"Wired" Enzyme Electrodes for Amperometric Determination of Glucose or Lactate in the Presence of Interfering Substances

Glucose oxidase (GOX) or lactate oxidase (LOX) were immobilized in an osmium-based three-dimensional redox hydrogel that electrically connected the enzyme's redox centers to electrodes. The enzyme "wiring" hydrogel was formed by cross-linking poly(1-vinylimidazole) (PVI) complexed with Os-(4,4'-dimethylbpy)2Cl (termed PVI15-dmeOs) with poly(ethylene glycol) diglycidyl ether (peg). Glucose and lactate sensors exhibited typical limiting current densities of 250 and 500 microA/cm2, respectively. When the electrodes were poised at 200 mV (SCE), the currents resulting from electrooxidation of ascorbate, urate, acetaminophen, and L-cysteine were negligible. When a Nafion film was employed, the linear range was extended from 6 to 30 mM glucose and from 4 to 7 mM lactate. The redox potential of the gel-forming polymer was 95 mV (SCE). Glucose and lactate measurements performed in bovine calf serum correlated well with a substrate calibration in phosphate buffer.