## 1 Introduction
Regardless of the configuration, with one or two electrodes, there are two types of DBD that can be distinguished: DBD without flow, in which the plasma is produced and remains to the space between the electrodes, and DBD with flow, also known as a plasma jet or atmospheric pressure plasma jet (APP), in which the plasma is located both in the space between the electrodes and in the post-electrode region [52; 58]. [PERSON] et al. [59] asserted that these two forms of plasma discharge may also be classified as direct discharge sources (DBD without flow) and indirect discharge sources (DBD with flow), based on the discharge mode presented above. Over the past decade, both DBD techniques have been explored for their potential use in the field of oncology, and they have been shown to be a promising alternative to traditional cancer therapies [48]. Regarding the treatment of tumor cells, two methods of CAP treatments are widely used, namely direct treatment and indirect treatment. In direct treatment, cells are directly subjected to CAP discharges, whereas in indirect treatment, plasma discharges are applied to a liquid which is then administered to the cells [12]. [PERSON] et al. assumed that the biological effects of CAP result in an interaction between cells and the plasma's physical (UV, electromagnetic field, heat) and chemical (short- and longed-lived reactive oxygen and nitrogen species (RONS)) elements, with RONS being responsible for oxidative damage, membrane alterations, apoptosis and double-strand breaks in DNA [60]. When a plasma discharge occurs over a liquid, the RONS formed at interfaces are partially transferred into the liquid, where, due to the interaction between them and the molecules in the liquid, secondary reactive species are formed [3; 9]. [PERSON] et al. state that CAP direct treatment only allows for a maximum plasma penetration depth of 60 \(\upmu\)m for anti-tumor effects, making it challenging to treat oncology patients using this technique. On the other hand, indirect treatment with plasma-activated medium (PAM) offers a significant advantage as it allows for targeting various regions of the body or tumor by injecting PAM at the therapeutic location. Moreover, from a technical standpoint, producing and storing PAM as an anti-tumor treatment is easier and more convenient. [61]. Therefore, from a translational perspective, the indirect method of treatment with CAP appears to be more promising. Viewed from the same perspective, it is important for a potential cancer-fighting therapy like CAP to possess certain essential qualities in addition to its targeted antitumor effects. These characteristics may include a reduced production time, the ability to be stored for subsequent use, an optimal balance between treatment duration and its efficacy and cost-effective production. Considering the previously mentioned aspects, the purpose of this study is to evaluate the potential of our custom-made CAP source to produce PAM, to establish the optimal exposure and treatment parameters in order to create a fast-obtaining treatment with rapid and efficient cytotoxic effect on HOS cells, as well as to characterize the produced PAM as a possible treatment in OS therapy.