A new practical method for inactivating endotoxin (ET) was investigated using plasma ashing equipment for semiconductor (PACK-III, YAC Co., Ltd., Japan). Dry ET (5×10^5pg/glassware bottle, 100pg = 1EU) used as a sample in the present study was derived from Escherichia coli R3F653. With fixing output (150W), chamber temperature (60℃) and discharge time (10min), plasma processing was performed under 6 conditions. Three samples under each condition were processed, and the ET activity (ETA) was measured by the Limulus gelatin activity method. The results obtained were as follows. 1. The mean value of remained ETA processed with dry oxygen gas at 25Pa was smallest among 6 conditions, and was double digits decrease for unprocessed ETA. The value of processed ETA was significant difference among both gas types and gas pressures (repeated measured ANOVA, p<0.05). 2. The time required for the entire automatic plasma processing was 14minutes. 3. The chamber temperature during plasma processing was less than 70℃
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