Oxygen electrodes, biosensors

The first enzyme biosensor was a glucose sensor reported by Clark in 1962 [194], This biosensor measured the product of glucose oxidation by GOD using an electrode which was a remarkable achievement even though the enzyme was not immobilized on the electrode. Updark and Hicks have developed an improved enzyme sensor using enzyme immobilization [194], The sensor combined the membrane-immobilized GOD with an oxygen electrode, and oxygen measurements were carried out before and after the enzyme reaction. Their report showed the importance of biomaterial immobilization to enhance the stability of a biosensor. 

Biosensors Biosensors are used in the final measurement stage of immunoassays such as an electrochemistry-based enzyme-linked immunoassay (ELISA) or the measurement of catalyse-labelled antigens at an antibody-coated oxygen electrode. 

Figure 3.18 — Microbiosensor types. (A) Oxygen electrode. (B) CO, (C) L-lysine, (D) hypoxanthine, and (E) glucose biosensors. (Reproduced from [109] and [111] with permission of Marcel Dekker, Inc., and Elsevier Science Publishers).

Oxygen electrodes, biosensors, 655, 664, 689 Oxygen-oxygen bonds... 

ReissM,TariA,HartmeierW (1993) BOD-Biosensor basing on an amperometric oxygen electrode covered by Lipomyces kononenkoae. Bioengineering 9 87... 

In general, the commercially available biosensors in the food industry are based on a very similar technology, either an oxygen electrode or a hydrogen peroxide electrode in conjunction with an immobilised oxidase. They are available in several forms, such as autoanalysers, manual laboratory instruments and portable devices. Nevertheless,... 

As can be seen in Tables 17.2 and 17.4, a wide variety of different enzymes present in vegetable tissue or in the crude extracts have been immobilized onto Clark-type oxygen electrode membranes or in carbon paste electrodes. To facilitate understanding of the operation of electrode containing PPO or peroxidase in combination with amperometric biosensors a brief discussion is provided below. 

Ammonia 368, 540 gas sensing electrodes 366 Ammonium 540-541 Amorphous silicon (a-Si) 99 Amperometric 907, 913 biosensors 359 detection 876, ell9 no sensor 930 oxygen electrodes 915 ultramicroelectrode 907 Amyloglucosidase 676 Analytical approximation 912 Anatoxin-a(s) 335 Aniline 985... 

Bioelectrochemical sensors can be divided into two groups poten-tiometric and amperometric. Since the description by Clark43 of the first electrochemical biosensor based on the oxygen electrode, many poten-tiometric and amperometric sensors using enzymes44 and other materials have been designed and applied. 

Fig. 17.11. (a) Potentiometric biosensor based on pH electrode (b) Poten-tiometric biosensor based on gas electrode (c) Oxygen electrode determination of oxygen (d) Oxygen electrode determination of hydrogen peroxide (from Ref. 

Enzyme electrodes play a vital role in the operation of - biosensor and -> biofuel cells. The term enzyme electrode was coined by Clark and Lyons after their first demonstration of a -> glucose sensor in which glucose oxidase was entrapped at a - Clark oxygen electrode using a dialysis membrane. The decrease in measured oxygen concentration was proportional to the glucose concentration. 

Electrochemical and biosensor systems have also been described for the measurement of uric acid. In all cases uricase is employed, being linked in examples to an oxygen electrode and to Teflon on the photomultiplier tube of a luminometer, ... 

Biosensors based on a Clark oxygen electrode, coupled to tyrosinase immobilized by three different methods, were investigated for the determination of phenol in real matrices, such as water of various natural sources, industrial wastes and oil press. The feasibility study included direct use of the biosensors and in situ analysis. An integrated system, incorporating SPE, desorption, fractionation and biosensor detection, was validated for screening phenolic compounds in water. Two types of electrode were tested, solid graphite and CPE incorporating tyrosinase. Correct analyses were found for river water samples spiked with phenol (10 p.gL ), p-cresol (25 p.gL ) and catechol (1 A mul-... 

Quinoprotein glucose dehydrogenase and recombinant tyrosinase from Streptomyces antibioticus were immobilized on polyvinyl alcohol and coupled to a Clark oxygen electrode. LOD was 5 nM for dopamine (10a), L-dopa (10b) and adrenaline (epinefrine, 15a). An electroimmunological biosensor for p-cresol was developed, based on the... 

The purpose of this study was to design biosensors on the basis of covalently immobilised lipoxygenase and oxygen electrodes. 

Oxygen electrodes are being used for the direct determination of oxygen concentration in biomedicine and biotechnological processes. For the development of biosensors they can be combined with a large number of biocatalytic processes such as the respiration of microorganisms, plant photosynthesis, and oxidase-catalyzed reactions. 

First microbe-based biosensor immobilized Acetobac-terxylinium in cellulose on an oxygen electrode for ethanol [10]... 

However, these reports of multitudinous enzyme-based biosensors should be viewed with some caution, as it is much easier to demonstrate the possibility of using an enzyme in a laboratory prototype than to convert these observations into a reliable, and reproducible, device that can meet commercial product requirements. This is illustrated by table 7.1, which lists the few enzymes that have been reported to have been used in commercial biosensors only about two dozen enzymes have been used commercially. Most of the enzymes are oxidases partly because of the stability of this class of enzyme, and partly because of ease of linking this type of enzyme with a Clark-type oxygen electrode. 

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