Glucose Biosensor Based on the Use of a Carbon Nanotube Paste Electrode Modified with Metallic Particles

This work reports on the performance of new glucose biosensors based on the combination of the electrocatalytic properties of metals and carbon nanotubes towards the reduction of hydrogen peroxide with the biocatalytic activity of glucose oxidase (GOx). The bioelectrodes were obtained by dispersing the metal particles, enzyme and multi-wall carbon nanotubes within a mineral oil binder. The strong electrocatalytic activity of copper and iridium towards the reduction of hydrogen peroxide has made possible an important improvement in the sensitivity for the determination of glucose compared to the carbon nanotube composite without metals. A highly sensitive and selective amperometric detection of glucose becomes possible at very low potentials (−0.100 V). The presence of the protein enables a better dispersion of the metals within the composite matrix, thus allowing an additional enhancement in the response to hydrogen peroxide. The influence of the amount of copper in the composite on the analytical performance of the bioelectrode is discussed. A biosensor containing 0.77% w/w Cu and 10.0% w/w GOx gave a fast response (10.0 s), a linear relationship between current and glucose concentration up to 1.20 × 10⁻² M, and a detection limit of 2.0 × 10⁻⁵ M. A similar behavior was found for a carbon nanotube-composite electrode containing iridium.