Covalent immobilization of avidin on glassy carbon electrodes as the basis for multivalent biosensors

One of the most crucial steps for the successful construction of a biosensor is the appropriate and reproducible coupling of the biological part (e.g. enzyme, antibody) to the inorganic moiety of the device (e.g. electrode, microchip). In this paper three methods of immobilization of avidin to a glassy carbon electrode are described. Depending on the type of immobilization, avidin may lose its biological activity as determined by an enzyme immunoassay, using biotinylated reagents. If avidin is covalently bound to the glassy carbon electrode via the bridge molecule 4.4'-diaminodiphenylamine, the biological activity is retained. About 1.5 pmol of avidin can be bound to the electrode (3 mm in diameter), resulting in a nearly complete monolayer of protein.