Inactivation of Escherichia coli using long-distance oxygen plasma

The concentration distribution of electrons, ions and free radicals in long-distance oxygen plasma and the Germicidal Effect (GE) of E. coli on the surface of medical Poly(tetrafluoroethylene) (PTFE) film by long-distance oxygen plasma were studied. The content of protein leakage and lipid peroxide production in bacterial suspension as well as DNA electrophoresis were measured after sterilization to analyse the inactivation mechanisms. The results show that electrons, ions concentration decreases rapidly with increasing the distance, which approximates to 0 at 30 cm, whereas the concentration of free radicals reduces slowly, which is still 70% of initial concentration at 40 cm. GE values reach 3.42 at discharge zone and exceed 3.32 within 40 cm with rather little time (60 s). Fast etching to cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by free radicals are primary reasons of oxygen plasma sterilization in the discharge and long-distance zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.