Lifetime and Bactericidal Effect of Plasma Activated Medium by Di-Electric Barrier Discharge Microplasma in Air

Abstract

Dielectric barrier discharge (DBD) microplasma 1 is a potential alternative to conventional methods for sterilization/inactivation of bacteria. In order to promote low temperature, discharge voltage, cost/high effective and fast plasma sterilization technique, the bactericidal efficacy of plasma activated medium 2 (PAM) and the lifetime of the reactive oxygen and nitrogen species (RONs) were assessed using synthetic dry air as a working gas on Staphylococcus aureus sterilization. 2 mL of 0.85% NaCl solution was treated by a microplasma generated at a discharge voltage of 1.04 kV and 1.18 kV, frequency of 10 kHz and 20 kHz respectively. Both treatments were carried out at a gas flow of 2 L/min. Bacteria were cultivated at a concentration of 10 8 CFU/mL and treated with microplasma for 1, 2 and 3 min. From the results obtained after incubation for 72 hours at 37 ºC, treated samples at 1.04 kV/10 kHz showed a bactericidal effect of 8 log reduction in CFU/mL after 3 min. of treatment. On the other hand, samples treated at 1.18 kV/20 kHz showed 8 log reduction in CFU/mL after 2 min. of treatment. UV-VIS analysis confirmed a slight decrease in the lifetime of PAM and absorption spectra of the RONs 30 days after treatment. These bactericidal effects were caused by the RONs generated by the microplasma 1 , 2 and these species could also enhance transdermal drug delivery 3 , 4 . Ozone generated during the microplasma discharge was completely removed using an activated charcoal as a catalyst.