The antibacterial and cell-proliferative character of atmospheric pressure plasma jets (APPJs) helps in the healing process of chronic wounds. However, control of the plasma-biological target interface remains an open issue. High vacuum ultraviolet/ultraviolet (VUV/UV) radiation and RONS flux from plasma may cause damage of a treated tissue; therefore, controlled interaction is essential. VUV/UV emission from argon APPJs and radiation control with aerosol injection in plasma effluent is the focus of this research. The aerosol effect on radiation is studied by a fluorescent target capable of resolving the plasma oxidation footprint. In addition, DNA damage is evaluated by plasmid DNA radiation assay and cell proliferation assay to assess safety aspects of the plasma jet, the effect of VUV/UV radiation, and its control with aerosol injection. Inevitable emission of VUV/UV radiation from plasmas during treatment is demonstrated in this work. Plasma has no antiproliferative effect on fibroblasts in short treatments (t < 60 s), while long exposure has a cytotoxic effect, resulting in decreased cell survival. Radiation has no effect on cell survival in the medium due to absorption. However, a strong cytotoxic effect on the attached fibroblasts without the medium is apparent. VUV/UV radiation contributes 70% of the integral plasma effect in induction of single- and double-strand DNA breaks and cytotoxicity of the attached cells without the medium. Survival of the attached cells increases by 10% when aerosol is introduced between plasma and the cells. Injection of aerosol in the plasma effluent can help to control the plasma–cell/tissue interaction. Aerosol droplets in the effluent partially absorb UV emission from the plasma, limiting photon flux in the direction of the biological target. Herein, cold and safe plasma-aerosol treatment and a safe operational mode of treatment are demonstrated in a murine model.

One of the driving forces behind the development of cold plasma sources at atmospheric pressure is an application in the biomedical field. In this respect, the radio-frequency (RF) plasma jets are of particular importance due to possible safe operation on humans and a generation of the high amount of reactive species. For this reason, we designed RF plasma jet in co-axial geometry with the possibility of aerosol introduction, where its characteristics were evaluated by electrical diagnostics, optical emission, and laser scattering spectroscopy. The RF plasma jet operation and stability of diffuse mode were analysed based on energy balance. It was observed that  mode diffuse discharge characterized by effluent length up to 5 mm was sustained at power density below 30 W/cm 3 . The gas and rotational temperature were determined by means of spectroscopy methods and compared with results of direct laser scattering. It was established that gas temperature obtained from N2 emission of transition C 3 ПuB 3 Пg (0,2) is highly overestimated whereas the gas temperature estimated from OH transition A 2 Σ+X 2 Пi (0,0) gave a reasonable agreement with both Rayleigh and Raman spectroscopy. Based on Rayleigh scattering method uniform gas temperature distribution in the discharge effluent was found at power below 15 W with average temperature below 340±15 K. The low gas temperature of Ar plasma jet allows using this source in temperature sensitive material applications including skin treatments.

A radio-frequency driven plasma jet in annular geometry coupled with an aerosol injection into the effluent is proposed for the controllable ROS/RNS production and delivery on biological targets in the context of plasma medicine, e.g. wound care. The role of the aqueous aerosol in modulating the reactive species production is investigated by combining physical and chemical analytics. Optical emission spectroscopy, electron paramagnetic resonance spectroscopy, and a biochemical model based on cysteine as a tracer molecule have been applied, revealing that aerosol injection shifts the production of ROS from atomic and singlet oxygen towards hydroxyl radicals, which are generated in the droplets. Species generation occurred mainly at the droplets boundary layer during their transport through the effluent, leading to a limited cysteine turnover upon introduction into the aerosol solution. The subsequent delivery of unmodified cysteine molecules at a target suggested the application of the plasma source for the topical delivery of drugs, expanding the potential applicability and effectiveness. The presence of reactive nitrogen species was negligible regardless of aerosol injection and only traces of the downstream products nitrate and nitrate were detected. In summary, the aerosol injection into the effluent opens new avenues to control UV radiation and reactive species output for the biomedical applications of non-thermal plasma sources, reaching out towards the regulation, safety, and efficacy of targeted applications.

Non-thermal plasmas operating at high pressure attract increasing attention for a variety of applications as an alternative to conventional chemical processes.In this study, an atmospheric pressure direct current non-self-sustained discharge in nitrogen is investigated as a source of non-thermal plasma capable of operating in a glow regime. The discharge is sustained between an internal source of ionization and a metal or liquid electrode and studied by electrical diagnostics as well as by spectroscopy methods. The work is focused on the determination of the discharge properties including vibrational and gas temperature. The effect of the liquid electrode on the discharge properties is studied and analyzed. The mechanisms of the discharge sustaining and pathways of nitrogen state excitation are discussed. K E Y W O R D Sliquid anode, nitrogen, non-self-sustained glow discharge, optical emission spectroscopy, vibrational excitation

The possible benefits of an atmospheric pressure plasma jet skin treatment have been tested in vivo on mouse skin. Many studies have been conducted in vitro on mouse skin cells, but only a few in vivo where, due to the complexity of the biological system, plasma can cause severe damages. For this reason, we investigated how kHz plasma generated in a jet that is known to inflict skin damage interacts with mouse skin and explored how we can reduce the skin damage. First, the focus was on exploring plasma effects on skin damage formation with different plasma gases and jet inclinations. The results pointed to the perpendicular orientation of a He plasma jet as the most promising condition with the least skin damage. Then, the skin damage caused by a He plasma jet was explored, focusing on damage mitigation with different liquid interfaces applied to the treatment site, adding N2 to the gas mixture, or alternating the gas flow dynamics by elongating the jet's glass orifice with a funnel. All these mitigations proved highly efficient, but the utmost benefits for skin damage reduction were connected to skin temperature reduction, the reduction in reactive oxygen species (ROS), and the increase in reactive nitrogen species (RNS).