Feeding‐Gas Effects of Plasma Jets on Escherichia coli in Physiological Solutions

Abstract

The effects of air and N2 plasma jets on Escherichia coli inside four different physiological solutions and deionized water are reported here. The feeding gases are found to influence the plasma compositions, the interactions with the liquids, and the subsequent bactericidal effects depending on the aqueous solutions to which they are exposed. Air plasma enhances the bactericidal effects of deionized water and saline by acidification. On the other hand, N2 plasma induces higher toxicity in phosphate buffered saline by generating more electrons. Little bactericidal effects of cell culture media and blood plasma may be due to the slight change in the pH and due to electron scavenging by organic components. Taken together, our study provides additional insight into the basic interactions between plasma and cells in physiological solutions.

Effects of Background Fluid on the Efficiency of Inactivating Yeast with Non-Thermal Atmospheric Pressure Plasma

“…However, environmental influences have not been frequently reported. A recent study demonstrated that the bactericidal effects of plasma in water and saline increase due to the acidification of solutions by air plasma and that PBS exposed to N 2 plasma becomes highly toxic to bacteria [18].…”

“…Plasma can produce different control outcomes to the same microbial species, depending on the surrounding environment. One study demonstrated that bacteria present in various physiological fluids are killed by plasma at different rates and that the different death rates are probably caused by differential changes in components and ions in the solutions caused by plasma [18]. In addition, plasma is more effective in eradicating bacteria on non-biological surfaces than on skin [19].…”

“…Many studies have revealed that plasma changes pH of water to become more acidic and this may affect microbial mortality [20]–[21]. Plasma changes the ion composition of solutions where microbes are submerged because many reactive and excited species produced by the plasma can react with component molecules in solutions [18]. Environments surrounding microorganisms usually provide elements that are crucially needed for microbial survival and propagation such as water, pH, nutrients, osmotic stability, and temperature.…”

Mechanisms of a novel anticancer therapeutic strategy involving atmospheric pressure plasma-mediated apoptosis and DNA strand break formation

“…It was also reported that the formation of DNA strand breaks resuspended in buffer such as phosphate buffered saline (PBS) or Tris-EDTA (TE) is significantly reduced compared to that in water (Leduc et al 2009;O'Connell et al 2011). There was almost no DNA damage after plasma treatment in culture media probably because radical/electron scavengers are enriched in the media and plasma-induced acidification of the media is much less than that of PBS or water (Leduc et al 2009;Baik et al 2013). However, even when dried DNA isolated from cells is exposed directly to plasma treatment, in order to exclude any contribution of surrounding environmental factors such as buffer and culture media, DNA strand breaks and degradation occur very rapidly suggesting that factors other than the chemical components of plasma might affect on DNA stability ( Fig.…”

“…1). Although the physical and chemical properties of plasma jet vary considerably according to the configurations of plasma sources, input power, type of feeding gas, and the aqueous environment to which the cells are exposed, there is no doubt that plasma used for medical therapy creates a large amount of ROS/RNS as its major compositions and that these influence the physiological milieu of cells and tissues (Graves 2012;Baik et al 2013). When present at low levels, ROS/RNS play an important role as regulatory mediators in various physiological signaling processes such as cell proliferation, migration, and vascular relaxation, whereas at high concentrations they are implicated in serious oxidative stress leading to the pathogenesis of cancer, diabetes, atherosclerosis, and neurodegenerative diseases as well as senescence (Dröge 2002).…”