title: Analysis of the antimicrobial effects of nonthermal plasma on fungal spores in ionic solutions.
abstract: The antimicrobial efficiency of reactive species-based control strategies is significantly affected by the dynamics of reactive species in the biological environment. Atmospheric-pressure nonthermal plasma is an ionized gas in which various reactive species are produced. The various levels of antimicrobial activity may result from the dynamic interaction of the plasma-generated reactive species with the environment. However, the nature of the interaction between plasma and environments is poorly understood. In this study, we analyzed the influence of the ionic strength of surrounding solutions (environment) on the antimicrobial activity of plasma in relation to the plasma-generated reactive species using a model filamentous fungus, Neurospora crassa. Our data revealed that the presence of sodium chloride (NaCl) in the background solution attenuated the deleterious effects of plasma on germination, internal structure, and genomic DNA of fungal spores. The protective effects of NaCl were not explained exclusively by pH, osmotic stability, or the level of reactive species in the solution. These were strongly associated with the ionic strength of the background solution. The presence of ions reduced plasma toxicity, which might be due to a reduced access of reactive species to fungal spores, and fungal spores were inactivated by plasma in a background fluid of nonionic osmolytes despite the low level of reactive species. Our results suggest that the surrounding environment may affect the behavior of reactive species, which leads to different biological consequences regardless of their quantity. Moreover, the microbicidal effect of plasma can be synergistically regulated through control of the microenvironment.
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Kang
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Young June
authors.initials: YJ
authors.lastname: Hong
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Attri
authors.affiliation: Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Geon Bo
authors.initials: GB
authors.lastname: Sim
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea; Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Geon Joon
authors.initials: GJ
authors.lastname: Lee
authors.affiliation: Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Kamonporn
authors.initials: K
authors.lastname: Panngom
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Gi Chung
authors.initials: GC
authors.lastname: Kwon
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea; Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea.
authors.forename: Eun Ha
authors.initials: EH
authors.lastname: Choi
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea; Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea. Electronic address: hsuhm@kw.ac.kr.
authors.forename: Han S
authors.initials: HS
authors.lastname: Uhm
authors.affiliation: Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701, Korea; Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea. Electronic address: gyungp@kw.ac.kr.
authors.forename: Gyungsoon
authors.initials: G
authors.lastname: Park
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D001128:Argon / Q000494:pharmacology*; D002942:Circular Dichroism; D007477:Ions; D058626:Plasma Gases / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D013172:Spores, Fungal / Q000254:growth & development*
chemical_list: D000890:Anti-Infective Agents; D007477:Ions; D058626:Plasma Gases; D017382:Reactive Oxygen Species; D001128:Argon
keywords: Filamentous fungus; Free radicals; Ionic strength; Neurospora crassa; Plasma toxicity; Reactive species