Effects of oxygen radicals in low-pressure surface-wave plasma on sterilization

Abstract

The effects of oxygen radicals on sterilization were studied using a 2.45GHz surface-wave oxygen plasma. A population of 1.5×106 Bacillus stearothermophilus spores was irradiated for 3min or more with oxygen plasma, generated at pressures between 6 and 14Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15–25s. Using only oxygen radicals, excluding all charged particles, the 1.5×106 spores were sterilized with a D value of 30–45s after 5min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.