Chemical sensing with chemically modified electrodes that mimic gating at biomembranes incorporating ion-channel receptors

Selective binding of electroinactive analytes to electrodes that are chemic ally modified with receptors can be used to control heterogeneous redox rea ctions of electroactive species. The latter are in this context often calle d markers because their use allows the indirect determination of the electr oinactive analytes with the inherent possibility for chemical signal amplif ication. Two different approaches can be distinguished. To structurally mim ic natural ion-channel proteins, electrodes are modified with artificial re ceptors having intramolecular channels that can be blocked by formation of inclusion complexes with the analyte. In more abstract analogy to the worki ng principle of ion-channel proteins, binding of usually charged analytes t o receptors without intramolecular channels is used to control redox reacti ons of the marker species on the basis of electrostatic interactions, and, occasionally, of steric repulsion. The versatility and general characterist ics of this type of chemically gated sensors are discussed, and specific ex amples from recent studies are presented.