Electrically induced deformation of giant liposomes monitored by thickness shear mode resonators.

Thickness shear mode resonators are capable of registering small changes in the thickness and viscoelastic properties of ultrathin films attached to their surface. It was found that it is possible to monitor the deformation of surface-bound giant liposomes by applying an electric field with small amplitudes. Changes in the apparent height of attached vesicles in the nanometer range were easily detected as a function of lipid composition. Increasing the bending modulus by adding cholesterol results in a significantly reduced deformation from 16.8 nm (5% cholesterol) down to 3.2 nm (20% cholesterol), rendering this new method a robust and sensitive tool to detect the bending elasticity of liposomes on small length scales. Deformation could be further suppressed by adding anchor groups (biotinylated lipids), resulting in a strongly flattened liposome on an avidin-coated resonator.