Influence of electric potential-induced by atmospheric pressure plasma on cell response.

Plasma irradiation leads not only active species, but also reactive chemical species, ultraviolet light, electric fields, magnetic fields, and shock waves. To date the effects of reactive chemical species have been mainly discussed. To understand the biological effect caused by an electric potential induced with an atmospheric-pressure plasma, the behavior of cell stimulated by electric potential was investigated using HeLa cell. The cell concentration assay revealed that less than 20% of cells inactivated by potential stimulation and the remained cells proliferate afterward. Fluorescent microscopic observation revealed that potential stimulation is appreciable to transport the molecules through membrane. These results show that potential stimulation induces intracellular and extracellular molecular transport, while the stimulation has a low lethal effect. A possible mechanism for this molecular transport by potential stimulation was also shown using numerical simulation based on an equivalent circuit of the experimental system including adhered HeLa cell. The potential formation caused by plasma generation is decisive in the contribution of plasma science to molecular biology and the elucidation of the mechanism underlying a biological response induction by plasma irradiation.

Effect of Nanosecond Pulsed Currents on Directions of Cell Elongation and Migration through Time-Lapse Analysis.

It is generally known that cells elongate perpendicularly to an electric field and move in the direction of the field when an electric field is applied. We have shown that irradiation of plasma-simulated nanosecond pulsed currents elongates cells, but the direction of cell elongation and migration has not been elucidated. In this study, a new time-lapse observation device that can apply nanosecond pulsed currents to cells was constructed, and software to analyze cell migration was created to develop a device that can sequentially observe cell behavior. The results showed nanosecond pulsed currents elongate cells but do not affect the direction of elongation and migration. It was also found the behavior of cells changes depending on the conditions of the current application.

Nanosecond pulsed current under plasma-producing conditions induces morphological alterations and stress fiber formation in human fibrosarcoma HT-1080 cells.

Cold atmospheric plasma (CAP) is a promising means for various biomedical applications, including cancer therapy. Although the biological action of CAP is considered to be brought about by synergistic effects of reactive species and electrical factors of CAP, limited information is currently available on the contribution of electrical factors to CAP-induced cell responses. We have previously demonstrated that nanosecond pulsed current (nsPC) under CAP-producing conditions significantly promoted the motility of human HT-1080 cells. In this study, we explored the effects of nsPC on cell morphology associated with cell motility. We observed that nsPC stimulation caused extended cell shape, membrane protrusion formation, and increased cell surface area, but not cell death induction. nsPC stimulation also caused elevated intracellular ROS and Ca2+. HT-1080 cells can undergo two modes of cell motility, namely mesenchymal and ameboid motility, and we found that morphological features of mesenchymal motility was partly shared with nsPC-stimulated cells. Furthermore, nsPC-stimulated cells had extended stress fibers composed of filamentous actin. Taken together, this study provides a novel insight into the electrical aspect of CAP action, and we speculate that nsPC activates a certain mechanism involving intracellular signaling for stress fiber formation, leading to altered cell morphology and increased cell motility.