Yutaro Hokari

Improvement of cell membrane permeability using a cell-solution electrode for generating atmospheric-pressure plasma

The cell membrane permeability, which is strongly related to gene transfection, is improved using a cell-solution electrode for generating atmospheric-pressure plasma (APP) just above the solution. In the case of the floating cells, the cell membrane permeability is significantly improved by the cell-solution electrode APP compared with the conventional diffusion type APP, because the distance between the plasma generation area and the cell solution surface becomes short, which could reduce the radial diffusion loss of the plasma irradiated to the cell suspended solution. In the case of the adherent cells, cell membrane permeability is found to be enhanced by the shorter distance between the solution surface and the adherent cells as well as using the cell-solution electrode, which means that the short-lived reactive oxygen species generated at the solution surface are essential for the improvement of cell membrane permeability.

Characterization of plasma-induced cell membrane permeabilization: focus on OH radical distribution

Non-equilibrium atmospheric-pressure plasma (APP) is used medically for plasma-induced cell permeabilization. However, how plasma irradiation specifically triggers permeabilization remains unclear. In an attempt to identify the dominant factor(s), the distribution of plasma-produced reactive species was investigated, primarily focusing on OH radicals. A stronger plasma discharge, which produced more OH radicals in the gas phase, also produced more OH radicals in the liquid phase (OHaq), enhancing the cell membrane permeability. In addition, plasma irradiation-induced enhancement of cell membrane permeability decreased markedly with increased solution thickness (<1 mm), and the plasma-produced OHaq decayed in solution (diffusion length on the order of several hundred micrometers). Furthermore, the horizontally center-localized distribution of OHaq corresponded with the distribution of the permeabilized cells by plasma irradiation, while the overall plasma-produced oxidizing species in solution (detected by iodine-starch reaction) exhibited a doughnut-shaped horizontal distribution. These results suggest that OHaq, among the plasma-produced oxidizing species, represents the dominant factor in plasma-induced cell permeabilization. These results enhance the current understanding of the mechanism of APP as a cell-permeabilization tool.

Roles of charged particles and reactive species on cell membrane permeabilization induced by atmospheric-pressure plasma irradiation

As factors that influence cell membrane permeabilization during direct and indirect atmospheric-pressure plasma irradiation, charged particle influx, superoxide anion radicals (O2 −), and hydrogen peroxide (H2O2) in plasma-irradiated solution were evaluated. These are the three strong candidate factors and might multiply contribute to cell membrane permeabilization. In particular, a shorter plasma diffusion distance leads to the enhancement of the direct effects such as charged particle influx and further increase cell membrane permeability. In addition, O2 − dissipates over time (a life span of the order of minutes) in plasma-irradiated water, and the deactivation of a plasma-irradiated solution in term of cell membrane permeabilization occurs in a life span of the same order. These results could promote the understanding of the mechanism of plasma-induced cell membrane permeabilization.