Comprehensive biomedical applications of low temperature plasmas

Decitabine combined with cold atmospheric plasma induces pyroptosis via the ROS/Caspase-3/GSDME signaling pathway in Ovcar5 cells

BACKGROUND

High methylation of the DFNA5 gene results in the absence of GSDME, a key protein that mediates pyroptosis, while decitabine demethylates the DFNA5 gene, resulting in high expression of the GSDME protein. Cold atmospheric plasma (CAP) is a novel anti-cancer method that induces tumor cell death.

METHODS

The pyroptosis induced by decitabine in combination with CAP in Ovcar5 cells was evaluated. In particular, mitochondrial membrane potential was estimated by JC-1 staining, dehydrogenase (LDH) release was assessed by ELISA, Annexin V/PI staining was detected by flow cytometry, the cell cycle changes were evaluated using PI staining followed by detection by flow cytometry, and Caspase-9 cleavage, Caspase-3 cleavage and GSDME expression were evaluated by western blot.

RESULTS

Decitabine resulted in high expression of the GSDME in Ovcar5 in a concentration-dependent manner and increased tumor cell sensitivity to CAP. CAP induced mitochondrial damage and activated the Caspase-9/Caspase-3 pathway. Therefore, decitabine combined with CAP induced Ovcar5 cell pyroptosis through Caspase-3 mediated GSDME cleavage. Reactive oxygen species (ROS) generated by CAP treatment played an important role in the CAP/decitabine combination-induced production of ROS, activation of Caspase-9/Caspase-3, GSDME cleavage and pyroptosis that ROS scavenger NAC inhibited all these processes.

CONCLUSIONS

CAP combined with decitabine induced Caspase-3 activation, which cleaved decitabine-upregulated GSDME and ediated pyroptosis.

Comparing Redox and Intracellular Signalling Responses to Cold Plasma in Wound Healing and Cancer

Cold plasma (CP) is an ionised gas containing excited molecules and ions, radicals, and free electrons, and which emits electric fields and UV radiation. CP is potently antimicrobial, and can be applied safely to biological tissue, birthing the field of plasma medicine. Reactive oxygen and nitrogen species (RONS) produced by CP affect biological processes directly or indirectly via the modification of cellular lipids, proteins, DNA, and intracellular signalling pathways. CP can be applied at lower levels for oxidative eustress to activate cell proliferation, motility, migration, and antioxidant production in normal cells, mainly potentiated by the unfolded protein response, the nuclear factor-erythroid factor 2-related factor 2 (Nrf2)-activated antioxidant response element, and the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway, which also activates nuclear factor-kappa B (NFκB). At higher CP exposures, inactivation, apoptosis, and autophagy of malignant cells can occur via the degradation of the PI3K/Akt and mitogen-activated protein kinase (MAPK)-dependent and -independent activation of the master tumour suppressor p53, leading to caspase-mediated cell death. These opposing responses validate a hormesis approach to plasma medicine. Clinical applications of CP are becoming increasingly realised in wound healing, while clinical effectiveness in tumours is currently coming to light. This review will outline advances in plasma medicine and compare the main redox and intracellular signalling responses to CP in wound healing and cancer.

Cold Atmospheric Pressure Plasma-Activated Medium Modulates Cellular Functions of Human Mesenchymal Stem/Stromal Cells In Vitro

Cold atmospheric pressure plasma (CAP) offers a variety of therapeutic possibilities and induces the formation of reactive chemical species associated with oxidative stress. Mesenchymal stem/stromal cells (MSCs) play a central role in tissue regeneration, partly because of their antioxidant properties and ability to migrate into regenerating areas. During the therapeutic application, MSCs are directly exposed to the reactive species of CAP. Therefore, the investigation of CAP-induced effects on MSCs is essential. In this study, we quantified the amount of ROS due to the CAP activation of the culture medium. In addition, cell number, metabolic activity, stress signals, and migration were analyzed after the treatment of MSCs with a CAP-activated medium. CAP-activated media induced a significant increase in ROS but did not cause cytotoxic effects on MSCs when the treatment was singular and short-term (one day). This single treatment led to increased cell migration, an essential process in wound healing. In parallel, there was an increase in various cell stress proteins, indicating an adaptation to oxidative stress. Repeated treatments with the CAP-activated medium impaired the viability of the MSCs. The results shown here provide information on the influence of treatment frequency and intensity, which could be necessary for the therapeutic application of CAP.

Cold Atmospheric Helium Plasma in the Post-COVID-19 Era: A Promising Tool for the Disinfection of Silicone Endotracheal Prostheses

Despite the excellent properties of silicone endotracheal prostheses, their main limitation is the formation of a polymicrobial biofilm on their surfaces. It can cause local inflammation, interfering with the local healing process and leading to further complications in the clinical scenario. The present study evaluated the inhibitory effect of cold atmospheric plasma (CAP) on multispecies biofilms grown on the silicone protheses' surfaces. In addition to silicone characterization before and after CAP exposure, CAP cytotoxicity on immortalized human bronchial epithelium cell line (BEAS-2B) was evaluated. The aging time test reported that CAP could temporarily change the silicone surface wetting characteristics from hydrophilic (80.5°) to highly hydrophilic (<5°). ATR-FTIR showed no significant alterations in the silicone surficial chemical composition after CAP exposure for 5 min. A significant log reduction in viable cells in monospecies biofilms (log CFU/mL) of C. albicans, S. aureus, and P. aeruginosa (0.636, 0.738, and 1.445, respectively) was detected after CAP exposure. Multispecies biofilms exposed to CAP showed significant viability reduction for C. albicans and S. aureus (1.385 and 0.831, respectively). The protocol was not cytotoxic to BEAS-2B. CAP can be a simple and effective method to delay multispecies biofilm formation inside the endotracheal prosthesis.

Applicability of Electron-Beam and Hybrid Plasmas for Polyethylene Terephthalate Processing to Obtain Hydrophilic and Biocompatible Surfaces

The applicability of beam-plasma chemical reactors generating cold hybrid plasma for the production of noncytotoxic polymeric surfaces with high hydrophilicity and good biocompatibility with human fibroblast culture and human red blood cells was studied. Oxygen hybrid plasma was excited by the joint action of a continuous scanning electron beam and a capacity-coupled RF-gas discharge. Experiments showed that hybrid plasma treatment caused polar oxygen-containing functional group formation in the surface layer of poly (ethylene terephthalate) films. No thermal or radiative damage in tested polymer samples was found. The plasma-modified polymers turned out to be noncytotoxic and revealed good biocompatibility with human fibroblasts BJ-5ta as well as lower hemolytic activity than untreated poly (ethylene terephthalate). Experiments also demonstrated that no phenomena caused by the electrostatic charging of polymers occur in hybrid plasma because the electron beam component of hybrid plasma eliminates the item charge when it is treated. The electron beam can effectively control the reaction volume geometry as well as the fluxes of active plasma particles falling on the item surface. This provides new approaches to the production of abruptly structured patterns or smooth gradients of functionalities on a plane and 3D polymeric items of complicated geometry.

Applications of cold atmospheric plasma in immune-mediated inflammatory diseases via redox homeostasis: evidence and prospects

As a representative technology in plasma medicine, cold atmospheric plasma (CAP) has beneficial outcomes in surface disinfection, wound repair, tissue regeneration, solid tumor therapy. Impact on immune response and inflammatory conditions was also observed in the process of CAP treatment. Relevant literatures were collected to assess efficacy and summarize possible mechanisms of the innovation. CAP mediates alteration in local immune microenvironment mainly through two ways. One is to down-regulate the expression level of several cytokines, impeding further conduction of immune or inflammatory signals. Intervening the functional phenotype of cells through different degree of oxidative stress is the other approach to manage the immune-mediated inflammatory disorders. A series of preclinical and clinical studies confirmed the therapeutic effect and side effects free of CAP. Moreover, several suggestions proposed in this manuscript might help to find directions for future investigation.

Charge decay in the spatial afterglow of plasmas and its impact on diffusion regimes

The spatial afterglow is a region at the boundary of a non-equilibrium plasma where charged species relax into ambient equilibrium. In many applications, the spatial afterglow is the part of the plasma that interacts with surfaces, such as suspended particles or a material substrate. However, compared to the bulk plasma, there has been little effort devoted to studying the properties of the spatial afterglow, and a fundamental analysis has not yet been developed. Here, we apply double Langmuir probe measurements and develop an advection-diffusion-recombination model to provide a detailed description of charged species in the spatial afterglow over a wide range of pressures, temperatures, plasma dimensions, and flow rates. We find that the density of charged species in the spatial afterglow decays by orders of magnitude, which leads to a transition from ambipolar to free diffusion. These insights can be used to explain or predict experimental observations of phenomena, such as the charging of dust grains and the dose of charged species to a biomaterial.

A Meaningful Attempt: Applying Dielectric Barrier Discharge Plasma to Induce Polarization of Macrophages

Macrophage polarization plays an important role in many macrophage-related diseases. This study was designed to preliminarily explore the effects of dielectric barrier discharge (DBD) plasma on the polarization direction and cell activity of macrophages with different phenotypes (ie, M0, M1, and M2). The M1 macrophage marker inducible nitric oxide synthase (iNOS) and M2 macrophage marker cluster of differentiation 206 (CD206) were detected by western blot (WB). The effects of DBD plasma on macrophage viability were analyzed by using a cell counting kit-8 detection kit. M0, M1, and M2 macrophages exhibited a decrease in iNOS expression and an increase in CD206 expression after the DBD plasma intervention. Additionally, the decrease in macrophage viability remained non-significant after initiating the intervention. DBD plasma can promote the transformation of M0 and M1 macrophages to M2 macrophages, and can further enhance the expression of the M2 macrophage phenotype marker CD206. Our study not only demonstrates the potential therapeutic value of DBD plasma for macrophage-related diseases, but it also provides a new direction for research to improve the treatment of macrophage-related diseases. © 2023 Bioelectromagnetics Society.

Low temperature plasma suppresses proliferation, invasion, migration and survival of SK-BR-3 breast cancer cells

BACKGROUND

Low temperature plasma (LTP) is a developing field in recent years to play important roles of sterilization, material modification and wound healing. Breast cancer is a common gynecological malignant tumor. Recent studies have shown that LTP is a promising selective anti-cancer treatment. The effect of LTP on breast cancer is still unclear. In this study, We treated breast cancer cell lines with low temperature plasma for different periods of time and analyzed the relevant differences.

METHODS AND RESULTS

SK-BR-3 cell nutrient solution was firstly treated by ACP for 0, 10, 20, 40, 80 and 120 s, which was next used to cultivateSK-BR-3cells for overnight.we found that LTP was able to suppress cell vitality, proliferation, invasion and migration of SK-BR-3 cells. Also, SK-BR-3 apoptosis was induced by LTP in a time-dependent manner.

CONCLUSION

These evidences suggest the negative effect of LTP on malignant development of SK-BR-3 cells, and LTP has the potential clinical application for breast cancer treatment.

Argon plasma-modified bacterial cellulose filters for protection against respiratory pathogens

In this work, we present novel, sustainable filters based on bacterial cellulose (BC) functionalized with low-pressure argon plasma (LPP-Ar). The "green" production process involved BC biosynthesis by Komagataeibacter xylinus, followed by simple purification, homogenization, lyophilization, and finally LPP-Ar treatment. The obtained LPP-Ar-functionalized BC-based material (LPP-Ar-BC-bM) showed excellent antimicrobial and antiviral properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, and an enveloped bacteriophage phage Φ6, with no cytotoxicity versus murine fibroblasts in vitro. Further, filters consisting of three layers of LPP-Ar-BC-bM had >99 % bacterial and viral filtration efficiency, while maintaining sufficiently low airflow resistance (6 mbar at an airflow of 95 L/min). Finally, as a proof-of-concept, we were able to prepare 80 masks with LPP-Ar-BC-bM filter and ~85 % of volunteer medical staff assessed them as "good" or "very good" in terms of comfort. We conclude that our novel sustainable, biobased, biodegradable filters are suitable for respiratory personal protective equipment (PPE), such as surgical masks and respirators.

Mechanical Properties of Calcium Aluminate Cement Reinforced with Plasma-Treated Basalt Fibers for In Situ Combustion

Brittleness and poor tensile/flexural properties restrict the application of calcium aluminate cement (CAC) in oil and gas wells. Reinforcing CAC with fibers is an effective method for improving its strength and toughness and overcoming the shortcomings of its mechanical properties. In this article, as an auxiliary cementing material, slag does not affect the thickening time of CAC. After adding slag, the cement slurry meets the thickening time during cementing construction, and basalt fiber is selected as the toughening material. The enhancement effect of basalt fiber on the mechanical properties of CAC slag composites is studied, including the evaluation of the macroscopic mechanical properties and microstructure at a high temperature (500 °C). The optimum composition of basalt and fiber-reinforced CAC was determined. Basalt fibers were added to CAC at different contents of 0, 0.1, 0.2, 0.3, 0.4, and 0.5% based on the weight of the cement. All the results showed that the introduction of basalt fibers could significantly enhance the strength of the cement at high temperatures. Compared with the control samples, an additional increase in the compressive and tensile strengths of the samples of 35.1 and 85.2%, respectively, was achieved at high temperature with approximately 0.4% fiber content. Plasma treatment further improved the reinforcing effect of the basalt fibers, where the high-temperature compressive and tensile strengths of the samples increased from 28.88 and 1.52 to 35.23 and 1.87 MPa, respectively, an increase of 21.98 and 20.6%, respectively, compared with the untreated basalt fibers. When the cement paste is cured by simulated curing for 28 d, the high-temperature compressive strength and tensile strength with plasma modification increased from 28.26 and 1.5 to 29.1 and 2.15 MPa, respectively, an increase of 3.0 and 43.3%, respectively. The structure of the formed hydrates was studied using scanning electron microscopy. Furthermore, toughening of the basalt fiber-reinforced CAC-based composites resulted mainly from crack bridging and fiber pull-out.

Non-thermal atmospheric-pressure plasma potentiates mesodermal differentiation of human induced pluripotent stem cells

Non-thermal atmospheric-pressure plasma has been used for biological applications, including sterilization and stimulation of cell growth and differentiation. Here, we demonstrate that plasma exposure influences the differentiation pattern of human induced pluripotent stem cells (hiPSCs). We treated hiPSCs with dielectric barrier-discharge air plasma and found an exposure dose that does not kill hiPSCs. Immunohistochemical staining for E-CADHERIN showed that the exposure affected cell-cell attachment and doubled the average size of the hiPSCs. Analysis of mRNAs in embryoid bodies (EBs) from plasma-treated hiPSCs revealed repression of ectoderm genes, including WNT1, and increased expression of mesoderm genes. Importantly, hiPSCs deficient in DNA repair only displayed minimal damage after plasma exposure. Collectively, our results suggest that plasma treatment can be another tool for directing the fate of pluripotent stem cells without disrupting their genomic integrity.

Reactive species variation in cold atmospheric pressure plasma jet discharge under the influence of intrinsic parameters and its effect on E. coli inactivation

Cold atmospheric pressure plasma jet (CAPJ) has piqued the interest of researchers for various antimicrobial applications such as disinfection, wound decontamination, etc. In the current context, a deeper understanding of the correlation between CAPJ's intrinsic parameters, discharge characteristics, species composition, and antimicrobial activity is required for any successful application. This research evaluated the effect of intrinsic operational parameters such as voltage, frequency, gas flow rate, and operating gas on the reactive species composition of an in-house-developed CAPJ discharge along with the antimicrobial activity. It was observed that the identified excited atoms (Ar I, He I, N2, and O I), ions (Ar+, N2+, N+, H2O+, H3O+, etc.), radical reactive oxygen and nitrogen species (RONS) (OH•), and nonradical RONS (O I, O+, OH+, NO+, O2+, O2-, NO2-, N2O2-, NO3-, N2O3-, etc.) might play a synergistic role in bacterial inactivation via oxidative and electrostatic stress. The variation in voltage, frequency, gas flow rate, and operating gas influenced the discharge chemistry, leading to variation in bacterial inactivation. The reactive species in the discharge responsible for such variation was evaluated extensively. This investigation into various operational parameters would aid in determining the most effective settings for a developed CAPJ to achieve high productivity.

Low-Temperature Plasma Short Exposure to Decontaminate Peri-Implantitis-Related Multispecies Biofilms on Titanium Surfaces In Vitro

BACKGROUND

The use of low-temperature plasma (LTP) is a novel approach to treating peri-implantitis. LTP disrupts the biofilm while conditioning the surrounding host environment for bone growth around the infected implant. The main objective of this study was to evaluate the antimicrobial properties of LTP on newly formed (24 h), intermediate (3 days), and mature (7 days) peri-implant-related biofilms formed on titanium surfaces.

METHODS

Actinomyces naeslundii (ATCC 12104), Porphyromonas gingivalis (W83), Streptococcus oralis (ATCC 35037), and Veillonella dispar (ATCC 17748) were cultivated in brain heart infusion supplemented with 1% yeast extract, hemin (0.5 mg/mL), and menadione (5 mg/mL) and kept at 37°C in anaerobic conditions for 24 h. Species were mixed for a final concentration of ~105 colony forming units (CFU)/mL (OD = 0.01), and the bacterial suspension was put in contact with titanium specimens (7.5 mm in diameter by 2 mm in thickness) for biofilm formation. Biofilms were treated with LTP for 1, 3, and 5 min at 3 or 10 mm from plasma tip to sample. Controls were those having no treatment (negative control, NC) and argon flow under the same LTP conditions. Positive controls were those treated with 14 μg/mL amoxicillin and 140 μg/mL metronidazole individually or combined and 0.12% chlorhexidine (n = 6 per group). Biofilms were evaluated by CFU, confocal laser scanning microscopy (CLSM), and fluorescence in situ hybridization (FISH). Comparisons among bacteria; 24 h, 3-day, and 7-day biofilms; and treatments for each biofilm were made. Wilcoxon signed-rank and Wilcoxon rank sum tests were applied (α = 0.05).

RESULTS

Bacterial growth was observed in all NC groups, corroborated by FISH. LTP treatment significantly reduced all bacteria species compared to the NC in all biofilm periods and treatment conditions (p ≤ 0.016), and CLSM corroborated these results.

CONCLUSION

Within the limitation of this study, we conclude that LTP application effectively reduces peri-implantitis-related multispecies biofilms on titanium surfaces in vitro.

Hemodynamic characteristics in a cerebral aneurysm model using non-Newtonian blood analogues

This study aims to develop an experimentally validated computational fluid dynamics (CFD) model to estimate hemodynamic characteristics in cerebral aneurysms (CAs) using non-Newtonian blood analogues. Blood viscosities varying with shear rates were measured under four temperatures first, which serves as the reference for the generation of blood analogues. Using the blood analogue, particle image velocimetry (PIV) measurements were conducted to quantify flow characteristics in a CA model. Then, using the identical blood properties in the experiment, CFD simulations were executed to quantify the flow patterns, which were used to compare with the PIV counterpart. Additionally, hemodynamic characteristics in the simplified Newtonian and non-Newtonian models were quantified and compared using the experimentally validated CFD model. Results showed the proposed non-Newtonian viscosity model can predict blood shear-thinning properties accurately under varying temperatures and shear rates. Another developed viscosity model based on the blood analogue can well represent blood rheological properties. The comparisons in flow characteristics show good agreements between PIV and CFD, demonstrating the developed CFD model is qualified to investigate hemodynamic factors within CAs. Furthermore, results show the differences of absolute values were insignificant between Newtonian and non-Newtonian fluids in the distributions of wall shear stress (WSS) and oscillatory shear index (OSI) on arterial walls. However, not only does the simplified Newtonian model underestimate WSS and OSI in most regions of the aneurysmal sac, but it also makes mistakes in identifying the high OSI regions on the sac surface, which may mislead the hemodynamic assessment on the pathophysiology of CAs.

Low Temperature Plasma Suppresses Lung Cancer Cells Growth via VEGF/VEGFR2/RAS/ERK Axis

Low temperature plasma (LTP) is a promising cancer therapy in clinical practice. In this study, dielectric barrier discharge plasma with helium gas was used to generate LTP. Significant increases in extracellular and intracellular reactive species were found in lung cancer cells (CALU-1 and SPC-A1) after LTP treatments. Cells viability and apoptosis assays demonstrated that LTP inhibited cells viability and induced cells death, respectively. Moreover, Western blotting revealed that the growth of CALU-1 cells was suppressed by LTP via the VEGF/VEGFR2/RAS/ERK axis for the first time. The results showed that LTP-induced ROS and RNS could inhibit the growth of lung cancer cells via VEGF/VEGFR2/RAS/ERK axis. These findings advance our understanding of the inhibitory mechanism of LTP on lung cancer and will facilitate its clinical application.

Effect of Non-Thermal Plasma Treatment of Contaminated Zirconia Surface on Porphyromonas gingivalis Adhesion and Osteoblast Viability

Plasma treatment on a zirconia surface prevents bacterial contamination and maintains osteoblast activity. To assess the degree of adhesion of Porphyromonas gingivalis on a zirconia surface after non-thermal plasma (NTP) treatment, specimens were treated with plasma for 60, 300, and 600 s, after which P. gingivalis was inoculated onto the surface and incubated for 48 h. To assess osteoblast activity after NTP treatment, osteoblasts (MC3T3-E1) were dispensed onto the specimens contaminated with P. gingivalis immediately after NTP for 60 and 120 s, followed by incubation for 48, 72, and 96 h. P. gingivalis was cultured after 60 s of NTP treatment of zirconia. The NTP and control groups showed no significant difference (p = 0.91), but adhesion was significantly increased following NTP treatment for 300 s or longer (300, 600 s groups) (p < 0.05). After NTP treatment of P. gingivalis-contaminated zirconia, osteoblast activity significantly increased at 72 and 96 h (I60 and I120 s group) in the groups treated with plasma (p < 0.017). Application of NTP to dental zirconia implants for 60 s not only inhibits the proliferation of P. gingivalis, which causes peri-implantitis but also increases osseointegration on zirconia surfaces contaminated with P. gingivalis.

Cold Plasma Irradiation Attenuates Atopic Dermatitis via Enhancing HIF-1α-Induced MANF Transcription Expression

Cold atmospheric plasma has been widely applied in medical treatment clinically, especially skin diseases. However, the mechanism of cold atmospheric plasma on the treatment of skin diseases is still undefined. In this study, dinitrofluorobenzene-induced atopic dermatitis mice model was constructed. Cold atmospheric plasma was able to decrease skin cells apoptosis, relieve skin inflammation, ER stress and oxidative stress caused by dinitrofluorobenzene stimulation, which was mediated by cold atmospheric plasma-induced MANF expression. In terms of mechanism, hypoxia-inducible factor-1α expression was increased intracellularly after cold atmospheric plasma treatment, which further bound to the promoter region of manf gene and enhanced MANF transcriptional expression. This study reveals that cold atmospheric plasma has a positive effect on atopic dermatitis treatment, also demonstrates the regulatory mechanism of cold atmospheric plasma on MANF expression via HIF-1α, which indicates the potential medical application of cold atmospheric plasma for atopic dermatitis treatment.

Therapeutic Effects of Cold Atmospheric Plasma on Solid Tumor

Cancer is a devastating disease, and there is no particularly effective treatment at present. Recently, a new treatment, cold atmospheric plasma (CAP), has been proposed. At present, CAP is confirmed to have selective killing effect on tumor by many studies in vitro and in vivo. A targeted literature search was carried out on the study of cold atmospheric plasma. Through analysis and screening, a narrative review approach was selected to describe therapeutic effects of cold atmospheric plasma on solid tumor. According to the recent studies on plasma, some hypothetical therapeutic schemes of CAP are proposed in this paper. The killing mechanism of CAP on solid tumor is expounded in terms of the selectivity of CAP to tumor, the effects of CAP on cells, tumor microenvironment (TME) and immune system. CAP has many effects on solid tumors, and these effects are dose-dependent. The effects of optimal doses of CAP on solid tumors include killing tumor cells, inhibiting non-malignant cells and ECM in TME, affecting the communication between tumor cells, and inducing immunogenic death of tumor cells. In addition, several promising research directions of CAP are proposed in this review, which provide guidance for future research.

Applications of Plasma Produced with Electrical Discharges in Gases for Agriculture and Biomedicine

The use of thermal and non-thermal atmospheric pressure plasma to solve problems related to agriculture and biomedicine is the focus of this paper. Plasma in thermal equilibrium is used where heat is required. In agriculture, it is used to treat soil and land contaminated by the products of biomass, plastics, post-hospital and pharmaceutical waste combustion, and also by ecological phenomena that have recently been observed, such as droughts, floods and storms, leading to environmental pollution. In biomedical applications, thermal plasma is used in so-called indirect living tissue treatment. The sources of thermal plasma are arcs, plasma torches and microwave plasma reactors. In turn, atmospheric pressure cold (non-thermal) plasma is applied in agriculture and biomedicine where heat adversely affects technological processes. The thermodynamic imbalance of cold plasma makes it suitable for organic syntheses due its low power requirements and the possibility of conducting chemical reactions in gas at relatively low and close to ambient temperatures. It is also suitable in the treatment of living tissues and sterilisation of medical instruments made of materials that are non-resistant to high temperatures. Non-thermal and non-equilibrium discharges at atmospheric pressure that include dielectric barrier discharges (DBDs) and atmospheric pressure plasma jets (APPJs), as well as gliding arc (GAD), can be the source of cold plasma. This paper presents an overview of agriculture and soil protection problems and biomedical and health protection problems that can be solved with the aid of plasma produced with electrical discharges. In particular, agricultural processes related to water, sewage purification with ozone and with advanced oxidation processes, as well as those related to contaminated soil treatment and pest control, are presented. Among the biomedical applications of cold plasma, its antibacterial activity, wound healing, cancer treatment and dental problems are briefly discussed.

Preliminary dynamic observation of wound healing after low-temperature plasma radiofrequency ablation for laryngeal leukoplakia

BACKGROUND

Low-temperature plasma ablation (LTPA) is an emerging technique for laryngeal leukoplakia (LL).

OBJECTIVE

To initially observe the healing process of trauma after LTPA for LL.

MATERIALS AND METHODS

Seventeen patients who underwent LTPA for LL were collected, and the degrees of wound healing were analyzed.

RESULTS

Only 1 patient in who dysbiosis of the pharyngeal flora was induced by self-administered hormone nebulization treatment during the follow-up period. In the remaining patients, the wound healing was characterized by a crater-shaped defect on the vocal folds surface with pseudo-membranes, congestion, and mild edema on postoperative day 1. These symptoms became worse on postoperative day 7. On postoperative day 15, the pseudo-membrane was fully formed and some patients had granulomatous swelling of the vocal cords. These symptoms became better and better on postoperative day 30 and day 45. On postoperative day 60, the mucosa of the vocal folds had essentially returned to normal. On postoperative day 90, the vocal folds morphology and function had recovered well.

CONCLUSION

It takes 2-3 months for the wound to heal completely after LTPA for LL.

SIGNIFICANCE

A proper understanding of the wound healing process can reduce unnecessary surgical and pharmacologic interventions and avoid excessive treatment.

Low-Temperature Gas Plasma Combined with Antibiotics for the Reduction of Methicillin-Resistant Staphylococcus aureus Biofilm Both In Vitro and In Vivo

Biofilm infections in wounds seriously delay the healing process, and methicillin-resistant Staphylococcus aureus is a major cause of wound infections. In addition to inactivating micro-organisms, low-temperature gas plasma can restore the sensitivity of pathogenic microbes to antibiotics. However, the combined treatment has not been applied to infectious diseases. In this study, low-temperature gas plasma treatment promoted the effects of different antibiotics on the reduction of S. aureus biofilms in vitro. Low-temperature gas plasma combined with rifampicin also effectively reduced the S. aureus cells in biofilms in the murine wound infection model. The blood and histochemical analysis demonstrated the biosafety of the combined treatment. Our findings demonstrated that low-temperature gas plasma combined with antibiotics is a promising therapeutic strategy for wound infections.

Transferred Cold Atmospheric Plasma Treatment on Melanoma Skin Cancer Cells with/without Catalase Enzyme In Vitro

Cold atmospheric plasma (CAP) is a promising tool to overcome certain cancerous and precancerous conditions in dermatology. A scheme of transferred CAP was first developed to treat melanoma (B16F10) skin cancer cells as well as non-malignant (L929) cells in vitro. CAP was transferred using a silicone tube with a jet system that was developed and was assessed as to whether it could generate reactive oxygen and nitrogen species (RONS) at near-room temperature. The transferred CAP was characterized electrically and spectroscopically. Biological data showed that the transferred CAP killed cancer cells but not non-malignant (L929) cells. Plasma treatment was effective with a time duration of 30 s, whereas non-malignant (L929) cells were less damaged during plasma treatment. In addition, catalase (CAT) enzyme was applied to neutralize and detoxify the RONS generated by the transferred CAP. These findings suggest that transferred CAP can be considered a melanoma cancer therapy.

Non-thermal plasma-induced DMPO-OH yields hydrogen peroxide

Recent developments in electronics have enabled the medical applications of non-thermal plasma (NTP), which elicits reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as hydroxyl radical (^●OH), hydrogen peroxide (H₂O₂), singlet oxygen (¹O₂), superoxide (O₂^●-), ozone, and nitric oxide at near-physiological temperatures. In preclinical studies or human clinical trials, NTP promotes blood coagulation, eradication of bacterial, viral and biofilm-related infections, wound healing, and cancer cell death. To elucidate the solution-phase biological effects of NTP in the presence of biocompatible reducing agents, we employed electron paramagnetic resonance (EPR) spectroscopy to quantify ^●OH using a spin-trapping probe, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO); ¹O₂ using a fluorescent probe; and O₂^●- and H₂O₂ using luminescent probes in the presence of thiols or tempol. NTP-induced ^●OH was significantly scavenged by dithiothreitol (DTT), reduced glutathione (GSH), and oxidized glutathione (GSSG) in 2 or 5 mM DMPO. NTP-induced O₂^●- was significantly scavenged by 10 μM DTT and GSH, while ¹O₂ was not efficiently scavenged by these compounds. GSSG degraded H₂O₂ more effectively than GSH and DTT, suggesting that the disulfide bonds reacted with H₂O₂. In the presence of 1-50 mM DMPO, NTP-induced H₂O₂ quantities were unchanged. The inhibitory effect of tempol concentration (50 and 100 μM) on H₂O₂ production was observed in 1 and 10 mM DMPO, whereas it became ineffective in 50 mM DMPO. Furthermore, DMPO-OH did not interact with tempol. These results suggest that DMPO and tempol react competitively with O₂^●-. Further studies are warranted to elucidate the interaction between NTP-induced ROS and biomolecules.

Could cold plasma act synergistically with allogeneic mesenchymal stem cells to improve wound skin regeneration in a large size animal model?

Skin wound healing may sometimes lead to open sores that persist for long periods and expensive hospitalization is needed. Among different kinds of therapeutic innovative approaches, mesenchymal stem cells (MSCs) and low-temperature atmospheric pressure cold plasma (ionized gas) have been recently tested to improve this regenerative process. To optimize wound healing the present study intended to combine, for the first time, these two novel approaches in a large size animal wound healing model with the aim of assessing the putative dual beneficial effects. Based on clinical, histopathological, and molecular results a synergistic action in a second intention healing wound in sheep has been observed. Experimental wounds treated with cold plasma and MSCs showed a slower but more effective healing compared to the single treatment, as observed in previous studies. The combined treatment improved the correct development of skin appendages and structural proteins of the dermis showing the potential of the dual combination as a safe and effective tool for skin regeneration in the veterinary clinical field.

Low-Temperature Plasma as an Approach for Inhibiting a Multi-Species Cariogenic Biofilm

This study aimed to determine how low-temperature plasma (LTP) treatment affects single- and multi-species biofilms formed by Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii formed on hydroxyapatite discs. LTP was produced by argon gas using the kINPen09™ (Leibniz Institute for Plasma Science and Technology, INP, Greifswald, Germany). Biofilms were treated at a 10 mm distance from the nozzle of the plasma device to the surface of the biofilm per 30 s, 60 s, and 120 s. A 0.89% saline solution and a 0.12% chlorhexidine solution were used as negative and positive controls, respectively. Argon flow at three exposure times (30 s, 60 s, and 120 s) was also used as control. Biofilm viability was analyzed by colony-forming units (CFU) recovery and confocal laser scanning microscopy. Multispecies biofilms presented a reduction in viability (log10 CFU/mL) for all plasma-treated samples when compared to both positive and negative controls (p < 0.0001). In single-species biofilms formed by either S. mutans or S. sanguinis, a significant reduction in all exposure times was observed when compared to both positive and negative controls (p < 0.0001). For single-species biofilms formed by S. gordonii, the results indicate total elimination of S. gordonii for all exposure times. Low exposure times of LTP affects single- and multi-species cariogenic biofilms, which indicates that the treatment is a promising source for the development of new protocols for the control of dental caries.

Deposition of Cell Culture Coatings Using a Cold Plasma Deposition Method

Collagen coatings were applied onto polystyrene microplates using a cold atmospheric pressure plasma process. The coatings were compared to standard wet chemical collagen thin films using microscopy, surface energy, infra-red spectroscopy, electrophoresis, and cell culture techniques. Thin films were also deposited on gold electrodes using both coating methods and their structural and barrier properties probed using cyclic voltammetry. While the wet chemical technique produced a thicker deposit, both films appear equivalent in terms of coverage, porosity, structure, and chemistry. Significantly, the cold plasma method preserves both the primary and secondary structure of the protein and this results in high biocompatibility and cell activity that is at least equivalent to the standard wet chemical technique. The significance of these results is discussed in relation to the benefits of a single step plasma coating in comparison to the traditional multi-step aseptic coating technique.