Carbon felt composite electrodes and their use in electrochemical sensing: a biosensor based on alcohol dehydrogenase

The preparation and electroanalytical utility of a novel type of microelectrode ensemble based on carbon felt/epoxy composite are described. The electrochemical behavior of these carbon felt microelectrode ensembles (CFMEs) have been characterized by cyclic voltammetry and chronoamperometry. The behavior of CFME is compared with and contrasted to those obtained at a conventional-sized vitreous carbon electrode (r=3 mm) and at a carbon fiber ultramicroelectrode (r=7 μm). CFMEs exhibit the nonlinear transport properties of microelectrodes for sweep rates of up to 400 mV/s, as well as large, easily measurable currents which are particularly valuable in biosensor applications. These CFMEs have been modified with electrodeposited films of 3,4-dihydroxybenzaldehyde (3,4-DHB) which exhibit very high and persistent electrocatalytic activity for the oxidation of NADH. The presence, in solution, of Ca2+ or Mg2+ results in a significant enhancement of the electrocatalytic current. By combining the electrocatalytic activity of the CFME, modified with electrodeposited films of 3,4-DHB, with the enzymatic activity of alcohol dehydrogenase immobilized on a nylon filter mesh, we have developed an alcohol biosensor which exhibits high sensitivity and a limit of detection of 2.0×10−4 M ethanol.