Effects of Cold Atmospheric Plasmas on Membranes

In a world of chemotherapeutic resistance, cold atmospheric plasmas (CAPs) have gained strong interest because they efficiently combat resistant bacterial infections and skin cancer without inducing serious side effects. CAPs are composed of electric fields, visible and UV-light, ionized gas and reactive nitrogen and oxygen species (RNOS), and can be delivered to any biological target because of their low heating capacity. Upon exposure of cells or tissues to plasma, the generated RNOS are solubilized in aqueous solution, where they target cell membranes, the natural barriers of cells. We therefore investigated how plasma generated RNOS interact with cell membranes. For this purpose we analysed biophysical and compositional changes of cellular and model membranes upon plasma exposure. We also investigated the relationship between diffusion, permeabilization and lipid oxidation of RNOS towards membranes of different degrees of lipid unsaturation. We were able to determine that plasma induces a donut shaped increase of several RNOS at the plasma/aqueous interface which are able to permeabilize and oxidize membranes depending on their unsaturation degree. Interestingly, bacterial cell death seemed less influenced by the amount of lipid oxidation, but to be caused by other plasma-induced effects. This study adds to the general understanding on how CAPs induce the formation of RNOS in solution and how cells are affected by their membrane disrupting properties.