Inactivation of bacteria using dc corona discharge: role of ions and humidity

Abstract

Here we present the results of an experimental study of the effect of ions produced in a dc corona discharge on inactivation of bacteria on the surface of agarose gel. Both positive and negative corona discharges in various gases at different humidities were studied. The measurements in air, O2, N2, Ar and He mixtures show that there is no inactivation in pure N2, pure O2 and an N2–H2O mixture. The best results were achieved in the case of direct treatment, when discharge was ignited in oxygen and water-containing mixtures. We show that neither UV radiation, ozone or H2O2 nor other neutral active species alone produced by corona have an effect on bacteria viability. It is shown that the main role of charged particles may be related to the faster transport of active peroxide species—cluster ions OH−(H2O)n and H3O+(H2O)n. The efficiency of these radicals is much higher than that of the oxygen radicals and ions (including O2−,O4+ and O3) and that of nitrogen and argon ions.

Efficacy of Different Carrier Gases for Barrier Discharge Plasma Generation Compared to Chlorhexidine on the Survival of <b><i>Pseudomonas aeruginosa</i></b> Embedded in Biofilm in vitro

“…Other authors reported an increased antimicrobial effect with additional gas humidification [47,48,49]. Hähnel et al [47] observed an improved effect for an air plasma by increasing the relative air humidity up to 70% against Bacillus atrophaeus spores.…”

“…The authors discussed that especially hydroxyl radicals have an erosive effect on cell surfaces. Indeed, it is known that a very small amount of moisture on the microbial target is needed for inactivation with species such as ·OH or H 2 O 2 [48,49,50]. This could explain why an increased effect was observed when humidified gas was applied on dry spores.…”

“…While in the experiments on B. atrophaeus spores [47] only the amount of water needed for the plasma decontamination process was used, the biofilm in our experiments already contained the water necessary for antimicrobial effects, leaving no chance for enhancement due to humidification. Dobrynin et al [48] observed an enhanced antimicrobial efficacy by carrier gas humidification (bubbled through distilled water) only if additional O 2 was admixed. Here, the relative gas humidity could be the same as in the present study and our plasma source worked in ambient air, which could provide the additional O 2 .…”

Methods of gas purification and effect on the ion composition in an RF atmospheric pressure plasma jet investigated by mass spectrometry

“…inactivation of the bacterium 'Escherichia coli' [13,14]. Moreover these ions are used for chemical ionization (mostly proton transfer reactions) used in analytical mass spectrometry [15].…”

Atmospheric‐pressure photoelectron emission from H‐terminated and amino‐terminated diamond

“…One important application of charged species in air is that electrons and ions in air have been shown to have anti-bacterial effects. However, the detailed origins of the effects have been unclear due in part to the high voltages and electric fields (typically >100 kV cm À1 ) [12][13][14]. Diamond's negative electron affinity and high chemical stability even in water suggest that it may also find utility as a source of low-energy electrons in air and other gases at atmospheric pressure.…”