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Biomolecules and Complex Biological Entities
Published in Simona Badilescu, Muthukumaran Packirisamy, BioMEMS, 2016
Simona Badilescu, Muthukumaran Packirisamy
The most widespread biosensor today is the glucose biosensor, used to measure the glucose concentration in blood. There are quite a few enzymes that could be used as glucose detectors. The following example shows the glucose enzyme reaction with glucose oxidase, one of the most stable enzymes for glucose detection. By using this enzymatic reaction, the glucose concentration is determined by measuring either the oxygen consumption or the hydrogen peroxide production. The presence of the second enzyme (catalase) enhances the first reaction by the decomposition of the hydrogen peroxide. Enzyme-based biosensors use semipermeable membranes. Target analytes diffuse toward the immobilized enzyme through this membrane. For example, L-glutamate oxidase is adsorbed onto a phosphatidylethanolamine-coated platinum electrode for the measurement of the neurotransmitter glutamate.15 The amperometric current due to oxidation of H2O2 is measured by a potentiostat. Various enzymatic biosensors for organophosphorous, carbamate pesticides, and other potentially harmful pollutants in the environment have been developed.16 These biosensors are based on the activity of the choline oxidase and the inhibition of cholinesterase enzymes by several toxic chemicals. Cholinesterases are important enzymes that hydrolyze acetylcoline in the nervous system. Enzyme-based biosensors will be described and discussed in Chapter 6. An example of using microfluidics to monitor cellular secretions by online fluorescence-based enzyme assay, as shown in Figure 3.43, is described in Clark et al.17
Development of choline biosensor using toluidine blue O as mediator
Published in Preparative Biochemistry & Biotechnology, 2020
Rüya Baskin, Elif (Aynaci) Koyuncu, Halit Arslan, Fatma Arslan
Choline is a product formed by the hydrolysis of acetylcholine with the acetylcholine esterase enzyme.[7] While choline oxidase (ChO) oxidizes choline to betaine, oxygen is reduced to H2O2 as a result of this reaction (Fig. 1).