The Periodic Cellular Behaviors Under the Physical Effects of Plasma Medicine

After more than a decade of study, plasma medicine has shown its capability for cancer therapies and sanitations due to its compounding dose of ultraviolet (UV), reactive oxygen, and nitrogen species (RONS) directly and indirectly applied on the targets such as tumors in vivo , bacteria and cancer cell colonies in vitro 1 . However, some recent studies introduced the necrosis of cancer cells after an in vitro cold atmospheric plasma (CAP) treatment with the cell colonies isolated from the plasma chemistry, UV, and thermal effects 2,3 . Apparently, under such a circumstance, only the radiofrequency (RF) emissions from CAPs can be applied to cells. Considering the streamer physics of CAPs, the RF spectrum should include a high-voltage pulse at the discharge frequency as a result of the streamer head approaching and a low-power microwave from the plasma oscillation 4 . According to a previously published simulation, due to the surface charges on the cell membrane, the oscillations of cell membranes occur in micrometer-scale regions at several micrometers-per-second velocities when we are applying an external electric field 5 . In this work, we observed the periodic mechanical cellular behaviors under the external RF using a laser Michelson interferometer. Synchronized with the external RF, a series of high-speed camera images of interference fringes produce 3D and temporally resolved single-cell geometry and membrane behaviors. Therefore, the comparison among various types of cells gives a clue to explain the selectivity and the physical mechanism behind CAP treatments.