Glucose microsensors based on carbon paste enzyme electrodes modified with cupric hexacyanoferrate

The incorporation of cupric hexacyanoferrate within a glucose-oxidase containing carbon paste microelectrode (200 mu m i.d.) results in a highly selective, fast-responding, reagentless glucose biosensor. The hexacyanometallate modifier retains its strong electroacatalytic action towards the reduction of the enzymatically liberated hydrogen peroxide upon confinement within the carbon-paste matrix, to allow tuning of the operating potential to a region (-0.2 to 0.0 V) where unwanted reactions are negligible. The use of cupric hexacyanoferrate circumvents stability problems inherent to Prussian-Blue films in alkaline solutions, ans hence permits convenient operation at the physiological pH of 7.4. Various parameters affecting the response have been examined and optimized. Such one-step route for preparing hexacyanometallate-modified bioelectrodes obviates the need for multistep electrodepostion/polymer-casting schemes, and holds great promise for selective detection of glucose in biological fluids. (C) 1999 Elsevier Science B.V. All rights reserved.