Issue 43, 2015

Nanoscale electric polarizability of ultrathin biolayers on insulating substrates by electrostatic force microscopy

Abstract

We measured and quantified the local electric polarization properties of ultrathin (∼5 nm) biolayers on mm-thick mica substrates. We achieved it by scanning a sharp conductive tip (<10 nm radius) of an electrostatic force microscope over the biolayers and quantifying sub-picoNewton electric polarization forces with a sharp-tip model implemented using finite-element numerical calculations. We obtained relative dielectric constants εr = 3.3, 2.4 and 1.9 for bacteriorhodopsin, dioleoylphosphatidylcholine (DOPC) and cholesterol layers, chosen as representative of the main cell membrane components, with an error below 10% and a spatial resolution down to ∼50 nm. The ability of using insulating substrates common in biophysics research, such as mica or glass, instead of metallic substrates, offers both a general platform to determine the dielectric properties of biolayers and a wider compatibility with other characterization techniques, such as optical microscopy. This opens up new possibilities for biolayer research at the nanoscale, including nanoscale label-free composition mapping.

Graphical abstract: Nanoscale electric polarizability of ultrathin biolayers on insulating substrates by electrostatic force microscopy

Supplementary files

Article information

Article type
Paper
Submitted
24 Jul 2015
Accepted
13 Oct 2015
First published
15 Oct 2015

Nanoscale, 2015,7, 18327-18336

Author version available

Nanoscale electric polarizability of ultrathin biolayers on insulating substrates by electrostatic force microscopy

A. Dols-Perez, G. Gramse, A. Calò, G. Gomila and L. Fumagalli, Nanoscale, 2015, 7, 18327 DOI: 10.1039/C5NR04983K

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