Electron Spin Resonance (ESR) Observation of Radicals on Biological Organism Interacted with Plasmas
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Electron Spin Resonance (ESR) Observation of Radicals on Biological Organism Interacted with Plasmas Kenji Ishikawa1, Hiroko Moriyama1, Kazuhiro Tamiya2, Hiroshi Hashizume2, Takayuki Ohta2, Masafumi Ito2, Sachiko Iseki1, Hiromasa Tanaka1, Keigo Takeda1, Hiroki Kondo1, Makoto Sekine1, Masaru Hori1 1 2
Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan Meijo University, Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan
ABSTRACT We report the kinetic analysis of radicals on fungal spores of Penicillium digitatum interacted with charged-neutral oxygen species (O*) generated plasma discharge using real time in situ electron spin resonance (ESR) measurements. The ESR signal from the spores was observed at a g-value of around 2.004 with a line width of approximately 5G. We have successfully obtained information regarding the reaction mechanism with free radicals and realtime in situ ESR has proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens. INTRODUCTION Recently, the potential applications of non-equilibrium atmospheric pressure discharge in biology and medicine has grown significantly [1]. Plasma interaction with living tissues and cells has not been understood to the extent of comprehensive biological and physical mechanisms, due to the complexity of both the plasma and tissue. Therapeutic effects, such where plasmas can trigger a complex sequence of biological responses in tissues and cells, are indeed complex. In addition, mammalian cells, but not bacteria, repair easily with participation of adducteddeoxyribonucleic-acid (DNA) intracellular activation [2]. Many interpretations of the biological responses for disinfection by plasma discharges have been reported, which has indicated that death is accompanied by (i) lethal oxidation of membranes, (ii) electrostatic disruption of cell membranes, such as cell lysis and fragmentation, and (iii) biological responses such as apoptosis [2]. A biological organism is catalytically oxidized by positive and negative ions both inside and outside of the biological organism in the presence of oxygen and reactive oxygen species. Therefore, not only ultraviolet photons, but also chemical species including (i) positive and negative ions, (ii) reactive oxygen species, (iii) hydrogen-peroxide, and (iv) ozone are considered to be provide to inactivate [3-5]. Kong et al. identified oxygen atoms as a major contributor in plasma inactivation [6], and Nagatsu et al. reported that spore forming bacteria, Geobacillus stearothermophilus, are inactivated by surface wave excited oxygen plasmas [7]. Penicillium digitatum is a post-harvest disease, which is difficult to inactivate, causes the green mold of citrus fruits, and differs from other microorganisms such as Escherichia coli and Bacillus subtilis that are typically found on medical instruments. In our recent publication, fungal spores of Penicillium digitatum were disinfected by applying atmospheric pressure plasmas of argon gas containing trace oxygen. The results of this experi
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