JPH0442049A - Biosensor - Google Patents

Abstract

PURPOSE:To make it possible to achieve high accuracy and low cost by using a porous body on which organism-associated material such as enzyme and microorganism is supported as a measuring electrode, and forming it as a nonreturnable electrode. CONSTITUTION:A measuring electrode 2 is a porous body on which organism-associated material such as enzyme and microorganism is supported and which is conductive material or material that is treated as conductive material. The electrode is used as follows. Ribon- shaped carbon cloth is impregnated with solution wherein glucose oxidase that is enzyme and potassium ferricyanide that is an electron acceptor are dissolved in phosphoric acid, and the cloth is dried. when the adequate amount of sample liquid is dropped, the glucose in the sample liquid is absorbed into a water-absorbing macromolecular film 6 and reaches the measuring electrode 2. The sample reacts with the potassium ferricyanide by the action of the supporting glucose oxidase, and potassium ferrocyanide is formed. At this time, a positive specified voltage is applied on the measuring electrode, and a current based on the concentration of the formed potassium ferrocyanide is obtained. this current value corresponds to the concentration of the glucose. Since the porous body serves the role of the measuring electrode 2, the structure is simple, and expensive electrode material such as platinum is not required. The sensor is highly accurate and nonreturnable.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is used in the fields of food analysis, medical analysis, environmental analysis, etc., to quantify minute amounts of specific components by simply dropping a liquid sample onto the sensor unit. The present invention relates to a biosensor that can be used as a biosensor.

(Prior Art) Conventionally, a biosensor as shown in Fig. 3 was disclosed in Japanese Patent Application Laid-open No. 59-166852 as a method for measuring specific components in the environment or biological samples with high precision without complex pretreatment. It has been proposed in In this biosensor, a measuring electrode 8 and a counter electrode 9 made of platinum or the like having leads vA10 and 11, respectively, are embedded in an insulating substrate 7, and the upper part of these electrode systems is covered with a porous body 12 carrying an oxidoreductase. It is something. When the sample liquid is dropped onto the porous body, the oxidoreductase in the porous body is dissolved in the sample liquid, and an enzyme reaction proceeds with the substrate in the sample liquid to generate hydrogen peroxide. This hydrogen peroxide is electrochemically oxidized, and the substrate concentration in the sample liquid is determined from the oxidation current value obtained at this time.

(Problems to be Solved by the Invention) In a biosensor having such a configuration, the porous body only needs to be replaced after each measurement, which is convenient, but the electrode system requires a cleaning operation. Therefore, it is desirable that the electrode system, including the electrode system, be disposable for each measurement, but this has the problem that platinum electrodes and the like are expensive.

1.1 The purpose of the present invention is to solve the above problems and provide a highly accurate and inexpensive disposable biosensor.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a bioelectrode system comprising an insulating substrate and an electrode system provided on the insulating substrate and having at least a co-measuring electrode and a counter electrode. In the sensor, the measurement electrode is made of a porous body that is conductive or has been treated to be conductive, and supports biological substances such as enzymes and microorganisms.

Further, the measurement electrode carries an electron acceptor as well as biologically related substances such as enzymes and microorganisms.

(Function) In the biosensor of the present invention, the measurement electrode and biologically related substances such as enzymes and microorganisms are made into an integral structure as described above, so that the sample liquid can be dropped directly onto the electrode part and the required amount can be applied to the image electrode part. Substrate concentration can be easily measured by applying voltage. Since biological substances exist inside the porous body that also serves as an electrode, and the contact area between the substance and the electrode is large, changes in the concentration of biological substances can be quickly detected and high sensor output can be obtained. .

(Example) Hereinafter, a case of a glucose sensor will be described as an example of the present invention. FIG. 1 is a front view showing the configuration of one embodiment, and FIG. 2 is a cross-sectional view taken along the line AA. 1 is an insulating substrate, 2 and 3 are a measurement electrode and a counter electrode, respectively, which are arranged in a recess provided in the insulating substrate 1. Measuring electrode 2 is a ribbon-shaped carbon cloth impregnated with glucose oxidase (1000 units) as an enzyme and 500 mg of potassium ferricyanide as an electron acceptor dissolved in phosphate buffer 1- of p) 17.0. , and use this after drying. Through such treatment, the measurement electrode 2 serves as both an electrode and an enzyme immobilization layer. The counter electrode 3 is made of ribbon-like carbon cloth, graphite, or the like.

4 and 5 are electrical connection terminals for the measurement electrode 2 and the counter electrode 3, respectively, which are provided on the surface of the insulating substrate 10 by printed wiring, and are connected to the picture electrode by a conductive adhesive. The connection part is covered with water-resistant resin to protect it from water. 6 is a water-absorbing polymer film in which an aqueous water-absorbing polymer solution (for example, 0.5% carboxymethyl cellulose) is applied to the electrode portion and dried.

The glucose sensor configured as described above is used in the following method. Quantitate the sample solution (e.g. approximately 30μ7) and drop it onto the electrode section. After 1 minute of dropping, apply the sample solution to the measuring electrode at a temperature of +70% relative to the counter electrode.
A voltage of 0 mV is applied, and the current (oxidation current) value is measured after a certain period of time. After the glucose in the sample liquid is dropped, it is quickly absorbed by the water-absorbing polymer membrane 6 and reaches the electrode section.

Glucose that has reached the measurement electrode 2 reacts with potassium ferricyanide due to the action of glucose oxidase carried on the electrode, and potassium ferrocyanide is produced.Therefore, by applying a constant voltage of 10 to the measurement electrode 2 as described above, A current (oxidation current) based on the generated potassium ferrocyanide concentration is obtained, and this current value corresponds to the glucose concentration. Therefore, by calibrating the characteristics of glucose concentration versus oxidation current in advance using a glucose standard solution, it becomes possible to measure the glucose concentration in the sample solution.

In addition, if there is enough dissolved oxygen in the sample solution,
The use of the electron acceptor (potassium ferricyanide) used in the above examples can be omitted. That is, in that case, hydrogen peroxide produced by an enzymatic reaction is oxidized on the electrode (
In this case, apply a voltage of +900 vsV to measurement pole 2)
The oxidation current value will be measured.

(Effect of the invention) As explained above, in the biosensor of the present invention,
The structure is extremely simple because the porous body supporting bio-related substances such as enzymes and microorganisms also serves as the measurement electrode, and as there is no need for expensive electrode materials such as platinum, it is possible to reduce costs and achieve high accuracy. However, a biosensor suitable as a disposable type can be obtained.

In particular, when highly accurate measurement is required, a highly accurate biosensor can be obtained by providing a so-called reference electrode as a third electrode in addition to the measuring electrode 2 and the counter electrode 3 in parallel with the picture electrode.

In addition, by impregnating the measurement electrode 2 with a water-absorbing polymer material along with enzymes, biological substances such as microorganisms, and electron acceptors,
The sample solution can be introduced more effectively and measurements can be performed more quickly.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the configuration of an embodiment of the present invention;
FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 3 is a longitudinal sectional view of a conventional biosensor. 1.7... Insulating substrate 2.8... Measuring electrode 3.9... Counter electrode 4.5... Terminal 6... Water-absorbing polymer film 10.11... Lead wire 12. ... Porous material containing enzyme patent applicant New Japan Radio Co., Ltd.

Claims (1)

[Scope of Claims] 1. A biosensor comprising an insulating substrate and an electrode system provided on the insulating substrate and having at least a co-measuring electrode and a counter electrode, wherein the measuring electrode is used to measure enzymes, microorganisms, etc. A biosensor comprising a porous body that is electrically conductive or has been treated to be electrically conductive and that supports a biologically related substance. 2. The biosensor according to claim 1, wherein the measuring electrode is made of a porous body that is conductive or has been treated to be conductive, and also carries an electron acceptor as well as biologically related substances such as enzymes and microorganisms. sensor.