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The plasma sporicidal effects on Bacillus atrophaeus spores were studied using a low-temperature atmospheric plasma brush in terms of the following conditions: 1) plasma conditions; 2) plasma gas compositions; 3) plasma exposure time; and 4) the types of supporting media. It was found that the plasma brush with O_2 addition was very effective in inactivating the Bacillus spores. With 0.33, 0.7, and 1 vol % (5, 10, and 15 sccm) oxygen addition, the plasma exposure time of achieving a 99.9999% reduction of the spores was less than 4, 2.5, and 1.5 min, respectively. It was noted that the plasma inactivation efficiency was also dependent on the type of supporting media, on which the spores were seeded. With plasma exposure, significant damages to sporal structure were observed by scanning electron microscopic (SEM) examination and leakage of intracellular proteins and DNAs were detected by monitoring the light absorbance at wavelengths of 280 and 260 nm, respectively. Results obtained in this paper indicate that the low-temperature atmospheric plasma technology is promising in various decontamination applications such as sterilization of daily used heat-sensitive items and emergency treatment of biological warfare agents.
Date of Publication: July 2010