Reactive species variation in cold atmospheric pressure plasma jet discharge under the influence of intrinsic parameters and its effect on E. coli inactivation

Abstract

Cold atmospheric pressure plasma jet (CAPJ) has piqued the interest of researchers for various antimicrobial applications such as disinfection, wound decontamination, etc. In the current context, a deeper understanding of the correlation between CAPJ's intrinsic parameters, discharge characteristics, species composition, and antimicrobial activity is required for any successful application. This research evaluated the effect of intrinsic operational parameters such as voltage, frequency, gas flow rate, and operating gas on the reactive species composition of an in-house-developed CAPJ discharge along with the antimicrobial activity. It was observed that the identified excited atoms (Ar I, He I, N2, and O I), ions (Ar+, N2+, N+, H2O+, H3O+, etc.), radical reactive oxygen and nitrogen species (RONS) (OH•), and nonradical RONS (O I, O+, OH+, NO+, O2+, O2−, NO2−, N2O2−, NO3−, N2O3−, etc.) might play a synergistic role in bacterial inactivation via oxidative and electrostatic stress. The variation in voltage, frequency, gas flow rate, and operating gas influenced the discharge chemistry, leading to variation in bacterial inactivation. The reactive species in the discharge responsible for such variation was evaluated extensively. This investigation into various operational parameters would aid in determining the most effective settings for a developed CAPJ to achieve high productivity.

Efficacy of argon cold atmospheric pressure plasma jet on hospital surface decontamination and its impact on the surface property

“…In the CAPJ discharge, cocktail of species such as electrons, ions, excited atoms and molecules, reactive oxygen and nitrogen species (RONS), etc along with UV and electric field, play a synergetic role in bacterial inactivation mechanism [17,24,30] as well as in alteration of surface characteristics [60]. The species in the discharge were determined through a combination of qualitative (OES) and quantitative (MBMS) techniques in this study.…”

“…Especially, these gas phase species are formed when energetic electrons, Ar I, and Ar + are expelled from the main discharge regime (between the electrodes) by gas flow and react with the ambient air, which consists of N 2 , O 2 , water vapour, etc. These intricate chemical interactions involve electron impact ionization or excitation, ion recombination, dissociative ionization or excitation, photodecomposition, etc [24,30,[61][62][63].…”

“…Further, the molecular beam mass spectrometer (MBMS) (HPR 60 MBMS, Hidden Analytics Ltd, UK) was used to acquire time-averaged mass spectra in the range of 1 to 100 amu (m/z). The relative yield percentage of a specific ion [24,30,59] was used for estimation of ion composition. The position of the MBMS entrance slit with respect to the CAP plume tip was 10 mm to ensure minimal discharge disturbances.…”

“…For antimicrobial activity evaluation, clinically isolated MDR E. coli (GNB) and MDR S. aureus (GPC) were used. The methodology details regarding the collection of isolates and antimicrobial susceptibility characterization of the MDR bacteria used in this study have been described elsewhere [24,30]. A 0.5 McFarland standard or 1.5 × 10 8 CFU/ml (checked using a densitometer, DENSICHECK PLUS, BIO MERIUX) bacterial suspension of the isolate was prepared in sterile 0.9% saline.…”

“…The copious of RONS, ions, electrons, and excited species integrates an antimicrobial nature to the discharge [17,[24][25][26][27][28][29]. The efficacy of CAP in removing the microbial load from nutrient culture media [24,[30][31][32][33][34] or liquid suspensions [24,31,[35][36][37] have been studied. Das et al [24] and Flynn et al [38] showed the efficacy of CAP jet on the inactivation of clinically isolated ESKAPE pathogens.…”