Glucose oxidase ferrocene electron shuttle

The reaction scheme used in the first commercial electrochemical test strip from MediSense (now Abbott Diabetes Care) is shown later. Electron transfer rates between the reduced form of glucose oxidase and ferricinium ion derivatives are very rapid compared with the unwanted side reaction with oxygen (Cass et al. 1984 Forrow et al. 2002). The Abbott Diabetes Care Precision QID strip includes the l,l -dimethyl-3-(2-amino-l-hydroxyethyl) ferrocene mediator, which has the desirable characteristics of high solubility in water, fast electron-shuttling (bimolecular rate constant of 4.3 X 10 M s ), stability, and pH independence of the redox potential (Heller and Feldman 2008). Electrochemical oxidation of the ferrocene derivative is performed at 0.6 V. Oxidation of interferences, such as ascorbic acid and acetaminophen present in blood, are corrected for by measuring the current at a second electrode on the strip that does not contain glucose oxidase. 

Depositing films of these copolymers on the surface of an electrode converts it into a derivatized electrode that is useful for reoxidizing reduced flavin enzymes, such as glucose oxidase. The immobilized ferrocene molecule serves as a shuttle for electron transport between the enzyme catalytic center and the electrode surface. 

A mediator is a low-molecular-weight redox couple such as ferrocene monocarboxylic acid (Fecp2R ) that shuttles electrons from the redox centre of the enzyme to the surface of the sensing electrode. Thus polymerization of the pyrrole monomer in the presence of glucose oxidase... 

---