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Issue 43, 2015
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Nanoscale electric polarizability of ultrathin biolayers on insulating substrates by electrostatic force microscopy

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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

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Article information


Submitted
24 Jul 2015
Accepted
13 Oct 2015
First published
15 Oct 2015

Nanoscale, 2015,7, 18327-18336
Article type
Paper
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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