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 enzyme glucose oxidase (GOx) and a conducting redox osmium bis-bipyridyl poly(4-vinylpyridine) polymer (Os-polymer) is described. The resulting enzyme electrodes were operated as amperometric glucose sensors in the presence or absence of a stabilizer, polyethyleneimine (PEI), mixed into the paste. Cyclic voltammetric studies showed that Os-polymer containing Os2+3+ redox couple mediated the electron transfer from reduced GOx to the carbon paste electrode material. Steady-state amperometric responses of the sensors to 2-120 mM glucose at an operating potential of 350mV (vs. Ag/AgCl) were determined in 0.1 M phosphate buffer (pH7.0) medium. The study showed that PEI enhances both, the sensitivity and stability of the carbon paste enzyme electrode and that a diffusion-limited step precedes electrocatalytic reactions of the biosensor. Cyclic voltammetric data and the Arrhenius analysis of the apparent turnover rate constant, k′cat, showed that PEI decreases the diffusion limitations of CPE, thereby increasing the frequency of collision of reacting species in this biosensor format.