Research Article
H Shintani
Abstract
Many papers have been published on gas plasma sterilization. Most have been conducted by engineers and physics researchers, so microbiological and chemical aspects are insufficient or inaccurate. Gas plasma sterilization research has significantly advanced since 2008 when biologists and chemists began contributing their expertise to the effort. However, the mechanism of sterilization by gas plasma has not yet been elucidated. Based on their life spans and other characteristics, metastables and/or photons can speculated to be the most likely candidates contributing to the mechanism of gas plasma sterilization. OH and/or NO radicals may be minor contributors due to significant short period of life. Spore death can be explained by the hydration of dipicolinic acid (DPA) in the spore core. The energy of metastables and/or photons can cause the formation of pin holes in spores that allow water to penetrate into the core and hydrate the DPA. Hydrated DPA transfers to the spore surface. DPA in the spore surface was collected by extraction with water and enriched by solid phase extraction. Eluted material was vaporized, condensed, and analyzed by the reverse phase C-18 HPLC. Elution from the C-18 column was carried out with acetonitrile/water (1/4, v/v, pH 5) and detected at 235 nm and by mass spectrometry (MS). Based on a comparison of the retention time and MS fragmentation pattern with that of standard DPA, the spore surface particles were confirmed to be composed of DPA. The hydration process occurred within the spore and did not cause any structural change within the spore. Therefore the structure of spores remained almost unchanged after sterilization.