JP-7855694-B2 - A reagent layer containing conductive carbon filler, a sensor having the reagent layer, and a method for forming the reagent layer.

Inventors

• 羽田 圭吾
• 林野 直

Assignees

• ＰＨＣホールディングス株式会社

Dates

Publication Date

20260508

Application Date

20230630

Priority Date

20220701

Claims (16)

1. A reagent layer comprising a conductive carbon filler (a), an anionic dispersant (b), and a cationic mediator (c) , A reagent layer in which the cationic mediator (c) is a compound in which a redox mediator compound (c1) and a cationic polymer (c2) having a quaternary ammonium cationic group are bonded via a linker portion (c3) as needed .
2. The reagent layer according to claim 1, wherein the anionic dispersant (b) is a polymer with a weight-average molecular weight of 70,000 or less.
3. The reagent layer according to claim 1, wherein the anionic dispersant (b) is a polymer having carboxyl groups and/or sulfo groups in its side chains.
4. The reagent layer according to claim 3, wherein the anionic dispersant (b) is a polymer comprising at least one selected from the group consisting of acrylic acid-derived units, maleic acid-derived units, and styrene sulfonic acid-derived units.
5. The reagent layer according to claim 1, wherein the conductive carbon filler (a) is carbon black.
6. The reagent layer according to claim 1, further comprising an oxidoreductase (e) for oxidizing or reducing the analyte.
7. The reagent layer according to claim 6 , wherein the oxidoreductase (e) is of the coenzyme-bound type.
8. The reagent layer according to claim 6 , wherein the oxidoreductase (e) is crosslinked with the cationic polymer (c2).
9. An electrochemical sensor for detecting or quantifying analytes, comprising a working electrode, a counter electrode, and a reagent layer according to any one of claims 1 to 8 .
10. The electrochemical sensor according to claim 9 , further comprising a reference electrode.
11. Furthermore, the electrochemical sensor according to claim 9 , further comprising a protective film covering at least the reagent layer.
12. (1) A step of preparing a reagent solution containing a conductive carbon filler (a), an anionic dispersant (b), and a cationic mediator (c), (2) A step of applying the reagent solution to the reagent layer formation area, and (3) A step of drying the applied reagent solution to form a reagent layer. A method for forming a reagent layer, including, A method for forming a reagent layer, wherein the cationic mediator (c) is a compound in which a redox mediator compound (c1) and a cationic polymer (c2) having a quaternary ammonium cationic group are bonded via a linker portion (c3) as needed .
13. The method for forming a reagent layer according to claim 12 , wherein the pH of the reagent solution is 8.0 or less.
14. The method for forming a reagent layer according to claim 13 , wherein the concentration of metal ions in the reagent solution is 200 mM or less.
15. The method for forming a reagent layer according to claim 14 , wherein the metal ion in the reagent solution is an alkali metal ion and its concentration is less than 100 mM.
16. The method for forming a reagent layer according to claim 12, wherein the anionic dispersant (b) is a polymer comprising at least one selected from the group consisting of acrylic acid-derived units, maleic acid-derived units, and styrene sulfonic acid-derived units, having a weight-average molecular weight of 70,000 or less.

Description

The present invention relates to a reagent layer and a sensor containing a conductive carbon filler. More specifically, the present invention relates to a conductive carbon filler dispersant as an agent for improving the dispersibility of the conductive carbon filler in an aqueous solvent, a reagent layer containing the dispersant, the conductive carbon filler and a cationic mediator, a sensor equipped with the reagent layer, and a method for forming the reagent layer. Conventionally, sensors that measure analytes in a sample by reacting them with proteins are known. Examples of such sensors include enzyme-based electrochemical sensors, such as glucose sensors fabricated using glucose oxidoreductase and, if necessary, redox mediators (oxidox substances that mediate electron transport) or redox polymers (polymers to which redox mediators are linked via linkers, etc.). Glucose sensors are used, for example, for self-testing blood glucose levels. While conventionally, samples were typically collected from small amounts of blood, in recent years, implantable electrochemical glucose sensors that are implanted in the body to continuously measure glucose in the blood or interstitial space have also been developed. Furthermore, glucose sensors are also used to measure glucose in samples outside of biological materials, such as in culture media. Such glucose sensors generally measure glucose concentration in samples continuously or semi-continuously over long periods, typically several days to several weeks. In recent years, conductive carbon fillers with high specific surface area, such as nanocarbon materials, have been used in electrodes for glucose sensors, typified by electrochemical glucose sensors, and in biofuel cells, with the aim of achieving higher sensitivity and higher output by improving the specific surface area of the electrodes. For example, Patent Document 1 discloses a sensor made from a carbon black dispersion using hydroxypropyl cellulose, and Patent Document 2 discloses an enzyme-immobilized electrode using ethyl cellulose as a binder and carbon particles. Japanese Patent Publication No. 2021-082394WO2013/065581 publication Figure 1 is a plan view of a sensor in one embodiment of the present invention. Figure 1(A) shows the entire sensor, and Figure 1(B) shows a magnified view of the tip portion of the sensor.Figure 2 is a cross-sectional view of the sensor in a specific part of Figure 1(B). Figure 2(A) is a cross-sectional view taken along the arrow AA in Figure 1(B). Figure 2(B) is a cross-sectional view taken along the arrow BB in Figure 1(B). Figure 2(C) is a cross-sectional view taken along the arrow CC in Figure 1(B).Figure 3 is a top view showing another example of the front side (the side having the working electrode and the reference electrode) of a sensor in one embodiment of the present invention.Figure 4 is a cross-sectional view taken along the line A-A' in Figure 3.Figure 5 is a cross-sectional view taken along the line B-B' in Figure 4.Figure 6 is a cross-sectional view along the C-C' line in Figure 4.Figure 7 is a plan view of a sensor in one embodiment of the present invention. Figure 7(A) shows the electrode pattern before the film (insulating resist film) is formed, and Figure 7(B) shows the electrode pattern after the film is formed.Figure 8 shows images of the recovered solution samples, derived from the various reagent solution samples prepared in Test Example 1, reflecting the dispersion effect of carbon black. [A] Recovered solution samples corresponding to reagent solution samples 1-1 to 1-8. [B] Recovered solution samples corresponding to reagent solution samples 1-9 to 1-11.Figure 9 shows the measurement results regarding the sensor responsiveness in Test Example 6. [A] Results of current response values. [B] Results of cyclic voltammetry.Figure 10 shows the measurement results regarding the durability of the sensor in Test Example 7. [A] Results for the sensor made using poly(acrylic acid). [B] Results for the sensor made using hydroxypropyl cellulose. — Reagent layer — The reagent layer of the present invention comprises a conductive carbon filler (a), an anionic dispersant (b), and a cationic mediator (c). The reagent layer of the present invention is a layer that can be formed by a formation method using a carbon dispersion as described later, that is, a reagent solution in which the conductive carbon filler (a) is dispersed, and preferably a layer in which the conductive carbon filler (a), anionic dispersant (b), and cationic mediator (c) are in a uniform state. (a) Conductive carbon filler The "conductive carbon filler" in the present invention is not limited to a specific type, and various conductive carbon fillers can be used depending on the embodiment of the present invention (e.g., reagent layer, electrochemical sensor application), effect, etc. Conductive carbon materials of various shapes such as spherical (particulate), flake, fibrous, porous, etc. may b