Comparison of colloidal gold electrode fabrication methods: the preparation of a horseradish peroxidase enzyme electrode

Abstract

In order to prepare biosensing electrodes which respond to hydrogen peroxide, horseradish peroxidase has been adsorbed to colloidal gold sols and electrodes prepared by deposition of these enzyme-gold sols onto glassy carbon using three methods: evaporation, electrodeposition and electrolyte deposition. In the latter method the enzyme-gold sol is applied to the surface of a glassy carbon disk electrode followed by an equal volume of 2 mM CaCl₂. The electrolyte causes the sol to precipitate on the electrode surface, producing an immobilized enzyme electrode. Satisfactory electrodes which gave an electro-chemical response to hydrogen peroxide in the presence of the electron transfer mediator ferrocenecarboxylic acid were produced by all three methods. Evaporation of horseradish peroxidase-gold sols produced electrodes with the best reproducibility and the widest linear amperometric response range. These electrodes can also easily be stored in a dry state. Although not as good as evaporation, electrodeposition also produced satisfactory electrodes. Electrodeposition provides the added advantage that it lends itself to the preparation of multi-enzyme/multi-analyte electrodes by the adsorption of different enzymes to separate gold sols, followed by sequential electrodeposition only discrete areas of multichannel electrode.