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A novel nonthermal plasma dielectric-barrier discharge (DBD) system for decontamination, sterilization, and medical applications has been developed. The discharge is physically removed from the disinfection zone, and plasma-induced free radicals are delivered through an air stream. The physical distance between the discharge and the treatment surface can be up to 3 m, making the technology robust and flexible for applications in the medical clinic. The bactericidal properties of the free-radical effluent are enhanced by hydrogen peroxide additives. We report a 6-log reduction in Staphylococcus aureus and Pseudomonas aeruginosa bacteria strains in under 1 min of exposure in vitro and inactivation of Bacillus atrophaes spores and Escherichia coli biofilms. The concentration of hydrogen peroxide additives is seen to be a key variable in inactivation efficacy, suggesting that active species in our experiment may be different than in other DBD configurations. Precise chemical concentration measurements using direct frequency comb spectroscopy show presence of ozone ( O3), hydrogen peroxide (H2O2), nitrous oxide (N2O), and nitrogen dioxide (NO2). In vivo multiple exposures of mouse skin to the plasma effluent do not yield any adverse effects.
Date of Publication: Aug. 2012