wound healing, facilitating corneal transplants, and enhancing outcomes in cataract surgeries deserves attention. The low-tension plasma blade (ie, the Fugo blade™, Medisurg Ltd. Norristown, PA), a controlled and precise form of CAP, has emerged as a game-changer in delicate eye surgeries. Its unmatched precision, minimal tissue damage, and surgeon-friendly nature have revolutionized ophthalmic procedures, including ptosis correction, dry eye treatment, and conjunctival cyst ablation. Despite conflicting findings on the efficacy of this technology in certain aspects, the extensive body of research on CAP underscores its potential for wider ophthalmic integration. Further investigation, including human trials, is crucial for understanding the in vivo safety profile of CAP for ophthalmic applications and optimizing its use, potentially revolutionizing ocular disease management and improving patient outcomes.

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.

The potential of multicylindrical dielectric barrier discharge plasma for diesel-contaminated soil remediation and biocompatibility assessment

This study explored the use of multicylindrical dielectric barrier discharge (MC-DBD) plasma technology to eliminate diesel fuel contamination from the soil. This study also assessed the environmental impact of plasma-generated reactive species on soil properties, plant growth, and the safety of microbial and human skin cells using various analytical methods. MC-DBD plasma was characterized using the current-voltage analysis and optical emission spectroscopy (OES). Gas Fourier transform infrared spectroscopy was employed to detect reactive species, such as O3, NO, NO2, N2O, and HNO3, in the plasma-treated air. The diesel fuel concentration in the soil was measured before and after plasma treatment using a gas chromatography-flame ionization detector. The efficacy of the MC-DBD plasma treatment was evaluated based on soil characteristics (pH and moisture), discharge parameters (power), and reactive species (O3 and NOx). Using only power of 30 W, the MC-DBD achieved a 94.19% removal of diesel fuel from the soil and yielded an energy efficiency of 1.78 × 10-2 m3/kWh within a 60-min treatment period. Neutral soil with a moisture content of 2% proved more effective in diesel fuel removal compared with acidic or alkaline soil with higher moisture content. O3 was the most efficient plasma-generated reactive species for diesel fuel removal and is involved in oxidation-induced fragmentation and volatilization. Overall, the potential of the MC-DBD plasma technology for remediating diesel fuel-contaminated soils is highlighted, and valuable insights for future applications are provided.

Cold atmospheric plasma fumigation suppresses postharvest apple Botrytis cinerea by triggering intracellular reactive oxygen species and mitochondrial calcium

Infection by Botrytis cinerea poses a great threat to the postharvest life of apple fruit. In this study, the effects of cold atmospheric plasma (CAP) fumigation on apple B. cinerea under different exposure times and intensities were investigated. The growth of B. cinerea in vitro and in vivo was significantly suppressed by the CAP fumigation at least 700 μL/L for 5 min. To reveal the possible mechanism of antifungal activity of CAP fumigation, the pathogen was exposed to 700 μL/L and 1000 μL/L for 5 min, respectively. The results indicated that the CAP-treated spores of the pathogen underwent shrinkage, cell membrane collapse and cytoplasmic vacuolation. The results obtained from the fluorescent probe assay and flow cytometry indicated that CAP caused the accumulation of reactive oxygen species (ROS), the elevation of mitochondrial and intracellular Ca2+ levels, and the decrease in mitochondrial membrane potential of the pathogen. Investigation on statues of cell life showed that typical hallmarks of apoptosis in the CAP-treated B. cinerea spores occurred, as indicted by a large degree of increased phosphatidylserine externalization, dysfunction of membrane permeability, DNA fragmentation, distortion of morphology, chromatin condensation, and metacaspase activation observed in B. cinerea spores after CAP fumigation. Overall, CAP fumigation triggered a metacaspase-dependent apoptosis of B. cinerea spores mediated by intracellular ROS burst and Ca2+ elevation via mitochondrial dysfunction and disruption, and therefore reduced the pathogenicity of B. cinerea and suppressed postharvest Botrytis rot of apple fruit. These results would provide an insight into the underlying mechanism of CAP fumigation acting on the pathogen. The CAP fumigation makes much convenient application of CAP in storage environment to deactivate microorganism.

Persistence of Coronavirus on Surface Materials and Its Control Measures Using Nonthermal Plasma and Other Agents

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been responsible for the initiation of the global pandemic since 2020. The virus spreads through contaminated air particles, fomite, and surface-contaminated porous (i.e., paper, wood, and masks) and non-porous (i.e., plastic, stainless steel, and glass) materials. The persistence of viruses on materials depends on porosity, adsorption, evaporation, isoelectric point, and environmental conditions, such as temperature, pH, and relative humidity. Disinfection techniques are crucial for preventing viral contamination on animated and inanimate surfaces. Currently, there are few effective methodologies for preventing SARS-CoV-2 and other coronaviruses without any side effects. Before infection can occur, measures must be taken to prevent the persistence of the coronavirus on the surfaces of both porous and non-porous inanimate materials. This review focuses on coronavirus persistence in surface materials (inanimate) and control measures. Viruses are inactivated through chemical and physical methods; the chemical methods particularly include alcohol, chlorine, and peroxide, whereas temperature, pH, humidity, ultraviolet irradiation (UV), gamma radiation, X-rays, ozone, and non-thermal, plasma-generated reactive oxygen and nitrogen species (RONS) are physical methods.

Characteristics of a Rollable Dielectric Barrier Discharge Plasma and Its Effects on Spinach-Seed Germination

We investigated the characteristics of a rollable dielectric barrier discharge (RDBD) and evaluate its effects on seed germination rate and water uptake. The RDBD source was composed of a polyimide substrate and copper electrode, and it was mounted in a rolled-up structure for omnidirectional and uniform treatment of seeds with flowing synthetic air gas. The rotational and vibrational temperatures were measured to be 342 K and 2860 K, respectively, using optical emission spectroscopy. The chemical species analysis via Fourier-transform infrared spectroscopy and 0D chemical simulation showed that O₃ production was dominant and NO_x production was restrained at the given temperatures. The water uptake and germination rate of spinach seeds by 5 min treatment of RDBD was increased by 10% and 15%, respectively, and the standard error of germination was reduced by 4% in comparison with the controls. RDBD enables an important step forward in non-thermal atmospheric-pressure plasma agriculture for omnidirectional seed treatment.

Plasma-Generated Nitric Oxide Water Mediates Environmentally Transmitted Pathogenic Bacterial Inactivation via Intracellular Nitrosative Stress

Over time, the proportion of resistant bacteria will increase. This is a major concern. Therefore, effective and biocompatible therapeutic strategies against these bacteria are urgently needed. Non-thermal plasma has been exhaustively characterized for its antibacterial activity. This study aims to investigate the inactivation efficiency and mechanisms of plasma-generated nitric oxide water (PG-NOW) on pathogenic water, air, soil, and foodborne Gram-negative and Gram-positive bacteria. Using a colony-forming unit assay, we found that PG-NOW treatment effectively inhibited the growth of bacteria. Moreover, the intracellular nitric oxide (NO) accumulation was evaluated by 4-amino-5-methylamino-2',7'-dichlorofluorescein diacetate (DAF-FM DA) staining. The reduction of viable cells unambiguously indicates the anti-microbial effect of PG-NOW. The soxR and soxS genes are associated with nitrosative stress, and oxyR regulation corresponds to oxidative stress in bacterial cells. To support the nitrosative effect mediated by PG-NOW, we have further assessed the soxRS and oxyR gene expressions after treatment. Accordingly, soxRS expression was enhanced, whereas the oxyR expression was decreased following PG-NOW treatment. The disruption of cell morphology was observed using scanning electron microscopy (SEM) analysis. In conclusion, our findings furnish evidence of an initiation point for the further progress and development of PG-NOW-based antibacterial treatments.