Gaining Insight In The Selectivity And Plasma-Liquid Chemistry For Plasma Treatment Of Cancer

The use of cold atmospheric plasma, and more specifically plasma-treated liquids (PTL), for cancer treatment is a very promising topic within the field of plasma medicine. [1,2] Simple solutions to be used as PTL (e.g. plasma-treated PBS (pPBS)) are more generally applicable than the plasma-treated media (PTM) that are now mostly reported, because they have a higher stability for storage and are not cell line dependent. [3,4] However, the underlying mechanisms of the plasma-liquid interactions as well as of the selectivity mechanisms of plasma cancer treatment are not yet fully understood. [5,6] In this study, we want to address these two major questions in plasma oncology. Firstly, we investigated the selectivity of plasma treatment for cancer cells vs normal cells. For this purpose, we studied the effect of plasma-treated PBS (pPBS) on the cell cytotoxicity of both non-small cell lung cancer (NSCLC) and normal lung cells. The effects on the cells were monitored by live cell imaging with the IncuCyte ZOOM ® . To gain insight in which species are crucial for this selectivity, we measured the concentrations of several reactive oxygen and nitrogen species (RONS, e.g. H 2 O 2 , NO 2 - , NO 3 - ) by UV-VIS spectrophotometry in the pPBS. Secondly, based on the knowledge on which species are important for the killing of and the selectivity towards cancer cells, we aim to promote the formation of these species in the liquid. Therefore, fundamental insight in the plasma-liquid chemistry is needed. In order to gain this insight, we performed both experimental and computational studies on the effect of the composition of the liquid on the formation of RONS in the liquid. For the computational work, we used 0D and 2D models to reveal the most important reactions and species in the gas and liquid phase. Experimentally, concentrations of RONS in the liquid were measured by both UV-VIS spectrophotometry (e.g. H 2 O 2 , NO 2 - , NO 3 - ) and electron paramagnetic resonance (EPR, e.g. OH, O 3 , O, 1 O 2 ). The effect of chlorine concentration, buffer capacity and pH of the liquid will be presented.