A new type of hydrophilic carbon paste electrodes for biosensor manufacturing: binder paste electrodes

The effect of two types of carbon pastes and two osmium-based redox mediators on the response of amperometric enzyme electrodes for glucose was examined. A hydrophobic mediator and a hydrophilic cationic mediator were prepared and mixed in a paste that contained either mineral oil as the pasting liquid, or a polycationic electrolyte without oil. It was found that the current densities were increased by a factor of 25 when the oil-based paste was replaced by the hydrophilic one (binder paste, BP) and five- to six-fold when the hydrophilic mediator was used in place of the hydrophobic. The linear range for the glucose oxidase electrodes was extended to concentrations higher than 60 mM. The glucose electrodes were preliminary optimized and their half-life time reached more than 12 h when operated continuously under vigorous stirring when the 'pasting' polyelectrolyte was crosslinked. At a working potential of 400 mV versus the Ag/AgCl saturated electrode, the saturating current densities per geometric surface area were 1.2 mA/cm2 +/- 0.2 (n = 7). These 'binder paste electrodes' are the first reported bulk modified electrodes without hydrophobic pasting liquid or cover membranes, and present an interesting research and application tool.