Plasma Interactions with Biological Molecules in Aqueous Solution
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Plasma Interactions with Biological Molecules in Aqueous Solution Yuichi Setsuhara1, Atsushi Miyazaki1, Kosuke Takenaka1 and Masaru Hori2 1 Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047, Japan 2 Plasma Nanotechnology Research Center, Nagoya University, Nagoya 464-8603, Japan ABSTRACT Plasma interactions with L-alanine in aqueous solution have been examined as a basis of fundamental processes in plasma medicine. The plasma interactions with L-alanine in aqueous solution have been examined for investigations of chemical modifications induced by exposures with the atmospheric-pressure hollow-cathode He plasma to the surface of the aqueous solution, which contained L-alanine as a solute in pure water, via chemical bonding states analyses using x-ray photoelectron spectroscopy (XPS). Measurement of hydrogen ion exponent (pH level) of pure water during the atmospheric plasma exposure showed that the pH level decreased to be acidic, but the water temperature did not change. The C 1s XPS spectrum from the L-alanine after the plasma exposure to the aqueous solution showed the decomposition of the -COOH group and the formation of -C=O group. INTRODUCTION Plasma applications in medical science and treatments have attracted expanding interests worldwide and have made remarkable progress recently [1,2]. For development of innovative plasma technologies for medical applications, it is of great significance to understand fundamental processes involved in plasma interactions with biological molecules, namely DNA, amino acids and proteins, which are the building blocks of cells and organs in a hierarchy manner, during exposure with plasmas, which contain ions, radicals, electrons and photons. In the plasma interactions with biological molecules, it is essential to note that the biological molecules are composed of organic materials (soft materials) and the bond-dissociation energies of soft materials are typically less than 10 eV. So far the authors have carried out a series of investigations on the plasma interactions with soft materials on the basis of surface analyses using x-ray photoelectron spectroscopy (XPS) in terms of physical interactions via ion kinetic energy and chemical interactions via radicals and photos from plasmas [3-5]. Furthermore, the plasma interactions with amino acid (L-alanine) in dry process have also been carried out recently [6]. In the present investigation, these studies mentioned above are extended further to examine plasma interactions with biological molecule, L-alanine, in aqueous solution via atmospheric-plasma exposure to the aqueous solution containing L-alanine as a solute in pure water. The plasma interaction with the biological molecule in aqueous solutions is considered to be essential and thus significant for understanding the fundamental processes in plasma medicine.
Figure 1. Illustration of experimental setup and image of the atmospheric-pressure hollowcathode He plasma source used in the present investigation. EXPERIMENT In this investigation, plasm
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