Electrochemical biosensor, molecular amperometric

The amperometric biosensor based on carbon paste electrode ensures proximity at the molecular level between the catalytic and electrochemical sites because the carbon electrode is both the biocatalytic phase and the electrode sensor (Table 17.2). The tissue containing carbon paste can be incorporated in various electrode configurations and these have very rapid response times, extended lifetimes, high rigidity, mechanical stability and very low cost. 

This enzyme-based biosensor uses glucose oxidase (GO) as a chemical recognition element, and an amperometric graphite foil electrode as the transducer. It differs from the first reported glucose biosensor discussed in the introduction to this chapter in that a mediator, 1,1 -dimethylferricinium, replaces molecular oxygen as the oxidant that regenerates active enzyme. The enzymatic reaction is given in Eq. 7.15, and the electrochemical reaction that provides the measured current is shown in Eq. 7.16. 

Conducting polymers have been used to modify the surface properties of metallic electrodes, in particular microelectrodes [49]. TTie prosthetic functional groups covalently attached to the polymer chains can be used as molecular sensors or molecular transducers that can reversibly transfer electrochemical information between the medium and the electrodes. These systems are useful for solution sensing in both amperometric and resistometric modes. Enzymes (for example, glucose oxidase) can be incorporated directly into the polymeric layer during polymerization and subsequently used as biosensors. 

---