Chemical glucose sensors

Entrapment of biochemically reactive molecules into conductive polymer substrates is being used to develop electrochemical biosensors (212). This has proven especially useful for the incorporation of enzymes that retain their specific chemical reactivity. Electropolymerization of pyrrole in an aqueous solution containing glucose oxidase (GO) leads to a polypyrrole in which the GO enzyme is co-deposited with the polymer. These polymer-entrapped GO electrodes have been used as glucose sensors. A direct relationship is seen between the electrode response and the glucose concentration in the solution which was analyzed with a typical measurement taking between 20 to 40 s. 

In the area of consumer products, amperometric glucose sensors hold high potential. Industrially, process monitors for the manufacture of consumer chemicals are under development. However, replacement of defective reference electrodes, which in a laboratory environment may be trivial, may be prohibitively difficult m vivo or in an industrial process environment. 

Several biosensors are commercially available. One of the most useful is the glucose sensor. The standard sensor determines glucose concentration based on the glucose oxidase enzyme. The chemical reaction for oxidation of glucose is ... 

Figure 3.12 — Interfacing of a fermenter to an FI system. The fermenter medium is continuously recycled by a pump to the filter unit, from which the filtrate is guided to a small reservoir (500 /xL). The sample solution is aspirated through a dialyser, the acceptor stream of which is fed to the injector of the FIA system. The analyte content is assayed amperometrically by using the glucose sensor incorporating the enzyme-containing chemically modified electrode. (Reproduced from [86] with permission of Elsevier Science Publishers).

Figure 4. Chemical reactions involved in electrochemical glucose sensor.

Figure 30. Principle of the D-glucose sensor based on the Na /D-glucose cotransporter-embedded BLM (reprinted with permission from Anal. Chem. 1993, 65, 364. Copyright 1993 American Chemical Society).

Due to their unique properties, a large number of groups all over the world are working in the area of CNTs for diverse applications and the most important are development and fabrication of sensors and thermal protection for atmospheric re-entry of space vehicles. Gas and glucose sensors based on CNTs have been developed. Some American researchers have recently claimed that they have developed CNT-based sensors for the detection of chemical warfare agents [80]. 

Glucose sensors based on this electrochemistry are now commercially available. Furthermore, it seems likely that this concept will soon be expanded to other types of enzyme-based sensors. Hence, sensor development is proving to be one of the great success stories of the chemically modified electrode research area. 

Marvin JS, Hellinga HW. Engineering biosensors by introducing fluorescent allosteric signal transducers construction of a novel glucose sensor. Journal of the American Chemical Society 1998, 120, 7-11. 

Kerner W, Lindquist S-E, Pishko MV, Heller A. Amperometric glucose sensor containing glucose oxidase cross-linked in redox gels. In Turner APF, Alcock SJ (Eds), In Vivo Chemical Sensors Recent Developments. Cranfield Press, Cranfield UK, 1993. 

Figure 9.4 NO-releasing xerogel particle/polyurethane glucose sensor. Reprinted with permission from Ref. 41. Copyright 2004 American Chemical Society.

In conclusion, a ferrocene-mediated glucose sensor was constructed by all-chemical means. They are easily and quickly constructed (<2 h) and show excellent linearity and stability. Also, this construction method is applicable to any graphite electrode, regardless of shape or size. Future work will focus on applying electron mediators to ultramicrobiosensors. 

Although not an ion, glucose can be detected by virtue of an MIP-derived ion. The pH electrode is simply an ISE for H". Glass and ion-selective field effect transistors pH electrodes are the best characterised and the most successful ISEs. Many sensors employ chemical reactions to produce H" or OH ions and employ pH electrodes for signal transduction. An imprinted sensor based on this approach is the glucose sensor produced by Arnold s group [10]. This polymer employs a metal ion (Cu " ) in the imprinted site and makes use of the metal s... 

Flexibility of the chemical structure which can be easily modified as required by the formation of blends or composites as demonstrated in pesticides and glucose sensors [100-102],... 

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