A new configuration of a discharge chamber and power source for the treatment of up to 1 L of liquid is presented. A leakage transformer, energizing two metal electrodes positioned above the liquid, limits the discharge current inductively by utilizing the weak magnetic coupling between the primary and secondary coils. No additional means to avoid arcing (electric short-circuiting), e.g., dielectric barriers or resistors, are needed. By using this technique, exceeding the breakdown voltage leads to the formation of transient spark discharges, producing non-thermal plasma (NTP). These discharges effected significant changes in the properties of the treated liquids (distilled water, physiological saline solution, and tap water). Considerable concentrations of nitrite and nitrate were detected after the plasma treatment. Furthermore, all tested liquids gained strong antibacterial efficacy which was shown by inactivating suspended Escherichia coli and Staphylococcus aureus. Plasma-treated tap water had the strongest effect, which is shown for the first time. Additionally, the pH-value of tap water did not decrease during the plasma treatment, and its conductivity increased less than for the other tested liquids.

Low temperature plasma jets gained increased interest in the last years as a potential device in many life science applications, including here human or veterinary medicine. Standardisation of plasma sources and biological protocols are necessary for quality assurance reasons, due to the fact that this type of atmospheric pressure plasma source is available in multiple configurations and their operational parameters span also on a broad range of items, such as all characteristics of high voltage pulses used for gas breakdown, geometrical characteristics, gas feed composition and conductive or biological target characteristics. In this paper we present results related to electrical, optical and molecular beam mass spectrometry diagnosis of a helium plasma jet, emphasising the influence of various operational parameters of the high voltage pulses on plasma jet properties. Discussion on physical parameters that influence the biological response is included, together with important results on plasma sources statistical behaviour until reaching a quasi-stationary working regime. The warm-up period of the plasma jet, specific to many other plasma sources, must be precisely known and specified whenever the plasma jets are used as a tool for life science applications.

Over the past decade, cold atmospheric plasma (CAP) has undergone extensive research as a promising therapeutic approach in oncology, with different treatment methods and exposure configurations being investigated and resulting in various biological effects, most of them after long exposure or treatment durations. This study aimed to evaluate the potential of a custom-made CAP generation source to produce plasma-activated medium (PAM) with cytotoxic effects and subsequently to establish the optimal exposure and treatment parameters. The exposure’s electrical parameters, as well as pH and ${\mathrm{NO}}_2^{-}$ content of PAM were analyzed. The cytotoxic potential and optimal parameters of the treatment were established by evaluating the viability of human osteosarcoma cells (HOS cell line) and human osteoblasts (HOB cell line) treated with PAM under different conditions. Our results showed that indirect treatment with CAP presents selective dose-dependent cytotoxic effects, while the cell viability decrease was not found to be correlated with the PAM acidification due to CAP exposure. The Griess assay revealed very high and long-term stable concentrations of ${\mathrm{NO}}_2^{-}$ in PAM. Overall, this study presents a simple and faster method of producing PAM treatment with cytotoxic effects on HOS cells, by using a custom-built CAP source.