Fluid electric force microscopy for the charge density mapping of biomembranes

Abstract

Electric force microscopy has been adapted for fast, high-resolution imaging of the charge density of biological systems. The electric double layer interaction between the tip and sample provides a contrast mechanism that is sensitive only to surface charge density, as other parameters are held constant. This contrast is well described by an expression for the tip-sample double layer interaction in electrolyte solutions. The resultant charge maps are acquired at typical atomic force microscopy scan rates. Fluid electric force microscopy has proven highly sensitive and non-destructive, as demonstrated with charge density maps of fluid-phase supported bilayer membranes and single DNA molecules