Bioabsorbable Cold Plasma-Generated Nitric Oxide Gas and Plasma-Activated Nitric Oxide Water: Inactivation of Oral Planktonic and Biofilm-Forming Streptococcus mutans

Abstract

Gas plasma exposure and plasma-activated water (PAW) containing long-lived reactive oxygen species (H₂O₂) and nitrogen species (NO₂^‒, NO₃^‒) generated by a multielectrode cylindrical dielectric barrier discharge plasma effectively inactivated oral bacteria Streptococcus mutans, opportunistic pathogen Staphylococcus aureus, and foodborne or intestinal Escherichia coli strains, which were used as comparator organisms. Gas plasma exposure to the water alters the water pH, H₂O₂, and NO_x (Combined NO₂^‒ & NO₃^‒) concentrations. Gas Plasma (NO_x and O₃) achieved a 4–6 log reduction of bacteria within 16 min, while PAW induced a 5–6 log reduction within 3 days and reduced biofilm formation by 50 ± 0.21% ~ 40 ± 8.65%. These results show that bacteria, surface morphology, live/dead and RONS imaging, and flow cytometry consistently demonstrate that biocompatible plasma treatment significantly controls oral pathogens. Plasma gas and both distilled and tap-water PAW effectively inhibited S. mutans, with higher selectivity than that of other bacteria. This study highlights the potential of PAW as a novel, biocompatible strategy to mitigate the virulence of oral bacteria.