Sterilization of bacteria suspensions and identification of radicals deposited during plasma treatment

Abstract

In this paper we will present results for plasma sterilization of planktonic samples of two reference strains of bacteria, Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212. We have used a plasma needle as a source of non-equilibrium atmospheric plasma in all treatments. This device is already well characterized by OES, derivative probes and mass spectrometry. It was shown that power delivered to the plasma is bellow 2 W and that it produces the main radical oxygen and nitrogen species believed to be responsible for the sterilization process. Here we will only present results obtained by electron paramagnetic resonance which was used to detect the OH, H and NO species. Treatment time and power delivered to the plasma were found to have the strongest influence on sterilization. In all cases we have observed a reduction of several orders of magnitude in the concentration of bacteria and for the longest treatment time complete eradication. A more efficient sterilization was achieved in the case of gram negative bacteria.

Study of Cold Atmospheric Plasma Jet at the End of Flexible Plastic Tube for Microbial Decontamination

“…The existence of ROS in the plasma plume is evidenced by the weak OI emissions at 777 and 844 nm. This finding demonstrates the efficient energy transfer from excited He atoms and metastables to nitrogen and oxygen molecules from the surrounding air . No emissions of excited OH and NO molecules were detected.…”

“…Most plasma devices are operated at fixed discharge power, while the process time is increased until a required dose of treatment is achieved. An alternative approach for varying the energy dose is to change the device power keeping the treatment time fixed . One manner for precise tuning of plasma jet power is the use of burst mode of operation, i.e., a constant period of voltage oscillations is followed by a break (no high voltage) period .…”

Analysis of reactive oxygen and nitrogen species generated in three liquid media by low temperature helium plasma jet

“…Nitric oxide in liquids arises after solvation of gaseous nitric oxide produced in the plasma plume observed using emission spectroscopy in our earlier study 15 . Production of nitric oxide in liquids has already been observed in Milli-Q water after its exposure to helium 56 or argon plasma 35 and also in buffered saline solution treated with air plasma 57 , 58 . In aqueous solution, nitric oxide is a highly reactive species that may react with oxygen to produce nitrite (NO 2 − ) (Reaction 1) 59 .…”

“…Moreover, long lifetime species (H 2 O 2 and nitrites/nitrates) can penetrate into cells and can be potential precursors of intracellular reactive oxygen species. Indeed, these species can lead in turn to the formation of • OH radical via a Fenton reaction involving H 2 O 2 and NO • synthesis via recycling of nitrites/nitrates anions by the cells 56 . • OH radical and NO • are highly cytotoxic and genotoxic for cells.…”

Roles of membrane protein damage and intracellular protein damage in death of bacteria induced by atmospheric-pressure air discharge plasmas

“…Plasma medicine is an emerging eld involving biological and medical applications of non-thermal plasmas, 1,2 such as deactivation of microorganisms, [3][4][5][6][7][8][9][10][11][12][13] blood coagulation, 14 wound healing, [15][16][17] cancer treatment, 18,19 and sterilization of medical devices. 20 Recent studies have revealed excellent antimicrobial and anticancer effectiveness by deactivation of various types of bacteria and apoptosis of a wide range of cancer cells.…”