The needle glucose electrode: in vitro performance and optimisation for implantation.

The classical glucose needle electrode based on detection of H2O2 from glucose oxidase has been studied. Dip-coating of a series of outer polyurethane layers of increasing concentration (10-50% W/V) achieved devices with extended linearity (greater than or equal to 30 mM glucose) with greater reliability than a single dip-coat. In vitro performance in unstirred whole blood was acceptable, and all devices were stir-independent. Nevertheless, signal size was affected by a high solution viscosity, and this may have implications for the use of enzyme electrodes in subcutaneous tissue.