No abstract

No abstract

One of the major concerns in the COVID-19 pandemic is related to the possible transmission in poorly ventilated spaces of SARS-CoV-2 through aerosol microdroplets, which can remain in the air for long periods of time and be transmitted to others over distances >1 m. Cold atmospheric pressure plasmas can represent a promising solution, thanks to their ability in producing a blend of many reactive species, which can inactivate the airborne aerosolized microorganisms. In this study, a dielectric barrier discharge plasma source is used to directly inactivate suitably produced bioaerosols containing Staphylococcus epidermidis or purified SARS-CoV-2 RNA flowing through it. Results show that for low residence times (<0.2 s) in the plasma region a 3.7 log R on bacterial bioaerosol and degradation of viral RNA can be achieved. K E Y W O R D S bioaerosol, cold plasma, inactivation, indoor airborne transmission, SARS-CoV-2 Alina Bisag and Pasquale Isabelli contributed equally to this study.

This work is focused on the use of non-thermal plasma to improve the electrospinnability of poly(L-lactic acid) (PLLA). The use of toxic high boiling point solvents is minimized to produce high quality solvent free nanofibrous scaffolds for biomedical applications. PLLA polymeric solutions dissolved in pure dichloromethane are exposed to the plasma plume of a jet developed by some of the authors and driven by high voltage pulses with rise rate of several kV ns À1 . The effects of peak voltage, pulse repetition frequency, volume of the solution and treatment time on the morphology of electrospun fibers are investigated by means of scanning electron microscope. Electrospinning is performed at different time lapses after the plasma treatment to study the durability of the induced effects. Figure 10. Spatially resolved optical emission spectrum of the plasma jet, operating conditions: PV ¼ 20 kV, PRF ¼ 330 Hz, Ar flow rate ¼ 1 slpm. V. Colombo et al.

Cold atmospheric plasma (CAP) has shown its antitumor activity in both in vitro and in vivo systems. However, the mechanisms at the basis of CAP-cell interaction are not yet completely understood. The aim of this study is to investigate CAP proapoptotic effect and identify some of the molecular mechanisms triggered by CAP in human T-lymphoblastoid leukemia cells. CAP treatment was performed by means of a wand electrode DBD source driven by nanosecond high-voltage pulses under different operating conditions. The biological endpoints were assessed through flow cytometry and real-time PCR. CAP caused apoptosis in Jurkat cells mediated by p53 upregulation. To test the involvement of intrinsic and/or extrinsic pathway, the expression of Bax/Bcl-2 and caspase-8 was analyzed. The activation of caspase-8 and the upregulation of Bax and Bcl-2 were observed. Moreover, CAP treatment increased ROS intracellular level. The situation reverts after a longer time of treatment. This is probably due to compensatory cellular mechanisms such as the posttranscriptional upregulation of SOD1, CAT, and GSR2. According to ROS increase, CAP induced a significant increase in DNA damage at all treatment conditions. In conclusion, our results provide a deeper understanding of CAP potential in the oncological field and pose the basis for the evaluation of its toxicological profile.

Front Cover: Non-thermal atmospheric pressure plasma allowed surface properties modification of electrospun poly(L-lactic acid) scaffold. Mouse embryonic fibroblast cells cultured on treated scaffolds showed a more elongated and ''dendritic'' morphology than cells cultured on the untreated ones. Further details can be found in the article by Maria Letizia Focarete et. al. on page 203. Back Cover: The characteristics of fluorinated carbon films plasma deposited by using c-C 4 F 8 as precursor have been correlated with the plasma parameters and properties. The self-bias voltage at the substrate and the type of intermediate species in the plasma control the composition and structure of the films from polymeric CFx to fluorinated DLC compositions. Further details can be found in the article by Agustín R. González-Elipe et. al. on page 290.

The structure, fluid-dynamic behavior, temperature, and radiation emission of a cold atmospheric pressure plasma jet driven by high-voltage pulses with rise time and duration of a few nanoseconds have been investigated. Intensified charge-coupled device (iCCD) imaging revealed that the discharge starts when voltage values of 5-10 kV are reached on the rising front of the applied voltage pulse; the discharge then propagates downstream the source outlet with a velocity around 10 7 -10 8 cm/s. Light emission was observed to increase and decrease periodically and repetitively during discharge propagation. The structure of the plasma plume presents a single front or either several branched subfronts, depending on the operating conditions; merging results of investigations by means of Schlieren and iCCD imaging suggests that branching of the discharge front occurs in spatial regions where the flow is turbulent. By means of optical emission spectroscopy, discharge emission was observed in the ultraviolet-visible (UV-VIS) spectral range (N 2 , N + 2 , OH, and NO emission bands); total UV irradiance was lower than 1 µW/cm 2 even at short distances from the device outlet (<15 mm). Plasma plume temperature does not exceed 45 °C for all the tested operating conditions and values close to ambient temperature were measured around 10 mm downstream the source outlet.

The analysis of the gas phase chemistry of a cold atmospheric plasma is a fundamental step for a more thorough understanding of the effects it can induce on target substrates. This work aims at investigating, by means of optical spectroscopic techniques, the kinetics of O 3 , NO 2 and NO 3 produced by a Surface Dielectric Barrier Discharge. The phenomenon of discharge poisoning (or ozone quenching) in static ambient air was investigated varying the electrical power density applied to the plasma source. Kinetics of the reactive oxygen and nitrogen species production were obtained by means of time resolved UV/VIS optical absorption spectroscopy and highlighted how the discharge poisoning takes place once the applied power density ovecomes a critical value of 0.11 W cm −2 . An ozone-enriched atmosphere (with a maximum O 3 density around 3000-4000 ppm) is thus obtained when the source is operated below the critical power density, while a NO x -enriched atmosphere (highest concentrations of NO 2 around 1250 ppm and NO 3 around 35 ppm) is obtained at higher applied power densities. Moreover, since the production of NO, one of the most important quenchers of O 3 , is directly related to the vibrational energy of nitrogen molecules, the vibrational population of N 2 , determined by processing emission spectra of N 2 (B→C) band, was studied. Finally, considerations regarding both the energy cost of production of a reactive oxygen species and reactive nitrogen species atmosphere and the possibility of on-line monitoring its chemical composition, were presented in order to emphasize the potential of optical absorption spectroscopy techniques for the on-line control of plasma assisted industrial processes.