Amperometric biosensors based on biocatalyst electrodes. mediated and mediatorless enzyme electrodes

An enzyme-modified electrode is constructed by immobilizing an oxidoreductase behind a dialysis membrane on a carbon paste electrode containing a redox compound. The redox compound functions as an electron transfer mediator between the electrode and the immobilized enzyme, thus the electrode can oxidize or reduce the substrate electro-enzymatically. Many oxidoreductases, especially dehydrogenases which use artificial electron acceptors are the enzymes suitable for constructing the enzyme-modified electrodes. They can be used as mediated amperometric biosensors which are insensitive to oxygen tension in test solutions. Examples of the mediated enzyme electrodes are given and characteristics of the current response of the electrodes to the substrates are described. Use of the mediated enzyme electrodes with high sensitivity are also described. Enzyme-modified electrodes based on oxidoreductases from bacterial membranes can oxidize the substrates electro-enzymatically in the absence of mediators. Such electrodes can be used as mediatorless enzyme electrodes.