Bioanodes for fuel cell applications require highly efficient oxidation reactions to achieve a sufficiently large current density. In this study, gold nanoparticles have been synthesized using branched polyethylenimine (bPEI), a well-known polymer that forms a hydrogel in water, as the stabilizer. Primary amine groups available in bPEI provide active sites for further conjugation with ferrocene propionic acid via the 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling reaction, with the enzyme glucose oxidase, using glutaraldehyde as linkers. This composite material was then used for the fabrication of glucose oxidase electrodes by drop casting of aqueous solutions onto glassy carbon electrodes. The three-dimensional structure offered by the new hydrogel facilitates communication between the enzyme and the electrode through the redox mediator ferrocene. This allows the glucose oxidase electrode to exhibit excellent activity towards electrocatalytic oxidation of glucose in phosphate buffer solutions at pH 7 with a maximum current density of approximately 800 μA cm−2, one of the highest values reported so far for redox hydrogel based glucose oxidase electrodes. Over a wide glucose concentration range, the enzyme response follows that predicted by the Michaelis-Menten equation with a Michaelis constant of 8.4 mM. In the sensing context, this electrode also exhibits a wide linear dynamic glucose concentration range of 0.5–10 mM with a limit of detection of 0.04 mM.
- Glucose oxidase