Lactate oxalate oxidase electrode

Assolant-Vinet and Coulet (1986) used a preactivated Biodyne Im-munoaffinity Membrane (Pall, USA) to cover two electrodes working in differential mode. Immobilization was performed by simply dropping the enzyme solution onto the membrane, i.e., the biosensor-users may prepare the enzyme membranes themselves. Good results were obtained with GOD, lactate oxidase, and oxalate oxidase (Coulet, 1987). 

Other examples of amperometric enzyme electrodes based on the measurement of oxygen or hydrogen peroxide include electrodes for the measurement of galactose in blood (galactose oxidase,enzyme), oxalate in urine (oxalate oxidase), and cholesterol in blood serum (cholesterol oxidase). Ethanol is determined by reacting with a cofactor, nicotinamide adenine dinucleotide (NAD" ) in the presence of the enzyme alcohol dehydrogenase to produce the reduced form of NAD", NADH, which is electrochemically oxidized. Lactate in blood is similarly determined (lactate dehydrogenase enzyme). 

The activity of the enzyme is also strongly affected by the presence of inhibitors. Fluoride ions inhibit urease (173) and oxalate ions inhibit lactate oxidase (174), but the major inhibitors are heavy-metal ions, such as Ag+, Hg +, Cu " ", organophosphates, and sulfhydryl reagents (/i-chloromercuribenzoate and phenylmercury(II) acetate), which block the free thiol groups of many enzyme active centers, especially oxidase (69). Inhibiting the enzyme electrodes makes it possible to quantify the inhibitors themselves (69), for example, H2S and HCN detection using a cytochrome oxidase immobilized electrode (176). 

The use of peroxide sensors has been extended to the sensing of glucose, lactate, alcohol, oxalate, glutamate and other amino acids by coimmobilization of the respective oxidase on top of the peroxidase [7,8,228,229], and furthermore, to afl nity-based assays [130,131,217,273]. An octane sensor was created by layering a porphyrin type P450-mimics on a screen-printed HRP-modified carbon electrode (Fig. 2.13) [106]. The biomimetic catalyst (iron(III)-meso-tetrakis-(pentafluorophenyl)-p-tetrasulfonatopor-phyrin chloride) was linked to the electrode with polyallylamine on the basis... 

---