JPH07104316B2 - Biosensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a biosensor capable of rapidly and easily quantifying a specific component in various samples.

2. Description of the Related Art In recent years, biosensors that measure a specific component in a sample by linking an enzyme reaction and an electrode reaction have been used.

The conventional biosensor will be described below. FIG. 3 is a sectional view of a conventional biosensor, 12 is an insulating substrate,
Reference numerals 13 and 14 are a measurement electrode and a counter electrode embedded in an insulating substrate, respectively. 16 is an adhesive structure installed on the electrode part via an insulating layer 15, and 17 and 18 are a liquid retaining layer and an overlayer fixed on the adhesive structure 16, and the liquid retaining layer has a strip shape. Cellulose paper is used, and a porous polycarbonate membrane with a thickness of 10 μm is used for the overlayer. 19 is a holding frame, 20 and 21 are a reaction layer and a developing layer fixed in the holding frame 19, the reaction layer carrying a redox enzyme and a conjugated electron acceptor in the porous body as a carrier, respectively, in the developing layer Cellulose woven fabric is used.

The operation of the biosensor configured as above will be described below. When the sample solution is dropped from the upper part, first, the sample solution spreads rapidly in the developing layer 21, and then the solution drops to the reaction layer 20. In the reaction layer, with specific components in the sample solution,
The redox reaction proceeds between the redox enzyme and the electron acceptor in the reaction layer, and the electron acceptor is reduced. The reduction amount of the electron acceptor generated at this time is proportional to the amount of the specific component in the sample solution. After completion of the reaction, the sample solution has macromolecules that interfere with the measurement removed in the overlayer 18, and then passes through the liquid retention layer 17 and then on the electrode.
It descends to 13,14. On the electrode, the reduced electron acceptor was oxidized by the electrode reaction, and the amount of the specific component in the sample solution was measured from the oxidation current value.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described conventional configuration, the dispersion of the sample liquid that has dropped onto the electrode is not uniform, and leakage of the electrode solution or residual bubbles is likely to occur, and the area of the electrode varies. To do.

In addition, the sample liquid is dispersed even in areas other than the electrode portion, and it is difficult to form a liquid film having a sufficient thickness on the electrode, which causes a variation in measured values.

The present invention solves the above-mentioned conventional problems, and by making the dispersion of the descending sample liquid uniform, it is possible to avoid residual wetting and residual air bubbles, and to form a liquid film layer with a sufficient thickness on the electrode. It is an object of the present invention to provide a biosensor that can obtain a stable measurement value by covering it.

Means for Solving the Problems In order to achieve this object, the biosensor of the present invention comprises a water-absorbing polymer having high dispersibility and a water-retaining polymer having high dispersibility between the electrode system and the reaction layer. Is used, the electrode system is covered with this layer, and the water-absorbing polymer having high dispersibility is positioned on the reaction layer side.

Action With this configuration, when the sample liquid that descends from the overlayer comes into contact with the liquid absorption layer, the liquid rapidly spreads evenly on the surface of the layer due to the action of the highly dispersible water-absorbing polymer, and penetrates into the layer. I will do it. Next, due to the action of the highly liquid-retaining water-absorbing polymer, the liquid is absorbed in the liquid-absorbing layer and forms a gel layer with high durability, and then the liquid in the water-absorbing state is retained without desorption. It In this way, by completely covering the electrode part with a gel layer having a stable liquid film thickness,
Since the interfering substances are prevented from adsorbing to the electrode and the electrode area during the measurement is kept constant, the measurement can be performed with high accuracy.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a sectional view of a biosensor according to an embodiment of the present invention. In FIG. 1, 1 is an insulating substrate, 2 is a measurement electrode, 3 is a counter electrode, 4 is an insulating layer, 5 is an adhesive structure, 6 is a liquid retaining layer, 7 is an overlayer, 8 is a holding frame, 9
Is a reaction layer and 10 is a spreading layer, which have the same structure as the conventional example. Reference numeral 11 denotes a liquid-absorbing layer, which is a feature of the present invention, and is formed of a layer in which carboxymethyl cellulose is mixed as a water-absorbing polymer having a high liquid retention property and polyethylene oxide is mixed as a water-absorbing polymer having a high dispersibility. The liquid absorption layer 11
Preparation of carboxymethylcellulose 0.5% aqueous solution 1
0 μ is directly applied on the electrode, dried at 45 ° C. for 30 minutes, 10 μ of 0.2% aqueous solution of polyethylene oxide is further applied, and similarly dried.

The operation of the biosensor having the above-described structure according to this embodiment will be described below. First, when the sample solution is dropped onto the upper part of the sensor in FIG. 1, potassium ferrocyanide is produced by the reaction of glucose in the sample solution with glucose oxidase and potassium ferricyanide in the reaction layer 9 after passing through the developing layer 10 as in the conventional example. To do. Further, when the sample liquid that has passed through the overlayer 7 drops to the liquid absorption layer 11, first the liquid absorption layer 11 is first operated by the action of the highly dispersible polyethylene oxide.
After being quickly and uniformly dispersed on the surface of the liquid, and then permeating into the liquid-absorbent layer, the liquid is sufficiently retained by the action of the highly liquid-retaining carboxymethyl cellulose so that it adheres to the electrode and
A gel layer of the sample solution having a uniform viscosity distribution, which completely covers a few layers, is formed. In this state, the glucose concentration in the sample can be detected by measuring the oxidation current value of the reaction product potassium ferrocyanide with the electrode systems 2 and 3.

FIG. 2 shows the relationship between the oxidation current value measured by the biosensor and the glucose concentration. A is a layer having a mixture of two kinds of water-absorbent polymer carboxymethyl cellulose and polyethylene oxide as the liquid absorbing layer of the present invention, and B is a layer having no liquid absorbing layer of the conventional example.

The measurement was performed 10 times at each glucose concentration, and the average value and the range of variation are shown in the figure. From this figure, A
Shows that the current value and glucose concentration show very good linearity up to 600 mg / dl, and stable measured values with little variation are obtained even at each glucose concentration. On the other hand, in the conventional example B, the linearity shows good linearity up to 600 mg / dl, but it can be seen that the variation in the measured values at each glucose concentration is considerably large.
Furthermore, after measuring the chip with a particularly small response value and disassembling the chip and observing the state on the electrode, it was confirmed that bubbles were generated on the electrode due to insufficient wetting.

As described above, according to the present embodiment, the amount of glucose in a sample can be accurately measured by mixing and using two kinds of water-absorbing polymers of carboxymethyl cellulose and polyethylene oxide in the liquid-absorbent layer. it can. this is,
It is considered that a uniform gel layer of the sample reaction solution can be formed on the electrode by mixing the water-absorbing polymers having different properties such as dispersibility and liquid retention.

Although polyethylene oxide is used as the highly dispersible water-absorbing polymer in this embodiment, polyvinyl pyrrolidone or polyvinyl alcohol may be used instead. Also,
As the highly liquid-retaining water-absorbing polymer, sodium polyacrylate, starch or the like may be used in addition to carboxymethyl cellulose of this embodiment. Each of the above-mentioned polymers is water-soluble, and a polymer aqueous solution can be easily prepared, and the necessary coating amount can be easily adjusted by coating an appropriate amount of the aqueous solution of the appropriate concentration.

Regarding the location of the liquid-absorbent layer, in this example, the electrode was coated with a mixed layer of a highly dispersible water-absorbing polymer and a highly liquid-retaining water-absorbing polymer, but each was separated into a single layer of polymer, The dispersible water-absorbent polymer layer may be provided in the reaction liquid descending passage such as the overlayer, the liquid-retaining layer, or the side surface of the adhesive structure, and the highly liquid-retainable water-absorbent polymer layer may be provided on the electrode. Further, in this case, since the inducing property of the falling liquid from the overmembrane to the electrode portion is increased, a simple structure in which the liquid retaining layer is removed becomes possible.

Regarding the place where glucose oxidase is carried, in the present embodiment, the reaction layer 9 in FIG. 1 is carried together with potassium ferricyanide, but the new structure is that the electrode is formed by the action of the highly liquid-retaining water-absorbing polymer in the liquid-absorbing layer. Because it protects
Glucose oxidase can be directly supported on the liquid absorption layer 11 on the electrode. In this configuration, glucose oxidase reacts with a macromolecule, for example, the perfusate from which solid components in blood are separated, so that the effect of enzyme inhibition by the macromolecule is removed, and the supported enzyme effectively contributes to the reaction. In addition, it becomes possible to carry out the measurement with a smaller amount than the conventional amount.

EFFECTS OF THE INVENTION As described above, according to the present invention, an electrode system including at least a measurement electrode and a counter electrode is subjected to a redox reaction via an oxidoreductase and an electron acceptor so that the concentration of a specific substance is electrochemically measured in the electrode system. A biosensor having a mechanism for detecting, in which a layer using a water-absorbing polymer having a high dispersibility and a liquid-retaining property is disposed between the electrode system and the reaction layer, and in this layer, By covering the electrode system and positioning a highly dispersible water-absorbing polymer on the reaction layer side, it is possible to cover the electrode with a uniform gel layer of the sample reaction solution, which improves the measurement accuracy. Is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a biosensor in one embodiment of the present invention, FIG. 2 is a response characteristic diagram of the biosensor, and FIG. 3 is a sectional view of a biosensor of a conventional example. 1 ... Insulating substrate, 2 ... Measuring electrode, 3 ... Counter electrode, 4 ...
Insulating layer, 6 ... Liquid retaining layer, 7 ... Overlayer, 9 ... Reaction layer,
11 ... Liquid absorption layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyomi Komatsu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Shiro Nankai 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Mariko Kawaguri 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. An electrode system comprising at least a measurement electrode and a counter electrode, and a reaction layer carrying an oxidoreductase and an electron acceptor.
A biosensor having a mechanism for electrochemically detecting the concentration of a specific substance in the electrode system by an oxidation-reduction reaction via an oxidoreductase and an electron acceptor, the dispersibility between the electrode system and a reaction layer. A layer (absorbent layer) using a highly absorbent polymer and a highly liquid-retaining polymer is placed, and the electrode system is covered with this layer and the highly dispersible polymer is reacted. A biosensor located on the layer side. 2. In a layer using a water-absorbing polymer having a high liquid retention property and a water-absorbing polymer having a high dispersibility, is each single layer composed of each polymer disposed at different positions on the electrode? Or the biosensor according to claim 1, which is a layer in which the two types of polymers are mixed.