Abstract
The acceleration of inactivating viable cells of Escherichia coli (E. coli), by using new direct and indirect innovative methods, is the targeted method of using an atmospheric pressure plasma jet (APPJ) operated by an AC high-voltage power source with variable frequency up to 60 kHz and voltage ranging from 2.5 to 25 kV. Discharges using dry argon (0% O2) discharges and different wet argon discharges using admixtures with O2/Ar ratios ranging from 0.25% to 1.5% were studied. The combined effects of dry and wet argon discharges, direct and indirect exposure using a mesh controller, and hollow magnets were studied to reach a complete bacterial inactivation in short application times. Survival curves showed that the inactivation rate increased as the wettability increased. The application of magnetized non-thermal plasma discharge with a 1.5% wetness ratio causes a fast inactivation rate of microbes on surfaces, and a dramatic decrease of the residual survival of the bacterial ratio due to an increase in the jet width and the enhanced ability of fast transport of the charges to viable cells, especially at the edge of the Petri dish. The membrane damage of E. coli mechanism factors in the activation process by APPJ is discussed.
Highlights
One of the fashionable targets in our life is to attain an eco-city and maintain good health
We suggest examining the inactivation characteristics of some microbes with a very short exposure time application, using a plume of cold plasma emerging from atmospheric pressure plasma jet (APPJ) to cause the inactivation of microbes attacking surfaces
The main important measured parameters, such as discharge current, discharge applied voltage, discharge power, consumed energy injected into the gas, width of the jet, charged particle sputtering of the samples, axial distance between the APPJ nozzle and the sample, and exposure time for direct or indirect exposure, are all shown to be important factors determining the amount of heat transferred to the contaminated samples in the inactivation process
Summary
One of the fashionable targets in our life is to attain an eco-city and maintain good health. Plasma plays an important role in the inactivation of microbes and will have a role during this century in the prevention of many diseases. New fields of biotechnology applications and the procedures of inactivation of microorganisms have been discovered by using non-thermal plasmas. The field of glow discharge plasma in atmospheric pressure has rapidly expanded by using the application of atmospheric pressure plasma jet (APPJ), leading to the evaluation of the roles in the disinfection of bacteria of air plasmas at atmospheric pressure [1]. Disinfection is based on physical, microbiological, and chemical processes to eliminate microorganisms. Sterilization by gamma rays, chemicals such as ethylene oxide (ETO), autoclaves, and ovens are traditional methods of sterilization, all of them not comparable with treatment by new techniques, such as cold plasma, because plasma technology involves a complete disinfection and sterilization process in a very low exposure time for contaminated surfaces. Traditional methods have their advantages as well as disadvantages [2]
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