## 5 Conclusions  
We found that the plasma treatment of fish cells requires lower dosages than of mammalian cells. The mortality of fish cells was in most of our setups higher than that of mammalian cells regardless of the plasma-treated media used (DMEM vs. L-15).  
A major shortcoming of many previous in vitro experiments is their experimental design, which has led to misconclusions regarding the sensitivity of the cells to plasma treatment. In light of the results of our current study, we suggest using similar cell densities, identical medium, or at least medium with identical antioxidant potential when studying plasma effects on different cells.  
Future studies on fish cell regeneration should involve not only viability studies but also wound healing assays and migration studies under consideration of short plasma treatment times. Plasma treated liquids could be a promising therapeutic tool for aquatic cultures in the future.  
The following are available online at [[https://www.mdpi.com/2076-3](https://www.mdpi.com/2076-3)]([https://www.mdpi.com/2076-3](https://www.mdpi.com/2076-3)) 417/11/6/2534/s1, Table S1: Overview of the cell lines used in this study. Table S2: List of the components of the cell culture media L-15 (Leibovitz's L-15 medium; Thermo Fisher Scientific; Cat.no. 11415) and DMEM (Dulbecco's modified Eagle's medium; Thermo Fisher Scientific, Cat.no. 10569) according to the manufacturers' protocol. Potentially antioxidative compounds are printed in bold. Figure S1: Wound-healing assay with OMYleb cells under the influence of short plasma treatment times. Exemplary images are shown in (a). The size of the gap between two near-confluent cell layers reduced after 24 h growth. We could not detect a difference between untreated cells or cells growing in PAM (b). \(n=4\) independent experiments in DMEM containing 1 mM pyruvate. Figure S2: Measurement of hydrogen peroxide in the different media used in this study at the time they were given to the cells. Plasma treatment was performed for the indicated times. Only L-15 medium and DMEM 5 mM pyruvate medium were treated for 240 s, but even at these long treatment times no peroxide was detectable (argon-treated medium (AAM) served as control; Quantofix peroxide, Macherey Nagel, Duren, Germany).  
Conceptualization, H.R. and A.R.; methodology, H.R. and C.B.; formal analysis, H.R.; investigation, H.R.; resources, S.R. and B.N.; data curation, H.R.; writing--original draft preparation, H.R. and A.R.; writing--review and editing, H.R., C.B., S.R., B.N. and A.R.; visualization, H.R.; funding acquisition, B.N. All authors have read and agreed to the published version of the manuscript.  
We acknowledge the support the European Social Fund (ESF), reference: ESF/14-BM-A55-0002/18, and the Ministry of Education, Science and Culture of Mecklenburg-Vorpommern, Germany for the joint research project ONCOTHER-H.  
Not applicable.  
The authors would like to thank [PERSON] and [PERSON] (University Medical Center Rostock) for qualified technical assistance. We kindly thank [PERSON] (University of South Bohemia in Ceske Budejovice; Faculty of Fisheries and Protection of Waters) for the help with the schematic illustration.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.