Abstract
The direct and indirect bactericidal effects of dielectric barrier discharge (DBD) cold atmospheric-pressure microplasma in an air and plasma jet generated in an argon-oxygen gas mixture was investigated on Staphylococcus aureus and Cutibacterium acnes. An AC power supply was used to generate plasma at relatively low discharge voltages (0.9–2.4 kV) and frequency (27–30 kHz). Cultured bacteria were cultivated at a serial dilution of 10−5, then exposed to direct microplasma treatment and indirect treatment through plasma-activated water (PAW). The obtained results revealed that these methods of bacterial inactivation showed a 2 and 1 log reduction in the number of survived CFU/mL with direct treatment being the most effective means of treatment at just 3 min using air. UV–Vis spectroscopy confirmed that an increase in treatment time at 1.2% O2, 98.8% Ar caused a decrease in O2 concentration in the water as well as a decrease in absorbance of the peaks at 210 nm, which are attributed NO2− and NO3− concentration in the water, termed denitratification and denitritification in the treated water, respectively.
Highlights
The bactericidal effect of the electric field was not considered, even though the bacterial fluid was not allowed to completely dry off before microplasma treatment and the distance between the electrode and samples was maintained at 2 mm
The main functional species of atmospheric pressure plasma sterilization were the chemical substances produced by the plasma [20,21,22,23,24]
We demonstrated the bactericidal efficiency of dielectric barrier discharge (DBD) microplasma through direct treatment and indirect bacterial inactivation through plasma activated water at low discharge voltages on S. aureus and C. acne
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A small fraction of gaseous atoms and molecules, which are the main carriers of heat, collide with the highly energetic free electrons resulting in further excitation, ionization, and dissociation, while the plasma remains cold [11] These properties permit the disinfection or sterilization of thermosensitive materials and allow in vivo applications, opening a new and larger spectrum of possible applications [7,8,13,14,15,16,17,18]. This research investigated the low discharge voltage bactericidal potential of direct microplasma treatment in comparison with indirect plasma jet treatment through plasma-activated water (PAW) using the most abundant gas (air, argon, and oxygen) on Staphylococcus aureus and Cutibacterium acnes. P. acnes has been recognized as an emerging cause of shoulder infections [38,39]
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