Impedance and shear wave resonance analysis of ligand-receptor interactions at functionalized surfaces and of cell monolayers.

The present paper scrutinizes the application of impedance spectroscopy and quartz-crystal microbalance (QCM) measurements in the analysis of composite layers of receptor containing lipid bilayers, and their interaction with external ligands or pore-forming peptides. The formation of supramolecular structures and their analysis will be discussed. Impedance measurement allows one to follow the adsorption of proteins on artificial membranes. This method is even more suitable for quantifying changes in membrane conductivity induced by channel peptides incorporated into the lipid membrane. The QCM is another sophisticated method for analyzing ganglioside-lectin and ganglioside-toxin interactions. A critical comparison between both methods will be given. Moreover, we will demonstrate that the QCM method, especially in combination with impedance analysis, is a completely new approach for determining electrical and viscoelastic properties of epithelial and endothelial cell monolayers that form controlled barriers in vivo.