Cold Atmospheric Plasma Exposure Research Articles

Cold atmospheric plasma enhances morphological and biochemical attributes of tomato seedlings

Cold atmospheric plasma (CAP) is a physical technology with notable effects on living organisms. In the present study, tomato seeds (Solanum lycopersicum var. Bassimo Mill.) were exposed to CAP for various time intervals, ranging from 1 to 5 min, in both continuous and intermittent periods, and were compared with a control group that received no CAP treatment. Seedlings grown from treated seeds exhibited improvements in levels of growth traits, photosynthetic pigments, and metabolite contents when compared to the control group. Seedlings from seeds treated with S04 displayed significant increases in shoot and root lengths, by 32.45% and 20.60% respectively, compared to the control group. Moreover, seedlings from seeds treated with S01 showed a 101.90% increase in total protein, whereas those treated with S02 experienced a 119.52% increase in carbohydrate content. These findings highlight the substantial improvements in growth characteristics, photosynthetic pigments, and metabolite levels in seedlings from treated seeds relative to controls. Total antioxidant capacity was boosted by CAP exposure. The activities of enzymes including superoxide dismutase, catalase, and peroxidases were stimulated by S02 and exceeded control treatment by (177.48%, 137.41%, and 103.32%), respectively. Additionally, exposure to S04 increased the levels of non-enzymatic antioxidants like flavonoids, phenolics, saponins, and tannins over the control group (38.08%, 30.10%, 117.19%, and 94.44%), respectively. Our results indicate that CAP-seed priming is an innovative and cost-effective approach to enhance the growth, bioactive components, and yield of tomato seedlings.

Exploring the Influence of Cold Plasma on Epidermal Melanogenesis In Situ and In Vitro.

Epidermal melanin synthesis determines an individual's skin color. In humans, melanin is formed by melanocytes within the epidermis. The process of melanin synthesis strongly depends on a range of cellular factors, including the fine-tuned interplay with reactive oxygen species (ROS). In this context, a role of cold atmospheric plasma (CAP) on melanin synthesis was proposed due to its tunable ROS generation. Herein, the argon-driven plasma jet kINPen® MED was employed, and its impact on melanin synthesis was evaluated by comparison with known stimulants such as the phosphodiesterase inhibitor IBMX and UV radiation. Different available model systems were employed, and the melanin content of both cultured human melanocytes (in vitro) and full-thickness human skin biopsies (in situ) were analyzed. A histochemical method detected melanin in skin tissue. Cellular melanin was measured by NIR autofluorescence using flow cytometry, and a highly sensitive HPLC-MS method was applied, which enabled the differentiation of eu- and pheomelanin by their degradation products. The melanin content in full-thickness human skin biopsies increased after repeated CAP exposure, while there were only minor effects in cultured melanocytes compared to UV radiation and IBMX treatment. Based on these findings, CAP does not appear to be a useful option for treating skin pigmentation disorders. On the other hand, the risk of hyperpigmentation as an adverse effect of CAP application for wound healing or other dermatological diseases seems to be neglectable.

Efficacy of Cold Atmospheric Plasma vs. Chemotherapy in Triple-Negative Breast Cancer: A Systematic Review.

Breast cancer is a growing disease, with a high worldwide incidence and mortality rate among women. Among the various types, the treatment of triple-negative breast cancer (TNBC) remains a challenge. Considering the recent advances in cold atmospheric plasma (CAP) cancer research, our goal was to evaluate efficacy data from studies based on chemotherapy and CAP in TNBC cell lines and animal models. A search of the literature was carried out in the PubMed, Web of Science, Cochrane Library, and Embase databases. Of the 10,999 studies, there were fifty-four in vitro studies, three in vivo studies, and two in vitro and in vivo studies included. MDA-MB-231 cells were the most used. MTT, MTS, SRB, annexin-V/propidium iodide, trypan blue, and clonogenic assay were performed to assess efficacy in vitro, increasing the reliability and comprehensiveness of the data. There was found to be a decrease in cell proliferation after both chemotherapy and CAP; however, different protocol settings, including an extensive range of drug doses and CAP exposure times, were reported. For both therapies, a considerable reduction in tumor volume was observed in vivo compared with that of the untreated group. The treatment of TNBC cell lines with CAP proved successful, with apoptosis emerging as the predominant type of cellular death. This systematic review presents a comprehensive overview of the treatment landscape in chemotherapy and CAP regarding their efficacy in TNBC cell lines.

Investigating the effect of cold atmospheric plasma treatment on the microbial load of raw potato slices.

Potatoes (Solanum tuberosum), as starchy plants, have been highly esteemed for their rich supply of nutrients. Numerous studies have investigated the potential health benefits of potatoes and explored potential solutions. Among these considerations, the discussion regarding microbial contaminants has remained an important topic. The present study used cold atmospheric plasma (CAP) to evaluate the microbial quality (including mesophilic and psychrotrophic bacteria and mold and yeasts) of raw potato slices during a 14-day storage period. To achieve this goal, the duration of CAP exposure was set at 5, 10, and 15 min, utilizing an electric voltage of 60 kV and a specific frequency of 20 kHz. The findings revealed the effectiveness of CAP pre-treatment in inhibiting microbial growth over the 14 days when compared to the control sample (untreated sample), with a statistically significant difference (P < 0.05). Moreover, with an extension of the CAP exposure duration to 15 min, there was a significant reduction in the logarithmic count of mesophilic, psychrotrophic microorganisms, molds, and yeasts (4.95, 2.85, and 2.22CFU/g, respectively) in comparison to the control groups (7.5, 5.62, and 5.5CFU/g) on days 0, 7, and 14 of the storage periods (P < 0.05). The results of this study highlight the potential of CAP pre-treatment on reducing the microbial load in raw potato slices prior to frying, which could potentially influence the overall quality of potato-based products.

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.

Helium Cold Atmospheric Plasma Causes Morphological and Biochemical Alterations in Candida albicans Cells

(1) Background: Previous studies reported the promising inhibitory effect of cold atmospheric plasma (CAP) on Candida albicans. However, the exact mechanisms of CAP’s action on the fungal cell are still poorly understood. This study aims to elucidate the CAP effect on C. albicans cell wall, by evaluating the alterations on its structure and biochemical composition; (2) Methods: C. albicans cells treated with Helium-CAP were analyzed by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) in order to detect morphological, topographic and biochemical changes in the fungal cell wall. Cells treated with caspofungin were also analyzed for comparative purposes; (3) Results: Expressive morphological and topographic changes, such as increased roughness and shape modification, were observed in the cells after CAP exposure. The alterations detected were similar to those observed after the treatment with caspofungin. The main biochemical changes occurred in polysaccharides content, and an overall decrease in glucans and an increase in chitin synthesis were detected; (4) Conclusions: Helium-CAP caused morphological and topographic alterations in C. albicans cells and affected the cell wall polysaccharide content.

The Molecular Basis for Selectivity of the Cytotoxic Response of Lung Adenocarcinoma Cells to Cold Atmospheric Plasma.

The interaction of cold atmospheric plasma (CAP) with biotargets is accompanied by chemical reactions on their surfaces and insides, and it has great potential as an anticancer approach. This study discovers the molecular mechanisms that may explain the selective death of tumor cells under CAP exposure. To reach this goal, the transcriptional response to CAP treatment was analyzed in A549 lung adenocarcinoma cells and in lung-fibroblast Wi-38 cells. We found that the CAP treatment induced the common trend of response from A549 and Wi-38 cells-the p53 pathway, KRAS signaling, UV response, TNF-alpha signaling, and apoptosis-related processes were up-regulated in both cell lines. However, the amplitude of the response to CAP was more variable in the A549 cells. The CAP-dependent death of A549 cells was accompanied by DNA damage, cell-cycle arrest in G2/M, and the dysfunctional response of glutathione peroxidase 4 (GPx4). The activation of the genes of endoplasmic reticulum stress and ER lumens was detected only in the A549 cells. Transmission-electron microscopy confirmed the alteration of the morphology of the ER lumens in the A549 cells after the CAP exposure. It can be concluded that the responses to nuclear stress and ER stress constitute the main differences in the sensitivity of tumor and healthy cells to CAP exposure.

Cold atmospheric plasma: a sustainable approach to inactivating viruses, bacteria, and protozoa with remediation of organic pollutants in river water and wastewater

Innovative technologies are needed to enhance access to clean water and avoid waterborne diseases. We investigated the performance of cold atmospheric plasma (CAP), a clean and sustainable approach for microbial inactivation and total organic carbon (TOC) degradation in environmental water. Water matrices played a crucial role in the performance of CAP efficacy; for example, complete removal of ɸX174 from dH2O required 1 min of treatment, while ɸX174 reductions of ~ 2log10 and 4log10 were obtained after 10 min of CAP exposure in river water and wastewater samples, respectively. Similarly, after 10 min of CAP treatment, bacterial concentrations decreased by 3 log10 and 4 log10, in river and wastewater samples, respectively. In contrast, after 30 s of contact time, a 4 log10 reduction of bacteria was accomplished in dH2O. Complete removal of Acanthamoeba from dH2O was found after 30 min of CAP treatment, whereas it was not removed from surface water or wastewater at the same exposure time. Additionally, the approach successfully reduced TOC, and the degradation kinetics of TOC were represented by pseudo-first-order. CAP showed higher rates of TOC degradation in the final effluent of the wastewater treatment plant compared to surface water. The difference in CAP performance between river water and wastewater could be attributed to the bulk structure of humic acids in river water compared to small organic byproducts in the final effluent of WWTP. Overall, the findings reported here support the idea that CAP holds promise as a sustainable solution for controlling pathogens, removing organic water pollution, and integrating with traditional purification processes. Low-cost systems may advance CAP technology and increase its widespread use.

Optimization of Indirect CAP Exposure as an Effective Osteosarcoma Cells Treatment with Cytotoxic Effects

Over the past decade, cold atmospheric plasma (CAP) has undergone extensive research as a promising therapeutic approach in oncology, with different treatment methods and exposure configurations being investigated and resulting in various biological effects, most of them after long exposure or treatment durations. This study aimed to evaluate the potential of a custom-made CAP generation source to produce plasma-activated medium (PAM) with cytotoxic effects and subsequently to establish the optimal exposure and treatment parameters. The exposure’s electrical parameters, as well as pH and NO2− content of PAM were analyzed. The cytotoxic potential and optimal parameters of the treatment were established by evaluating the viability of human osteosarcoma cells (HOS cell line) and human osteoblasts (HOB cell line) treated with PAM under different conditions. Our results showed that indirect treatment with CAP presents selective dose-dependent cytotoxic effects, while the cell viability decrease was not found to be correlated with the PAM acidification due to CAP exposure. The Griess assay revealed very high and long-term stable concentrations of NO2− in PAM. Overall, this study presents a simple and faster method of producing PAM treatment with cytotoxic effects on HOS cells, by using a custom-built CAP source.

Applying Cold Atmospheric Plasma to Preserve the Postharvest Qualities of Winter Jujube (Ziziphus jujuba Mill. cv. Dongzao) During Cold Storage.

Winter jujube (Ziziphus jujuba Mill. cv. Dongzao) is a very popular horticultural fruit worldwide, which contains a high number of bioactive compounds. Nevertheless, jujube is perishable by microbial contamination and has a short shelf life under non-controlled conditions. Cold atmospheric plasma (CAP) presents a great potential for food sterilization, maintain postharvest quality, and prolonged storage time. Herein, this study investigated the potential effect of CAP with different exposure times (0, 5, 10, and 20 min) on the physicochemical and biochemical changes in jujube during 15-day storage at 4°C and 90% relative humidity (RH). The results showed that CAP treatment could obviously delay ripening, but displayed no effects on the speed of weight loss and moisture content. Meanwhile, the total native aerobic bacterial count in each jujube group was restrained during whole storage. However, CAP treatment showed a time-dependent manner to improve gene expression (PAL, 4CL, DFR, ANS, LAR, and ANR) related to phenolic biosynthesis. As compared to other groups, 20-min CAP treatment can keep or increase total phenolic content (TPC), maintain antioxidant activity, and reduce oxidative damage. Furthermore, the hydrogen peroxide (H2O2) and malondialdehyde (MDA) content in jujube during middle storage were visibly reduced by 20-min CAP treatment. All in all, our findings concluded that appropriate CAP exposure time can be a promising candidate for the postharvest preservation of jujube.

Cold atmospheric plasma inhibits vesicle transport of human osteosarcoma cells visualized by super‐resolution fluorescence microscopy

AbstractVesicle transport plays a key role in cancer invasion and metastasis. As a promising cancer treatment modality, the impact of cold atmospheric plasma (CAP) on vesicle transport has been barely examined. In this study, super‐resolution structured illumination microscopy (SIM) was employed to track the intracellular vesicles of osteosarcoma cells. Results indicated that CAP exposure could disintegrate vesicle clusters and individual vesicles. After 20 s of CAP treatment, the average velocity of intracellular vesicles decreased from 0.140 to 0.037 μm/s, while the 60 s maximum displacement declined from 7.76 to 3.26 μm. Significant inhibition of vesicle transport between osteosarcoma cells and human bronchial epithelium was observed after CAP treatment. These findings may shed some light on understanding CAP–cancer cell interactions.

Hsa_circRNA_0040462: a sensor of cells' response to CAP treatment with double-edged roles on breast cancer malignancy.

Cold atmospheric plasma (CAP) represents a novel onco-therapeutic approach that has demonstrated its efficacy in many types of tumors. The efficacy of CAP is dose-dependent that determines the panel of tumors feasible for receiving CAP treatment under a certain parameter configuration. Identifying markers for easy and fast prognosis of tumors' sensitivity in response to CAP exposure is of critical value towards optimized therapeutic outcome, the lack of which has largely limited the translation of CAP into clinics. Circular RNAs represent a novel type of biomarkers for disease diagnosis that is featured by easy detection and stability. Through whole transcriptome sequencing, followed by in vitro validations, computational predictions and preliminary functional studies, we identified hsa_circRNA_0040462 as a sensor of breast cancer cells' response to CAP treatment. Yet we warrant the use of hsa_circRNA_0040462 as an onco-therapeutic target given its double-edged roles on breast cancer progression, i.e., suppressive on the growth and promotive on the migrative ability of triple negative breast cancer cells. Our study for the first time focused on markers prognostic of CAP's efficacy and tumors' sensitivity to CAP treatment under a certain parameter configuration, and reported hsa_circRNA_0040462 as a sensor of cells' response to CAP treatment. Also, the uncovered dual roles of hsa_circRNA_0040462 further advanced our knowledge on the complex yet critical regulatory functionalities of circular RNAs in cancer progression.

Influence of Redox Stress on Crosstalk between Fibroblasts and Keratinocytes.

Simple SummaryThere has been significant scientific progress in skin care and skin damage repair, but the complete understanding of skin homeostasis is still beyond our reach. With an increase in environmental stress factors, the incidence rates of skin cancer and skin disorders are on the rise. Taken together with the incidence of scar- and burn-related morbidities, there is an urgent need to understand interactions between skin cells to develop novel therapies for the regeneration of healthy skin. One of the recurrent stress factors affecting the skin are the harmful free radicals, also referred to as oxidative stress. This study aimed to address the influence of oxidative stress on the interaction between two types of skin cells, keratinocytes and fibroblasts. The study utilized cold atmospheric plasma (CAP) to induce oxidative stress in cells and to assess the interactions between the two cell types. We showed that CAP can stimulate cells to enhance their proliferation and migration. This study provides a further understanding of skin cell regulation under stress conditions. Such knowledge may help in designing treatment therapies for rapid wound healing and skin repair.Although the skin is constantly subjected to endogenous and exogenous stress, it maintains a homeostatic state through wound repair and regeneration pathways. Treatment for skin diseases and injury requires a significant understanding of the various mechanisms and interactions that occur within skin cells. Keratinocytes and fibroblasts interact with each other and act as key players in the repair process. Although fibroblasts and keratinocytes are widely studied in wound healing and skin remodeling under different conditions, the influence of redox stress on keratinocyte-fibroblast crosstalk has not been thoroughly investigated. In this study, we used cold atmospheric plasma (CAP) to generate and deliver oxidative stress to keratinocytes and fibroblasts and to assess its impact on their interactions. To this end, we used a well-established in vitro 3D co-culture model imitating a realistic scenario. Our study shows that low CAP exposure is biocompatible and does not affect the viability or energetics of fibroblasts and keratinocytes. Exposure to low doses of CAP enhanced the proliferation rate of cells and stimulated the expression of key genes (KGF, MMP2, GMCSF, IL-6, and IL-8) in fibroblasts, indicating the activation and initiation of the skin repair process. Additionally, enhanced migration was observed under co-culture conditions under the given redox stress conditions, and expression of the upstream regulator and the effectors of the Hippo pathway (YAP and CYR61, respectively), which are associated with enhanced migration, were elevated. Overall, this study reinforces the application of CAP and redox stress in skin repair physiology.

Nitrogen Accumulation in Oyster (Crassostrea gigas) Slurry Exposed to Virucidal Cold Atmospheric Plasma Treatment

Viral contamination of edible bivalves is a major food safety issue. We studied the virucidal effect of a cold atmospheric plasma (CAP) source on two virologically different surrogate viruses [a double-stranded DNA virus (Equid alphaherpesvirus 1, EHV-1), and a single-stranded RNA virus (Bovine coronavirus, BCoV)] suspended in Dulbecco’s Modified Eagle’s Medium (DMEM). A 15 min exposure effectuated a statistically significant immediate reduction in intact BCoV viruses by 2.8 (ozone-dominated plasma, “low power”) or 2.3 log cycles (nitrate-dominated, “high power”) of the initial viral load. The immediate effect of CAP on EHV-1 was less pronounced, with “low power” CAP yielding a 1.4 and “high power” a 1.0 log reduction. We observed a decline in glucose contents in DMEM, which was most probably caused by a Maillard reaction with the amino acids in DMEM. With respect to the application of the virucidal CAP treatment in oyster production, we investigated whether salt water could be sanitized. CAP treatment entailed a significant decline in pH, below the limits acceptable for holding oysters. In oyster slurry (a surrogate for live oysters), CAP exposure resulted in an increase in total nitrogen, and, to a lower extent, in nitrate and nitrite; this was most probably caused by absorption of nitrate from the plasma gas cloud. We could not observe a change in colour, indicative for binding of NOx to haemocyanin, although this would be a reasonable assumption. Further studies are necessary to explore in which form this additional nitrogen is deposited in oyster flesh.

Carrier-Free Cellular Transport of CRISPR/Cas9 Ribonucleoprotein for Genome Editing by Cold Atmospheric Plasma.

Simple SummaryCRISPR/Cas9 system as a potential gene editing platform has been widely applied in biological engineering and disease therapies. To achieve precise gene targeting, active CRISPR/Cas9 components must be efficiently transported to targeted cells. As a simple and effective strategy, Cold Atmospheric Plasma (CAP) treatment has been demonstrated for the transmembrane delivery of various exogenous materials. In comparison with carrier-dependent delivery methods, this carrier-free platform provides a promising alternative to circumvent the obstacles of biosafety and complicated preparation processes. In this work, a CAP-based CRISPR/Cas9 carrier-free delivery platform has been established and corresponding mechanism related to efficient transportation has been explored. Briefly, the efficient production of bioactive species in culture media after CAP treatment alters cell membrane potential and permeability, which facilitates cytosolic delivery of active CRISPR/Cas9 components via passive diffusion and ATP-dependent endocytosis pathways, resulting in efficient genome editing and gene silencing. This carrier-free strategy using CAP-based transportation may also be extended to other active biomolecules in drug delivery and gene therapy.A carrier-free CRISPR/Cas9 ribonucleoprotein delivery strategy for genome editing mediated by a cold atmospheric plasma (CAP) is described. The CAP is promising in many biomedical applications due to efficient production of bioactive ionized species. The MCF-7 cancer cells after CAP exposure exhibit increased extracellular reactive oxygen and nitrogen species (RONS) and altered membrane potential and permeability. Hence, transmembrane transport of Ca2+ into the cells increases and accelerates ATP hydrolysis, resulting in enhanced ATP-dependent endocytosis. Afterwards, the increased Ca2+ and ATP contents promote the release of cargo into cytoplasm due to the enhanced endosomal escape. The increased membrane permeability also facilitates passive diffusion of foreign species across the membrane into the cytosol. After CAP exposure, the MCF-7 cells incubated with Cas9 ribonucleoprotein (Cas9-sgRNA complex, Cas9sg) with a size of about 15 nm show 88.9% uptake efficiency and 65.9% nuclear import efficiency via passive diffusion and ATP-dependent endocytosis pathways. The efficient transportation of active Cas9sg after the CAP treatment leads to 21.7% and 30.2% indel efficiencies in HEK293T and MCF-7 cells, respectively. This CAP-mediated transportation process provides a simple and robust alternative for the delivery of active CRISPR/Cas9 ribonucleoprotein. Additionally, the technique can be extended to other macro-biomolecules and nanomaterials to cater to different biomedical applications.

Impact of cold atmospheric plasma on microbial safety, total phenolic and flavonoid contents, antioxidant activity, volatile compounds, surface morphology, and sensory quality of green tea powder

The effects of cold atmospheric plasma (CAP) at different voltages of 20, 22, and 25 kV for 2, 4, 6, and 8 min were investigated on microbial safety, total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (AA), volatile compounds profile, microstructure and sensory properties of green tea powder. CAP treatments effectively reduced the total microbial, mold and yeast, total coliform, Escherichia coli, and Entrococcus faecalis counts of green tea. E. coli and E. faecalis were completely deactivated in the sample exposed to plasma treatment at 25 kV for 8 min. E. coli showed higher minimum inhibitory and minimum bactericidal concentrations compared to Staphylococcus aureus. TPC, TFC and AA of green tea decreased with increases in CAP voltage and exposure time. GC–mass spectrometry identified 48 different volatile components in green tea. CAP treatment profoundly influenced the amounts of volatile compounds but the trends of changes did not follow the same pattern as the time and/or voltage of the process increased. SEM analysis showed that CAP at 20 kV for 2 or 4 min did not change the surface morphology of green tea powder while higher exposure times and voltages caused substantial ruptures in microstructure of the samples. Sensory acceptability of green tea decreased noticeably after plasma treatment at 25 kV for longer than 4 min. In conclusion, CAP treatment at 22 kV for 4 or 6 min considerably diminished microbial load of green tea powder while relatively satisfactorily preserved its TPC, TFC, AA, volatile components and sensory desirability.

Cold atmospheric plasma: A non-negligible strategy for viral RNA inactivation to prevent SARS-CoV-2 environmental transmission.

Cold atmospheric plasma (CAP), regarded as a powerful physics technology, displays antimicrobial, antitumor, and even antiviral properties, but the underlying mechanism is rarely studied. In this study, four CAP exposure doses (30, 60, 120, and 240 s) were applied to inactivate a severe acute respiratory syndrome coronavirus 2 like pseudovirus on a stainless steel disk, which comprised spike protein on its membrane and can express a green fluorescent protein. In order to unravel the potential effects of CAP irradiation on pseudovirus, infection assay, optical emission spectra analysis, transmission electron microscopy (TEM), sodium dodecyl sulfate polyacrylamide gel electrophoresis, ELISA, and qPCR experiments were carried out. As a result, our study indicated that CAP irradiation can significantly decrease the infectivity of pseudovirus in a dose dependent manner through destroying the cell membrane and further damaging viral RNA, with the molecular weight and conformation of spike receptor binding domain protein unchanged.

Time-dependent behavior of the Staphylococcus aureus biofilm following exposure to cold atmospheric pressure plasma.

Objective(s):Formation of Staphylococcus aureus biofilm leads to persistent infection in tissue or on exter-nal and indwelling devices in patients. Cold atmospheric plasma (CAP) is used for eradication of bacterial biofilms and it has diverse applications in the healthcare system. However, there is not sufficient information on the behavior of biofilms during the CAP exposure period.Materials and Methods:Pre-established S. aureus biofilms were exposed to CAP for 0 to 360 sec, then subjected to washing steps and sonication. Subsequently, biomass, number of colonies, vitality of bacteria, structure of colonies, size of produced particles, and viability of bacteria were evaluated by different assays including crystal violet, colony-forming unit, MTT, scanning electron mi-croscopy, confocal laser scanning microscopy, and dynamic light scattering assays.Results:The results showed that the strength of biomass increased in the first 60 sec, then decreased to less than no-CAP treated controls. Moreover, short CAP exposure (≤60 sec) ehances the fusion of the biofilm extracellular matrix and other components, which results in preservation of bacteria during ultra-sonication and washing steps compared with control biofilms. The S. aureus biofilm structure only breaks down following more CAP exposure (> 90 sec) and demolition. Interestingly, the 60 sec CAP exposure could cause the fusion of biofilm compo-nents, and large particles are detectable.Conclusion:According to this study, an inadequate CAP exposure period prevents absolute eradication of biofilm and enhances the preservation of bacteria in stronger biofilm compartments.

Open-Air Cold Plasma Device Leads to Selective Tumor Cell Cytotoxicity

The need for effective and safe therapies for cancer is growing as aging is modifying its epidemiology. Cold atmospheric plasma (CAP) has gained attention as a potential anti-tumor therapy. CAP is a gas with enough energy to ionize a significant fraction of its constituent particles, forming equal numbers of positive ions and electrons. Timely-resolved output voltage measurement, emission spectroscopy, and quantification of reactive species (RS) in plasma-activated media (PAM) were performed to characterize the physical and chemical properties of plasma. To assess the cytotoxicity of cold atmospheric plasma in human tumors, different cell lines were cultured, plated, and exposed to CAP, followed by MTT and SRB colorimetric assays 24 h later. Human fibroblasts, phenotypically normal cells, were processed similarly. Plasma cytotoxicity was higher in cells of breast cancer, urinary bladder cancer, osteosarcoma, lung cancer, melanoma, and endometrial cancer. Cytotoxicity was time-dependent and possibly related to the increased production of hydrogen peroxide in the exposed medium. Sixty seconds of CAP exposure renders selective effects, preserving the viability of fibroblast cells. These results point to the importance of conducting further studies of the therapy with plasma.

Efficacy of Cold Atmospheric Plasma Treatment on Chemical and Microbial Pollutants in Water

AbstractHere, we studied the effect of cold atmospheric plasma (CAP) on chemical and microbial pollutants. A model compound for organic water pollutants, crystal violet dye (CV), was used as a chemical probe to monitor a rapid change in the reactive oxygen and nitrogen species (ROS/RNS) in water. We used a point electrode to generate plasma above the treated liquid. Three variables (the gap distance between the point electrode and the water surface, the input voltage, and the water thickness below the point electrode) have been studied to show their effects on CV percent removal as a response. Additionally, the microbicidal effect of CAP against rotavirus (RoV), φX174, E. coli, and S. aureus in water was investigated. A rapid virucidal activity was observed, up to 5 log10 reduction in 1 min for φX174 and 4.3 log10 reduction of RoV in 5 min CAP exposure. Viral removal could be due to the fact that plasma produced active species which have an oxidative effect on viral capsid protein. As expected, bacteria were more sensitive to CAP than viruses, as ∼4log10 removal was observed after 30s exposure. The potent antibacterial effect of CAP could be due to the reaction of free radicals with the outer membrane of bacteria or even the penetration of the bacterial cells. CAP has the potential to control microbial and chemical pollution in water. However, further work should be conducted to determine the efficacy of CAP treatment in complex water matrices.