Shielding-gas-controlled atmospheric pressure plasma jets: optical emission, reactive oxygen species, and the effect on cancer cells

Shielding‐gas‐controlled helium atmospheric pressure plasma jets (APPJs) in contact with conductive or nonconductive liquid are investigated. Two‐dimensional (2D) optical emission intensity maps of plasma species directly above the liquid, the 2D distribution of reactive oxygen species (ROS) on the liquid surface, and the 2D distribution of DNA double‐strand breaks (DSBs) induced in epithelial cancer cells are provided. When conductive liquid is used, the plasma jet develops a glow‐discharge‐like structure at the liquid surface. The ROS distribution is found to be strongly dependent on both the shielding gas composition and the liquid conductivity. The amount of DNA DSBs is found to be largest when using N 2 shielding gas and almost negligible when using O 2 shielding gas.