Berlin 2015 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 1: Imaging

BP 1.11: Vortrag

Montag, 16. März 2015, 12:30–12:45, H 1028

High resolution surface charge mapping with a scanning ion-conductance microscope — •Lasse Hyldgaard Klausen, Thomas Fuhs, Flemming Besenbacher, and Mingdong Dong — Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark

Characterising the surface charge density (SCD) is important in interface and colloid science, and especially local variations in SCD of biological samples are of keen interest. The surface charge of lipid bilayers governs the uptake of charged particles and guides cell-cell interactions. As the electrostatic potential is screened by high physiological salt concentrations, direct probing of the potential can only be performed at a sub nanometre distance; therefore it is challenging to measure the local SCD under physiological conditions.

In this study we measure SCD using a scanning ion-conductance microscope (SICM) setup, where the electrolyte current through a nanopipette is monitored as the pipette is positioned in the vicinity of the sample. We investigate the current dependency of SCD and pipette potential using numerical solutions to Poisson and Nernst-Planck equations and characterise a complex system governed by a multitude of factors such as pipette size, geometry and charge. We then propose an imaging method and prove its feasibility by mapping the surface charge density of phase separated lipid bilayers with sub micrometre spatial resolution.