JPS59151051A - Biocatalyst electrode - Google Patents

Abstract

PURPOSE:To increase the surface area of a biocatalyst electrode and to improve considerably the sensitivity in measurement by forming a composite plating layer consisting of a metallic layer dispersed therein with a granular material on the surface of a base metallic plate, forming a platinum metallic electrode on said layer and forming a biocatalyst film on the metallic layer. CONSTITUTION:A base body 1 of a conductive material such as copper or the like is electroplated in a plating bath incorporated therein with an insoluble and conductive granular material such as WC or the like together with an electrolyte of Ni, Au, Cu or the like alone or Pd-Ni, etc. to form a composite plating layer 2 dispersed therein with a granular material 2b in a metallic layer 2a. A metallic layer 3 is formed on the layer 2 by vapor deposition or plating of a platinum group metal. A biocatalyst film 5 of enzyme, etc. is then formed on the layer 3. The surface area of the film 5 is increased considerably by incorporating the granular material in the layer 2. The biocatalyst electrode having the sensitivity several times higher than that in the case of the smooth film 5 is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a biocatalytic electrode used for detecting substrate concentration, etc.

[Background technology]

In recent years, resource conservation and energy conservation have become one of the major issues in industrial manufacturing processes. As one solution to this problem, technology is being established to industrially utilize biocatalysts such as microorganisms and enzymes, which naturally catalyze chemical reactions very gently and quickly inside living organisms. . Because biocatalysts promote reactions under mild conditions of room temperature and pressure, they are not only energy-efficient compared to conventional chemical reaction processes, but they also cause pollution and noise problems and are harmful to the outside world. There are very few negative effects. In addition, when a biocatalyst is used, a process that conventionally required multiple reaction steps can now be completed with a single reaction step. However, biocatalysts such as microorganisms and enzymes are generally water-soluble;
Normally, the reaction is carried out with the biocatalyst dissolved in water, so after the reaction is complete, it is removed from the reaction system.
It was technically difficult to reuse it. Therefore, various methods have been proposed to immobilize the biocatalyst, such as making the biocatalyst insoluble in water by some means.

By fixing the biocatalyst, it has become possible to replace the previously used batch-type bioreactor with a continuous flow bioreactor and use the biocatalyst repeatedly. In addition, since the biocatalyst does not mix into the reaction solution,
The purity of the reaction product has been significantly improved. Moreover, biocatalysts utilize Kokichi, which has extremely high substrate specificity.
．． This has made it possible to create biosensors that detect the concentration of specific substances.

A biosensor generally includes a biocatalyst electrode having a biocatalyst film formed on the surface of the electrode body and a counter electrode. Biosensors combine changes in the concentration of substrates or products that occur with biological reactions with electrode reactions, and quantify changes in the concentration of substrates or products using an electrochemical method (debaine). Kokichi can analyze it. Furthermore, as mentioned above, biocatalysts have high substrate specificity, so even systems containing other components can be analyzed without having to perform sample separation and purification operations.

Furthermore, since biocatalysts carry out reactions rapidly, it is possible to amplify chemical components that are detected electrochemically, and even very dilute solutions of the components can be analyzed.

[Object of the Invention] An object of the present invention is to provide a biocatalyst electrode with high measurement sensitivity.

[Disclosure of the invention]

The inventors have developed an electrode body with a large surface area, rather than an electrode body with a flat surface and a small surface area, as in conventional biocatalytic electrodes that have been commonly used. Research has been conducted in an attempt to improve the measurement sensitivity of biocatalytic electrodes by increasing the number of active sites for electrode reactions. the result,
As the main body of the biocatalyst electrode, it is advisable to use one in which a composite plating layer consisting of granules and a metal layer is formed on the surface of a base material, and a platinum metal layer is further formed on the surface of the composite plating layer. This discovery led to the completion of this invention.

That is, the present invention provides a biocatalyst electrode in which a biocatalyst film is formed on the surface of an electrode body, the electrode body comprising a base material and a metal layer-granule composite plating layer formed on the surface of the base material. The gist of this invention is a biocatalytic electrode characterized by comprising a platinum metal layer formed on the surface of a composite plating layer. The present invention will be described in detail below.

As shown in FIG. 1, the biocatalytic electrode according to the present invention has particles 2b in a metal layer 2a on the surface of a base material 1.
Composite plating layer containing 2. It has an electrode body 4 in which a platinum metal layer 3 is further formed on the surface of the composite plating layer 20, and a biocatalyst film 5 is formed on the surface of the electrode body 4, that is, on the surface of the platinum metal layer 3. The surface of the electrode body 4 has many irregularities, and the surface area is extremely large. This is a problem for the following reasons. When composite plating is performed on the substrate 1 to form the composite plating layer 2, metal is deposited and fixed on the surface of the substrate 1, and the granules 2b are also fixed. Therefore,
The surface of the composite plating layer 2 has many irregularities. Therefore, when the white metal layer 3 is formed on the surface of this composite plating layer 2, the white metal layer 3
The surface becomes extremely uneven.

This biocatalyst electrode has a large surface area of the electrode main body 4, that is, a large active area for electrode reaction, and therefore has high measurement sensitivity.

Here, as the base material 1, various conductive materials such as copper are used. As the granules 2b included in the composite plating layer 2, at least one of metal oxides, carbides, nitrides, borides, fluorides, organic compounds, etc. is used. Therefore, it is preferable to use a highly conductive material such as WC. Further, the granules 2b are used when performing composite plating on the base material 1 to form the composite plating layer 2.
It is necessary to avoid exposure to plating solution. The metals included in the composite plating layer 2 include nickel (Nt) and gold (A
u) , copper (Cu) etc. are used alone,
Two or more types are sometimes used at the same time, such as a combination of palladium (Pd) and nickel. For the purpose of improving the performance of the biocatalyst electrode, the composite plating layer 2 may contain the granules 2b and other materials other than metal. For example, when the composite plating layer contains 2Vc nickel, phosphorus (P) may also be included.

Platinum metals include platinum (Pt) and palladium (P
d) At least one selected from rhodium (Rh), ruthenium (Ru), etc. is used. Conventionally, the electrode body was mostly made of platinum, but in the present invention, other platinum metals may be used as the material for the electrode body. The biocatalyst has an electrochemically detectable substance in its reaction system, and its type is not particularly limited.

Note that the composite plating layer is usually formed using an electroplating method. That is, the granules are suspended in a plating solution containing metal, and the base material and the counter electrode are immersed in this plating solution. Next, electrolysis is performed to simultaneously fix the metal and the granules to the surface of the base material. As a method for forming platinum edge metal on the composite plating layer, electroplating method, vacuum evaporation method, etc. are used.
Wet type.

Doesn't matter if it's a dry method. Since the composite plating layer has many irregularities on the surface and internal stress is generated in the precipitated white metal, the thickness of the white metal layer can be made relatively thick even if the white metal has poor adhesion. The method of forming the biocatalyst film on the surface of the electrode body is not particularly limited. For example, a biocatalyst film is formed by immersing the electrode body in a mixed solution containing a biocatalyst, paraformaldehyde, and albumin and then drying it, or by crosslinking the electrode body and the biocatalyst with a crosslinking agent.

〔Effect of the invention〕

The biocatalytic electrode according to the present invention includes an electrode body in which a composite plating layer containing granules and metal is formed on the surface of the base material, and a platinum metal layer is further formed on the surface of the composite plating layer. The sensitivity was high.

Next, Examples and Comparative Examples will be described.

[Example 1] The biocatalytic electrode of Example 1 was made in the following manner.

First, composite plating is performed using an electroplating method, and a 3 to 4 μm thick composite plating containing palladium, nickel, and tungsten carbide is applied to the surface of a 0.2 mttr thick copper plate, which is a square with 5 eyebrows on each side. A layer was formed.

The plating solution (plating bath) used was one with a composition similar to the one shown below.

Varadanuamine chloride 40g/ICPd(N
H3) 2Cl21 Nickel sulfate [N15o4・6H2o] 5og/I! Ammonium sulfate ((NH4)2SO4 350g/l Sodium polyoxyethylene 3g/l Tungsten carbide (WC, 0.71℃m diameter) 25
g/'1 The plating solution as described above was preliminarily stirred for 8 hours, and composite plating was performed using the plating conditions as described above.

Current density 0.5 A/dm2pH 8.8 Temperature 30℃ Plating time 24 minutesNext, electroplating was performed to form a platinum layer on the surface of the composite plating* to form the electrode body. The composition of the tamping solution used is as shown below.

H2PtCl6・6H204g/1(NH4)2H
PO420g/1 Na2HP04・12 N20 1
The plating conditions were as follows.

Temperature: 60°C Current density: IA/dm2 Plating time: Approximately 60 seconds After this, a biocatalyst (enzyme) was immobilized on the electrode body by the following method.

First, place the electrode body in concentrated nitric acid (conc HNO3) for 5 minutes.
It was soaked for 1 hour at 0°C and then washed. After washing, add hydrochloric acid (HCI) dropwise to the trichlorosilane-hexane water bath solution. The electrode body was immersed in the solution having a pH of 3 to 4 at 75° C. for 2 hours. After washing the electrode body, it was dried at 100° C. for 10 minutes. After this, 1 μm of the 2-part formaldehyde a solution and 2 μl of the 4-'ly/lucose oxidase solution! A mixed solution prepared by mixing 1.5 μl of trigrams and Group 35 albumin was applied to the electrode body and air-dried to obtain a biocatalyst electrode.

A biocatalytic electrode made as described above.

The counter electrode was placed in glucose solutions of various concentrations, and the current value associated with the electrode reaction was measured. However, the applied voltage is 0.
It was set as 7■. The measurement results are shown in Figure 2.

[Example 2] The biocatalyst electrode of Example 2 was made in the following manner.

Without stirring, α-alumina (aluminum oxide + Al2O3, 0.3 μm) was added to the composition of the composite plating solution shown in Example 1.
The operation was carried out in the same manner as in Example 1, except that a composite plating solution was used with a concentration of 3 g/l by adding plating solution (n diameter). .2
A composite plating layer containing palladium, nickel, tungnuten carbide, and α-alumina was formed on the surface of a copper plate having a diameter of 1 mm. Thereafter, platinum plating and immobilization of the biocatalyst (glucose oxidase) were performed in the same manner as in Example 1 to obtain a biocatalyst electrode.

[Example 3] The biocatalyst electrode of Example 3 was made in the following manner.

First, in the same manner as in Example 1, a composite plating layer containing palladium, nickel, and tungnuten carbide was formed on the surface of a copper plate having a square shape of 5 mm on a side and a thickness of 0.2 myr. Next, a palladium layer was formed on the surface of the composite plating layer using a tetraaminodinitric acid plating method (electroplating method) to produce an electrode body.

However, 30 g/l of Pd (NH3
) 4 (NO3)2 bath solution was used. The plating conditions were a temperature of 70°C.

The current density was set to IA/dm2. Thereafter, a biocatalyst (glucose oxidase) was immobilized in the same manner as in Example 1 to obtain a biocatalyst electrode.

[Example 4] The biocatalyst electrode of Example 4 was made in the following manner.

First, composite plating was performed using an electroplating method to form a composite plating layer containing gold and α-alumina on the surface of a copper plate having a square shape of 5 nodes on each side and a thickness of 0.2 rim, which served as a base material.

A plating solution having the following composition was used.

KAu(CN)z 5 g/
1KCN 15
g/l K2CO3 15g/l Na2HP94 15
g/lα-Al2O3 (0.3pm diameter) 5
The g/l plating conditions were as follows.

Temperature: 60° C. Electrical current: 0.5 A/dm 2 Plating time: 30 minutes Thereafter, platinum plating and immobilization of the biocatalyst (glucose oxidase) were performed in the same manner as in Example 1 to obtain a biocatalyst electrode.

[Example 5] The biocatalyst electrode of Example 5 was made in the following manner.

A composite plating layer containing nickel and α-alumina was formed on the surface of a 0.2 mm thick copper plate with a square shape of 5 spaces on each side as a base material by performing composite plating using an electroplating method.

A plating solution having the following composition was used.

Ni 504 ・7H20240g / lNiC12
・6H2020g/I H3B03 20g
/ 1tx-Ah03 (0.3pm diameter) 1
0g/l! Preliminarily stir the plating solution as described above for 8 hours,
Composite plating was performed using plating conditions similar to those described above.

Temperature: 50° C. Electric current: 4 A/dm 2 Next, electroplating was performed to form a rhodium layer on the surface of the composite plating layer. The composition of the plating solution was 2 g/l of metal rhodium and 50 me/l of H2SO4.

The plating conditions were as follows.

Temperature 50°C Electrostatic dust 3A/dm2 Plating for 2 hours, 10 minutes [Comparative example] Glucose oxidase was applied to the surface of a 5 m x 5 w x 70 μm platinum plate using the same immobilization method as described in Example 1. It was fixed to obtain a biocatalyst electrode of a comparative example.

Using the biocatalyst electrodes of Examples 2 to 5 and Comparative Example, the output current characteristics in a glucose solution were investigated in the same manner as in Example 1. The results are shown in FIG. 3 for Examples 2 to 5 and in FIG. 4 for Comparative Example.

From Figures 2 to 4, when the biocatalytic electrode of Example 1 was used, it was about 10 times as large, when the biocatalytic electrode of Examples 2 to 5 was used, it was about 4 to 6 times, and that of the comparative example was used. It can be seen that the output current is higher than that in the case, and the sensitivity is higher and more vibrant in all examples than in the comparative example.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the structure of the biocatalyst electrode according to the present invention;
FIG. 2 shows Example 1. FIG. 3 is a graph showing the relationship between glucose concentration and output current of biocatalyst electrodes of Examples 2 to 5, and FIG. 4 of comparative examples. 1... Base material 2... Composite plating layer 2a... Granular body 3... White metal metal layer 4... Electrode body 5...
・Membrane agent for biocatalyst Patent attorney Takehiko Matsumoto Figure 1: Curose concentration (×163M > Figure 2)

Claims (1)

[Claims] Q) A biocatalyst electrode in which a biocatalyst film is formed on the surface of an electrode body, the electrode body comprising a base material, a metal layer-granular composite plating layer formed on the surface of the base material, and a composite plating layer. A biocatalytic electrode comprising a platinum metal layer formed on the surface of the electrode.