Deactivation of bilirubin oxidase by a product of the reaction of urate and O ₂

The "wired" bilirubin oxidase (BOD) bioelectrocatalyst is superior to pure platinum as an electrocatalyst of the four-electron electroreduction of O ₂ to water. Not only is its overpotential for O ₂ reduction lower, but unlike platinum, it is not affected by organic compounds like glucose. The "wired" BOD-coated carbon cathode operates for >1 week at 37°C in a glucose-containing physiological buffer solution. One of its key applications would be in a glucose-O ₂ biofuel cell, which would operate in living tissues. The cathode is, however, short-lived in serum, losing its electrocatalytic activity in a few hours. Here we show that the damaging serum component is a product of the reaction of urate and dissolved oxygen. Exclusion of urate, by application of Nafion™ film on the cathode, improves the stability in serum.