Host-guest interactions in thin membranes: selective ion transport and transduction into electronic signals

Synthetic receptor molecules that selectively complex with charged guest molecules can be used to transport salts through liquid membranes and to transduce chemical information into electronic signals. In both cases the receptor molecules are present in thin membranes in contact with aqueous solutions. Extreme lipophilicity of the receptor molecules is therefore required: calix crown ethers and calixspherands meet these requirements. Their synthesis and complexation properties will be discussed. In order to mimic the large rates of transport through biomembranes, thin supported liquid membranes (less than 100 microns), in which the receptor molecules are present, were investigated. The selective ion transport has been studied as a function of the experimental parameters and interpreted via computer simulations of the transport processes. The transduction of complexation into electronic signals can be achieved via the 'immobilization' of receptor molecules on the gate surface of an ISFET chip. Parameters that govern the signal transduction in multilayer systems have been studied and stimulated.