Comparison of oxygen-rich and mediator-based glucose-oxidase carbon-paste electrodes

The oxygen-independence and analytical performance of amperometric glucose carbon-paste biosensors based on oxygen-rich biocomposites and artificial mediators are critically compared. The oxygen demand is examined over a wide range of glucose concentrations or oxygen levels, and using different physiological electron acceptors and various sensing scenarios. The dimethyl-ferrocene (DMF)-, methylene-green (MG)-, and phenazinemethosulfate (PMS)-mediator carbon-paste biosensors display significant oxygen dependence over the entire concentration range tested, with substantially larger signals under severe oxygen-deficit conditions. In contrast, the fluorocarbon-oil based probe offers a total oxygen independence up to 1×10-2M glucose, with some sensitivity loss at higher levels in deoxygenated media. The oxygen-rich biocomposites are thus particularly advantageous in connection to the detection of hypoglycemia and mild hyperglycemia (but not in connection to severe hyperglycemia). The resistance to oxygen effect of the three mediators follows the order DMF>PMS>MG, reflecting the rates of their reaction with the enzyme (relative to the competing oxygen-glucose oxidase (GOx) reaction). The resistance to oxygen effects is demonstrated also under flow conditions relevant to commercial blood analyzers. Other analytical "figures of merit" of the mediator- and oxygen-rich carbon-paste biosensors are also compared.