Fig 1.
Schematic illustration of the plasma jet used in this study.
Fig 2.
Cell death induced by He + H2O and Ar plasma.
(A) Viability of MSCs 24 h after treatment with plasma for the indicated times. (B) Morphological changes in MSCs 24 h after treatment with plasma for 120 s. Ar gas flow without discharge was used as control. (C) Time course of MSC cell apoptosis by flow cytometry after Ar plasma treatment for 60 s.
Fig 3.
Plasma-induced cell death is reversed by reactive species scavengers.
(A) Computer simulation of the distribution of various species in liquid. (B, C) MSC viability and morphological changes 24 h after treatment with He + H2O plasma for 60 s in the presence of various scavengers.
Fig 4.
Contribution of H2O2 to plasma-induced cell death.
(A) Viability of MSCs treated with different concentrations of H2O2 for 24 h. (B) H2O2 concentration measured by the hydrogen peroxide assay after He+H2O and Ar plasma treatment for the indicated times. (C) H2O2 concentration measured relative to the control (20 μM H2O2 solution) after adding H2O2 scavenger. (D) Morphological changes in MSCs treated with indicated H2O2 concentrations for 24 h.
Fig 5.
A schematic diagram for applying a bias voltage.
Fig 6.
Contribution of O2− and H2O2 in plasma-induced cell death.
(A) The O2− and H2O2 distribution in liquid determined after applying a +20 V bias voltage by computer simulation. Broken and the solid lines represent concentrations of O2− and H2O2, before and after voltage application, respectively,. (B) Experimental setup for application of bias voltage. A and B indicate cover node and bias voltage, respectively. (C) MSCs treated with He + H2O or Ar plasma for 60 s while applying a +20 V bias voltage. The histogram displays the diameter of the cell death area relative to the control. *P < 0.05.
Fig 7.
Decreased sensitivity to plasma by knockdown of iron protein expression.
(A) Gel electrophoresis of holo- and apo-transferrin treated with Ar plasma for 2 or 8 min. (B) Sequences of miR-200b and the complementary site in the FTH1 gene. (C) Viability of MSCs transfected with control miRNA or miR-200b for 24 or 48 h. (D) FTH1 expression in MSCs transfected for 48 h, as determined by western blotting. (E) Viability of transfected MSCs 24 h after 20 s of Ar plasma treatment. *P < 0.05. Lipo indicates that only the transfection agent (Lipofectamine 2000) was added to cells.
Fig 8.
Iron enhances plasma-induced cell death.
(A) Viability and (B) apoptosis of LP-1 cells 24 h after a 20-s He + H2O or Ar plasma treatment in the presence of Fe(III)-EDTA. *P < 0.05.
Fig 9.
Model for a plasma-treated cell system and the mechanism of in situ OH generation.