title: Nanoscale Electric Permittivity of Single Bacterial Cells at Gigahertz Frequencies by Scanning Microwave Microscopy.
abstract: We quantified the electric permittivity of single bacterial cells at microwave frequencies and nanoscale spatial resolution by means of near-field scanning microwave microscopy. To this end, calibrated complex admittance images have been obtained at ∼19 GHz and analyzed with a methodology that removes the nonlocal topographic cross-talk contributions and thus provides quantifiable intrinsic dielectric images of the bacterial cells. Results for single Escherichia coli cells provide a relative electric permittivity of ∼4 in dry conditions and ∼20 in humid conditions, with no significant loss contributions. Present findings, together with the ability of microwaves to penetrate the cell membrane, open an important avenue in the microwave label-free imaging of single cells with nanoscale spatial resolution.
authors.affiliation: Institut de Bioenginyeria de Catalunya (IBEC), c/Baldiri i Reixac 11-15, 08028 Barcelona, Spain.
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Biagi
authors.affiliation: Institut de Bioenginyeria de Catalunya (IBEC), c/Baldiri i Reixac 11-15, 08028 Barcelona, Spain.
authors.forename: Rene
authors.initials: R
authors.lastname: Fabregas
authors.affiliation: Institute for Biophysics, Johannes Kepler University Linz , Gruberst. 40, 4020 Linz, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Gramse
authors.affiliation: Institut de Bioenginyeria de Catalunya (IBEC), c/Baldiri i Reixac 11-15, 08028 Barcelona, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Van Der Hofstadt
authors.affiliation: Institut de Bioenginyeria de Catalunya (IBEC), c/Baldiri i Reixac 11-15, 08028 Barcelona, Spain.|Departament de Microbiologia, Universitat de Barcelona , Av. Diagonal 643, 08028 Barcelona, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Juárez
authors.affiliation: Keysight Lab, Keysight Technologies Austria GmbH , Gruberst. 40, 4020 Linz, Austria.
authors.forename: Ferry
authors.initials: F
authors.lastname: Kienberger
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Fumagalli
authors.affiliation: Institut de Bioenginyeria de Catalunya (IBEC), c/Baldiri i Reixac 11-15, 08028 Barcelona, Spain.|Departament d'Electrònica, Universitat de Barcelona , C/Martí i Franqués 1, 08028 Barcelona, Spain.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gomila
mesh_terms: D025802:Electric Capacitance; D004553:Electric Conductivity; D004926:Escherichia coli / Q000502:physiology / Q000648:ultrastructure*; D008853:Microscopy / Q000295:instrumentation / Q000379:methods*; D008872:Microwaves; D059010:Single-Cell Analysis / Q000295:instrumentation / Q000379:methods*
keywords: electric permittivity; scanning microwave microscopy; single bacteria; topographic cross-talk