Effects of control parameters on apoptosis in atmospheric pressure pulsed helium plasma jet

The study of the effects of operating parameters on cellular changes in plasma-cell interaction is an important research issue for successful biomedical application of atmospheric pressure plasmas. The control parameters of atmospheric pressure plasma jet include applied voltage, driving frequency, pulse duty ratio, gas flow rate and additive oxygen gas. The effects of these parameters on the plasma-cell interaction are investigated. A plasma jet is driven by pulsed dc voltage with low frequency and human bladder cancer cells (EJ) is employed as a living tissue. The plasma-cell interaction in EJ cells triggers typical apoptosis. Especially, helium plasma with additive oxygen gas was found to be effective in the apoptosis. Reactive oxygen species (ROS) which causes damage to cell membranes and leads to DNA fragmentation in cells is generated by plasma jet. It plays an important role in apoptosis induction. To identify the correlation between the apoptosis rate and the amount of ROS in plasma jet, staining assay analysis and the measurement of extracellular ROS are compared. The apoptotic changes in cell with plasma treatment are detected by fluorescence microscopy and flow cytometry. Fluorescence microscopy could be used by DAPI staining and TUNEL assay to confirm morphological changes and DNA fragmentation characteristics of cells undergoing apoptosis. Flow cytometry could be used by Annexin-V/PI staining to quantify the percentage of apoptotic cells present in a cell population. Also, the extracellular ROS was measured by optical emission spectroscopy (OES). A portion of EJ cells was observed to undergo apoptosis in plasma treatment clearly. The number of apoptotic cells increased with applied voltage, repetition frequency, gas flow rate, and additive oxygen gas, while they decreased with working media and pulse duty ratio. And the variation of apoptosis rates was similar to that of ROS intensities. The result indicated that the apoptosis rate correlated well with- the level of extracellular ROS.