Test strips and devices containing the test strips

Abstract

The present invention addresses the problem of providing a test strip for immunochromatography, the test strip having a short reaction completion time and excellent accuracy.　This test strip detects a substance to be detected, by developing a sample that is likely to contain the substance to be detected, wherein the test strip includes (1) a sample pad having a sample supply unit that supplies a sample, and (2) an insoluble membrane carrier having at least one detection unit that captures and detects the substance to be detected, a labeling unit, in which a labeling substance that directly or indirectly binds to the substance to be detected and generates a signal in the detection unit is disposed, is provided between the sample supply unit and the detection unit, and a line-shaped surfactant unit including a surfactant is provided between the labeling unit and the detection unit. The problem can be solved by the test strip.

Description

[Technical Field]

[0001] The present invention relates to a test strip for detecting a target substance and a device including the test strip. [Background technology]

[0002] Rapid assays such as dipstick assays and lateral flow assays have been used for many years in various diagnostic and testing procedures. Among these, immunochromatographic test strips are widely used as a method for detecting analyte substances in a sample through antigen-antibody reactions. In immunochromatography, the analyte substance (antigen) or its corresponding antibody or antigen is immobilized on an insoluble membrane carrier, which serves as a chromatographic medium, to create a stationary phase (detection region). A conjugate (detection reagent), a label sensitized with an antibody or antigen capable of binding to the analyte, is then used as the mobile phase. The analyte substance is specifically reacted with the conjugate (mobile phase). Furthermore, in the detection region (stationary phase), the analyte bound to the conjugate is specifically reacted with the antibody or antigen immobilized in the detection region. Typically, fluorescent substances, colloidal metal particles such as gold colloids, or colored latex particles are used as labels. In the detection region, the presence, or in some cases the amount, of the analyte substance in the sample is detected based on signals derived from these labels.

[0003] Rapid assays, especially immunochromatography, are prone to nonspecific reactions when samples contain contaminants such as heterophilic antibodies. Furthermore, the amount and nature of coexisting substances (e.g., autoantibodies) other than the target substance vary from sample to sample. Conjugate autoagglutination can occur due to the amount and nature of the coexisting substances. Such nonspecific reactions can hinder accurate measurement and interpretation, posing a problem. Inaccurate measurements can result in falsely high or low values ​​in quantitative assays, and false positives or false negatives in qualitative assays.

[0004] Various studies have been conducted to suppress nonspecific reactions in rapid assay methods. Patent Document 1 discloses a porous solid phase for binding assays, which is characterized by containing a specific surfactant before the addition of a measurement sample. Patent Document 2 also discloses a chromatographic analysis strip that includes a means for capturing a target substance in a sample and a means for capturing factors that cause false positives upstream of the means. However, even with these techniques, the effect of suppressing nonspecific reactions may not be sufficient, and further techniques that can efficiently suppress nonspecific reactions have been needed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 043746 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-120193 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a test strip and a device including the test strip that can suppress non-specific reactions and obtain accurate measurement values ​​or determination results when measuring the amount of a substance to be detected or when qualitatively determining whether it is present or absent, i.e., positive or negative. [Means for solving the problem]

[0007] The inventors discovered that by adopting the following configuration for the test strip, accurate measurement values ​​or determination results can be obtained in measuring the amount of the substance to be detected or in qualitative determination, and have thus completed the present invention. Specifically, the present invention is as follows. <1> A test strip for detecting a substance to be detected by developing a sample that may contain the substance to be detected, the test strip comprising: (1) A sample pad having a sample supply portion for supplying a sample. (2) An insoluble membrane carrier having at least one detection portion for capturing and detecting a substance to be detected. Including, The test strip has a labeling section between the sample supply section and the detection section, in which a labeling body is disposed that directly or indirectly binds to the substance to be detected and generates a signal in the detection section, and a linear surfactant section containing a surfactant is provided between the labeling section and the detection section. <2> an antibody or antigen that immunologically reacts with the substance to be detected is immobilized on the label; an antibody or an antigen that immunologically reacts with a substance to be detected is immobilized on the detection section; and the antibody or antigen immobilized on the label and immunologically reacting with the substance to be detected is different from the antibody or antigen immobilized on the detection part and immunologically reacting with the substance to be detected; <1> The test strip according to claim 1. <3> It is a lateral flow type. <1> or <2> The test strip according to claim 1. <4> The surfactant contained in the surfactant portion is a nonionic surfactant. <1> ~ <3> 10. The test strip according to claim 9, wherein <5> the substance to be detected is a substance of biological origin; <1> ~ <4> 10. The test strip according to claim 9, wherein <6> the substance of biological origin is troponin, the antibody or antigen that immunologically reacts with the substance to be detected immobilized on the label, and the antibody or antigen that immunologically reacts with the substance to be detected immobilized on the detection part are both anti-troponin monoclonal antibodies; <5> The test strip according to claim 1. <7> The sample that may contain the substance to be detected is at least one selected from the group consisting of blood, serum, and plasma. <1> ~ <6> 10. The test strip according to claim 9, wherein <8> The sample that may contain the substance to be detected is a sample that has not been pretreated. <1> ~ <7> 10. The test strip according to claim 9, wherein <9> Between the (1) and (2), as the sign part (3) a label-containing pad in which a label that generates a signal in the detection unit is disposed, and The surfactant portion is provided on an insoluble membrane carrier. <1> ~ <8> 10. The test strip according to claim 9, wherein <10> The line width of the surfactant portion is 0.5 to 10 mm. <1> ~ <9> 10. The test strip according to claim 9, wherein <11> The surfactant contained in the surfactant portion is a surfactant solution having a concentration equal to or higher than the critical micelle concentration, the surfactant being contained in the test strip. <1> ~ <10> 10. The test strip according to claim 9, wherein <12> The line width of the surfactant portion is 0.5 to 2 mm, and the line width is within a range of ±0.2 mm over the entire line. <1> ~ <11> 10. The test strip according to claim 9, wherein <13> The surfactant contained in the surfactant portion is an alkyl glucoside surfactant. <1> ~ <12> 10. The test strip according to claim 9, wherein <14> The alkyl glucoside surfactant is at least one selected from the group consisting of n-octyl-β-D-glucoside, n-decyl-β-D-glucoside, n-dodecyl-β-D-glucoside, n-heptyl-β-D-thioglucoside, and n-octyl-β-D-thioglucoside; <13> The test strip according to claim 1. <15> the alkyl glucoside surfactant is n-heptyl-β-D-thioglucoside, the n-heptyl-β-D-thioglucoside solution is applied to the test strip in a line to form a linear surfactant portion, and the concentration of the n-heptyl-β-D-thioglucoside solution is 0.88% (w / v) or more; <14> The test strip according to claim 1. <16> The detection unit is in a line shape with a line width of 0.5 to 2 mm, the line width of the detection unit is within a range of ±0.2 mm over the entire line, and the distance between the linear detection unit and the surfactant unit on the line is 3 to 8 mm. <12> ~ <15> 10. The test strip according to claim 9, wherein <17> <1> ~ <16> A device comprising the test strip described in any one of the above. [Effects of the Invention]

[0008] According to the test strip of the present invention, non-specific reactions can be suppressed in the detection of a target substance in a sample, and accurate measurement values ​​or determination results can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of an immunochromatographic test strip according to one embodiment of the test strip of the present invention, and shows a side view of the structure of the immunochromatographic test strip before lamination. [Figure 2] FIG. 1 shows a top view (partial view) of one embodiment of an insoluble membrane support. [Figure 3]10 is a graph showing the measurement results of a target substance using a test strip of a comparative example. [Figure 4] 1 is a graph showing the measurement results of a substance to be detected using a test strip according to one embodiment of the present invention. [Figure 5] 1 is a graph showing bias between measurements of a comparative test strip or measurements of one embodiment of the present invention and known cTnI concentrations. [Figure 6] 10 is a graph showing the measurement results of the target substance using a test strip of a comparative example. [Figure 7] 1 is a graph showing the measurement results of a substance to be detected using a test strip according to one embodiment of the present invention. [Figure 8] 10 is a photograph showing the analysis results of a divergent sample using a test strip of a comparative example and a test strip of one embodiment of the present invention. [Figure 9] 10 is a graph showing the measurement results of the target substance using a test strip of a comparative example. [Figure 10] 1 is a graph showing the measurement results of a substance to be detected using a test strip according to one embodiment of the present invention. [Figure 11] 10 is a graph showing the measurement results of a substance to be detected using a test strip (not in a line shape) containing a surfactant portion. [Figure 12] 10 is a graph showing the measurement results of a substance to be detected using a test strip that does not contain a surfactant portion. [Figure 13] 1 is a graph showing the correlation between measurements taken using a test strip that does not contain a surfactant portion and measurements taken using a test strip that does contain a surfactant portion (not in a line shape). DETAILED DESCRIPTION OF THE INVENTION

[0010] (Substance to be detected) The substances to be detected in the test strip of the present invention include physiologically active substances such as viruses, proteins, etc. Examples of the substances to be detected in the test strip of the present invention are as follows. Myocardial markers such as CK-MB, H-FABP, troponin (troponin I, troponin T), and myoglobin; coagulation and fibrinolysis markers such as fibrin degradation products (e.g., D-dimer), soluble fibrin, TAT (thrombin-antithrombin complex), and PIC (plasmin-plasmin inhibitor complex); circulation-related markers such as oxidized LDL and BNP (brain natriuretic peptide); metabolism-related markers such as adiponectin; CEA (carcinoembryonic antigen), AFP (alpha-fetoprotein), and C Tumor markers such as A19-9, CA125, and PSA (prostate-specific antigen); inflammation-related markers such as CRP (C-reactive protein), IgA, IgG, and IgM; infectious disease-related markers such as influenza, HIV (human immunodeficiency virus), HBV (hepatitis B virus), HCV (hepatitis C virus), toxoplasmosis, chlamydia, syphilis, Staphylococcus aureus, and E. coli; allergen-specific IgE (immunoglobulin E); hormones; drugs; allergens; nucleic acid chains and fragments thereof related to SNPs (single nucleotide polymorphisms).

[0011] The substance to be detected is preferably a substance that can be measured using an antigen-antibody reaction, preferably a substance contained in a living organism, and more preferably troponin. Troponin is one of the proteins that make up muscle. Troponin forms a complex with troponin T, troponin I, and troponin C, and is responsible for regulating cardiac and skeletal muscle contraction. Troponins that regulate cardiac muscle contraction are called cardiac troponins. Human cardiac troponin I and human cardiac troponin T are used as markers for acute myocardial infarction. In the immunochromatographic test strip of the present invention, either troponin T or troponin I can be used as the detected substance, but it is more preferable to use troponin I as the detected substance, and it is even more preferable to use human cardiac troponin I (cTnI) as the detected substance.

[0012] The test strip of the present invention can also be used in nucleic acid chromatography. Nucleic acid chromatography refers to chromatography for detecting a specific nucleic acid sequence, such as DNA or RNA, from a sample. The test strip of the present invention can be used in nucleic acid chromatography for the purpose of detecting allergens (such as buckwheat or egg), genetic polymorphisms, or specific bacteria or viruses. In one embodiment in which the test strip of the present invention is used in nucleic acid chromatography to detect a target nucleic acid sequence, a fluorescently labeled nucleic acid sequence complementary to at least a portion of a detection target sequence, a fluorescently labeled nucleic acid aptamer, or the like is used as the label, and a substance that captures the target nucleic acid sequence to form a complex is used as the detection reagent, and a nucleic acid sequence or nucleic acid aptamer different from the detection reagent that is complementary to at least a portion of the detection target sequence can be placed in the detection section.

[0013] (sample) In the present invention, samples that may contain the analyte include primarily biological substances and extracts obtained by extracting the analyte from such substances. Food samples, such as liquid beverages, semi-solid foods, and solid foods; natural samples such as soil, rivers, and seawater; and swab samples from factory production lines or clean rooms can also be used as samples that may contain the analyte. Specific examples of biological substances include blood (whole blood), serum, plasma, lymph, urine, feces, ascites, pleural effusion, tissues, and cells. In the present invention, body fluids, particularly blood (whole blood), serum, or plasma, are preferably used as samples that may contain the analyte. Samples that may contain the analyte include test sample components separated or fractionated from whole blood by means such as centrifugation, filtration, or purification; test sample components extracted with organic solvents; test sample components solubilized with surfactants; test sample components diluted with buffer solutions; and test sample components modified or altered by chemical reactions. In the case of nucleic acid chromatography, a sample in which nucleic acid has been amplified in advance by PCR, etc., can also be used. Samples that may contain the target substance may be pretreated by dilution, extraction, mixing with additives, etc., or may not be pretreated.

[0014] (labeled substance) As used herein, the term "label" refers to a substance that generates a signal in the detection unit when it binds directly or indirectly to a substance to be detected. The signal derived from the label may be measured according to a known method. For example, the absorbance or intensity of reflected light may be measured. The signal may be confirmed visually or using a specific measuring device.

[0015] The label used in the present invention may be a known label that has been conventionally used in test strips. For example, colloidal metal particles such as gold colloid particles and platinum colloid particles, colored latex particles, and magnetic particles are preferred, with gold colloid particles being particularly preferred. In order to be detected in the detection section, the label is preferably modified with a tag or the like, or has an antibody or antigen that immunologically reacts with the substance to be detected immobilized thereon. It is preferable to use a label with an appropriate particle size depending on the type of label. For example, when gold colloid particles are used as the label, the particle size is preferably 20 to 70 nm, and particularly preferably 45 to 65 nm. The above gold colloid particles can be produced by a commonly known method, for example, by adding a trisodium citrate aqueous solution dropwise to a heated aqueous tetrachloroauric (III) acid solution and stirring the mixture.

[0016] (Antibodies or antigens that react immunologically with the substance to be detected) The test strip of the present invention is preferably an immunochromatographic test strip. In this case, it is preferable that an antibody or antigen that immunologically reacts with the analyte be immobilized on the label, and that an antibody or antigen that immunologically reacts with the analyte be immobilized on the detection section. Hereinafter, a label on which an antibody or antigen that immunologically reacts with the analyte is immobilized may be referred to as a conjugate. In the present invention, immobilizing an antigen or antibody means physically or chemically supporting the antigen or antibody on the label or insoluble membrane carrier. Furthermore, it is more preferable that the antibody that immunologically reacts with the analyte immobilized on the label and the antibody that immunologically reacts with the analyte immobilized on the detection unit are different. Note that "different" refers to different types, i.e., antibodies that recognize different epitopes. Preparing an immunochromatography test strip using different antibodies immobilized on the label and the detection unit can suppress competition between the reaction between the analyte and the antibody in the detection unit and the reaction with unreacted conjugate. Furthermore, it is possible to increase the reactivity between the analyte bound to the conjugate and the antibody in the detection unit. As a result, the sensitivity of the immunochromatography test strip is improved. Furthermore, the antibodies immobilized on the label and the detection unit are preferably monoclonal antibodies. Using monoclonal antibodies can increase the specificity of the reaction. In addition to these whole antibody molecules, the term "antibody" as used herein also includes functional fragments of antibodies that have antigen-antibody reaction activity. Examples of functional antibody fragments include those obtained through animal immunization, those obtained using genetic recombination techniques, and chimeric antibodies. Examples of functional antibody fragments include F(ab')2 and Fab'. These functional fragments can be produced by treating the antibody with a protease (e.g., pepsin, papain, etc.).

[0017] (conjugate) The label, i.e., the conjugate, used in the test strip of the present invention, in which an antibody or antigen that reacts immunologically with the substance to be detected is immobilized is preferably a gold colloid particle in which an anti-troponin monoclonal antibody is immobilized when the substance to be detected is troponin. Methods for immobilizing an antibody or antigen that immunologically reacts with a substance to be detected to a label include physical adsorption and chemical bonding. Physical adsorption is common. For example, when immobilizing an anti-troponin monoclonal antibody to gold colloid particles, the gold colloid particles and the anti-troponin monoclonal antibody are typically added to a buffer solution, and immobilization is carried out by physical adsorption. In this case, the antibody concentration is preferably adjusted to 20 to 100 μg / mL. Furthermore, it is preferable to block the areas on the label such as gold colloid particles to which no antibody or antigen is bound with BSA or the like. The labeling portion on which the conjugate is to be placed may be provided in a line on the sample pad described below, or may be provided as a label-containing pad described below between the sample pad and the insoluble membrane carrier.

[0018] (Sample Pad) In the test strip of the present invention, a pad-shaped porous material capable of retaining a conjugate can be used as a sample pad. The sample pad has a sample supply section in a portion thereof. A porous material section is located downstream of the sample supply section. The sample supplied to the sample supply section develops in the porous material section and reaches the label section. The sample supply section is a portion for supplying a sample that may contain a substance to be detected. This sample supply section is formed in a part of the porous material, and is located upstream of the sample pad.

[0019] (Surfactant part) The surfactant section is a portion containing a surfactant. The surfactant section can be formed in a line on the sample pad or on the insoluble membrane carrier downstream of the label section. When a label-containing pad is provided in addition to the sample pad, the surfactant section can be formed on the insoluble membrane carrier downstream of the label-containing pad. The linear surfactant section is preferably arranged in a line in the direction of sample development, i.e., perpendicular to the line connecting the center of the sample supply section of the sample pad and the center of the downstream end of the insoluble membrane carrier described below. In other words, the linear surfactant section is preferably arranged in a line perpendicular to the longitudinal direction of the sample pad and the insoluble membrane carrier. The surfactant section is preferably formed on the insoluble membrane carrier. The position of the surfactant portion can be adjusted to an appropriate position by a person skilled in the art, but the center line of the linear surfactant portion is preferably located 1 to 25 mm downstream from the downstream end of the labeling portion, and more preferably 10 to 20 mm downstream. Furthermore, the center line of the linear surfactant portion is preferably located at least 1 mm upstream from the upstream end of the detection portion. Note that, in this specification, the "center line" of the surfactant portion refers to a center line drawn perpendicular to the longitudinal direction of the sample pad, and does not refer to a center line drawn parallel to the longitudinal direction of the sample pad. In this specification, the length of the linear surfactant portion in the longitudinal direction of the sample pad is referred to as the "line width" of the surfactant portion. The line width of the linear surfactant portion may be such that the amount of surfactant necessary to obtain the effects of the present invention is contained therein. The line width is, for example, 0.5 to 10 mm, 0.5 to 5 mm, or 0.5 to 2 mm. It is preferable that the line width of the linear surfactant portion is approximately the same across the entire line (i.e., a width of ±1 mm, ±0.5 mm, or ±0.2 mm across the entire line). It is also conceivable that a portion of the linear surfactant portion protrudes downstream and / or upstream. In this case, it is sufficient that either the non-protruding portion or the protruding portion has the above-mentioned line width, but it is preferable that the non-protruding portion has the above-mentioned line width. Furthermore, it is not necessary for the entire linear surfactant portion to contain a surfactant, and as long as the effects of the present invention are obtained, there may be portions within the line that do not contain a surfactant. Examples of embodiments in which there are portions within a line that do not contain a surfactant include when the line is formed by dots and when there are multiple linear, thin surfactant portions (for example, a line width of 1 mm). The test strip of the present invention is believed to be effective by disposing the surfactant in a limited area so that it can be evenly eluted against the movement of the analyte and the label. This configuration is believed to prevent the occurrence of agglutinations that can cause false low and high values ​​or false negative and false positive results, thereby resulting in accurate measurement values.

[0020] The surfactants used in the present invention include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of anionic surfactants include cholic acids, alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, and alkylbenzene sulfonates. Examples of amphoteric surfactants include alkyl betaine, alkylamine oxide, and cholamide. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkylamines, fatty acid alkanolamides, alkyl imidazolines, alkyl glucosides, alkyl mannosides, alkyl maltosides, and trehalose compounds. The surfactant used in the present invention is preferably a nonionic surfactant, and more preferably an alkyl glucoside surfactant. In this specification, "alkyl glucoside surfactant" refers to a nonionic surfactant in which a sugar molecule and a higher alcohol are bonded via a glycosidic bond. In this case, "glucosidic bond" has a broad meaning, and for example, an S-glycosidic bond (thioglucosidic bond) or an N-glycosidic bond is also included in the "glucosidic bond". The sugar molecule is preferably a monosaccharide molecule, and glucose is more preferred. The higher alcohol is preferably a C6 to C22 alkyl alcohol. The alkyl alcohol may be linear or branched, and is preferably linear. In addition, the alkyl alcohol preferably has one OH group. Specific alkyl glucoside surfactants include n-octyl-β-D-glucoside (CAS No. 29836-26-8), n-decyl-β-D-glucoside (CAS No. 58846-77-8), n-dodecyl-β-D-glucoside (CAS No. 59122-55-3), n-heptyl-β-D-thioglucoside (CAS No. 85618-20-8), and n-octyl-β-D-thioglucoside (CAS No. 85618-21-9). n-Heptyl-β-D-thioglucoside is the most preferred.

[0021] In the present invention, it is preferable to apply a line of a surfactant solution having a concentration equal to or greater than the critical micelle concentration (CMC) to the test strip. The CMC is the minimum concentration at which a surfactant forms micelles. The CMC of n-heptyl-β-D-thioglucoside is 30 mmol / L, which corresponds to 0.88% by mass / volume (w / v). In the present invention, the concentration of the surfactant solution applied in a line to the test strip is, for example, 0.01% by volume or more, 0.05% by volume or more, 0.1% by volume or more, 0.5% by volume or more, or 1% by volume or more. Linear surfactant moieties can be prepared on an insoluble membrane carrier as follows: A surfactant moiety solution containing a predetermined concentration of surfactant moiety is prepared. Next, using a device having a mechanism capable of discharging a liquid from a nozzle at a constant speed while moving the liquid in a direction perpendicular to the longitudinal direction of the insoluble membrane carrier, the liquid is applied to the insoluble membrane carrier in a line shape, for example, with a line width of 0.5 to 10 mm, 0.5 to 5 mm, or 0.5 to 2 mm, in a direction perpendicular to the longitudinal direction of the insoluble membrane carrier, and then dried.

[0022] The sample pad is laminated with the insoluble membrane carrier so that the lower surface of the downstream end of the sample pad contacts the upper surface of the insoluble membrane carrier described below. In the sample pad, the lower surface of the sample supply section may or may not contact the upper surface of the insoluble membrane carrier. If the sample pad is provided with a labeling section, the lower surface of the labeling section may or may not contact the upper surface of the insoluble membrane carrier. If a label-containing pad is provided as a labeling section separate from the sample pad, the sample pad and the label-containing pad are laminated, and the lower surface of the downstream end of the label-containing pad contacts the upper surface of the insoluble membrane carrier. A porous material may be further provided between the sample pad and the label-containing pad or between the label-containing pad and the insoluble membrane. The upstream and downstream ends may be laminated appropriately so that the sample can reach the insoluble membrane from the sample supply section by capillary action. When a sample possibly containing the analyte is supplied to the sample supply section of the sample pad, the sample flows from the upstream sample supply section through the porous material portion to the downstream labeling section. At the labeling portion, the substance to be detected in the sample (for example, troponin) and the conjugate (for example, gold colloid particles to which anti-troponin monoclonal antibodies have been immobilized) form a complex.

[0023] Porous materials constituting the sample pad and label-containing pad include pads made of nonwoven fibers such as paper, cellulose mixtures, nitrocellulose, polyester, acrylonitrile copolymer, glass, rayon, etc. Among these, pads made of glass fibers (glass fiber pads) are preferred.

[0024] The overall length of the sample pad, i.e., the length from the upstream end to the downstream end of the sample pad, can be adjusted to an appropriate length by those skilled in the art. Specifically, it can be adjusted to 5 to 40 mm, 10 to 30 mm, or 10 to 20 mm. When a labeled-form-containing pad is provided, the length from the upstream end of the sample pad to the downstream end of the labeled-form-containing pad may be adjusted to an appropriate length, but it is preferable to adjust it to within the above range.

[0025] (Insoluble membrane carrier) The insoluble membrane carrier that can be used in the present invention has at least one detection unit for capturing and detecting a substance to be detected. The detection unit is preferably linear. An antibody or antigen that immunologically reacts with the substance to be detected is preferably immobilized on the detection unit. When the detection unit is linear, it is preferably arranged in a line in a direction perpendicular to the sample development direction, i.e., the line connecting the center of the sample supply unit of the sample pad and the center of the downstream end of the insoluble membrane carrier. In other words, the linear detection unit is preferably arranged in a line in a direction perpendicular to the longitudinal direction of the insoluble membrane carrier. The antibody or antigen that immunologically reacts with the substance to be detected can be immobilized on the insoluble membrane carrier by a conventionally known method. When the present invention is a lateral flow immunochromatography test strip, immobilization can be performed as follows. A solution containing the above-mentioned antibody or antigen at a predetermined concentration is prepared. Then, using a device having a mechanism capable of discharging the solution from a nozzle at a constant speed while moving it in a direction perpendicular to the longitudinal direction of the insoluble membrane carrier, the solution is applied to the insoluble membrane carrier in a line shape, for example, a line width of 0.5 to 5 mm or 0.5 to 2 mm, in a direction perpendicular to the longitudinal direction of the insoluble membrane carrier, and then dried to achieve immobilization. In this specification, the length of the linear detection section in the longitudinal direction of the insoluble membrane carrier is referred to as the "line width" of the detection section. It is preferable that the line width of the detection section be approximately the same across the entire line (i.e., ±0.2 mm across the entire line). It is also conceivable that a portion of the linear detection portion protrudes downstream and / or upstream. In this case, either the non-protruding portion or the protruding portion may have the above-mentioned line width, but it is preferable that the non-protruding portion has the above-mentioned line width. When the detection unit is linear, the distance between the linear detection unit and the surfactant unit on the line is preferably 2 mm to 12 mm, more preferably 2 to 10 mm, even more preferably 3 to 8 mm, even more preferably 4 to 7 mm, and most preferably 4.5 to 6.5 mm. By keeping the distance between the linear detection unit and the surfactant unit on the line within the above range, the surfactant does not diffuse, and the effects of the present invention can be effectively achieved. Note that the "distance between the linear detection unit and the surfactant unit on the line" refers to the shortest length when the linear detection unit and the surfactant unit on the line are connected by a straight line parallel to the longitudinal direction of the insoluble membrane carrier. The concentration of the antibody or antigen in the above solution is preferably 0.1 to 5 mg / mL, more preferably 0.5 to 3 mg / mL. The measurement method using the lateral flow test strip is a method in which the sample supplied from the portion of the sample pad that comes into contact with the insoluble carrier is developed so as to move parallel to the longitudinal direction of the insoluble membrane carrier by capillary action. The test strip of the present invention can also be used in measurement methods in which the test strip is immersed in a sample extract (dipstick method) in addition to the lateral flow method. Furthermore, a solution containing the above-mentioned antibody or antigen at a predetermined concentration can be prepared by adding the antibody or antigen to a buffer solution. Examples of the buffer solution include commonly used buffer solutions such as phosphate buffer, Tris buffer, and Good's buffer. The pH of the buffer solution is preferably in the range of 6.0 to 9.5, more preferably 6.5 to 8.5, and even more preferably 7.0 to 8.0. The buffer solution may further contain salts such as sodium chloride, stabilizers and preservatives such as sucrose, and antiseptics such as Proclin. After immobilizing an antibody or antigen on an insoluble membrane carrier, a commonly used blocking agent can be used in solution or vapor form to cover the areas other than the areas where the antibody or antigen is immobilized, thereby performing blocking. A control capture reagent, which has traditionally been used in immunochromatographic test strips, may be immobilized on the insoluble membrane carrier. The control capture reagent is a reagent for ensuring the reliability of the assay and captures the control reagent contained in the sample pad. For example, if the sample pad contains labeled KLH as a control reagent, an anti-KLH antibody or the like would be the control capture reagent. The position at which the control capture reagent is immobilized can be appropriately selected to suit the design of the assay system. For example, it can be designed to be located 2 to 15 mm, 2 to 10 mm, or 3 to 8 mm downstream from the center line of the most upstream detection section. Hereinafter, the position at which the control capture reagent is immobilized on the insoluble membrane carrier may be referred to as the control capture reagent immobilization section. The control capture reagent immobilization section is preferably linear. The preferred range and definition of the line width are the same as those for the detection section. When the control capture reagent immobilized section is linear, the distance between the linear capture reagent immobilized section and the linear surfactant section is preferably 6 mm to 16 mm, more preferably 6 to 14 mm, even more preferably 7 to 12 mm, even more preferably 8 to 11 mm, and most preferably 8.5 to 10.5 mm. Note that the "distance between the linear capture reagent immobilized section and the linear surfactant section" refers to the shortest length when the linear capture reagent immobilized section and the linear surfactant section are connected by a straight line parallel to the longitudinal direction of the insoluble membrane carrier.

[0026] The membrane constituting the insoluble membrane carrier used in the present invention can be any known membrane conventionally used as an insoluble membrane carrier for test strips. Examples include membranes composed of fibers such as polyethylene, polyethylene terephthalate, nylons, glass, polysaccharides such as cellulose and cellulose derivatives, and ceramics. Specific examples include glass fiber filter paper and nitrocellulose membranes commercially available from Sartorius, Merck, Toyo Roshi, and Whatman. The average pore size or retention particle size of the insoluble membrane carrier is not limited to, but can be 0.1 to 20 μm, more preferably 0.5 to 16 μm, and even more preferably 0.7 to 10 μm. In terms of flow rate, for example, a membrane with a flow rate of 70 to 300 seconds can be used, with 90 to 200 seconds being preferred and 120 to 180 seconds being more preferred. The flow rate refers to the number of seconds required for water to spread 4 cm at one end of the insoluble membrane carrier. The total length of the insoluble membrane carrier, i.e., the length from the upstream end to the downstream end of the insoluble membrane carrier, can be adjusted to an appropriate length by a person skilled in the art, and specifically, it can be adjusted to a length of 15 to 40 mm, 18 to 35 mm, or 20 to 30 mm.

[0027] (Label-containing pad) As used herein, a "label-containing pad" refers to a material suitable for a label-containing pad, which will be described later, that is impregnated with a conjugate and then dried. The label-containing pad has the function of forming a complex between the conjugate and the analyte when a sample passes through the label-containing pad. The label-containing pad may be placed in contact with the porous membrane on which the specific binding substance is immobilized, or may be placed in contact with the sample pad, receive the sample that has passed through the sample pad by capillary flow, and subsequently transport the sample by capillary flow to a 3rd pad that contacts the sample pad on a surface different from the surface that contacts the sample pad.

[0028] Suitable materials for the label-containing pad include, but are not limited to, paper, cellulose blends, nitrocellulose, polyester, acrylonitrile copolymers, glass fiber, or nonwoven fabrics such as rayon. Preferably, a glass fiber pad is used.

[0029] The label-containing pad may contain, as needed, a "control reagent" to ensure the reliability of the immunochromatographic detection method, such as an antibody that does not react with the sample component labeled with the label, or a highly antigenic protein such as KLH (keyhole limpet hemocyanin) labeled with the label. These control reagents are components (substances) that are unlikely to be present in the sample, and can be selected appropriately.

[0030] (absorbent pad) In the test strip of the present invention, it is preferable to provide an absorbent pad at the downstream end of the insoluble membrane carrier. The absorbent pad is a liquid-absorbent portion that controls the development of the sample by absorbing the sample that has moved through or passed through the insoluble membrane carrier. As the absorbent pad, a known absorbent pad that has been conventionally used in test strips can be used, and for example, filter paper can be used. The total length of the absorbent pad, i.e., the length from the upstream end to the downstream end of the absorbent pad, is believed to be adjustable by a person skilled in the art to an appropriate length, and specifically, it can be adjusted to a length of 5 to 100 mm, 20 to 80 mm, or 20 to 60 mm.

[0031] (Test Strips) The test strip is preferably placed on a solid support such as a plastic adhesive sheet. The solid support is made of a material that does not interfere with the capillary flow of the sample and conjugate. Alternatively, the test strip may be immobilized on the solid support using an adhesive or the like. In this case, the adhesive components or the like are also made of a material that does not interfere with the capillary flow of the sample and conjugate. It is also possible to laminate a polyester film or the like as a top film to increase the mechanical strength of the insoluble membrane carrier and prevent evaporation (drying) of water during the assay. The test strip can be stored and mounted in an appropriate container (housing) that takes into consideration the size of the test strip, the method and location of sample addition, the location of the detection portion on the insoluble membrane carrier, the signal detection method, and the like. This stored and mounted state is referred to as a "device." The test strip of the present invention includes a sample pad and an insoluble membrane carrier, and may further include other reagents and components depending on the measurement conditions and sample. Examples of other reagents include a blocking agent to prevent nonspecific reactions, and other components include an additional pad to remove components in the sample that are not required for measurement. For example, a third pad can be provided between the sample pad and the porous membrane to allow the analyte or a complex containing the analyte to smoothly spread across the insoluble membrane carrier.

[0032] (Test Strip Manufacturing Method) A method for producing an immunochromatographic test strip, which is one embodiment of the test strip of the present invention, will be described below. For example, the method for producing an immunochromatographic test strip of the present invention includes the following steps (1) to (4). (1) An antibody-immobilized porous membrane is attached to a backing sheet, and an application section is arranged on the upstream side of the development so that the surfactant section, the antibody that binds to the analyte, and then the control antibody are applied in this order. The surfactant section is formed by applying or spraying a surfactant solution in a line perpendicular to the direction of sample development. (2) A polysulfone porous membrane (3rd Pad) is attached so that it is partially laminated on the upstream part of the membrane. (3) Next, the labeled substance-containing pad is placed and attached so that a portion of it is layered on the upstream development portion of the 3rd Pad, and the sample pad is placed and attached so that it overlaps this labeled substance-containing pad. (4) An absorbent pad is placed and attached to the downstream end of the antibody-immobilized porous membrane, and finally, the surface of the absorbent pad and antibody-immobilized membrane is covered with a top film so that part of the antibody-immobilized membrane is exposed. In the above step (1), the concentration of the surfactant solution is preferably equal to or higher than the critical micelle concentration.

[0033] In this specification, the term "detection" includes not only qualitative detection but also quantitative detection for analyte substances that can be quantified. As used herein, the term "non-specific reaction" includes a case where a signal derived from a label or conjugate is detected and judged as positive even though the substance to be detected is not present or substantially not present in the sample (so-called false positive), and a case where a signal derived from a label or conjugate is not detected and judged as negative even though a considerable amount of the substance to be detected is present in the sample (so-called false negative). In the case of quantitative detection, this includes a case where the measured value fluctuates to a low value (false low value) or a high value (false high value).

[0034] (others) The immunochromatographic test strip of the present invention can be prepared by appropriately modifying or altering the method described in the Examples.

[0035] The present invention will now be described in detail with reference to examples, but these examples are not intended to limit the scope of the present invention. Unless otherwise specified, % means % by mass or volume. [Example]

[0036] [Test Example 1] Preparation of immunochromatographic test strips A test was conducted to confirm the effect of inhibiting non-specific reactions using an immunochromatographic test strip, which is one embodiment of the test strip of the present invention.

[0037] 1) Preparation of colloidal gold-labeled anti-cTnI monoclonal antibody (anti-cTnI antibody conjugate) (i) Preparation of colloidal gold solution (60 nm) To 5000 mL of purified water heated to 93°C, 10 mL of a 7% (w / v) aqueous solution of triammonium citrate was added and mixed with stirring. Next, 10 mL of a 5% (w / v) aqueous solution of tetrachloroauric(III) acid was added, and the mixture was allowed to react for 10 minutes with stirring, after which the reaction solution was brought to a boil. After this, the mixture was cooled in ice water to prepare a solution of gold colloids with an average particle size of 60 nm. This solution of gold colloids with an average particle size of 60 nm was adjusted with purified water to an absorbance of 1 OD / mL at the maximum absorption wavelength of gold colloids.

[0038] (ii) Preparation of anti-cTnI antibody conjugate To 200 mL of the 1 OD / mL 60 nm gold colloid solution (pH 8.0), 10 mL of anti-cTnI monoclonal antibody diluted to 20 μg / mL in 2 mM Tris-HCl buffer (pH 7.0) was added and stirred at room temperature for 10 minutes. To the gold colloid and antibody mixture, 10 mL of purified water containing 0.5% (w / v) Neo Protein Saver (Toyobo Co., Ltd., No. NPS-301) was added and stirred at room temperature for 5 minutes. The mixture was then centrifuged at 11,900 × g for 45 minutes at 10°C. After removing the supernatant, 10 mL of 0.2% (w / v) Neo Protein Saver aqueous solution was added to the resulting sediment to suspend the conjugate, yielding the anti-cTnI antibody conjugate.

[0039] (iii) Preparation of colloidal gold solution (40 nm) To 5000 mL of purified water heated to 73°C, 10 mL of a 5% (w / v) aqueous solution of triammonium citrate was added and mixed with stirring. Next, 10 mL of a 5% (w / v) aqueous solution of tetrachloroauric(III) acid was added, and the mixture was allowed to react for 10 minutes while stirring. The reaction solution was then boiled. After this, the mixture was cooled in ice water to prepare a solution of gold colloids with an average particle size of 40 nm. This solution of gold colloids with an average particle size of 40 nm was adjusted with purified water to an absorbance of 1 OD / mL at the maximum absorption wavelength of gold colloids.

[0040] (iv) Preparation of colloidal gold-labeled KLH (KLH conjugate) for control line To 200 mL of the 1 OD / mL 40 nm gold colloid solution (pH 6.1), 2.67 mL of KLH (Sigma) dissolved in 2 mM phosphate buffer (pH 6.1) at 375 μg / mL was added and stirred at room temperature for 10 minutes. To the mixture of gold colloid and KLH, 20 mL of 10% bovine serum albumin (BSA) solution was added and stirred at room temperature for 5 minutes. The mixture was then centrifuged at 10°C for 45 minutes, and the supernatant was removed. 10.7 mL of Conjugate Dilution Buffer (Scripps) was added to the resulting sediment to suspend the conjugate, yielding the KLH conjugate.

[0041] 2) Preparation of sample pad 20 mM MOPS (pH 7.2) containing 0.5% glucose and 2% polybrene was prepared as a sample pad pretreatment solution. A glass fiber pad (Lydall) was cut to the required size and soaked in the sample pad pretreatment solution at a volume 1.5 times the volume of the pad. The pad was dried in a dry oven at 70°C for 45 minutes and used as a sample pad.

[0042] 3) Preparation of labeled pads A conjugate solution was prepared by mixing 3 OD of anti-cTnI antibody conjugate, 0.75 OD of KLH conjugate, 0.5% Lipidure BL-1301, 2.0 mg / mL HBR (Scantibodies), 2.4% glucose, 2.0% NPS, 20 mM MOPS (pH 7.6), and one-sixth of the total volume of Conjugate Dilution Buffer. This solution was then impregnated into a glass fiber pad (Merck Millipore) at a volume 1.2 times the pad volume. The pad was then dried at 70°C for 45 minutes in a dry oven to obtain a labeled pad. 4) Preparation of an insoluble membrane carrier containing a detection area immobilized with anti-cTnI antibody, a control reagent detection area immobilized with anti-KLH antibody, and a linear surfactant area. For the test line, anti-cTnI monoclonal antibody was diluted to 3 mg / mL in 10 mM PB (containing 0.09% NaN3) (pH 8.0) containing 2.5% fructose. For the control line, rabbit anti-KLH polyclonal antibody (Bethyl) was diluted to 1 mg / mL in 10 mM PB (containing 0.09% NaN3) (pH 7.2) containing 2.5% sucrose. The anti-cTnI monoclonal antibody was applied in a line at a concentration of 1 μL / cm using an immunochromatography dispenser (BIO DOT) at a location 9 mm from the upstream end of the nitrocellulose membrane. The line width was approximately 0.7 mm. Anti-KLH polyclonal antibody was similarly applied at a location approximately 4 mm downstream from the test line to form a control line. The line width was approximately 0.7 mm. To form the linear surfactant area, a surfactant solution was prepared by diluting n-heptyl-β-D-thioglucoside to 1.0% by mass / volume. This surfactant solution was applied in a line at 1 μL / cm, 3.5 mm from the upstream end of the membrane carrier, and then dried. The line width was approximately 1 mm. Therefore, the distance between the detection area (test line) and the surfactant area was 5.5 mm. The membrane was dried in a dry oven at 70°C for 45 minutes to obtain an antibody-immobilized membrane.

[0043] 5) Preparation of immunochromatographic test strips An antibody-immobilized porous membrane (b) was attached to a backing sheet (a), and an application section was arranged upstream of the development section, with the surfactant section (j), anti-cTnI antibody (c), and then anti-KLH antibody (d) in that order. A polysulfone porous membrane (3rd Pad) (e) was then attached on top of the membrane. Next, the labeled-containing pad (f) prepared in 3) above was placed and attached, followed by the sample pad (g) prepared in 2) above, overlapping the labeled-containing pad. An absorbent pad (h) was then attached to the opposite end. Finally, the surfaces of the absorbent pad and antibody-immobilized membrane were covered with a top film (i) so that a portion of the antibody-immobilized membrane was exposed. The resulting structure was then cut into layers of each component, creating an immunochromatography test strip 1.

[0044] [Test Example 2] Preparation of immunochromatographic test strips for comparison Comparative immunochromatography test strip 2 was prepared using the same procedure as the immunochromatography test strip prepared in 1 above, except that no linear surfactant portion was prepared.

[0045] [Example 1] Confirmation test 1 of the effect of inhibiting non-specific reactions A detection test for human cardiac troponin I (cTnI) was conducted using immunochromatography test strips 1 and 2 prepared in Test Examples 1 and 2. 120 μL of plasma sample solution containing cardiac troponin I (cTnI) was added to the upstream end of the sample pad of immunochromatography test strips 1 and 2 prepared above, and the color development of the test line was measured after 15 minutes. 19 samples were used. The results are shown in Figures 3 and 4. In Figures 3 and 4, the horizontal axis represents the measured value obtained using E-test "TOSOH" II (cTnI3), an in vitro diagnostic drug for detecting cardiac troponin I (cTnI) manufactured by Tosoh Corporation. The measurement procedure was performed according to the attached documents.

[0046] Compared with the immunochromatography test strip 2 of the comparative example, the immunochromatography test strip 1 of the example showed a smaller deviation in the measurement value from E-test "TOSOH" II (cTnI3). The correlation coefficient (R value), which indicates the correlation of the measurement value with E-test "TOSOH" II (cTnI3), was 0.897 for the immunochromatography test strip 2 of the comparative example, but 0.935 for the immunochromatography test strip 1 of the example. Therefore, the presence of a linear surfactant portion enabled more accurate measurement values ​​to be obtained. Furthermore, more accurate measurements were obtained for samples with significantly different measurement values ​​from those of E-test "TOSOH" II (cTnI3) (plotted with black diamonds in Figures 3 and 4). Specifically, the measurement value for E-test "TOSOH" II (cTnI3) was 1379 pg / mL, while that for immunochromatography test strip 2 of the comparative example was 581.5 pg / mL. On the other hand, that for immunochromatography test strip 1 of the example was 775.6 pg / mL. Figure 5 is a graph showing the ratio of the measurement value of the immunochromatographic test strip 2 of the comparative example or the measurement value of the immunochromatographic test strip 1 of the example to the measurement value of "TOSOH" II (cTnI3). Not only the deviation samples, but also many other samples were found to have values ​​approaching the measurement value of "TOSOH" II (cTnI3). 6 and 7 show a comparison of the measured values ​​with those obtained using the Architect High Sensitive Troponin I ST (manufactured by Abbott Japan Co., Ltd.), an in vitro diagnostic reagent for detecting cardiac troponin I (cTnI). The measured values ​​obtained using the immunochromatographic test strip 1 of the example (Fig. 7: R = 0.934) were closer to the actual measured values ​​obtained using the Architect High Sensitive Troponin I ST than the measured values ​​obtained using the immunochromatographic test strip 2 of the comparative example (Fig. 6: R = 0.900).

[0047] [Example 2] Visual confirmation of the divergent specimen after development For the samples (plotted with black diamonds in Figures 3 to 7) in Example 1 that showed measurement values ​​significantly different from those measured by Etest "TOSOH" II (cTnI3), the development of the conjugate was observed 15 minutes after application to the upstream end of the sample pad of immunochromatographic test strips 1 and 2. The results are shown in Figure 8. In Test Strip 2, delayed development of the conjugate was observed as a reddish background before the test line. In Test Strip 1, delayed development of the conjugate was reduced, and the test line was darker than in Test Strip 2. In Test Strip 1, it is believed that most of the conjugate reached the test line and was captured.

[0048] [Example 3] Confirmation test 2 of the effect of inhibiting non-specific reactions A similar test to that in Example 1 was performed using 13 other plasma specimens. In Example 3, the results were compared with those measured using the Architect High Sensitive Troponin I ST. The results are shown in Figures 9 and 10.

[0049] The correlation coefficient (R value), which indicates the correlation between the measured value and Architect High Sensitive Troponin I ST, was 0.797 for the comparative immunochromatography test strip 2, but was 0.845 for the example immunochromatography test strip 1. Therefore, the presence of a linear surfactant portion enabled more accurate measured values ​​to be obtained.

[0050] [Comparative Example 1] Confirmation of the effect of non-linear surfactant portion The nonspecific reaction suppression effect of immunochromatography test strips with non-linear surfactant portions was tested. The anti-cTnI antibody conjugate and the gold colloid-labeled KLH (KLH conjugate) for the control line were prepared in the same manner as in Test Example 1. Comparative immunochromatography test strip 3 was prepared in the same manner as the immunochromatography test strip prepared in Test Example 1, except that a surfactant solution was prepared by diluting n-heptyl-β-D-thioglucoside to 0.05% by mass / volume, which was then applied at a volume of 37 μL / cm and then dried. When applying the solution, the volume was sprayed onto the entire antibody-immobilized membrane. Immunochromatography test strip 4 was also prepared using the same procedure, except that the surfactant solution was not applied to the antibody-immobilized membrane. Immunochromatography test strip 4 was prepared and tested in order to compare it with immunochromatography test strip 3 and to verify the effect of applying a surfactant to the entire antibody-immobilized membrane.

[0051] 120 μL of plasma sample solution containing cardiac troponin I (cTnI) was added to the upstream end of the sample pad of the immunochromatographic test strips 3 and 4 prepared above, and the color development of the test line was measured after 15 minutes. 20 samples were used. The measured values ​​of each of the two types of immunochromatographic test strips prepared were compared with the measured values ​​of the Architect High Sensitive Troponin I ST, an in vitro diagnostic reagent for detecting cardiac troponin I (cTnI). The results are shown in Figures 11 to 13.

[0052] For immunochromatography test strip 3, the correlation coefficient (R value) indicating the correlation between the measured value and the architect was 0.879 (Figure 11). For immunochromatography test strip 4, the correlation coefficient (R value) indicating the correlation between the measured value and the architect was 0.864 (Figure 12). The correlation coefficient between the values ​​of both immunochromatography test strips was 0.984. Therefore, it was found that applying a surfactant to the entire antibody-immobilized membrane did not improve the correlation coefficient much. [Industrial Applicability]

[0053] According to the immunochromatographic test strip of the present invention, it is possible to provide an immunochromatographic test strip which has a short reaction completion time and excellent accuracy. [Explanation of symbols]

[0054] (a) Backing sheet (b) Antibody-immobilized membrane (c) Anti-cTnI antibody (test line: detection area) (d) Anti-KLH antibody (control line: control capture reagent immobilized area) (e) 3rd Pad (f) Label-containing pad (g) Sample pad (h) Absorbent pad (i) Top film (j) Surfactant part (W) Line width of surfactant part

Claims

1. A test strip for detecting a substance to be detected by developing a sample that may contain the substance to be detected, the test strip comprising: (1) A sample pad having a sample supply portion for supplying a sample. (2) An insoluble membrane carrier having at least one detection portion for capturing and detecting a substance to be detected. Including, a labeling section in which a label that directly or indirectly binds to the substance to be detected and generates a signal in the detection section is disposed is provided between the sample supplying section and the detection section, and a linear surfactant section containing a surfactant is provided between the labeling section and the detection section, the surfactant section is formed in a line on the sample pad or the insoluble membrane carrier downstream of the label section, an antibody or an antigen that immunologically reacts with the substance to be detected is immobilized on the label; The test strip as described above, wherein an antibody or antigen that immunologically reacts with the substance to be detected is immobilized on the detection portion.

2. 2. The test strip according to claim 1, wherein the antibody or antigen immobilized on the label and immunologically reacting with the substance to be detected is different from the antibody or antigen immobilized on the detection portion and immunologically reacting with the substance to be detected.

3. The test strip according to claim 1 or 2, which is of a lateral flow type.

4. The test strip according to any one of claims 1 to 3, wherein the surfactant contained in the surfactant portion is a nonionic surfactant.

5. The test strip according to any one of claims 1 to 4, wherein the substance to be detected is a substance of biological origin.

6. the substance of biological origin is troponin, the antibody or antigen that immunologically reacts with the substance to be detected immobilized on the label, and the antibody or antigen that immunologically reacts with the substance to be detected immobilized on the detection part are both anti-troponin monoclonal antibodies; The test strip of claim 5 .

7. 7. The test strip according to claim 1, wherein the sample that may contain the substance to be detected is at least one selected from the group consisting of blood, serum, and plasma.

8. The test strip according to any one of claims 1 to 7, wherein the sample that may contain the substance to be detected is a sample that has not been pretreated.

9. Between the (1) and (2), as the marking part (3) a label-containing pad in which a label that generates a signal in the detection unit is disposed; and The test strip according to any one of claims 1 to 8, wherein the surfactant portion is provided on an insoluble membrane carrier.

10. The test strip according to any one of claims 1 to 9, wherein the surfactant portion has a line width of 0.5 to 10 mm.

11. The test strip according to any one of claims 1 to 10, wherein the surfactant contained in the surfactant portion is a surfactant solution having a concentration equal to or higher than the critical micelle concentration.

12. A device comprising a test strip according to any one of claims 1 to 11.

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