Oxygen glucose sensors

Figure 4.5 A planar 1.2 cm diameter oxygen-glucose sensor array. The small (125 pm) dots are the oxygen electrodes, the ribbon-like counter electrode is visible, and the Ag reference electrodes can be seen. Four of the oxygen electrodes have circular pockets of glucose oxidase integrated into the overlying membrane.

Trettnak / Wolfbeis 1988 dual glucose sensor with compensation for oxygen supply... 

Rosenweig Z., Kopelman R., Analytical properties of miniaturized oxygen and glucose sensors, Sensor Actuat B-Chem. 1996 35-36 475-483... 

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. 

Schmid et al. used the same principle to develop sensors to be incorporated into FI systems for the determination of ascorbic acid in fruit juices [38] and that of lactic acid in dairy products [39]. The membrane used in both applications consisted of decacyclene dissolved in silicone rubber that was treated similarly as the membrane in glucose sensors (Fig. 3.4.B). The oxygen optrode was coated with a sheet of carbon black as optical insulation in order to protect it from ambient light or intrinsic sample fluorescence. Ascorbic acid oxidase or lactic acid oxidase was immobilized by adsorbing it onto carbon black and cross-linking it with glutaraldehyde. The FI system automatically buffered and diluted the food samples, thereby protecting the biosensor from a low pH and interferents. 

Fig. 2.15 Theoretical (open points) and experimental (full points) calibration curve for glucose sensor for (a) 100% oxygen in 0.2 mM buffer, (b) 25% oxygen and 0.2 mM buffer, and (c) 100% oxygen and 1 mM buffer (adapted from Caras et al., 1985b, p. 1921)...

Fig. 7.13 Dual glucose sensor based on two oxygen electrodes, one (a) covered with active glucose oxidase and other (b) with deactivated glucose oxidase...

Fig. 7.14 Two-dimensional, cylindrical glucose sensor. Glucose diffuses to the sensor only in direction z whereas oxygen can reach the electrode by diffusion through the walls of the cylinder of length L...

In the previous papers(12,13), we reported on the vessel access type, i.e. tubular type, glucose sensor. It consisted of a glucose electrode system with a GOX enzyme immobilized Nylon membrane and a glucose semipermeable membrane, and a reference oxygen electrode system. The sensor could directly measure up to 700 mg/dl of BGL in an arterial blood stream when it was placed into an external A-V shunt. This sensor, however, has some problems such as thrombus during in vivo testing without heparin and clinical complexity associated with implanting the sensor in a blood stream. 

Figure 1. Schematic diagram of oxygen electrode systems for subcutaenous type glucose sensors.

The calibration curves of the glucose sensor I are shown in Figure 6 and the linear range of the curves gradually decrease with decreasing of the oxygen tension from 21 to 5 %. 

Glucose sensors II and HI were prepared from the semipermeable membrane of PMSP, poly(1-trimethylsilyl-l-propyne), which has 4 times the oxygen permeability compared with that of FEP membrane. The response properties of sensor H, using a PMSP membrane with 25 Um diameter pinhole, were almost similer to that of the sensor I, so that their calibration curves were not presented in this paper. 

Figure 5. Dynamic response curves of glucose sensor I under various oxygen tensions (%)...

Figure 1.1 Multilayer sensor structure showing control of oxygen, glucose, and electroactive interferences.

USE OF OXYGEN SENSORS AS A SURROGATE GLUCOSE SENSOR FOR IN VIVO TESTING AND IMPORTANT ISSUES RELATED TO IN VITRO SENSOR CALIBRATION... 

---