STABILIZATION OF AN OSMIUM BIS-BIPYRIDYL POLYMER-MODIFIED CARBON-PASTE AMPEROMETRIC GLUCOSE BIOSENSOR USING POLYETHYLENEIMINE

The modification of carbon paste electrodes by incorporation of the en zyme glucose oxidase (GOx) and a conducting redox osmium bis-bipyridyl poly(4-vinylpyridine) polymer (Os-polymer) is described. The resultin g enzyme electrodes were operated as amperometric glucose sensors in t he presence or absence of a stabilizer, polyethyleneimine (PEI), mixed into the paste. Cyclic voltammetric studies showed that Os-polymer co ntaining Os2+/3+ redox couple mediated the electron transfer from redu ced GOx to the carbon paste electrode material. Steady-state amperomet ric responses of the sensors to 2-120 mM glucose at an operating poten tial of 350 mV (vs. Ag/AgCl) were determined in 0.1 M phosphate buffer (pH 7.0) medium. The study showed that PEL enhances both. the sensiti vity and stability of the carbon paste enzyme electrode and that a dif fusion-limited step precedes electrocatalytic reactions of the biosens or. Cyclic voltammetric data and the Arrhenius analysis of the apparen t turnover rate constant, k(cat)', showed that PET decreases the diffu sion limitations of CPE, thereby increasing the frequency of collision of reacting species in this biosensor format.