Antibacterial plasma at safe levels for skin cells

Plasmas produce various reactive species, which are known to be very effective in killing bacteria. Plasma conditions, at which efficient bacterial inactivation is observed, are often not compatible with leaving human cells unharmed. The purpose of this study was to determine plasma settings for inactivation of Pseudomonas aeruginosa, without damaging skin cells in vitro under the same treatment conditions. An RF argon plasma jet excited with either continuous or time modulated (20 kHz, 20% duty cycle) voltages was used. To compare these two operation modes, only the input voltage was adjusted in order to obtain the same average power (1.7 W) for both modes. All other settings, i.e. gas flow, distance plasma tip to liquid surface, were kept constant. Bacteria or skin cells in physiological salt solution were exposed to direct non-contact plasma treatments. Short plasma treatments of up to 2 min resulted in a high reduction of bacterial numbers and did not affect dermal fibroblasts or keratinocytes. Bacterial inactivation has been previously ascribed to peroxynitrite, nitrite and H2O2 while eukaryotic cell viability is proposed to be reduced in the long term by the presence of H2O2 and is less affected by reactive nitrogen species. The remote RF plasma jet treatment was highly effective for bacterial inactivation while skin cell viability was preserved

Nitric oxide density distributions in the effluent of an RF argon APPJ : effect of gas flow rate and substrate

The effluent of an RF argon atmospheric pressure plasma jet, the so-called kinpen, is investigated with focus on the nitric-oxide (NO) distribution for laminar and turbulent flow regimes. An additional dry air gas curtain is applied around the plasma effluent to prevent interaction with the ambient humid air. By means of laser-induced fluorescence (LIF) the absolute spatially resolved NO density is measured as well as the rotational temperature and the air concentration. While in the laminar case, the transport of NO is attributed to thermal diffusion; in the turbulent case, turbulent mixing is responsible for air diffusion. Additionally, measurements with a molecular beam mass-spectrometer (MBMS) absolutely calibrated for NO are performed and compared with the LIF measurements. Discrepancies are explained by the contribution of the and to the MBMS NO signal. Finally, the effect of a conductive substrate in front of the plasma jet on the spatial distribution of NO and air diffusion is also investigate