title: 18 GHz electromagnetic field induces permeability of Gram-positive cocci.
abstract: The effect of electromagnetic field (EMF) exposures at the microwave (MW) frequency of 18 GHz, on four cocci, Planococcus maritimus KMM 3738, Staphylococcus aureus CIP 65.8(T), S. aureus ATCC 25923 and S. epidermidis ATCC 14990(T), was investigated. We demonstrate that exposing the bacteria to an EMF induced permeability in the bacterial membranes of all strains studied, as confirmed directly by transmission electron microscopy (TEM), and indirectly via the propidium iodide assay and the uptake of silica nanospheres. The cells remained permeable for at least nine minutes after EMF exposure. It was shown that all strains internalized 23.5 nm nanospheres, whereas the internalization of the 46.3 nm nanospheres differed amongst the bacterial strains (S. epidermidis ATCC 14990(T) ~  0%; Staphylococcus aureus CIP 65.8(T) S. aureus ATCC 25923, ~40%; Planococcus maritimus KMM 3738, ~ 80%). Cell viability experiments indicated that up to 84% of the cells exposed to the EMF remained viable. The morphology of the bacterial cells was not altered, as inferred from the scanning electron micrographs, however traces of leaked cytosolic fluids from the EMF exposed cells could be detected. EMF-induced permeabilization may represent an innovative, alternative cell permeability technique for applications in biomedical engineering, cell drug delivery and gene therapy.
authors.affiliation: School of Science, Swinburne University of Technology, Melbourne, Australia.
authors.forename: The Hong Phong
authors.initials: TH
authors.lastname: Nguyen
authors.affiliation: School of Science, Swinburne University of Technology, Melbourne, Australia.
authors.forename: Yury
authors.initials: Y
authors.lastname: Shamis
authors.affiliation: 1] Illawarra Health and Medical Research Institute, Wollongong, Australia [2] Australian Centre for Electromagnetic Bioeffects Research, Australia.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Croft
authors.affiliation: 1] Australian Centre for Electromagnetic Bioeffects Research, Australia [2] School of Health Sciences.
authors.forename: Andrew
authors.initials: A
authors.lastname: Wood
authors.affiliation: 1] Australian Centre for Electromagnetic Bioeffects Research, Australia [2] School of Health Sciences.
authors.forename: Robert L
authors.initials: RL
authors.lastname: McIntosh
authors.affiliation: School of Science, Swinburne University of Technology, Melbourne, Australia.
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Crawford
authors.affiliation: 1] School of Health Sciences, Swinburne University, Melbourne, Australia [2] Australian Centre for Electromagnetic Bioeffects Research, Australia.
authors.forename: Elena P
authors.initials: EP
authors.lastname: Ivanova
mesh_terms: D001692:Biological Transport; D002463:Cell Membrane Permeability / Q000528:radiation effects; D004574:Electromagnetic Fields; D060733:Electromagnetic Radiation; D050296:Microbial Viability / Q000528:radiation effects; D046529:Microscopy, Electron, Transmission; D054118:Nanospheres / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D010316:Particle Size; D058642:Planococcus Bacteria / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D011419:Propidium; D012822:Silicon Dioxide / Q000737:chemistry / Q000378:metabolism; D013211:Staphylococcus aureus / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D013212:Staphylococcus epidermidis / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure
chemical_list: D011419:Propidium; D012822:Silicon Dioxide