Plasma inactivation of Escherichia coli cells by atmospheric pressure air brush-shape plasma

In this study, we designed one portable plasma device to generate a stable and brush-shape air discharge at atmospheric pressure for the plasma inactivation of Escherichia coli cells. The design of the portable plasma device based on the alignment of tens of air microplasmas resulted in the room-temperature and brush-shape plasma (50 mm in length and 5 mm in width). The brush-shape plasma was very efficient for the large-area inactivation of E. coli cells, and E. coli cells in direct contact with the air plasma were completely killed within the treatment time of 1 min. XPS analysis showed that the surface of plasma-activated E. coli cells was predominantly composed of C–O or C=O groups, indicating the oxygen-containing species in the air plasma were able to break the C–C or C–H bonds and cause the etching of organic compounds. Analysis indicated that lethal effects on E. coli cells were largely ascribed to the chemical erosion, i.e. damage to the cell wall or cell membrane. Analysis also indicated that both short-living species, such as O and OH radicals, and ozone molecules could play a crucial role in the plasma inactivation process by this method.