Changes of cellular structure and behavior induced by atmospheric pressure plasmas

Abstract

The biomedical applications using the atmospheric pressure plasma (APP) came into widespread in recent years. The APP has been applied to many different kinds of cells (from prokaryotic to eukaryotic cells) and come up with interesting results. Yet, those studies tend to incline toward the application outcomes and pay less attention to the underlying physical, chemical, or biochemical mechanisms of the plasma which induced the cellular changes. Needless to say, not only the plasma but also the cells have complicated systems, and thus, there are many issues to be addressed for the effective utilization of the APP as the biomedical application tools.

In this thesis, starting from understanding the APP`s of the radio frequency (RF) large area and the low frequency (LF) micro-jet, optimal plasma conditions for the bio-applications were found, and then the cellular changes induced by the plasma were investigated by adopting both prokaryotic, \textit{E. coli} and eukaryotic human cells as bio-targets. The 13.56 MHz RF and the 50 kHz LF plasmas were produced in the ambient air using helium gas. The role of the plasma including heat, UV photon, and radicals induced by the plasma was investigated in the \textit{E. coli} inactivation, and the importance of the oxygen radicals was revealed. After a comparative study, it was found that both LF and RF plasmas have their own merits and drawbacks for treating bio-medical targets. For instance the LF plasma exhibited some merits such as lower gas temperature and easier accessibility to the target with its longer plasma length.

Based on the preliminary study, the LF plasma was applied to the eukaryotic cells of THLE-2 and human dermal fibroblast. A direct contact with the LF plasma, generated at the applied electrode voltage of 1200 V for only 2 minutes resulted in various phenotypic intracellular changes which in turn induced the cell death and detachment from the substrate. Using the immunofluorescence assay, the necrotized...