The aim of the present study is to determine the deoxyribonucleic acid (DNA) damage by cells exposed to atmospheric pressure non-thermal plasma (APNTP). Mouse leukocytes embedded in agarose were exposed to the plasma at two different distances from a helium plasma needle outlet and during three different exposure periods. Damage was assessed by the single cell gel electrophoresis assay. The results indicate that, at 0.1 cm from the plasma needle, the exposure caused complete DNA fragmentation determined by the presence of so called “clouds”. Samples exposed at 0.5 cm from the slide sample surface presented damage proportional to the exposure periods in terms of tail intensity, tail moment and “clouds” frequency. Studies performed with alkaline single cell gel electrophoresis assay to determine DNA breaks and alkali-labile sites, indicates that DNA damage produced by exposure to APNTP was caused mainly by oxidative radicals, rather than by UV light which causes cyclobutane pyrimidine dimers. These results allow us to conclude that plasma needle induced DNA breaks in mice leukocytes proportionally to exposure time.

The aim of this study is to determine the toxic and genotoxic damages produced by a helium plasma needle upon HeLa and E. coli (OG100 and PQ30) cell cultures. For HeLa cells survival (MTT) and microelectrophoresis comet) assays were performed; meanwhile in E. coli, viable count and genotoxicity by the chromotest were evaluated. The outcomes indicate that the plasma exposures on HeLa cells undergo more toxicity and genotoxicity as treatment time increases. With respect to E. coli , plasma exposure generated toxicity, but no genotoxicity could be detected with this system. In the strain OG100, defective in a protection mechanism to oxidizing agents, there was a reduction in the survival of one order of magnitude compared to the wild type strain PQ30. It suggests that such reduction is due to the plasma by means of the reactive oxygen and nitrogen species (RONS) generated during atmospheric air interaction.

This paper presents an experimental study of the inactivation in water of two representative classes of bacteria, Gram-negative Escherichia coli and Gram-positive Bacillus subtilis, using pulsed dielectric barrier discharges (PDBDs) in a coaxial arrangement. To this purpose, an adjustable plasma source supplies 25-kV/500-Hz pulses, 30 μs long, at atmospheric pressure, with total energy consumption estimated at about 100 mJ/pulse. The inactivation effect of a PDBD on these types of microorganisms has been previously studied in dependence on an oxygen gas flow mode (null, continuous, and modulate). The results have shown a significant bacterial reduction rate from 10⁸ to 10³ cells/mL with E. coli and from 10⁷ to 10³ cells/mL with B. subtilis. The inactivation effectiveness is substantially similar in both kinds of bacteria, although some data suggest a greater susceptibility of the Gram-negative E. coli to plasma exposure. Plasma diagnostics was carried out using optical emission spectroscopy whereby the OH radical and reactive oxygen species formation rates in solution were found and the level of ozone produced by the discharge was monitored. Finally, a kinetics model was developed to characterize the chemical species taking place in nonthermal plasma inactivation processes in water.