Comparison of oxygren-rich and mediator-based glucose-oxidase carbon-pasteelectrodes

The oxygen-independence and analytical performance of amperometric glucose carbon-paste biosensors based on oxygen-rich biocomposites and artificial m ediators are critically compared. The oxygen demand is examined over a wide range of glucose concentrations or oxygen levels, and using different phys iological electron acceptors and various sensing scenarios. The dimethyl-fe rrocene (DW)-, methylene-green (MG)-, and phenazine-methosulfate (PMS)-medi ator 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 x 10(-2) M glucose, with s ome sensitivity loss at higher levels in deoxygenated media. The oxygen-ric h biocomposites are thus particularly advantageous in connection to the det ection of hypoglycemia and mild hyperglycemia (but not in connection to sev ere hyperglycemia). The resistance to oxygen effect of the three mediators follows the order DMF > PMS > MG, reflecting the rates of their reaction wi th the enzyme (relative to the competing oxygen-glucose oxidase (GOx) react ion). The resistance to oxygen effects is demonstrated also under flow cond itions relevant to commercial blood analyzers. Other analytical "figures of merit" of the mediator- and oxygen-rich carbon-paste biosensors are also c ompared. (C) 2001 Elsevier Science B.V. All rights reserved.