Substrate for chemical sensor

Abstract

To provide a substrate for a chemical sensor having high sensor precision in the detection of optical response.SOLUTION: A substrate for a chemical sensor where a sensing area is formed is a substrate for chemical sensor that comprises a paper substrate containing linter pulp and has a size degree of the paper substrate of 0 s or over and 10 s or under. A content of the linter pulp in the paper substrate is preferably 50 mass% or over and 100 mass% or under.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a substrate for a chemical sensor. [Background technology]

[0002] 2. Description of the Related Art Microplates made of resins such as polyethylene, polypropylene, polystyrene, etc. are commonly used as culture and analysis plates for analytical chemistry and microbiology purposes. Patent Document 1 discloses a sensor array chip in which a sensor material for detecting taste components is immobilized on a hydrogel in a plurality of microwells. Furthermore, Patent Document 2 discloses a sensor material for detecting glyphosate, which uses a complex of a π-conjugated polymer and a transition metal ion as a sensor material and immobilizes the complex on a microwell array.

[0003] On the other hand, attempts have been made to use paper as a substrate for chemical sensors because of its stability, high surface porosity, and three-dimensional network structure (see Non-Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 049539 [Patent Document 2] JP 2020-197426 A [Non-patent literature]

[0005] [Non-Patent Document 1] GM Whitesides et al., Anal. Chem. 2009, 81, 5990 [Non-Patent Document 2] D. Citterio et al., Angew. Chem. Int. Ed. 2015, 54, 5294 Summary of the Invention [Problem to be solved by the invention]

[0006] Resin microplates are designed for single-mode detection, i.e., colorimetric or fluorescent detection, in detecting optical responses, and have the problem that it is difficult to observe colorimetric and fluorescent responses simultaneously. In addition, although resin microplates are highly portable, they are not very versatile, and there are concerns about the environmental impact of disposal. In view of the above-mentioned background, the applicants have filed an invention (Patent Application No. 2023-074708) that enables multi-component detection in unknown samples by optical response using a paper-based microtiter plate. The detection method of the invention related to the previous application is a method for simultaneously detecting multiple target substances, and is characterized by including the following steps A) to D): A) preparing a microtiter plate having a plurality of sensing regions for detecting a target substance on a substrate, the substrate being a paper material, the plurality of sensing regions forming a pattern with a predetermined distance from each other, the plurality of sensing regions each containing a probe reagent, which may be the same or different, coated on the substrate, the probe reagent containing a molecule that shows an optical response by a change in fluorescence or absorbance in the presence of the target substance; B) adding a sample solution containing two or more target substances onto the microtiter plate; C) imaging the whole or a part of the microtiter plate by an imaging means to obtain an image showing the optical response based on the target substance; and D) A step of identifying the type and / or concentration of the target substance contained in the sample solution by analyzing the imaged image using image pattern recognition. Step A) is a step of preparing a microtiter plate to be used for detecting a target substance. The microtiter plate has a plurality of sensing regions for detecting a target substance on a substrate, and the substrate is not made of conventional polyethylene, acrylic resin, glass, etc. but is made of paper, which is a major feature of the method. Paper has the advantages of being very inexpensive, having high surface porosity, and being easy to handle. According to the invention of the previous application, a chemical sensor array capable of multi-component and colorimetric / fluorescent detection can be realized by using a paper-based microtiter plate. In addition, by imaging the detection response with a CCD camera or the like and using an automatic image analysis algorithm and a pattern recognition method on the image, on-site qualitative / quantitative analysis can be performed by a simplified sensing process. In addition, detection by fluorescence change and detection by absorbance change (color change) can be performed simultaneously in one microtiter plate, and by combining these results, it is possible to widen the concentration range of the target substance that can be measured. Furthermore, the paper-based microtiter plate is suitable for mass production because it can be manufactured by a simple and inexpensive method using a printer. However, in the detection method of the invention of the previous application, when imaging color development and light emission in the visible to ultraviolet range as a detection response with a CCD camera or the like and performing pattern recognition on the image with an automatic image analysis algorithm, weak fluorescence from the paper-based microplate is observed, resulting in a problem of reduced sensor accuracy. For these reasons, no paper-based microplate with high accuracy capable of simultaneously detecting multiple components has been realized. The present invention has been made in view of the above circumstances, and has an object to provide a chemical sensor substrate having high sensor accuracy in detecting optical responses. [Means for solving the problem]

[0007] Pulp, which is the raw material of paper, contains multiple components derived from wood, such as cellulose, hemicellulose, and lignin, and may contain a small amount of fluorescent substances. It is not clear which component in the pulp this fluorescent substance comes from. The inventors speculated that the fluorescent substance comes from lignin contained in wood, or a substance that has been transformed into a fluorescent substance during the pulp process. Therefore, the inventors used linter pulp, which is a part that is not usually used, and were able to obtain a paper base material with no fluorescent coloring derived from wood pulp and high sensor accuracy, which led to the present invention.

[0008] That is, the present invention relates to a substrate for a chemical sensor in which a sensing region is formed, which is made of a paper substrate containing linter pulp, and the sizing degree of the paper substrate is from 0 seconds to 10 seconds.

[0009] The content of linter pulp in the paper base material is preferably 50% by mass or more and 100% by mass or less.

[0010] The thickness of the paper base material is preferably 50 μm or more and 200 μm or less.

[0011] The beating degree of the linter pulp as measured by the Shopper-Riegler method is preferably 20° SR or more and 50° SR or less.

[0012] The paper base material has a basis weight of 60 g / m 2 More than 120g / m 2 It is preferable that: Effect of the Invention

[0013] According to the present invention, a chemical sensor substrate having high sensor accuracy in detecting optical response can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Substrate for chemical sensors] The present invention relates to a substrate for a chemical sensor in which a sensing region is formed, which is made of a paper substrate containing linter pulp, and the sizing degree of the paper substrate is from 0 seconds to 10 seconds. In this specification, the term "chemical sensor" is intended to include sensors such as gas sensors, sugar sensors, virus sensors, and bacteria sensors.

[0015] (Paper base material) The paper substrate in the present invention contains linter pulp. The content of linter pulp in the paper substrate is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and particularly preferably 100% by mass. In this specification, "linter pulp" includes the concept of non-wood pulp including seed hair fibers attached to plant seeds and bast fibers in skins and stems. Specifically, cotton linter pulp made from linters (short hairs attached to cotton seeds), hemp pulp (divided into several types depending on the type, characteristics, and production area), bagasse pulp made from sugarcane pomace, kenaf pulp made from kenaf (a plant of the Malvaceae family), and the like can be mentioned. Among these, the paper substrate is preferably made of cotton linter pulp in terms of high cellulose purity, industrial ease of availability, and stability of quality. Since linter pulp does not emit fluorescence, it is possible to perform more accurate analysis by using it as a material for a substrate for a chemical sensor.

[0016] The linter pulp is preferably fibrillated (beaten). Beating can be performed using devices such as a beater, a PFI mill, a single disc refiner (SDR), a double disc refiner (DDR), a ball mill, a dyno mill, a mixer, a grinding device, a rotary blade homogenizer that applies shear force using a high-speed rotary blade, a double-cylinder high-speed homogenizer that generates shear force between a cylindrical inner blade rotating at high speed and a fixed outer blade, an ultrasonic crusher that pulverizes by ultrasonic impact, and a high-pressure homogenizer.

[0017] The beating degree of the linter pulp as measured by the Shopper-Riegler method is preferably 20° SR or more and 50° SR or less, and more preferably 25° SR or more and 45° SR or less. When the beating degree of the linter pulp is 20°SR or more, stable paper strength, i.e., tear strength, tensile strength, etc., can be obtained. Also, when the beating degree of the linter pulp is 50°SR or less, fiber falling off can be prevented. The degree of beating is the value determined by the Shopper-Riegler method based on JIS P 8121-1:2012.

[0018] -Thickness- The thickness of the paper substrate is preferably 50 μm or more and 200 μm or less, and more preferably 70 μm or more and 180 μm or less. When the thickness of the paper substrate is 50 μm or more, the paper substrate has sufficient strength when the sensor material is applied by an inkjet printer, and it is possible to prevent the paper substrate from being punctured. Furthermore, when the thickness of the paper substrate is 200 μm or less, it is possible to prevent the paper from jamming or wrinkling in the inkjet printer.

[0019] -Size- The sizing degree of the paper substrate is 0 seconds or more and 10 seconds or less. By being 0 seconds or more, as described below, when forming a pattern having a predetermined interval between each other so that a plurality of sensing regions are provided in a separated arrangement by impregnating the surface of the paper substrate with wax or the like, and when printing or dropping a target substance, no problems such as printing occur. By being 10 seconds or less, for example, when patterning and printing the sensing regions with wax on the paper substrate, the wax can be easily permeated. The sizing degree of the paper base material can be adjusted by the content of cotton linter pulp, the degree of beating, and the like. The sizing degree of the base paper is a value measured by the Stockigt method based on JIS P 8122:2004.

[0020] -Basic weight- The paper base material has a basis weight of 60 g / m 2 More than 120g / m2 The paper base material preferably has a basis weight of 60 g / m or less. 2 By setting the base material at 120 g / m or more, it is possible to prevent holes from being formed in the base material and to obtain sufficient strength. 2 By satisfying the above, it is possible to prevent paper jams or wrinkles in an inkjet printer.

[0021] It is preferable that the paper base material does not contain a sizing agent, whether internally or externally added, such as an alkyl ketene dimer-based, alkenyl succinic anhydride-based, higher fatty acid-based, petroleum resin-based, rosin-based, etc. The absence of a sizing agent in the paper base material has the advantage that hydrophobic materials such as wax for patterning the sensing region can easily penetrate. When making paper substrate, various internal additives can be appropriately selected and used as necessary. Various nonionic, cationic, amphoteric retention improvers, freeness improvers, paper strength improvers, various starches such as cationic starch, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide, polyamine resin, polyamine, polyethyleneimine, vegetable gum, polyvinyl alcohol, latex, polyethylene oxide, hydrophilic crosslinked polymer particle dispersions and their derivatives or modified products, basic aluminum compounds such as aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum chloride, and basic polyaluminum hydroxide, water-soluble aluminum compounds such as alumina sol that is easily decomposed in water, polyvalent metal compounds such as ferrous sulfate and ferric sulfate, silica sol, defoaming agents, coloring dyes, coloring pigments, fluorescent whitening agents, pH adjusters, pitch control agents, slime control agents, etc. are listed. Among these, from the viewpoint of improving the texture of the paper substrate, it is preferable to contain polyethylene oxide, etc. Since this makes it easier to obtain agricultural ground covering paper with excellent texture, the content of these is preferably 0.05% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 2.0% by mass or less, relative to 100% by mass of the total of the cotton linter pulp and fiber.

[0022] [Use of chemical sensor substrates] The chemical sensor substrate of the present invention can be used, for example, in an analytical method for simultaneously detecting multicomponent target substances by the microtiter method described in Japanese Patent Application No. 2023-074708. In the analysis by the microtiter method, a microtiter plate can be made by providing a plurality of sensing regions on the paper substrate of the present invention. The plurality of sensing regions are provided in a separate arrangement so that a multi-component substance contained in a sample solution can be detected, that is, they form a pattern with a predetermined interval between them. In some cases, the predetermined interval is preferably a constant distance. For this reason, each of the plurality of sensing regions is divided by an outer frame of a hydrophobic material (water-repellent material) applied to the paper substrate. As the hydrophobic material, an inactive material that does not interact with the target substance in the sample solution, such as a chemical reaction, when a probe reagent is applied to each sensing region is preferably used. As the hydrophobic material, waxy substances such as natural wax (paraffin, etc.) and synthetic wax (polyethylene wax, etc.), fluororesins, etc. can be mentioned. The hydrophobic material can be applied using a printing device such as an inkjet printer.

[0023] The multiple sensing regions may all be coated with different probe reagents, or may be configured to have two or more sensing region groups coated with the same probe reagent and two or more sensing region groups coated with different probe reagents. These can be appropriately adjusted depending on the number of target substances contained in the sample solution, the purpose of detection, etc. The application of the probe reagent to the sensing regions can be performed using a printing device such as an inkjet printer.

[0024] Since the chemical sensor substrate of the present invention is made of linter pulp with a high cellulose purity, there is no fluorescence caused by impurities, and highly accurate analysis results can be obtained. EXAMPLES

[0025] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0026] Details of the materials listed in Table 2 are as follows: Linter pulp: Cotton linter pulp NBKP: Bleached softwood kraft pulp LBKP: Bleached hardwood kraft pulp NUKP: Softwood unbleached kraft pulp

[0027] [Example 1] Cotton linter pulp was beaten to a degree of beating of 30°SR by the Schopper-Riegler method, and dispersed in water to a pulp slurry concentration of about 2.7% by mass to obtain a pulp slurry. Using this pulp slurry, paper with a thickness of 200 μm was made on a fourdrinier multi-cylinder papermaking machine.

[0028] [Example 2] Cotton linter pulp was beaten to a degree of beating of 30°SR by the Schopper-Riegler method, and dispersed in water to a pulp slurry concentration of about 2.7% by mass to obtain a pulp slurry. 0.1 parts by mass of polyethylene oxide was added to 100 parts by mass of pulp in this pulp dispersion to obtain a pulp slurry. Next, using this pulp slurry, paper with a thickness of 180 μm was made using a fourdrinier multi-cylinder papermaking machine.

[0029] [Comparative Examples 1 to 11] Paper was made in the same manner as in Example 1, except that the pulp composition was as shown in Table 2.

[0030] [Rating 1] The paper substrates of the above examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 2.

[0031] (Thickness measurement) The thickness of the paper substrate was measured using an ISO thickness gauge (product name "MEI-11", manufactured by CITIZEN).

[0032] (Size Rating) The sizing degree of the paper base material was measured by the Stoeckigt method based on JIS P 8122:2004.

[0033] [Preparation of paper-based microtiter plates] In the same manner as described in paragraphs

[0055] to

[0058] of Japanese Patent Application No. 2023-074708, a microtiter plate having an array of sensing regions on the paper substrate of the examples and comparative examples was prepared. Specifically, the printing pattern was designed as a 96-well microtiter plate using Microsoft PowerPoint. In order to print the pattern, the paper substrate of the examples and comparative examples was adjusted to A4 size. A wax pattern was printed on the surface of the paper substrate of the Examples and Comparative Examples using an office wax printer (ColorQube 8580N, Xerox Corporation). For 384 and 1536 wells, a wax layer was applied to the back side of the paper substrate of the Examples and Comparative Examples. The printed paper substrates of the examples and comparative examples were then treated with a hot plate (NHS-450ND, NISSIN Co.) at 150° C. During the heating process, the wax melted and diffused into the paper substrates of the examples and comparative examples to form a hydrophobic barrier. Thereafter, the backside of each of the paper substrates of the Examples and Comparative Examples was covered with a laminating film (LZ-A4100, IRIS Ohyama Co., Ltd.) and heated with an office laminator (QHE325, Meiko Sho Co., Ltd.). After the paper substrates of the Examples and Comparative Examples were cooled to room temperature, various probe reagents containing the following catechol compounds and auxiliary reagents in the combinations shown in Table 1 were applied to the printed patterns using an inkjet printer (Canon PIXUS TS203, Cannon). The ratios of the catechol compounds and auxiliary reagents were selected according to titration, and the printing time was determined by optimizing the experimental parameters. The obtained paper substrate microtiter plates were dried at room temperature and stored in the dark.

[0034] [ka]

[0035] The compounds shown above are, from left to right, Alizarin Red S (ARS), Bromopyrogallol Red (BPR), Pyrogallol Red (PR), Pyrocatechol Violet (PV), Esculetin (EL), and 4-methylesculetin (ML). The combination of reagents used is shown in Table 1.

[0036] [Table 1]

[0037] [Rating 2] The obtained paper-based microtiter plate was subjected to the following evaluations. The evaluation results are shown in Table 2. (Wrinkles during printing) When printing was performed using an office wax printer (ColorQube 8580N, Xerox Corporation), the presence or absence of wrinkles on the printed paper was visually confirmed. The evaluation criteria are as follows: ○: No wrinkles ×: If wrinkled

[0038] (Wax bleeding) When printing was performed using an office wax printer (ColorQube 8580N, Xerox Corporation), the wax bleeding on the printed paper was visually confirmed. The evaluation criteria are as follows: ○: When the printed wax does not bleed when visually inspected ×: When the printed wax is visually blurred

[0039] (Bleeding of sensor material) The obtained paper-based microtiter plate was visually inspected to check for bleeding of the applied probe reagent onto the printed pattern. The evaluation criteria are as follows: ○: When the printed probe reagent does not bleed when visually inspected ×: When the printed probe reagent is visually blurred

[0040] [Multi-component detection] In a manner similar to that described in paragraphs

[0060] to

[0063] of Patent Application No. 2023-074708, multi-component detection of a sample solution containing various components was performed using the paper-based microtiter plate prepared in the examples and comparative examples.

[0041] (Colorimetric and Fluorescent Sensing) Multicomponent detection was performed using a paper-based microtiter plate. The prepared sample solution was added to the paper-based microtiter plate, and the color and fluorescence changes were imaged. The color change was imaged using a flatbed scanner (Canon Scanner 9000f Mark II) with a resolution of 600 dpi. The fluorescence response was imaged using a CCD camera equipped with an optical filter. In order to analyze the obtained images quickly and accurately, a unique algorithm was used that implemented both morphological analysis and colorimetric information extraction. The algorithm was developed using MATLAB (registered trademark). Since the selection of the region of interest (ROI) is a challenge in morphological analysis, the raw data pixels were first imported and multiple color channels were extracted. The saturation intensity data in each color channel was analyzed using an algorithm created in MATLAB. When imaged, the wax outer frame of the paper substrate microtiter plate appears light black, and the untreated hydrophilic paper substrate portion appears white. Therefore, in order to eliminate pixels related to the background of these two regions, the intensity of the red channel was selected as the evaluation criterion, and only the pattern area where the probe reagent was printed was applied to the image analysis. This process resulted in a data matrix containing eight channels (RGB color, grayscale, YCbCr). The obtained data group was input into SYSTAT software manufactured by HULINKS, and LDA (Linear discriminant analysis), a type of cluster analysis, was performed. As a result, an LDA plot was obtained that classified the target substances contained in the sample specimens, and the probability of successful discrimination (Classification) was evaluated for colorimetric sensing and fluorescent sensing according to the following criteria. The evaluation criteria are as follows: 〇: The probability of successful classification is 100% ×: The probability of successful classification is 90% or more but less than 100%. -: Classification success rate is less than 90%

[0042] (Paper Texture) The texture of the paper base material was visually observed on a B4-sized paper base material in the transmission light under sunlight and fluorescent lamps, and was evaluated on a three-level scale based on the following criteria. "Good" is the best. ◯: There is almost no difference in the intensity contrast of the transmitted light within the plane, and the intensity of the transmitted light is uniform. △: There is a slight difference in the intensity contrast of transmitted light within the plane. ×: A clear difference in the intensity contrast of transmitted light within the plane can be confirmed.

[0043] [Table 2]

[0044] As shown in Table 2, Examples 1 and 2, which used cotton linter pulp, had better workability during printing and higher sensor accuracy than the comparative examples, which used only other wood pulp or contained other wood pulp and cotton linter pulp.

Claims

1. A substrate for a chemical sensor in which a sensing region is formed, The paper base material contains linter pulp, A substrate for chemical sensors, wherein the sizing degree of the paper substrate is from 0 seconds to 10 seconds.

2. 2. The chemical sensor substrate according to claim 1, wherein the content of the linter pulp in the paper substrate is 50% by mass or more and 100% by mass or less.

3. 2. The chemical sensor substrate according to claim 1, wherein the thickness of the paper substrate is from 50 μm to 200 μm.

4. 2. The substrate for chemical sensors according to claim 1, wherein the degree of beating of said linter pulp according to the Shopper-Riegler method is 20° SR or more and 50° SR or less.

5. The paper base material has a basis weight of 60 g / m ２ 120g / m or more ２ 2. The substrate for chemical sensors according to claim 1, wherein:

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