JPS6275344A - Biosensor - Google Patents

Abstract

PURPOSE:To keep the electrode surface thoroughly wet even with a reduction in amount of blood sampled, by arranging three electrodes of measuring electrode, counter electrode and reference electrode in a triangular position relationship. CONSTITUTION:A circular groove 12 is formed on an upper end face of a cylindrical insulating substrate 11 made of a polyvinyl chloride resin and an ABS resin. Electrodes made of platinum are buried so as to be exposed in the groove 12. These electrodes each make up an electrode section 6 which is provided with an electrode system having a measuring electrode 7, a counter electrode 8 and a reference electrode 9. Then, three electrodes are arranged in a triangle. A cut groove 10 is so arranged as to facilitate the escaping of air in the groove 12 to output when a reaction liquid stays in the groove 12. A chip 5 comprising a triple laminate layer of a reaction layer 1, a filtration layer 2 and a liquid retaining layer 3 held with a frame body 3 is placed covering the electrode section 6. The triangular arrangement of three electrodes on the top of the electrode section 6 helps reduce the outer diameter of the electrode section 6 and the inner diameter of the frame body 4 of the chip 5 thereby ensuring accurate wetting of the three electrodes with a reaction liquid with a small amount of blood dripping to the chip 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a biosensor that detects a specific component in a biological sample, and particularly relates to an improvement in the installation position of a detection electrode, and is widely used in the medical field, food engineering, etc. It is applicable.

BACKGROUND ART Conventionally, a glucose sensor known as this type of sensor had a configuration as shown in FIG. In FIG. 3, 1 is a reaction layer, 2 is a retraction layer, 3 is a liquid retaining layer, and 4 is a frame that holds the periphery of these three layers. 6 shows a chip constructed in this manner. 6 is a cylindrical electrode portion having an outer diameter smaller than the inner diameter of the frame 4;
Measurement electrode 7, counter electrode 8, and reference electrode 9 are exposed on the top surface 01
Reference numeral 1 denotes an insulating base through which the three electrodes mentioned above pass.

A groove 10 is provided in the exposed portion of the electrode. FIG. 4 shows a perspective view of this electrode section.

When a blood sample is dropped onto the chip from the top, the reaction liquid first advances in the reaction layer 1, and the reaction liquid is filtered out (2) to remove solid components such as red blood cells and platelets in the reaction liquid that interfere with the reaction of the measurement electrode. removed. Furthermore, the reaction solution is added to the liquid retaining layer 3.
absorbed into. This liquid retaining layer 3 allows for prompt filtration. The reaction liquid transferred to the liquid retaining layer 3 filled the exposed grooves 10 of the three electrodes of the cylindrical electrode part 6, and this reaction liquid was detected by electrode reaction.

Problems to be Solved by the Invention However, with such a conventional structure, there is a problem that unless the amount of sample blood is large, the measurement electrode will not get wet and measurement will not be possible.

The reason for this is that the measurement electrode, counter electrode, and reference electrode are arranged in a straight line. Therefore, the inner diameter of the chip frame became large, and a large amount of sample blood was required to wet the upper surfaces of the measurement electrode, counter electrode, and reference electrode with the reaction liquid. In order to reduce the exposed area of the electrodes, the inner diameter of the chip frame can also be reduced by shortening the diameter of the exposed electrodes or shortening the interval. However, reducing the area of the electrode increases the measurement error, and the thickness of the electrode is limited to one diameter. On the other hand, there is a limit to making the electrode spacing small in terms of electrode production, and it is up to 0.6 IflI.

The present invention solves the problem of poor wetting of the electrode surface when the sample blood volume is not large. By arranging three electrodes, the measuring electrode, the counter electrode, and the reference electrode in a triangular positional relationship, The purpose of this is to sufficiently wet the electrode surface even if the sample blood volume is reduced by making the chip container smaller. In this method, the three electrodes exposed on the top surface of the electrode section are arranged in a triangular manner, the outer diameter of the top surface of the electrode section is made small, and the inner diameter of the chip frame placed on the electrode section is made small. Even if the amount of blood dropped is reduced, the three electrodes on the upper surface of the electrode section are reliably wetted with the reaction liquid.

Function: With such an electrode configuration, the area of the top surface of the electrode section containing the three electrodes is small, so the tip can also be small, and even a small amount of sample blood can sufficiently wet the three electrodes.

EXAMPLE In the following, the present invention will be explained using a glucose sensor as a biosensor. Fig. 1 is a perspective view of an electrode section of an embodiment of the present invention, and Fig. 2 is a diagram of a glucose sensor using the same electrode section. Figure 3 shows a cross-sectional view of the embodiment.

A circular groove 12 with a depth of 0.1 ff++ is formed in the upper end surface of a cylindrical insulating substrate 11 made of polyvinyl chloride resin or ABS resin, and an electrode made of platinum is buried so as to be exposed in this groove. 7, 8.9 are measurement poles, respectively.
It is the opposite pole, the reference pole. A feature of the present invention is that these three electrodes are arranged in a triangle. The notched groove 10 is provided so that when the reaction liquid accumulates in the circular groove 12, air within the groove 12 can easily escape to the outside. The diameter of platinum is approximately 1m
+a, and the interval between each electrode is 0.5 mm. Further, the outer diameter of the electrode portion 6 is 3rmn. Note that conventionally, the outer diameter of the electrode part was 5 mm.

A chip 5 consisting of a three-layer stack of a reaction layer 1, a cavity 2, and a liquid retaining layer 3 held by a frame 4 is placed so as to cover the electrode section 6. The glucose sensor of this example used glucose oxidase as an oxidoreductase and potassium ferricyanide as an oxidized dye conjugated with the oxidoreductase. The reaction layer 1 is made of a nonwoven pulp fabric, and supports the above-mentioned glucose oxidase and potassium ferricyanide fine crystals at a high density. Filter exit 2 has a hole diameter of 11Ixn
It is made of a porous polycarbonate membrane that removes solid components such as red blood cells from blood. The liquid retaining layer 3 was made of hydrophilic rayon paper.

The inner diameter of the frame 4 of the chip 5 of the present invention is about 4 mm, which is smaller than the conventional 6-gourd.

The operating method of this glucose sensor will be explained based on FIG. 2. 10 μm of blood is added to the reaction layer 1 as a sample. Drip. When the dripped glucose in the blood is oxidized by glucose oxidase supported on the reaction layer, potassium ferricyanide is reduced by an enzyme-dye co-reaction, and potassium ferrocyanide is produced. The reacted blood then passes through a polycarbonate filter 2.

As it passes through, large solid components such as red blood cells are filtered out. After 5 filtration, the reaction solution is retained in the liquid retaining layer 3 of hydrophilic rayon paper. Furthermore, the reaction liquid moves from the liquid retaining layer to the groove 12 where the three triangular electrodes on the top surface of the electrode section are exposed, and the distance between the three electrodes is narrower, so that the distance between the three electrodes is 10μ! The electrode surface can be sufficiently wetted with the reaction solution. Note that the conventional structure in which electrodes are arranged in a straight line requires a reaction solution of 30 p13 or more. The reaction solution on the electrode detects the glucose concentration through an electrochemical reaction. The method is to change the voltage of the measuring electrode 7 from 0 to +o, 1■ in a sawtooth pattern based on the reference electrode 8.
．． Change at 1v/sec. Potassium ferrocyanide in the reaction solution is oxidized by sweeping the voltage of the measurement electrode, and the oxidation current at that time is measured.

This oxidation current is proportional to the amount of change in the pigment, making it possible to detect the concentration of glucose.

As described above, in the conventional linear array electrode structure, 30 μl or more of the reaction liquid was required to wet the electrode surface, but in the present invention, the electrode surface can be sufficiently wetted with 10 μl of the reaction liquid.

Effects of the Invention As described above, according to the present invention, even if the blood sample to be dropped is small, it can wet the exposed electrode surface arranged in a triangular shape, and the glucose concentration can be detected by electrochemical measurement. .

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an electrode section of a biosensor in an embodiment of the present invention, FIG. 2 is a cross-sectional view of a biosensor using the same electrode section, FIG. 3 is a cross-sectional view of a conventional biosensor, and FIG.
The figure is a perspective view of the electrode section. 1... Reaction layer, 4... Frame, 5...
...Chip, 6...Electrode section, 7...
Measuring electrode, 8...Counter electrode, 9...Reference electrode,
1o... Notch groove, 11... Base body, 12
・・・・・・Circular groove. Name of agent: Patent attorney Toshio Nakao and 1 other person7-
--JII Teikoku Otsu-Ichiden Hatsumyuko 11-m-Base figure 3

Claims (1)

[Claims] A biosensor in which a chip having a reaction layer carrying an oxidoreductase and an oxidized dye conjugated with the enzyme is placed on an electrode part that has an electrode system consisting of a measurement electrode, a counter electrode, and a reference electrode on an insulating substrate. The biosensor is characterized in that the measurement electrode, the counter electrode, and the reference electrode are in a triangular positional relationship.