JPS5885147A - Glucose sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor of high accuracy and durability by impregnating albumin in a porous thin film that has electrical conductivity and superposing it on a glucose oxidase fixed electrode to fix as one body the glucose oxidase and albumin at the same time. CONSTITUTION:A Pt electrode layer 3 is formed by spattering or other method on one side of a porous film (pore diameter is about 2,000Angstrom shown by enlarged white section) such as poly-carbonate and so on, and into the layer 3 glucose oxidase 4 is impregnated. A Pt electrode 5 is formed on another porous film, and albumin 6 is impregnated into it. After both films are stacked with the electrodes 3 and 5 facing outside and they are set on an electrode holder, both films are fixed at the same time in the glutaraldehyde vapor, and an enzyme electrode 7 that has a glucose oxidase electrode 1 and an obstructing substance removing electrode 2 for a specimen liquid is fixed on the main body 9 by means of an outer mantle pipe 8 with the electrode 1 positioned inside of the holder. With this arrangement quick, and exact measurement that is continuous can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glucose oxidase immobilized electrode that can rapidly and accurately measure the concentration of a substrate (particularly glucose) that undergoes the specific catalytic action of an enzyme, and can be used continuously.

The reaction in the glucose sensor is expressed as follows (11, (2+
As shown in the formula. Glucose, which is a substrate, is oxidized by the action of glucose oxidase to generate H2O2, and then this H2O2 is oxidized using a platinum electrode, and the concentration of glucose is detected from the oxidation current value obtained.

Gluconolactone + H2O2...(1) H2O2
-n2H+2e-1-02・・・・・・・・・・・・(2
) When measuring the concentration of glucose by applying this principle,
Coexisting substances contained in the specimen and directly electrochemically oxidized on the platinum electrode pose a problem. For example, when measuring glucose in blood, uric acid, ascorbic acid, etc. may be used. Since these are oxidized at the same time as H2O2 is oxidized in the 021 formula, they increase the current value and give an error.

As a countermeasure against such interfering substances, attempts have been made to install a membrane made of cellulose acetate, silicone rubber, etc. in front of the immobilized enzyme electrode to stop the interfering substances. However, the film made of cellulose acetate or silicone rubber interferes with contact with the substrate, resulting in a decrease in sensitivity and response speed.

Therefore, a method was attempted in which a porous thin film made of platinum was placed in front of the immobilized enzyme electrode and the interfering substances were removed by electrolysis. With this method, interfering substances could also be removed and good results were obtained in terms of sensitivity and response speed, but with continuous use, the sensitivity and response speed decreased. This is because a thin film for removing interfering substances is simply layered on the immobilized enzyme electrode, so there is a space between the two films, and it takes time for glucose to reach the electrode. Conceivable.

In the present invention, as a result of various improvements in the above-mentioned performance, a glucose sensor has been discovered that has good sensitivity and response speed, and maintains excellent performance even during continuous use. A feature of the present invention is that albumin is impregnated into a conductive porous thin film, which is superimposed on a glucose oxidase-immobilized electrode, and albumin and glucose oxidase are integrally immobilized with glutaraldehyde. This results in
Albumin and glucose oxidase are cross-linked by glutaraldehyde, and the electrode for removing interfering substances and the glucose oxidase-immobilized electrode are in close contact with each other, so that deterioration in sensitivity and response speed can be prevented even when used continuously. Furthermore, immobilized albumin itself can also help remove interfering substances and increase accuracy. It is necessary to set the amount of albumin immobilized on the conductive thin film to such an extent that it does not completely interfere with the diffusion of glucose.

The present invention will be explained below with reference to one embodiment thereof.

A polycarbonate porous membrane (diameter 10 mm) was used as a carrier for the immobilized electrode on glucose oxidizer and the interference substance removal membrane.
A platinum layer (thickness, several hundred to several thousand angstroms) was formed on one side of this film by sputtering to form an electrode. The first electrode was developed with glucose oxidase (100 μ/cc), and the second electrode was impregnated with albumin (10 μ/cc). The two membranes were placed on a stacked electrode holder with the platinum layer facing outward, and then fixed in glutaraldehyde vapor.

FIG. 1 shows an enlarged schematic cross-sectional view of the entire enzyme electrode after immobilization. 1 is a glucose oxidase immobilized electrode, which has a platinum layer 3 on the inside of the electrode.

Ihi 4 is glucose oxitase that remains in the pores of the membrane and between the two membranes. Reference numeral 2 denotes an electrode for removing interfering substances, which has a platinum layer 5 on the test liquid side. 6 shows the pores of the membrane and albumin immobilized between the membranes.

Cylindrical electrode boulder equipped with the thin film electrode described in ``2.''
The cross section and electrode system are schematically shown in Figure 2. In the figure, 7 is the enzyme electrode described above, which is attached to the main body 9 through the outer tube 8 so that 1 in FIG. 1 is inside the holder. The platinum layer 3 in FIG. 1 is in contact with the inner platinum lead 1o, and the platinum layer 6 is in contact with the outer platinum lead 11. Aqlm (JC) for glucose oxidase immobilized electrode
A β reference electrode 12 and a counter electrode 13 are arranged inside the electrode holder, and an Aq/AqCA reference electrode 14 and a counter electrode 15 for the electrode for removing interfering substances are arranged outside the electrode holder to form an electrode system. Further, the inside of the electrode holder is filled with an electrolytic solution 16.

The above electrode was immersed in a buffer solution of pH s, e, glucose was added, and its sensitivity and response speed were measured. In FIG. 3, mu is the response in the case of an electrode in which glucose oxidase and albumin are integrally immobilized according to the present invention. For comparison with humans, we prepared an electrode in which a porous thin film with a platinum layer was placed in front of a conventional glucose oxidase immobilized electrode. , 2 electrodes -1-
It was set at 0,6 V VS Muq/Aqcll and glucose was added to 2×1 o mol/l). In Figure 3, the horizontal axis is the time since glucose was added (sea).
, and the vertical axis is the current increase (lzA) relative to glucose.
It fully represents. Humans reached a steady state value in just 6 seconds, and the current increase (sensitivity) was also better than B and C.

Next, the same electrode was repeatedly used for cleaning and measurement, and the results are shown in FIG. 4. When the initial sensitivity of each of A, B, and C was set to 100, and the subsequent sensitivity was measured, the sensitivity of B and C decreased from around 8 o's, and the response speed (time at 1 when the current reaches a steady value) was associated with this. compared to
The system maintained almost its original performance until the 150s. The reason why the initial excellent performance can be maintained even during continuous use is because glucose oxidase and albumin are immobilized and both electrodes are in close contact with each other. Glucose oxidase and albumin are immobilized on each electrode, and in the boundary layer between both electrodes, glucose oxidase and albumin are cross-linked and immobilized together.

As described above, the glucose sensor according to the present invention has excellent performance in that it can quickly and accurately measure glucose concentration and can be used continuously.

[Brief explanation of the drawing]

Fig. 1 is an enlarged schematic cross-sectional view of an enzyme electrode of a glucose sensor that is an embodiment of the present invention, Fig. 2 is a schematic diagram showing the cross-section of the glucose sensor and the electrode system, and Fig. 3 shows the response of the glucose sensor to glucose. FIG. 4 is a diagram showing the relationship between continuous use and the response of the glucose sensor. 1...Glucose oxidase immobilization 1t&,
2... Interfering substance removal electrode, 3... Platinum layer, 4... Immobilized curcose oxidase, 6
...Platinum layer, 6 ... Immobilized albumin, 7 ... Enzyme electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 12 Figure 1113 Figure Length Answer Ren Mera (42c) 1h number of 4 sliding doors (tie)

Claims (1)

[Claims] A glucose sensor characterized in that a conductive thin film impregnated and immobilized with albumin is placed on the surface of a glucose oxidase immobilized electrode, and glucose oxidase and albumin are simultaneously immobilized integrally with glutaraldehyde.