Enzyme electrode, for measurement

FIGURE 23-13 Enzyme electrodes for measuring urea. (Reprimed with permission from D. N. Gray. M. H. Keyes, and B. Wafson. Anal. Chem.. 1977,49,1067A. Copyright 1977 American Chemical Socieiy.)... 

Nielsen PM, Olsen HS (2002) Enzymic modification of food protein. In Whitehurst RJ, Law BA (eds). Enzymes in food technology. CRC Press, Boca Raton, pp 109-143 Nilsson H, Mosbach K, Enfors SO et al. (1978) An enzyme electrode for measurement of penicillin in fermentation broth a step toward the application of enzyme electrodes in fermentation control. Biotechnol Bioeng 20(4) 527-539... 

FIGURE 23-13 Enzyme electrodes for measuring urea. (Reprinted with permission from D. N. Gray. M. H. 

Enfors S.O. and Nilson H. (1979) Design and response characteristics of an enzyme electrode for measurement of penicillin in fermentation broth. Enzyme Microb. Technol., 1, 260-264. 

J. Wang and X. Zhang, Screen printed cupric-hexacyanoferrate modified carbon enzyme electrode for single-use glucose measurements. Anal. Lett. 32, 1739-1749 (1999). 

The classic potentiometric enzyme electrode is a combination of an ion-selective electrode-based sensor and an immobilized (insolubilized) enzyme. Few of the many enzyme electrodes based on potentiometric ion- and gas-selective membrane electrode transducers have been included in commercially available instruments for routine measurements of biomolecules in complex samples such as blood, urine or bioreactor media. The main practical limitation of potentiometric enzyme electrodes for this purpose is their poor selectivity, which does not arise from the biocatalytic reaction, but from the response of the base ion or gas transducer to endogenous ionic and gaseous species in the sample. 

M. Kyrolainen, H. Hakanson, B. Mattiasson and P. Vadgama, Minimal fouling enzyme electrode for continuous flow measurement of whole blood lactate, Biosens. Bioelectron., 11 (1997) 1073-1081. 

The gas-sensing electrodes also are used for the potentiometric measurement of biologically important species. An enzyme is immobilized at or near the gas probe. The gas sensor measures the amount of characteristic gas produced by the reaction of the analyzed substance with the enzyme. For example, an enzyme electrode for urea [NH2C(0)NH2] determination is constructed by the immobilization of urease onto the surface of an ammonia-selective electrode. When the electrode is inserted into a solution that contains urea, the enzyme catalyzes its conversion to ammonia ... 

An electrode for measuring urea has been described (Gll), consisting of a thin film of urease, immobilized in acrylamide gel, on the surface of a glass electrode responsive to NH. Conditions are carefully selected to ensure stability of the enzyme, and the potential developed is proportional to the logarithm of the urea concentration. Blood glucose and lactate have been determined with a membrane electrode in which the enzyme (glucose oxidase or lactate dehydrogenase) is trapped in a porous or jellied layer at the membrane surface (W20). 

E581 Wiese, D.A., Bowen, T.P. and Kost, G.J. (1989). Enzyme electrode for glucose measurement in whole blood with a critical care profiling instrument. Clin. Chem. 35, 1098, Abstr. 152. 

Rahni et al. (1986b) combined immobilized salicylate hydroxylase with an oxygen electrode. With a linear measuring range of 0.01-0.7 mmol/l, salicylate concentrations in serum could be measured without preconcentration. The sensitivity of the enzyme electrode for aspirin and gentisate was 20 times lower than for salicylate. 

An early reference to the concept of a biosensor is from Dr. Leland C. Clark, who worked on biosensors in the early 1960s (2) developing an enzyme electrode for glucose concentration measurement with the enzyme glucose oxidase, a measurement that is important in the diagnosis and treatment of disorders of carbohydrate metabolism in diabetes patients. Still today, the most common biosensors used are for glucose analysis. 

An example of a sensor utilizing these three components is illustrated in figure 1.2, which shows a schematic of a typical enzyme electrode for the detection of glucose (also see chapter 17 of this text). The bioactive surface consists of immobilized glucose oxidase (GOD) sandwiched between a polycarbonate and cellulose acetate membrane. The transducer is a platinum electrode and the electronics are those typically found in any polarograph, i.e. an electronic system to measure low currents (on the order of microamperes) at a fixed voltage bias on the platinum electrode. The action of glucose... 

P0TEI m08VIETRSC ENZYME-BASED ELECTRODES FOR MEASUREMENT OF SUBSTRATES... 

The use of a second downstream electrode to monitor chemical fluxes at the working electrode is proving to be an important technique for the investigation of electrode mechanisms. This is particularly true for electrodes which have a more complicated structure than a simple metallic surface. Examples are modified electrodes, oxide electrodes, or enzyme electrodes. For these more complex systems, the separate measurement of the fluxes at the electrolyte-electrode interface provides unique and valuable information. Double electrodes can be constructed for all three hydrodynamic systems. A crucial parameter for such a double electrode is the collection efficiency, N, which, in the steady state, relates the flux of material detected as a limiting current on the downstream electrode to the flux of material generated on the upstream electrode. The collection efficiency is a function of the geometry of the electrode and is given for all three systems by [4, 9]... 

The continuous measurement of urea in blood during dialysis is an important precondition for monitoring of the treatment of patients with chronic kidney failure. An enzyme electrode for the semi-continuous assay of urea in dialyzate has been designed and integrated in an ar-... 

A significant proportion of the published work has been concerned with the study of glucose oxidase (GOx EC 1.1.3.4) immobilized in poly(pyrrole). This is in part due to interest in amperometric enzyme electrodes for glucose measurement and in part to the fact that GOx is a very robust enzyme and poly(pyrrole) is very easy to polymerize from aqueous solutions thus conditions required to immobilize the enzyme are not demanding. In addition to the GOx/poly(pyrrole) system, a range of other enzymes and other electropolymerized films have been investigated. 

The basic glucose sensor may be extended to multiple enzyme electrodes for the measurement of the concentration of various analytes which may be converted to glucose (i.e., oligo-, polysaccharides, a- and jS-glycosides). A few examples of such sequence electrodes are given below [160, 161] ... 

The original electrode was developed for detecting urea in blood and urine samples. An enzyme sensor for measuring urea in milk has been reported by an Indian group [31]. The working principle is identical to that of Guilbault s sensor. The sensor prepared for milk analysis, however, is a flat cell fabricated with screen-printed technology. 

MuUen WH, Churchouse SJ, Keedy FH, Vadgama PM. Enzyme electrode for the measurement of lactate in undiluted blood. Clinica Chimica Acta 1986 157(2) 191-8. 

Maines A, Prodromidis MI, Tzouwara-Karayanni SM, Karayannis MI, Ashworth D, Vadgama P. An enzyme electrode for extended linearity citrate measurements based on modified polymeric membranes. Electroanalysis 2000 12(14) 1118-23. 

Blood Compatibility Tests. The aim of this study is to develop an enzyme electrode for the measurement of glucose levels mainly in vivo. In addition to developing a system that is linear over the physiological range another goal was to develop a system that is biocompatible. For this purpose, we conducted the following standard blood-compatibility tests. 

Glutaraldehyde cross-linked with Enzyme electrode for the measurement of 182 ... 

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