Glucose electrodes based on cross-linked bis(2,2'-bipyridine)chloroosmium(+/2+) complexed poly(1-vinylimidazole) films

Abstract

Enzyme electrodes based on a redox hydrogel formed upon complexing water-soluble poly(1-vinylimidazole) (PVI) with [Os(bpy)2Cl]+ and cross-linked with water-soluble poly(ethylene glycol) diglycidyl ether (molecular weight 400, peg 400) are described. The properties of the electrodes depended on their polymers' osmium content, the extent of cross-linking, the pH, and the ionic strength in which they were used. The redox hydrogels' electron diffusion coefficients (De) increased with osmium content of their polymers. The De values were 1.5 x 10(-8), 1.3 x 10(-8), and 4.3 x 10(-9) cm2/s for PVI3-Os, PVI5-Os, and PVI10-Os, respectively, the subscripts indicating the number of monomer units per osmium redox center. De decreased with increasing ionic strength and increased upon protonation of the polymer. In glucose electrodes, made by incorporating into their films glucose oxidase (GOX) through covalent bonding in the cross-linking step, glucose was electrooxidized at > 150 mV (SCE). The characteristics of these electrodes depended on the GOX concentration, film thickness, O2 concentration, pH, NaCl concentration, and electrode potential. The steady-state glucose electrooxidation currents were independent of the polymers' osmium content in the studied (3-10 monomer units per osmium center) range. Electrodes containing 39% GOX reached steady-state glucose electrooxidation current densities of 400 microA/cm2 and, when made with thick gel films, were selective for glucose in the presence of physiological concentrations of ascorbate and acetaminophen.