Atmospheric pressure plasma jets for biomedical applications are often sustained in He with small amounts of, for example, O2 impurities and typically propagate into ambient air. The resulting poorly ...controlled generation of reactive species has motivated the use of gas shields to control the interaction of the plasma plume with the ambient gas. The use of different gases in the shield yields different behavior in the plasma plume. In this paper, we discuss results from experimental and computational investigations of He plasma jets having attaching and non-attaching gas shields. We found that negative ion formation in the He-air mixing region significantly affects the ionization wave dynamics and promotes the propagation of negative guided streamers through an electrostatic focusing mechanism. Results from standard and phase resolved optical emission spectroscopy ratios of emission from states of N2 and He imply different electric fields in the plasma plume depending on the composition of the shielding gas. These effects are attributed to the conductivity in the transition region between the plasma plume and the shield gas, and the immobile charge represented by negative ions. The lower conductivity in the attaching mixtures enables more extended penetration of the electric field whereas the negative ions aid in focusing the electrons towards the axis.
Treatment of aqueous liquids by surface‐DBD in atmospheric air resulted in bactericidal activity of the liquid itself. A 7 min treatment of sodium chloride (NaCl) solution and its immediate addition ...to Escherichia coli resulted in a complete bacteria inactivation (≥7 log) after 15 min exposure time. With a 30 min delay between plasma treatment of liquid and its addition to the bacteria, bactericidal effect was reduced but still detectable. Nitrate (${\rm NO}_{2}^{{-} } $), nitrite (${\rm NO}_{2}^{{-} } $), and hydrogen peroxide (H2O2), respectively, as well as strong acidification are detected in plasma treated liquids and can explain this bactericidal activity partially. Combination of 1.5 mg · L−1 ${\rm NO}_{2}^{{-} } $ and 2.5 mg · L−1 H2O2 at pH 3 results in maximum 3.5 log E. coli reduction within 60 min. Plasma diagnostics and liquid analytics are combined with theoretical considerations to focus possible reaction channels of plasma–water interactions. Using FT‐IR, stable molecules like nitrous oxide (N2O), ozone (O3), carbon dioxide (CO2), and traces of nitric acid (HNO3) and/or peroxynitrous acid (ONOOH) were measured. Reactions of these molecules from the plasma/gas phase with the aqueous liquid can result in acidification and generation of H2O2, ${\rm NO}_{2}^{{-} } $, and ${\rm NO}_{3}^{{-} } $ or peroxynitrite (ONOO−), respectively, via reactions which are associated with the occurrence of several more or less stable but biologically active chemical intermediates like ${\rm NO}^{ \bullet } $ or nitrogen dioxide (${\rm NO}_{2}^{ \bullet } $). On the other hand, H2O2, ${\rm NO}_{2}^{{-} } $, and ${\rm NO}_{3}^{{-} } $/ONOO− could serve as starting reaction partners to generate ${\rm NO}^{ \bullet } $, ${\rm HO}^{ \bullet } $, ${\rm NO}_{2}^{ \bullet } $, or hydroxyl radicals (${\rm HOO}^{ \bullet } $) in the liquid.
Aqueous liquid treated by surface DBD in air causes bactericidal effects comparable to plasma treatment of bacteria‐containing liquid. Based on chemical liquid analytics, FT‐IR and OES measurements of plasma/gas phase as well as theoretical considerations, possible reaction mechanisms of complex interactions at the plasma/gas–liquid‐interface and subsequent reactions in the liquid volume are hypothesized to explain these experimental results.
The influence of ambient air species especially humidity is an ever-present challenge for atmospheric pressure plasma jet applications. Especially, where the plasma-induced effects are extremely ...sensitive to humidity, such as in the field of plasma medicine, an understanding of the influence of ambient species diffusion on plasma chemistry and on reactive component composition is crucial. In this paper, we investigate the influence of ambient humidity versus feed gas humidity on the production of reactive components by atmospheric pressure plasma jets. By the use of a shielding gas curtain, we control the surrounding atmosphere around the active effluent region of the investigated argon RF-plasma jet (kinpen) and control the gas humidity of the ambient gas. By quantum cascade laser absorption spectroscopy and by Fourier transformed infrared (IR) absorption spectroscopy, the effect of diffusing surrounding molecular species on the chemistry of the long-living reactive oxygen species is investigated. Mechanisms of H 2 O 2 and O 3 production are studied. In this paper, we have quantified the influence that ambient species, namely, water molecules, have on the reactive species' generation in the gas phase. It is shown that the effect of ambient humidity is important for the long-living species production, feed gas humidity, however, has the much stronger effect. Finally, with the focus of applications in plasma medicine, the cell viability of human skin cells (HaCaT keratinocytes) as a function of feed gas and ambient gas humidity is compared.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019, and the outbreak rapidly evolved into the current coronavirus disease pandemic. SARS-CoV-2 is a respiratory virus ...that causes symptoms similar to those caused by influenza A and B viruses. On July 2, 2020, the US Food and Drug Administration granted emergency use authorization for in vitro diagnostic use of the Influenza SARS-CoV-2 Multiplex Assay. This assay detects influenza A virus at 102.0, influenza B virus at 102.2, and SARS-CoV-2 at 100.3 50% tissue culture or egg infectious dose, or as few as 5 RNA copies/reaction. The simultaneous detection and differentiation of these 3 major pathogens increases overall testing capacity, conserves resources, identifies co-infections, and enables efficient surveillance of influenza viruses and SARS-CoV-2.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Finding a solution for air species contamination of atmospheric pressure plasmas in plasma medical treatment is a major task for the new field of plasma medicine. Several approaches use complex ...climate chambers to control the surrounding atmosphere. In this paper, ambient species are excluded in plasma-human-skin-cell treatment by ensheathing the plasma jet effluent with a shielding gas. Not only does this gas curtain protect the plasma jet effluent from inflow of air species but it also, more importantly, allows controlling the effluent reactive species composition by adjusting the mixture of the shielding gas. In the present investigations, the mixture of nitrogen to oxygen within the gas curtain around an argon atmospheric pressure plasma jet (kinpen) is varied. The resulting reactive plasma components produced in the jet effluent are thus either oxygen or nitrogen dominated. With this gas curtain, the effect of reactive oxygen species (ROS) and reactive nitrogen species (RNS) on the cell viability of indirectly plasma-treated HaCaT skin cells is studied. This human keratinocyte cell line is an established standard for a skin model system. The cell viability is determined by a fluorometric assay, where metabolically active cells transform nonfluorescent resazurin to the highly fluorescent resorufin. Plasma jet and gas curtain are characterized by numerical flow simulation as well as by optical emission spectroscopy. The generation of nitrite within the used standard cell culture medium serves as a measure for generated RNS. Measurements with the leukodye dichlorodihydrofluorescein diacetate show that, despite a variation of the shielding gas mixture, the total amount of generated reactive oxygen plus nitrogen species is constant. It is shown that a plasma dominated by RNS disrupts cellular growth less than a ROS-dominated plasma.
The influence of ambient air species is an ever-present problem for atmospheric pressure plasma jet applications. In particular, applications where the plasma-induced effects are extremely sensitive ...to specific types of ambient species (oxygen, nitrogen, humidity) - as, for example, in plasma medicine - require concepts to exclude or to control ambient species flux into the jet effluent that go beyond an environmental control via process chambers or even vacuum systems. In this paper, we demonstrate how to eliminate ambient species influence on effluent chemistry by ensheathing the effluent. With a designed shielding gas composition, we control the species flowing into the jet effluent and thus control the effluent chemistry. The proposed approach can be applied to the majority of possible jet plasma sources. Flow simulations as well as VUV-absorption spectroscopy measurements prove the gas curtain to be effective in shielding the jet gas from ambient species and show that a control of reactive species within the jet effluent is possible. On the example of plasma treatment of a NaCl solution, we demonstrate that, by adjusting the shielding gas composition, the generation of nitrite and nitrate in the solution can be finely controlled.
Young, healthy children shedding cytomegalovirus (CMV) in urine and saliva appear to be the leading source of CMV in primary infection of pregnant women.
We screened 48 children 6 months - 5 years ...old for CMV IgG and measured levels of CMV IgG, IgM and IgG avidity antibodies, frequency of CMV shedding, and viral loads in blood, urine, and saliva. Thirteen of the 48 children (27%) were CMV IgG positive, among whom 3 were also CMV IgM positive with evidence of recent primary infection. Nine of the 13 seropositive children (69%) were shedding 102-105 copies/ml of CMV DNA in one or more bodily fluid. Among seropositive children, low IgG antibody titer (1:20-1:80) was associated with the absence of shedding (p = 0.014), and enrollment in daycare was associated with the presence of CMV shedding (p = 0.037).
CMV antibody profiles correlated with CMV shedding. The presence of CMV IgM more often represents primary infection in children than in adults. Correlating antibodies with primary infection and viral shedding in healthy children adds to the understanding of CMV infection in children that can inform the prevention of CMV transmission to pregnant women.
Based on a capacitively coupled plasma jet concept, an enhanced atmospheric pressure plasma jet setup for endoscopic applications is presented. Besides the favourable features of small dimension, ...flexibility and ability to operate in hollow bodies, new approaches for low patient leakage current, enhanced biological efficacy and reduced material erosion are subject of this work. It is found that a combination of neon feed gas, CO2 shielding gas and a current limited high voltage supply gives the best bactericidal results and, at the same time, reduces material erosion as well as patient leakage current.
Replication of influenza A virus (IAV) from negative-sense viral RNA (vRNA) requires the generation of positive-sense RNA (+RNA). Most molecular assays, such as conventional real-time reverse ...transcriptase PCR (rRT-PCR), detect total RNA in a sample without differentiating vRNA from +RNA. These assays are not designed to distinguish IAV infection versus exposure of an individual to an environment enriched with IAVs but wherein no viral replication occurs. We therefore developed a strand-specific hybridization (SSH) assay that differentiates between vRNA and +RNA and quantifies relative levels of each RNA species. The SSH assay exhibited a linearity of 7 logs with a lower limit of detection of 6.0 × 10
copies of molecules per reaction. No signal was detected in samples with a high load of nontarget template or influenza B virus, demonstrating assay specificity. IAV +RNA was detected 2 to 4 h postinoculation of MDCK cells, whereas synthesis of cold-adapted IAV +RNA was significantly impaired at 37°C. The SSH assay was then used to test IAV rRT-PCR positive nasopharyngeal specimens collected from individuals exposed to IAV at swine exhibitions (
= 7) or while working at live bird markets (
= 2). The SSH assay was able to differentiate vRNA and +RNA in samples collected from infected, symptomatic individuals versus individuals who were exposed to IAV in the environment but had no active viral replication. Data generated with this technique, especially when coupled with clinical data and assessment of seroconversion, will facilitate differentiation of actual IAV infection with replicating virus versus individuals exposed to high levels of environmental contamination but without virus infection.
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