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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.

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Plasma immersion ion implantation (PIII) of stainless steels with nitrogen has been successfully used for surface hardening purposes. This process has been carried out inside a toroidal discharge chamber in a DC/RF plasma. The RF plasma was created by one antenna located inside the chamber, diametrically opposite to the DC electrode. The latter is polarized with 1 kV and then the discharge is controlled by varying the gas pressure before the RF signal is applied. The main plasma parameters were established by means of double electric probes yielding electron temperature values within 0.5-1.5 eV and density values within 1.5×1015 to 4×10 15 m −3 for the DC case while 1.5-3.0 eV and 7×10 14 to 3×10 15 m −3 were reached with RF assisted DC. We present in this work the experimental results obtained from a PIII process applied to AISI 304 stainless steel plates. The outcome shows that the Vickers hardness has been incremented according to the gas pressure within the 1×10 −1 to 1×10 −3 mbar range. The treated plates were analyzed by scanning electron microscopy (SEM) and the results point to an increased percentage of nitrogen, around 20%. By means of x-ray diffractometry (XRD) the gamma expanded phase and compounds such as Fe3NiN, Ni4N, FeNiN and Fe3N were determined.