INERT METAL-MODIFIED, COMPOSITE CERAMIC-CARBON, AMPEROMETRIC BIOSENSORS - RENEWABLE, CONTROLLED REACTIVE LAYER

A new type of sol-gel-derived, inert metal-modified, composite, ampero metric biosensor is developed. The electrodes are comprised of a dispe rsion of biochemically and chemically modified graphite powder in a po rous, organically modified silicate (Ormosil) network. The percolating carbon dispersion provides electrical conductivity, oxidoreductase en zymes (e.g., glucose oxidase, lactate oxidase, or L-amino acid oxidase ) are used for biocatalysis, metallic palladium is used for electrocat alysis of the biochemical reaction product, and the porous organically modified silica provides a rigid skeleton. The hydrophobicity of this composite material guarantees that only a limited section of the elec trode is wetted by the aqueous analyte, thus providing a controlled-th ickness reactive layer. The thickness of the reaction layer can be tun ed by the addition of hydrophilic components, The electrode can be rep roducibly renewed by removing its upper layer and exposing a new, thin , porous bioreactive section, The same technology is applicable for th e production of thick-film, low-leaching, disposable sensors. In this configuration, the analysis is conducted using a single drop of the an alyte applied on the hydrophobic film. The sensors are found to be sta ble over long periods.