Sensor for glucose

Sittampalam and Wilson described the preparation and use of an amperometric sensor for glucose. " The sensor is calibrated by measuring the steady-state current when it is immersed in standard solutions of glucose. A typical set of calibration data is shown in the following table. 

Sensors for glucose are most important and have received most attention. The preferred format still is based on the use of glucose oxidase (GOx). Other glucose biosensors using immobilized glucose oxidase132 134 or a pH... 

D. Gough, J. Lucisano, and P. Tse, Two-dimensional enzyme electrode sensor for glucose. Anal. Chem. 57, 2351-2357 (1985). 

Apart from electron promoters a large number of electron mediators have long been investigated to make redox enzymes electrochemically active on the electrode surface. In the line of this research electron mediators such as ferrocene and its derivatives have successfully been incorporated into an enzyme sensor for glucose [3]. The mediator was easily accessible to both glucose oxidase and an electron tunnelling pathway could be formed within the enzyme molecule [4]. The present authors [5,6] and Lowe and Foulds [7] used a conducting polymer as a molecular wire to connect a redox enzyme molecule to the electrode surface. 

Appropriate combinations of boronic acid and fluorophores lead to a remarkable class of fluorescent sensors of saccharides (Shinkai et ah, 1997, 2000, 2001). The concept of PET (photoinduced electron transfer) sensors (see Section 10.2.2.5 and Figure 10.7) has been introduced successfully as follows a boronic acid moiety is combined intramolecularly with an aminomethylfluorophore consequently, PET from the amine to the fluorophore causes fluorescence quenching of the latter. In the presence of a bound saccharide, the interaction between boronic acid and amine is intensified, which inhibits the PET process (Figure 10.42). S-l is an outstanding example of a selective sensor for glucose based on this concept (see Box 10.4). 

J. S. Schultz, S. Mansouri, and I. Goldstein, Affinity sensor A new technique for developing implantable sensors for glucose and other metabolites, Diabetes Care 5, 245-253 (1982). 

Koschinsky T, Heinemann L. Sensors for glucose monitoring technical and clinical aspects. Diabetes Metab Res Rev 2001 17(2) 113-23. 

Figure 1. Schematic diagram of the microbial electrode sensor for glucose.

Wilson GS, Zhang Y, Reach G, Moatti-Sirat D, Poitout V, Thevenot DR, Lemmonnier F, Klein J. Progress toward the development of an implantable sensor for glucose. Clinical Chemistry 1992, 38, 1613-1617. 

Ballerstadt R, Polak A, Beuhler A, Frye J. In vitro long-term performance study of a near-infrared fluorescence affinity sensor for glucose monitoring. Biosensors Bioelectronics 2004, 19, 905-914. 

Phillips MD, James TD. Boronic acid based modular fluorescent sensors for glucose. Journal of Fluorescence 2004, 14, 549-559. 

Ballerstadt R, Gowda A, McNichols R. Fluorescence resonance energy transfer-based near-infrared fluorescence sensor for glucose monitoring. Diabetes Technology Therapeutics 2004, 6, 191-200. 

Ballerstadt R, Kholodnykh A, Evans C, Boretsky A, Motamedi M, Gowda A, McNichols R. Affinity-based turbidity sensor for glucose monitoring by optical coherence tomography toward the development of an implantable sensor. Analytical Chemistry 2007, 79, 6965-6974. 

Fig. 2. Photograph of a flexible polyimide-based in vivo sensor for glucose, lactate and pH measurements...

Enzyme sensors can measure analytes that are the substrates of enzymatic reactions. Thermometric sensors can measure the heat produced by the enzyme reaction [31], while optical or electrochemical transducers measure a product produced or cofactor consumed in the reaction. For example, several urea sensors are based on the hydrolysis of urea by urease producing ammonia, which can be detected by an ammonium ion-selective ISE or ISFET [48] or a conductometric device [49]. Amperometric enzyme sensors are based on the measurement of an electroactive product or cofactor [50] an example is the glucose oxidase-based sensor for glucose, the most commercially successful biosensor. Enzymes are incorporated in amperometric sensors in functionalised monolayers [51], entrapped in polymers [52], carbon pastes [53] or zeolites [54]. Other catalytic biological systems such as micro-organisms, abzymes, organelles and tissue slices have also been combined with electrochemical transducers. 

To date various polymeric electron transfer systems have been incorporated to enzyme sensors for glucose, lactate, aldose, pyruvate, ascorbate, choline, acetylcholine, cholesterol, formaldehyde, phenoUcs, nitrate, sulfite and histamine. 

Sun, X. Y. Liu, B. Jiang, Y. B. An Extremely Sensitive Monoboronic Acid Based Fluorescent Sensor for Glucose. Anal. Chim. Acta 2004, 515, 285-290... 

In the early stage of Investigation, GOD was entrapped In a thin membrane of polyacrylamide gel. The gel membrane provided poor permeability to substrates, which resulted In a slow sensor response. Great effort has been made to Improve the membrane matrix (80-82). The response time of the sensor has been reduced to less than 10 seconds (82). Some of these enzyme sensors for glucose have been commercialized. 

---