JP5128256B2 - Immunochromatographic method - Google Patents

Description

  The present invention relates to a highly sensitive immunochromatographic method using amplification.

  As a method for qualitatively or quantitatively measuring the presence of a test substance present in a biological sample such as urine or blood, an immunological measurement method is widely used. Among them, the immunochromatography method is commonly used because it is easy to operate and can be measured in a short time.

  The current general immunochromatography method has a problem that the antigen is not detected due to low sensitivity, resulting in false negatives. Therefore, further enhancement of sensitivity of immunochromatography is desired.

  In an immunochromatography method using colloidal gold as a label, a silver amplification method is known as a method for increasing sensitivity. In Patent Document 1, after a sample solution is flowed, a solution for silver amplification is dropped onto a detection line portion to perform amplification and achieve high sensitivity.

Japanese Patent Laid-Open No. 2002-202307

  In the immunological measurement method, high sensitivity has been demanded, and high sensitivity has been achieved by silver amplification. In order to detect a test sample contained in a very small amount in a relatively minimally invasive specimen such as gargle or urine, higher sensitivity is required. An object of the present invention is to provide a highly sensitive immunochromatographic method.

  In the present invention, when performing an immunochromatography method, a test substance is detected by sensitizing with an amplification solution containing a silver-containing compound and a reducing agent for silver ions, and further a solid in the amplification solution. It has been found that a highly sensitive immunochromatographic method can be provided by including particles. The present invention has been completed based on the above findings.

  That is, according to the present invention, a test substance and a labeling substance modified with a first antibody against the test substance are developed on an insoluble carrier in a state in which these complexes are formed, and a second substance against the test substance is obtained. In an immunochromatographic method including detecting the test substance by capturing the test substance and the labeling substance at a reaction site on an insoluble carrier having the antibody of, comprising a compound containing silver and a reducing agent for silver ions There is provided an immunochromatographic method characterized in that a test substance is detected by sensitizing with an amplification solution, and further, solid particles are contained in the amplification solution.

Preferably, the insoluble carrier is a porous carrier.
Preferably, the average particle size after amplification of the labeling substance captured at the reaction site is 1/10 or more and 1 or less with respect to the average pore size of the porous carrier.

Preferably, the particle size of the particles contained in the amplification solution is 0.5 μm or more and 50 μm or less.
Preferably, the particles contained in the amplification liquid are metal particles, metal compound particles, colored particles, or carbon particles.
Preferably, the metal particles or metal compound particles are silver particles or silver compound particles.

  The present invention further includes (a) an insoluble carrier, (b) a labeling substance containing a metal modified with a first antibody against the test substance, (c) a second antibody against the test substance, and (d) silver. There is provided an immunochromatographic kit for use in the above-described method of the present invention, comprising at least a compound, a reducing agent for silver ions, and an amplification solution containing solid particles.

  In the present invention, it is easy to visually recognize the label in the detection line portion by silver amplification, and at the same time, by further putting solid particles in the amplification solution, the flow path becomes narrow due to silver particles amplified in the flow path. The solid particles are captured by the detection unit, and the visibility of the detection line unit is further increased, thereby enabling a highly sensitive immunoassay method.

1. Immunochromatography In general, the immunochromatography method is a method for determining and measuring an analyte simply, quickly, and specifically by the following method. That is, a chromatographic carrier having at least one reaction site containing an immobilization reagent (antibody, antigen, etc.) that can bind to an analyte is used as a stationary phase. On the chromatographic carrier, a dispersion liquid in which a detection label modified by a reagent capable of binding to the analyte is dispersed is used as a moving layer to move chromatographically in the chromatographic carrier, and the analysis target The product reaches the reaction site while specifically binding to the detection label. In the reaction site, the immobilization reagent part is only present when the analyte is present in the analyte solution by specifically binding the complex of the analyte and the label for detection to the immobilization reagent. This is a technique for qualitatively and quantitatively analyzing the presence of the detected substance in the liquid to be analyzed by using the fact that the labeled substance for detection is concentrated on the liquid and visually or using an appropriate instrument.

  The apparatus for performing the immunochromatography method in the present invention may contain a compound containing silver and a reducing agent for silver ions, and a complex of the analyte bound to the immobilized reagent and a label for detection. The signal can be amplified by an amplification reaction using as a nucleus, and as a result, high sensitivity can be achieved. According to the present invention, a rapid and highly sensitive immunochromatograph can be performed.

2. Test sample The test sample that can be analyzed by the immunochromatography method of the present invention is not particularly limited as long as it is a sample that may contain an analysis target. For example, a biological sample, In particular, animal (especially human) body fluids (eg blood, serum, plasma, spinal fluid, tears, sweat, urine, pus, runny nose or sputum) or excreta (eg feces), organs, tissues, mucous membranes, Mention may be made of the skin, swollen specimens suspected of containing them, gargles, or the animals and plants themselves or their dried bodies.

3. Pretreatment of test sample In the immunochromatography method of the present invention, the test sample is used as it is or in the form of an extract obtained by extracting the test sample using a suitable extraction solvent, The extract can be used in the form of a diluted solution obtained by diluting the extract with an appropriate diluent, or in the form obtained by concentrating the extract by an appropriate method. As the solvent for extraction, a solvent (for example, water, physiological saline, or buffer solution) used in usual immunological analysis methods, or direct antigen-antibody reaction by diluting with the solvent It is also possible to use a water-miscible organic solvent capable of

4). Structure The immunochromatographic strip that can be used in the immunochromatographic method of the present invention is not particularly limited as long as it is an immunochromatographic strip that can be used in a normal immunochromatographic method. For example, FIG. 1 schematically shows a plan view of a conventional immunochromatographic strip. FIG. 2 is a longitudinal sectional view schematically showing a longitudinal section of the immunochromatographic kit shown in FIG. FIG. 3 schematically shows a cross-sectional view of another example of an immunochromatographic strip that can be used in the present invention.

  The immunochromatographic strip 10 of the present invention comprises a sample addition pad 5, a labeled substance holding pad (for example, a colloidal gold antibody holding pad) 2, from upstream to downstream in the developing direction (direction indicated by arrow A in FIG. 1), A chromatographic carrier (for example, an antibody-immobilized membrane) 3 and an absorption pad 4 are arranged on the adhesive sheet 5 in this order.

  The chromatographic carrier 3 includes a detection zone (which may be referred to as a detection unit) 31 that has a supplementary site 3a and is an area in which an antibody or antigen that specifically binds to an analyte is immobilized. If desired, it further has a control zone (which may be referred to as a control part) 32 which is a region where a control antibody or antigen is immobilized. Furthermore, the detection zone 31 and the control zone 32 contain an organic silver salt for amplification and a reducing agent for silver ions.

  The labeling substance holding pad 2 is prepared by preparing a suspension containing the labeling substance, applying the suspension to an appropriate absorbent pad (for example, a glass fiber pad), and then drying the suspension. be able to.

  As the sample addition pad 1, for example, a glass fiber pad can be used.

4-1. Label for detection Colored particles used for immunoagglutination can be used as the label for detection. For example, a metal such as a metal colloid can be used. The average particle size of the carrier particles (or colloid) is preferably in the range of 0.02 to 10 μm. Liposomes and microcapsules containing pigments can also be used as colored particles. Any conventionally known colored metal colloid can be used as colored particles for labeling. Examples thereof include a gold colloid, a silver colloid, a platinum colloid, an iron colloid, an aluminum hydroxide colloid, and a composite colloid thereof, and a gold colloid, a silver colloid, a platinum colloid, and a composite colloid thereof are preferable. In particular, gold colloid and silver colloid are preferable in that the gold colloid is red and the silver colloid is yellow at appropriate particle sizes. The average particle size of the metal colloid is preferably about 1 nm to 500 nm, more preferably 1 to 50 nm. 1-15 nm is particularly preferable. The metal colloid and the specific binding substance can be bound according to a conventionally known method (for example, The Journal of Histochemistry and Cytology, Vol. 30, No. 7, pp 691-696, (1982)). That is, a metal colloid and a specific binding substance (for example, an antibody) are mixed in an appropriate buffer at room temperature for 5 minutes or more. After the reaction, the target metal colloid-labeled specific binding substance can be obtained by dispersing the precipitate obtained by centrifugation in a solution containing a dispersant such as polyethylene glycol. When gold colloid particles are used as the metal colloid, commercially available products may be used. Alternatively, colloidal gold particles can be prepared by a conventional method, for example, a method of reducing chloroauric acid with sodium citrate (Nature Phys. Sci., Vol. 241, 20, (1973), etc.).

  According to the present invention, in an immunochromatograph using a metal colloid label or a metal sulfide label, other metal alloy label (hereinafter sometimes referred to as a metal-based label), or a polymer particle label containing a metal as a label for detection. The signal of the metallic label can be amplified. Specifically, after the complex of the analyte and the label for detection is formed, a reducing agent is brought into contact with silver ions and silver ions supplied from a silver-containing compound such as an organic silver salt. When the silver ions are reduced to produce silver particles, the silver particles are deposited on the metal label using the metal label as a nucleus, so that the metal label is amplified and analysis of the analyte is enhanced. Sensitivity can be implemented. Therefore, in the immunochromatography method of the present invention, the reaction of depositing on the label of the immune complex is carried out using silver particles generated by the reducing action of silver ions by the reducing agent, and thus the amplified signal is analyzed. Except for the above, conventionally known immunochromatographic methods can be applied as they are.

  In the immunochromatography method of the present invention, a metal colloid label or a metal sulfide label is used as a label used to label an antibody or antigen that specifically binds to an analyte (antigen or antibody) or a standard compound. The metal colloid label or metal sulfide label is not particularly limited as long as it is a label that can be used in a normal immunochromatographic method. Examples of the metal colloid label include platinum colloid, gold colloid, and palladium. Colloids or silver colloids and mixtures thereof can be mentioned. Examples of metal sulfide labels include iron, silver, palladium, lead, copper, cadmium, bismuth, antimony, tin, or mercury sulfides. Can be mentioned. In the immunochromatographic method of the present invention, one or more of these metal colloid labels and / or metal sulfide labels can be used as labels.

4-2. Antibody In the immunochromatography method of the present invention, the antibody having specificity for the analyte is not particularly limited. For example, an antiserum prepared from the serum of an animal immunized with the analyte An immunoglobulin fraction purified from the antiserum, a monoclonal antibody obtained by cell fusion using the spleen cells of an animal immunized with the analyte, or a fragment thereof [eg F (ab ′) 2, Fab , Fab ′, or Fv] can be used. These antibodies can be prepared by a conventional method.

4-3. Chromatographic carrier The chromatographic carrier is preferably a porous carrier. In particular, a nitrocellulose film, a cellulose film, an acetylcellulose film, a polysulfone film, a polyethersulfone film, a nylon film, a glass fiber, a nonwoven fabric, a cloth, or a thread is preferable.

  Usually, a detection zone is prepared by immobilizing a detection substance on a part of a chromatographic carrier. The detection substance may be directly immobilized on a part of the chromatographic carrier by physical or chemical bonding, or the detection substance may be physically or chemically bonded to fine particles such as latex particles. The fine particles may be trapped and immobilized on a part of the chromatographic carrier. The chromatographic carrier is preferably used after immobilizing the detection substance and then subjecting it to nonspecific adsorption prevention treatment by treatment with an inactive protein or the like.

4-4. Sample addition pad Examples of the material of the sample addition pad include, but are not limited to, cellulose filter paper, glass fiber, polyurethane, polyacetate, cellulose acetate, nylon, and cotton cloth having uniform characteristics. The sample addition unit not only accepts a sample containing the added analysis target, but also has a function of filtering insoluble matter particles and the like in the sample. In addition, in order to prevent the analyte in the sample from adsorbing nonspecifically on the material of the sample addition part and reducing the accuracy of the analysis, the material constituting the sample addition part is preliminarily nonspecific. In some cases, the anti-adsorption treatment is used.

4-5. Labeling substance holding pad Examples of the material of the labeling substance holding pad include cellulose filter paper, glass fiber, and non-woven fabric. The labeling substance holding pad is impregnated with a predetermined amount of the detection label prepared as described above and dried. To do.

4-6. Absorption pad The absorption pad is a part that absorbs and removes unreacted labeling substances that are not insolubilized in the detection part of the chromatographic carrier while the added sample is physically absorbed by the chromatographic movement. Cellulose filter paper, non-woven fabric Water-absorbing materials such as cloth and cellulose acetate are used. The chromatographic speed after the chromatographic tip of the added sample reaches the absorber varies depending on the material, size, etc. of the absorbent, so it is possible to set a speed that suits the measurement of the analyte. it can.

5. Hereinafter, the sandwich method, which is a specific embodiment of the chromatographic method of the present invention, will be described. In the sandwich method, although not particularly limited, for example, analysis of an analysis object can be performed by the following procedure. First, a first antibody and a second antibody having specificity for an analyte (antigen) are prepared in advance by the method described above. In addition, the second antibody is labeled in advance. The first antibody may be immobilized on a suitable insoluble thin film support (for example, a nitrocellulose membrane, a glass fiber membrane, a nylon membrane, or a cellulose membrane) and may contain an analyte (antigen). When contacted with a test sample (or an extract thereof), an antigen-antibody reaction occurs when an analyte is present in the test sample. This antigen-antibody reaction can be performed in the same manner as a normal antigen-antibody reaction. At the same time as or after the antigen-antibody reaction, when an excessive amount of the labeled second antibody is further contacted, if the analyte is present in the test sample, the immobilized first antibody and the analyte (antigen) ) And a labeled second antibody is formed.

  In the sandwich method, after the reaction between the immobilized first antibody, the analyte (antigen) and the second antibody is completed, the labeled second antibody that did not form the immune complex is removed, and then, for example, Then, by supplying a metal ion and a reducing agent to the region where the immobilized first antibody is immobilized on the insoluble thin film support, a signal from the label of the labeled second antibody that forms the immune complex is amplified. Alternatively, a metal ion and a reducing agent are added to the labeled second antibody and simultaneously added to the thin film support, thereby amplifying the signal from the label of the labeled second antibody that has formed the immune complex.

6). Solid particles contained in amplification solution In the present invention, the test substance is detected by sensitization using an amplification solution containing a compound containing silver and a reducing agent for silver ions as described below. The amplification liquid used in the invention is characterized by containing solid particles. In the present invention, the amplification liquid containing solid particles may be prepared in advance, and then the amplification liquid may be flowed on the insoluble carrier, or the solid particles may be added to the amplification liquid during the flow of the amplification liquid onto the insoluble carrier. May be included, and the detection line part (part to be detected) may be passed.

  The type of solid particles contained in the amplification liquid is not particularly limited as long as it can be visually recognized, and may be, for example, metal particles, metal compound particles, colored particles, or carbon particles. Specific examples of the metal particles or metal compound particles include silver particles or silver compound particles. The solid particles may be, for example, silver particles having a colloidal gold colloid generated by an amplification solution as in the examples of the present specification as a nucleus.

  The particle size of the particles contained in the amplification solution is not particularly limited as long as the effect of the present invention can be achieved, but preferably as a size with a certain degree of visibility and the fluidity in the solution is maintained. 0.5 μm or more and 50 μm or less. The average particle size after amplification of the labeling substance captured at the reaction site is preferably 1/10 or more and 1 or less with respect to the average pore size of the porous carrier.

7. Amplification solution In the present invention, the amplification solution that can be used is a general book in the field of photographic chemistry (for example, “Basics of Revised Photographic Engineering-Silver Salt Photography Edition” (Japan Photographic Society, Corona), It is a so-called developer as described in “Photochemistry” (Akira Sakurai, Photographic Publishing Co., Ltd.), “Latest Prescription Handbook” (Shinichi Kikuchi et al., Amiko Publishing Co., Ltd.).

  In the present invention, any so-called physical developer that contains silver ions in the solution and is reduced mainly by metal colloids or the like in which the silver ions in the solution become the core of development is used as the amplification solution. be able to.

8). Compound containing silver As the silver-containing compound used in the present invention, an organic silver salt, an inorganic silver salt, or a silver complex can be used.

  The organic silver salt used in the present invention is an organic compound containing a reducible silver ion. The compound containing reducible silver ions used in the present invention may be any organic silver salt, inorganic silver salt, or silver complex. For example, silver nitrate, silver acetate, silver lactate, silver butyrate and the like are known.

  Further, it may be a silver salt or a coordination compound that forms metallic silver that is relatively stable to light when heated to 50 ° C. or higher in the presence of a reducing agent.

  The organic silver salt used in the present invention may be a compound selected from a silver salt of an azole compound and a silver salt of a mercapto compound. Preferably, the azole compound is a nitrogen-containing heterocyclic compound, more preferably a triazole compound or a tetrazole compound. The mercapto compound is a compound having at least one mercapto group or thione group in the molecule.

The silver salt of the nitrogen-containing heterocyclic compound in the present invention is preferably a silver salt of a compound having an imino group. Representative compounds are listed below, but are not limited to these compounds. Silver salt of 1,2,4-triazole, or silver salt of benzotriazole and its derivatives (eg, methylbenzotriazole silver salt or 5-chlorobenzotriazole silver salt), US Pat. 1H-tetrazole compounds such as phenyl mercaptotetrazole described in US Pat. No. 4,220,709, and imidazole and imidazole derivatives described in US Pat. No. 4,260,677. Among such silver salts, particularly preferred compounds are silver salts of benzotriazole derivatives or mixtures of two or more thereof.
The silver salt of the nitrogen-containing heterocyclic compound used in the present invention is most preferably a silver salt of a benzotriazole derivative.

  The compound having a mercapto group or thione group in the present invention is preferably a heterocyclic compound containing 5 or 6 atoms. In this case, at least one of the atoms in the ring is a nitrogen atom, and the other atoms are carbon, oxygen, and sulfur atoms. Such heterocyclic compounds include, but are not limited to, triazoles, oxazoles, thiazoles, thiazolines, imidazoles, diazoles, pyridines, and triazines. I don't mean.

Representative examples of the silver salt of a compound having a mercapto group or a thione group are listed below, but are not limited thereto.
Silver salt of 3-mercapto-4-phenyl-1,2,4-triazole, silver salt of 2-mercapto-benzimidazole, silver salt of 2-mercapto-5-aminothiazol, silver of mercaptotriazine Salts, silver salts of 2-mercaptobenzoxazole, and silver salts of the compounds described in US Pat. No. 4,123,274.

As the compound having a mercapto group or thione group in the present invention, a compound containing no heterocycle can also be used. As the mercapto or thione derivative not containing a heterocyclic ring, an aliphatic or aromatic hydrocarbon compound having a total carbon number of 10 or more is preferable.
Among the mercapto or thione derivatives that do not contain a heterocycle, useful compounds include the following, but are not limited thereto.
Silver salt of thioglycolate (for example, silver salt of S-alkylthioglycolic acid having an alkyl group having 12 to 22 carbon atoms), silver salt of dithiocarboxylic acid (for example, silver salt of dithioacetic acid or silver salt of thioamide) )

An organic compound having a silver salt of carboxylic acid is also preferably used. For example, a linear carboxylic acid. Specifically, a C 6-22 carboxylic acid is preferably used. In addition, it is a silver salt of an aromatic carboxylic acid. Examples of aromatic carboxylic acids and other carboxylic acids include, but are not limited to, the following compounds.
Substituted or unsubstituted silver benzoate (eg, silver 3,5-dihydroxybenzoate, silver o-methylbenzoate, silver m-methylbenzoate, silver p-methylbenzoate, silver 2,4-dichlorobenzoate, acetamide Silver benzoate and silver p-phenylbenzoate), silver tannate, silver phthalate, silver terephthalate, silver salicylate, silver phenylacetate, or silver pyromellitic acid.

In the present invention, fatty acid silver containing a thioether group as described in US Pat. No. 3,330,663 is also preferably used. Soluble having a hydrocarbon chain containing an ether or thioether bond or having a sterically shielded substituent in the α-position (above the hydrocarbon group) or the ortho-position (above the aromatic group) Silver carboxylate can also be used. These have improved solubility in a coating solvent and become a coated product with little light scattering.
Such silver carboxylates are described in US Pat. No. 5,491,059. Any of the silver salt mixtures described herein can be used as needed in the present invention.
The silver salts of sulfonates described in US Pat. No. 4,504,575 can also be used in embodiments of the present invention.

  Further, in the present invention, for example, acetylene silver salts described in US Pat. No. 4,761,361 and US Pat. No. 4,775,613 can be used. It can also be provided as a core-shell type silver salt as described in US Pat. No. 6,355,408. These silver salts are composed of a core made of one or more silver salts and a shell made of one or more different silver salts.

In the present invention, another useful non-photosensitive silver source is a silver dimer composition composed of two different silver salts described in US Pat. No. 6,472,131. Such non-photosensitive silver dimer composites consist of two different silver salts. When the two kinds of silver salts contain a linear saturated hydrocarbon group as a silver ligand, the difference in the number of carbon atoms of the ligands is 6 or more.
The organic silver salt is generally contained in an amount of 0.001 mol / m ^{2 to} 0.2 mol / m ² , preferably 0.001 mol / m ^{2 to} 0.05 mol / m ^{2 as} silver.

The inorganic silver salt or silver complex used in the present invention is a compound containing a reducible silver ion. Preferably, it is an inorganic silver salt or silver complex that forms metallic silver that is relatively stable to light when heated to 50 ° C. or higher in the presence of a reducing agent.
The inorganic silver salt used in the present invention is, for example, silver halide (silver chloride, silver bromide, silver chlorobromide, silver iodide, silver chloroiodide, silver chloroiodobromide, silver iodobromide, etc.) Silver salts of thiosulfates (eg, sodium, potassium, or ammonium salts), silver salts of thiocyanate (eg, sodium, potassium, or ammonium salts), and sulfites (eg, sodium) Salt, potassium salt, or ammonium salt).

The inorganic silver salt used in the present invention is preferably silver halide.
Silver halide grain formation methods used in the present invention are well known in the photographic industry and are described, for example, in Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458. Can be used, but is specifically prepared by adding a silver-feeding compound (eg, silver nitrate) and a halogen-feeding compound into gelatin or other polymer solution.

  The grain size of silver halide is preferably fine in order to reduce inspection noise, specifically 0.20 μm or less, more preferably 0.10 μm or less, and still more preferably in the range of nanoparticles. The grain size here means the diameter when converted into a circular image having the same area as the projected area of silver halide grains (in the case of tabular grains, the projected area of the main plane).

  Silver thiosulfate, silver thiocyanate, silver sulfite, and the like can be obtained from a silver supply compound (for example, silver nitrate) and thiosulfate (for example, sodium salt, potassium salt, or ammonium salt) by the same grain forming method as silver halide. It is prepared by mixing a silver salt, a silver salt of thiocyanate (for example, sodium salt, potassium salt, or ammonium salt) and a sulfite (for example, sodium salt, potassium salt, or ammonium salt).

  In general, if the silver ion concentration in the amplification solution is too high, silver ions are reduced in the amplification solution. To prevent this, silver ions may form a complex using a complexing agent. Good. Such complexing agents include amino acids and heterocyclic bases such as glycine and histidine, imidazole, benzimidazole, pyrazole, purine, pyridine, aminopyridine, nicotinamide, quinoline, and other similar aromatic heterocyclic groups. Systems are known and are described, for example, in EP 0293947. Further, as the complex salt forming agent, thiosulfate and thiocyanate can be used. Specific examples of the silver complex used in the present invention include, for example, a thiosulfate and silver ion complex, a thiocyanate and silver ion complex, or a complex silver complex thereof, and a sugar thione derivative and a silver ion complex. And a complex of a cyclic imide compound (for example, uracil, urazole, 5-methyluracil, barbituric acid, etc.) and silver ion, or a complex of 1,1-bissulfonylalkane and silver ion. A preferable silver complex used in the present invention is a complex of a cyclic imide compound (for example, uracil, urazole, 5-methyluracil, barbituric acid, etc.) and silver ion.

  The silver complex used in the present invention can be prepared by a generally known salt forming reaction. For example, it is prepared by mixing a water-soluble silver supplier (for example, silver nitrate) and a ligand compound corresponding to the silver complex in water or a water-miscible solvent. The prepared silver complex can be used after removing by-product salts by a known desalting method such as dialysis or ultrafiltration.

The inorganic silver salt or silver complex is generally contained in an amount of 0.001 mol / m ^{2 to} 0.2 mol / m ² , preferably 0.01 mol / m ^{2 to} 0.05 mol / m ^{2 as} silver.

  Moreover, when using inorganic silver salt or a silver complex, it is preferable to contain the solvent of an inorganic silver salt or a silver complex. As the solvent used in the present invention, a compound used as a ligand for forming the silver complex described in the section of the silver complex is preferably used. For example, thiosulfate, thiocyanate, sugar thione derivative, cyclic imide compound, and 1,1-bissulfonylalkane sugar. The solvent used in the present invention is more preferably a cyclic imide compound such as uracil, urazole, 5-methyluracil, and barbituric acid. The solvent used in the present invention is preferably used in the range of 0.1 to 10 moles with respect to silver ions.

9. Reducing agent for silver ions The reducing agent for silver ions can be any inorganic or organic material that can reduce silver (I) ions to silver, or a mixture thereof.
As the inorganic reducing agent, there are known reducing metal salts and reducing metal complex salts whose valence can be changed by metal ions such as Fe ²⁺ , V ²⁺ , Ti ³⁺ , etc., and can be used in the present invention. it can. When using an inorganic reducing agent, it is necessary to complex or reduce the oxidized ions to remove or render them harmless. For example, in a system using Fe ⁺² as a reducing agent, a complex of Fe ³⁺ that is an oxide can be formed using citric acid or EDTA, and can be rendered harmless.
In this system, it is preferable to use such an inorganic reducing agent, more preferably a metal salt of Fe ²⁺ .

  Further, developing agents used in wet silver halide photographic light-sensitive materials (for example, methyl gallate, hydroquinone, substituted hydroquinone, 3-pyrazolidones, p-aminophenols, p-phenylenediamines, hindered phenols, amidoximes , Azines, catechols, pyrogallols, ascorbic acid (or derivatives thereof, and leuco dyes), and other materials apparent to those skilled in the art, for example, see US Pat. , 020, 117 (Bauer et al.) Can be used in the present invention.

  “Ascorbic acid reducing agent” means a complex of ascorbic acid and its derivatives. Ascorbic acid reducing agents are described in many documents as described below, for example, US Pat. No. 5,236,816 (Purol et al.) And the literature cited therein.

As the reducing agent in the present invention, an ascorbic acid reducing agent is preferable. Useful ascorbic acid reducing agents include ascorbic acid analogs, isomers and derivatives thereof. Such compounds include, but are not limited to, those listed below.
D- or L-ascorbic acid and sugar derivatives thereof (eg, γ-lactoascorbic acid, glucoascorbic acid, fucoscorbic acid, glucoheptascorbic acid, maltoascorbic acid), sodium salt of ascorbic acid, potassium salt of ascorbic acid, Isoascorbic acid (or L-erythroascorbic acid), salts thereof (eg, alkali metal salts, ammonium salts or salts known in the art), enediol type ascorbic acid, enaminol type ascorbic acid, thioeno- Type ascorbic acid), e.g. U.S. Pat. No. 5,498,511, EP-A-0585,792, EP-A-0573700, EP-A-0588408, U.S. Pat. No. 5,089,819, U.S. Pat. 278,035, US patent 5,384,232, U.S. Pat. No. 5,376,510, JP7-56286, U.S. Patent No. 2,688,549, and Reseach Disclosure37152 compound as described in (March 1995).

  Among these compounds, D, L or D, L-ascorbic acid (and its alkali metal salt) or isoascorbic acid (or its alkali metal salt) is preferable, and a sodium salt is a preferable salt. A mixture of these reducing agents can be used as necessary.

Hindered phenols are also preferably used alone or in combination with one or more contrast reducing agents and contrast enhancing agents.
A hindered phenol is a compound having only one hydroxyl group on the benzene ring and having at least one substituent in the ortho position relative to the hydroxyl group. The hindered phenol reducing agent may have a plurality of hydroxyl groups as long as it has a plurality of hydroxyl groups in separate benzene rings.
Hindered phenol reducing agents include, for example, binaphthols (ie dihydroxybinaphthols), biphenols (ie dihydroxybiphenols), bis (hydroxynaphthyl) methanes, bis (hydroxyphenyl) methanes (ie bisphenols), hinders Examples include dophenols and hindered naphthols, which may be substituted.

Representative binaphthols are the following compounds, but are not limited thereto.
1,1′-bi-2-naphthol, 1,1′-bi-4-methyl-2-naphthol, and described in US Pat. No. 3,094,417 and US Pat. No. 5,262,295 Compound.

Representative biphenols are the compounds listed below, but are not limited thereto.
2- (2-Hydroxy-3-tert-butyl-5-methylphenyl) -4-methyl-6-n-hexylphenol, 4,4'-dihydroxy-3,3 ', 5,5'-tetra-t -Butylbiphenyl, 4,4'-dihydroxy-3,3 ', 5,5'-tetramethylbiphenyl, and compounds described in US Pat. No. 5,262,295.

Representative bis (hydroxynaphthyl) methanes are the following compounds, but are not limited thereto.
4,4′-Methylenebis (2-methyl-1-naphthol), a compound described in US Pat. No. 5,262,295.

Representative bis (hydroxyphenyl) methanes are the compounds listed below, but are not limited thereto.
Bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane (CAO-5), 1,1′-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethyl Hexane (NONOX or PERMANAX WSO), 1,1′-bis (3,5-di-t-butyl-4-hydroxyphenyl) methane, 2,2′-bis (4-hydroxy-3-methylphenyl) propane, 4,4'-ethylidene-bis (2-t-butyl-6-methylphenol), 2,2'-isobutylidene-bis (4,6-dimethylphenol) (LOWINOX 221B46), 2,2'- Bis (3,5-dimethyl-4-hydroxyphenyl) propane and the compounds described in US Pat. No. 5,262,295.

Representative hindered phenols are the compounds listed below, but are not limited thereto.
2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,4-di-t-butylphenol, 2,6-dichlorophenol, 2,6-dimethylphenol, and 2-t-butyl-6-methylphenol.

Representative hindered naphthols are the following compounds, but are not limited thereto.
1-naphthol, 4-methyl-1-naphthol, 4-methoxy-1-naphthol, 4-chloro-1-naphthol, 2-methyl-1-naphthol, and compounds described in US Pat. No. 5,262,295 .

In addition, they are disclosed as reducing agents for the following compounds.
Amidoximes (eg phenylamidoxime), 2-thienylamidoxime, p-phenoxyphenylamidoxime, combinations of aliphatic carboxylic acid allyl hydrazide and ascorbic acid (eg 2,2′-bis (hydroxymethyl) -propionyl-β-phenylhydrazide and Combinations of ascorbic acid), at least one of polyhydroxybenzene and hydroxylamine, reductone and hydrazine (for example, a combination of hydroquinone and bis (ethoxyethyl) hydroxylamine), piperidi-4-methylphenylhydrazine, hydroxamic acid (for example, phenylhydroxam) Acid, p-hydroxyphenyl hydroxamic acid, and o-alanine hydroxamic acid), combinations of azines and sulfonamidophenols (for example, Phenothiazine and 2,6-dichloro-4-benzenesulfonamidophenol), α-cyanophenylacetic acid derivatives (eg ethyl-α-cyano-2-methylphenylacetic acid, ethyl-α-cyanophenylacetic acid), bis-o-naphthol (For example, 2,2′-dihydroxy-1-binaphthyl, 6,6′-dibromo-2,2′-dihydroxy-1,1′-binaphthyl, bis (2-hydroxy-1-naphthyl) methane),

A combination of bis-naphthol and a 1,3-dihydroxybenzene derivative (for example, 2,4-dihydroxybenzophenone, 2,4-dihydroxyacetophenone), 5-pyrazolone (for example 3-methyl-1-phenyl-5-pyrazolone), Reductones (eg, dimethylaminohexo-reductone, anhydrodihydro-aminohexo-reductone, or anhydrodihydro-piperidone-hexose reductone), indan-1,3-diones (eg, 2-phenylindan-1,3) -Diones), chromans (eg 2,2-dimethyl-7-t-butyl-6-hydroxychroman), 1,4-dihydroxypyridines (eg 2,6-dimethoxy-3,5-dicarbethoxy-1,4) -Dihydropyridine), ascorbic acid derivatives (1- Ascorbic acid Parumite - DOO, ascorbic acid Suteare - g), unsaturated aldehydes (ketones), 3-pyrazolidones.

  Reducing agents that can be used in the present invention include substituted hydrazines including sulfonyl hydrazines as described in US Pat. No. 5,464,738. Other useful reducing agents are described, for example, in US Pat. No. 3,074,809, US Pat. No. 3,094,417, US Pat. No. 3,080,254, and US Pat. No. 3,887,417. Yes. Also useful are the auxiliary reducing agents described in US Pat. No. 5,981,151.

  The reducing agent may be used in combination with a hindered phenol reducing agent and other compounds selected from various auxiliary reducing agents as listed below. Also useful are mixtures of three-component reducing agents with contrast enhancing agents. As the auxiliary reducing agent, trityl hydrazide and formyl-phenyl hydrazide described in US Pat. No. 5,496,695 can be used.

Contrast enhancing agents can be used with reducing agents. For example, the following compounds are useful as the contrast enhancer, but are not limited thereto.
Hydroxylamine (including hydroxylamine and alkyl and aryl substituted derivatives), alkanolamine and ammonium phthalate as described in US Pat. No. 5,545,505, hydroxamic acid compound as described in US Pat. No. 5,545,507, N-acylhydrazine compounds described in US Pat. No. 5,558,983 and hydrogen atom donor compounds described in US Pat. No. 5,637,449.

  Not all reducing agents and organic silver salt combinations are equally effective. One of the preferable combinations is a silver salt of benzotriazole or an organic compound thereof, a substituted compound thereof, or a mixture thereof, and an ascorbic acid type reducing agent as a reducing agent.

  The reducing agent in the present invention is contained in an amount of 1% by mass to 10% by mass (dry mass) with respect to silver in the organic silver. In a multilayer structure, if the reducing agent is added to a layer other than the layer containing the organic silver salt, the proportion is slightly higher, more preferably about 2% to 15% by weight. The auxiliary reducing agent is contained in an amount of approximately 0.001% by mass to 1.5% by mass (dry weight).

10. Other auxiliaries Other auxiliaries for the amplification solution may include buffers, preservatives such as antioxidants or organic stabilizers, and rate regulators. As a buffering agent, for example, a buffering agent using acetic acid, citric acid, sodium hydroxide or any salt thereof, tris (hydroxymethyl) aminomethane, or a buffering agent used for general chemical experiments is used. Can do. These buffers can be used as appropriate to adjust the pH to the optimum value for the amplification solution.

  The following examples further illustrate the present invention, but the present invention is not limited to the examples.

(1) Preparation of immunochromatography kit for hCG detection (1-1) Preparation of gold colloid modified with anti-hCG antibody 50 mM KH ₂ PO ₄ buffer (pH 7.0) in 9 mL of 50 nm diameter gold colloid solution (EM.GC50, BBI) 1 mL of a 50 μg / mL anti-hCG monoclonal antibody (Anti-hCG 5008 SP-5, Medix Biochemica) solution was added to the gold colloid solution adjusted to pH by adding 1 mL and stirred. After standing for 10 minutes, 550 μL of 1% polyethylene glycol (PEG Mw. 20000, product number 168-11285, Wako Pure Chemical Industries) aqueous solution was added and stirred, followed by 10% bovine serum albumin (BSA FractionV, product number A-7906, SIGMA) 1.1 mL of aqueous solution was added and stirred. After centrifuging this solution at 8000 × g, 4 ° C. for 30 minutes (himacCF16RX, Hitachi), the supernatant was removed except for about 1 mL, and the gold colloid was redispersed with an ultrasonic washer. After that, it is dispersed in 20 mL of colloidal gold preservation solution (20 mM Tris-HCl buffer (pH 8.2), 0.05% PEG (Mw. 20000), 150 mM NaCl, 1% BSA, 0.1% NaN ₃ ), and again 8000 After centrifuging at × g and 4 ° C. for 30 minutes, the supernatant was removed except for about 1 mL, and the gold colloid was redispersed with an ultrasonic washer to obtain an antibody-modified gold colloid (50 nm) solution.

(1-2) Preparation of colloidal gold antibody retaining pad Each antibody-modified gold colloid prepared in (1-1) is mixed with gold colloid coating solution (20 mM Tris-Hcl buffer (pH 8.2), 0.05% PEG (Mw. 20000)). ), 5% sucrose) and water, and diluted so that the OD at 520 nm was 1.5. 0.8 mL of this solution was uniformly applied to each glass fiber pad (Glass Fiber Conjugate Pad, Millipore) cut to 8 mm × 150 mm and dried under reduced pressure overnight to obtain a colloidal gold antibody holding pad.

(1-3) Preparation of antibody-immobilized membrane (chromatographic carrier)
An antibody-immobilized membrane was prepared by immobilizing an antibody by the following method with respect to a nitrocellulose membrane (with plastic backing, HiFlow Plus HF120, Millipore) cut to 25 mm × 200 mm. Inkjet immobilization anti-hCG monoclonal antibody (Anti-Alpha subunit 6601 SPR-5, Medix Biochemica) solution prepared at a position of 8 mm from the bottom with the long side down and 0.5 mg / mL The coating was applied in a line shape having a width of about 1 mm using a system coating machine (BioDot). Similarly, an anti-mouse IgG antibody for control (anti-mouse IgG (H + L), rabbit F (ab ') 2, part number 566-70621, prepared to be 0.5 mg / mL at a position 12 mm from the bottom) Wako Pure Chemicals) solution was applied in a line. The coated membrane was dried at 50 ° C. for 30 minutes with a hot air dryer. 500 mL of blocking solution (50 wm borate buffer (pH 8.5) containing 0.5 w% casein (milk-derived, product number 030-01505, Wako Pure Chemical Industries)) was placed in a vat and allowed to stand for 30 minutes. After that, transfer to 500 mL of washing / stabilizing solution (50 mM Tris-HCl (pH 7.5) buffer containing 0.5 w% sucrose and 0.05 w% sodium cholate) in the same vat, soak for 30 minutes. did. The membrane was removed from the solution and dried overnight at room temperature to obtain an antibody-immobilized membrane.

(1-4) Preparation of immunochromatography kit The antibody-immobilized membrane prepared in (1-3) was attached to a back adhesive sheet (ARcare9020, Nipple Technocluster). In this case, the anti-hCG antibody line side is the lower side of the membrane long side. Attach the gold colloid antibody holding pad prepared in (1-2) to the lower side of the antibody-immobilized membrane (1-2), and add about 4 mm to the lower side of the gold colloid antibody holding pad. A glass fiber pad (Glass Fiber Conjugate Pad, Millipore) cut to 18 mm × 150 mm) was laminated and pasted. Further, an absorption pad (a cellulose glass membrane (CF6, Whatman) cut into 80 mm × 150 mm) was overlaid and pasted on the upper side of the antibody-immobilized membrane so as to overlap by about 5 mm. These lap-bonded members are cut into 5 mm x 55 mm immunochromatography by cutting the guillotine cutter (CM4000, NIPPN Technocluster) in parallel with the short side so that the long side of the member is 5 mm wide. A strip was created. These were put in a plastic case (Nippon Techno Cluster Co., Ltd.) to prepare an immunochromatography kit for testing.

(1-5) Preparation of silver amplification solution
1) Preparation of amplification solution A-1 Prepared by dissolving iron nitrate (III) nonahydrate (Wako Pure Chemicals, 095-00995) in 325 g of water in water.
40 mL of 1 mol / L iron nitrate aqueous solution, citric acid (Wako Pure Chemical, 038-06925) 10.5 g, dodecylamine (Wako Pure Chemical, 123-00246) 0.1 g, C ₉ H ₁₉ -C ₆ H ₄ -O- ( 0.1 g of CH ₂ CH ₂ O) ₅₀ H is dissolved. When all are dissolved, add 40 mL of nitric acid (10 wt%) while stirring with a stirrer. 80 mL of this solution was measured, and 11.76 g of ammonium iron (II) sulfate hexahydrate (Wako Pure Chemical Industries, Ltd., 091-00855) was added to obtain an amplification solution A-1.

2) Preparation of amplification solution A-2 Amplification solution A-2 (10 wt% aqueous silver nitrate solution) was prepared by adding water to 10 mL of silver nitrate solution (containing 10 g of silver nitrate) to make the total amount 100 g.

3) Preparation of amplification solution A Amplification solution A-1 40 mL was measured, and 4.25 mL of amplification solution A-2 was added and stirred to obtain amplification solution A.

(2) Evaluation method (1) Minimum detection sensitivity test method with hCG (1-1) Minimum detection sensitivity test method after amplification hCG (recombinant hCG R-506, Roto Pharmaceutical Co., Ltd.) in PBS buffer containing 1% by mass BSA (Made by Co., Ltd.) was dissolved to prepare test hCG solutions of various concentrations.
100 μL of each test hCG solution at each concentration was dropped into each test immunochromatography kit and allowed to stand for 10 minutes. The membrane was taken out from the case, the water absorbing pad was removed, and 3 pieces of cellophane tape were attached to the place where 5 × 20 mm (Cellulose Fiber Sample Pad, Millipore) was removed as a new water absorbing pad.

This membrane was stood so that the specimen dropping part was immersed in the liquid in a microtube (BM equipment Co., BM4020) containing 200 μL of the amplification liquid A. The amplification solution was sucked up, the time when the amplification solution reached the detection line was set to 0 minute, and after 2 minutes, the membrane was taken out and immediately washed with water for 3 minutes. At this time, the degree of coloring when visually observing the detection line was determined in four stages: "++" with clear coloring, "++" with coloring, "+" with light coloring, and "-" without coloring. .
The density ("+" judgment) that could be discriminated with the lowest density was defined as the minimum detection sensitivity when amplified with the kit.

(2) Shape observation of particles in the amplification solution After attaching the back side of the sample to the sample stage with carbon paste, carbon was vapor-deposited, and the surface of the sample was reflected by reflected electrons at an acceleration voltage of 10 KV using FE-STEM S-5500 made by Hitachi High Technologies. Observation was performed with SEM. Thereafter, 100 particles were selected, the equivalent circle diameter of the projected area of the particles was measured, and the average value was calculated.

<Comparative example>
In (1-1) of (2), the remaining gold colloid reacts with the amplification solution by cutting about 2 mm upstream of the membrane with a lot of movable residual gold colloid with the membrane after feeding the sample liquid. The silver particles (= particles in the amplification solution) produced in this way were almost eliminated.
The visual recognition result (photograph) of the detection line at the time of amplification is shown in FIG.
Table 1 shows the results of the minimum detection sensitivity experiment at this time.

<Example>
In (1-1) of (2), the remaining gold colloid reacts with the amplification solution without cutting about 2 mm upstream of the membrane with a lot of movable remaining gold colloid in the membrane after the sample solution is sent. In this way, a large number of silver particles formed in the amplification solution was present. At this time, the average size of the silver particles was 8 μm, and the average pore diameter of the membrane was 15 μm.
FIG. 4 (bottom) shows the visual recognition result (photograph) of the detection line during amplification.
Table 1 shows the results of the minimum detection sensitivity experiment at this time.

  From FIG. 4, it can be seen that the visibility of the detection line is improved due to particles caught in the detection line portion (particles contained in the amplification liquid) as compared with the comparative example. From Table 1, it can be seen that the visibility is improved at each hCG concentration and the minimum detection sensitivity is increased by 8 times.

It is a top view which shows typically the one aspect | mode of the immunochromatography kit which can be used by this invention. It is a longitudinal cross-sectional view which shows typically the longitudinal cross-section of the immunochromatography kit shown by FIG. It is a longitudinal cross-sectional view which shows typically the longitudinal cross-section of another aspect of the immunochromatography kit which can be used by this invention. The photograph of the detection line in hCG antigen concentration 1.8E-11M is shown.

Explanation of symbols

1: Back adhesive sheet 2: Gold colloid antibody holding pad 3: Antibody-immobilized membrane 3a: Capture site 31: Detection unit 32: Control unit 4: Absorption pad 5: Sample addition pad 6: Sensitization sheet 10: Immunochromatography kit

Claims (3)

Porous carrier having a test substance, and a labeling substance modified with a first antibody against the test substance to expand in the porous carrier in a state of being formed these complexes, a second antibody against the test substance In an immunochromatographic method including capturing the test substance and the labeling substance at the reaction site above and detecting the test substance, an amplification solution containing a compound containing silver and a reducing agent for silver ions is used. The test substance is detected by sensing, and the amplification liquid contains solid particles, and the average particle diameter after amplification of the labeling substance captured at the reaction site is 1 with respect to the average pore diameter of the porous carrier. / 10 1 or less or more, immunochromatography the particle size of the particles contained in the amplification solution Ri der than 50μm below 0.5 [mu] m, the reducing agent for silver ions is characterized in that it is a salt of Fe ²⁺ . The immunochromatographic method according to claim 1, wherein the particles contained in the amplification liquid are metal particles, metal compound particles, colored particles, or carbon particles. The immunochromatographic method according to claim 2 , wherein the metal particles or metal compound particles are silver particles or silver compound particles.