The present study demonstrated for the first time that screen-printed carbon microband electrodes fabricated from water-based ink can readily detect H(2)O(2) and that the same ink, with the addition of lactate oxidase, can be used to construct microband biosensors to measure lactate. These microband devices were fabricated by a simple cutting procedure using conventional sized screen-printed carbon electrodes (SPCEs) containing the electrocatalyst cobalt phthalocyanine (CoPC). These devices were characterised with H(2)O(2) using several electrochemical techniques. Cyclic voltammograms were found to be sigmoidal; a current density value of 4.2 mA cm(-2) was obtained. A scan rate study revealed that the mass transport mechanism was a mixture of radial and planar diffusion. However, a further amperometric study under quiescent and hydrodynamic conditions indicated that radial diffusion predominated. A chronoamperometric study indicated that steady-state currents were obtained with these devices for a variety of H(2)O(2) concentrations and that the currents were proportional to the analyte concentration. Lactate microband biosensors were then fabricated by incorporating lactate oxidase into the water-based formulation prior to printing and then cutting as described. Voltammograms demonstrated that lactate oxidase did not compromise the integrity of the electrode for H(2)O(2) detection. A potential of +400 mV was selected for a calibration study, which showed that lactate could be measured over a dynamic range of 1-10mM which was linear up to 6mM; a calculated lower limit of detection of 289 microM was ascertained. This study provides a platform for monitoring cell metabolism in-vitro by measuring lactate electrochemically via a microband biosensor.

A new method of using screen-printed carbon electrodes (SPCEs) incorporating the electrocatalyst cobalt phthalocyanine (CoPC) for the manufacture of tubular microband electrodes for hydrogen peroxide detection is described. Characterisation of these electrodes using potassium ferrocyanide, with cyclic voltammetry, has shown that steady state behaviour is displayed which is indicative of microelectrode behaviour. The current density obtained from the voltammogram was compared to that obtained for a conventional sized CoPC–SPCE, and the values were 5618 and 35.65μAcm−2, respectively. Cyclic voltammetry was carried out for the same electrodes, using 7mM H2O2 prepared in phosphate buffer at scan rates between 1 and 50mVs−1 and no significant increase in current response was observed. The application of these tubular microband CoPC–SPCEs, to the measurement of H2O2 using chronoamperometry was investigated. A calibration study was performed and the plot showed a sensitivity value of 252μAmM−1cm−2 and a lower detection limit of 70μM. We have shown that the chronoamperometric current response could be calculated using a modified equation originally developed for a plain microband electrode. This study provides a platform for using screen-printed carbon electrodes for the fabrication of oxidase based microbiosensors, for the determination of a variety of cellular metabolites.