SENSITIVE DETECTION OF PROTEIN ADSORPTION TO SUPPORTEDLIPID BILAYERS BY CAPACITANCE MEASUREMENTS

Abstract

Wereport experiments on the sensitive detection of protein adsorption to lipid bilayers deposited onto chromium electrodes on glass substrates by capacitance measurements. The sensitivity of the present type of sensor (better than 3A average protein layer thickness) is at least equivalent to that of ellipsometry. A high specific resistance of the supported bilayer of (1-5)-10%cm® is achieved by deposition of a tightly packed (crystalline) cadmium arachidate monolayer in contact with the substrate, whereas the outer monolayer can be more loosely packed (fluid phase or state of fluid-solid coexistence) which is essential for the incorporation of receptors. In the present work, charged lipids are incorporated as nonspecific receptors for polylysine and cytochrome c. Furthermore, the capacitance measurements provide a very sensitive test for the tightness and long-time stability of supported bilayers.