Glucose Oxidase Directly Immobilized onto Highly Porous Gold Electrodes for Sensing and Fuel Cell applications

A novel bioelectrochemical interface based on in situ synthesis of gold nanostructures on electrode surfaces and surface activation by Meerwein's salt. A bioelectrochemical sensor for glucose determination

A novel effective bioelectrochemical sensor interface for enzyme biosensors is proposed. The method is based on in situ synthesis of gold nanostructures (5-15 nm) on the thin-film electrode surface using the oleylamine (OA) method, which provides a high-density, stable, electrode interface nanoarchitecture. New method to activate the surface of the OA-stabilized nanostructured electrochemical interface for further functionalization with biomolecules (glucose oxidase enzyme) using Meerwein's salt is proposed. Using this approach a new biosensor for glucose determination with improved analytical characteristics: wide working range of 0.06-18.5mM with a sensitivity of 22.6 ± 0.5 μAmM(-1)cm(-2), limit of detection 0.02 mM, high reproducibility, and long lifetime (60 d, 93%) was developed. The surface morphology of the electrodes was characterized by scanning electron microscopy (SEM). The electrochemical properties of the interface were studied by cyclic voltammetry and electrochemical impedance spectroscopy using a Fe(II/III) redox couple. The studies revealed an increase in the electroactive surface area and a decrease in the charge transfer resistance following surface activation with Meerwein's reagent. A remarkably enhanced stability and reproducibility of the sensor was achieved using in situ synthesis of gold nanostructures on the electrode surface, while surface activation with Meerwein's salt proved indispensable in achieving an efficient bioelectrochemical interface.

Continuous power generation from glucose with two different miniature flow-through enzymatic biofuel cells

Enzymatic biofuel cells (EBFCs) can generate energy from metabolites present in physiological fluids. They represent an attractive alternative to lithium batteries to power implantable devices, as they work at body temperature, are light and easy-to-miniaturise. To be implantable in blood vessels, EBFCs should not only be made of non-toxic and biocompatible compounds but should also be able to operate in continuous flow-through mode. The EBFC devices reported so far, however, implement carbon-based materials of questionable toxicity and stability, such as carbon nanotubes, and rely on the use of external redox mediators for the electrical connection between the enzyme and the electrode. With this study, we demonstrate for the first time continuous power generation by flow through miniature enzymatic biofuel cells fed with an aerated solution of glucose and no redox mediators. Non-toxic highly porous gold was used as the electrode material and the immobilisation of the enzymes onto the electrodes surface was performed via cost-effective and easy-to-reproduce methodologies. The results presented here are a significant step towards the development of revolutionary implantable medical devices that extract the power they require from metabolites in the body.