Nonthermal Bioplasma Diagnostics and its Applications to the Microbial and Living Cells
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Nonthermal Bioplasma Diagnostics and its Applications to the Microbial and Living Cells Eun-Ha Choi*, Gyungsoon Park, Ku Y. Baik, Ran J. Jung, Nagendra K. Kaushik, Guangsup Cho, Geon J. Lee, Bong J. Park, Byoungchoo Park, Gi C. Kwon, and Han S. Uhm Department of Electrophysics & Plasma Bioscience, Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea *[email protected] ABSTRACT We have investigated the nonthermal bioplasma sources and their characteristics as well as their interactions with biological cells. The electron temperature and plasma density are measured to be about 1.5 eV and 3×1012 cm-3 , respectively, for the direct palsma jet under Ar gas flow. The hydroxyl radical density has also been investigated and measured to be maximum value of about 3 ×1015 cm-3 and 8 ×1014 cm-3 in the direct plasma jet and dielectric barrier discharge bioplasma, respectively, by the ultraviolet optical absorption spectroscopy. Herein, we have investigated the basic interactions of these nonthermal bioplasma with the living organisms in morphological and biomolecular aspects. We found that the secondary electron emision coefficient of the biological surface has been drastically increased by atmospheric bioplasma, which indicates the biological surface to be oxidized especially by the hydroxyl (OH) radical species. In order to elucidate the basic mechanisms for the cell shrinking and apoptosis leading to a cell death by the nonthermal bioplasma, the cell membrane potential has been estimated based on the ROS density as well as cell capacitances. It is also found that the molecular electron energy band structure in the biological cells have been shifted closer toward the vacuum surface and accordingly their central energy of molecular band becomes small by the nonthermal bioplasma due to cell oxidation caused by OH radicals. INTRODUCTION Over the past several years, many plasma jet and dielectric barrier discharge (DBD) devices that produce a cold atmospheric-pressure (AP) plasma plume have been investigated for their use for thermally sensitive materials and medical applications. Especially, this nonthermal atmospheric pressure bioplasma should have high plasma stability during the bioplasma interactions with biological cells [1] under low electrical power to avoid the electrical shock and heat. These AP plasma sources can generate so many chemical species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) when it contacts with biological cells. ROS have very short lifetime of nano second level [2] and are highly toxic to cells, resulting in damage of biomolecules and the cell structures. Especially, hydroxyl OH radical has a most destructive effect on the fatty acid side chains of lipids in membranes such as mitochondrial membranes of the cell [2] among other reactive species such as superoxide anions O2*- and nitric oxide NO. These hydroxyl radical, OH, and superoxide anions, O2*-, as well as nitric oxide, NO, can be generated by simple AP nonthernal bioplasma sources when it contac
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