WO2014103553A1 - 夾雑物の影響を低減する免疫測定法 - Google Patents
夾雑物の影響を低減する免疫測定法 Download PDFInfo
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- WO2014103553A1 WO2014103553A1 PCT/JP2013/080928 JP2013080928W WO2014103553A1 WO 2014103553 A1 WO2014103553 A1 WO 2014103553A1 JP 2013080928 W JP2013080928 W JP 2013080928W WO 2014103553 A1 WO2014103553 A1 WO 2014103553A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
- G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
- G01N33/54393—Improving reaction conditions or stability, e.g. by coating or irradiation of surface, by reduction of non-specific binding, by promotion of specific binding
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/645—Specially adapted constructive features of fluorimeters
- G01N21/648—Specially adapted constructive features of fluorimeters using evanescent coupling or surface plasmon coupling for the excitation of fluorescence
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
- G01N33/574—Immunoassay; Biospecific binding assay; Materials therefor for cancer
- G01N33/57484—Immunoassay; Biospecific binding assay; Materials therefor for cancer involving compounds serving as markers for tumor, cancer, neoplasia, e.g. cellular determinants, receptors, heat shock/stress proteins, A-protein, oligosaccharides, metabolites
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N2021/6439—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" with indicators, stains, dyes, tags, labels, marks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
- G01N2333/415—Assays involving biological materials from specific organisms or of a specific nature from plants
- G01N2333/42—Lectins, e.g. concanavalin, phytohaemagglutinin
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
- G01N2333/435—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans
- G01N2333/46—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans from vertebrates
- G01N2333/47—Assays involving proteins of known structure or function as defined in the subgroups
- G01N2333/4701—Details
- G01N2333/4724—Lectins
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
- G01N2333/90—Enzymes; Proenzymes
- G01N2333/914—Hydrolases (3)
- G01N2333/948—Hydrolases (3) acting on peptide bonds (3.4)
- G01N2333/95—Proteinases, i.e. endopeptidases (3.4.21-3.4.99)
- G01N2333/964—Proteinases, i.e. endopeptidases (3.4.21-3.4.99) derived from animal tissue
- G01N2333/96425—Proteinases, i.e. endopeptidases (3.4.21-3.4.99) derived from animal tissue from mammals
- G01N2333/96427—Proteinases, i.e. endopeptidases (3.4.21-3.4.99) derived from animal tissue from mammals in general
- G01N2333/9643—Proteinases, i.e. endopeptidases (3.4.21-3.4.99) derived from animal tissue from mammals in general with EC number
- G01N2333/96433—Serine endopeptidases (3.4.21)
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2400/00—Assays, e.g. immunoassays or enzyme assays, involving carbohydrates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2400/00—Assays, e.g. immunoassays or enzyme assays, involving carbohydrates
- G01N2400/02—Assays, e.g. immunoassays or enzyme assays, involving carbohydrates involving antibodies to sugar part of glycoproteins
Definitions
- the present invention relates to a method for measuring the amount of a compound having a sugar chain in a biological sample by using an immunoassay by a sandwich method using a labeled lectin. More specifically, the present invention is a method for measuring the amount of a compound having a sugar chain in a biological sample by using an immunoassay by a sandwich method using a labeled lectin, and reduces noise derived from contaminants. Related measurement methods.
- An immunoassay method is used as a method for specifically detecting a trace amount of a measurement target compound (antigen).
- One of the immunoassay methods is the sandwich method in which the antigen captured by the primary antibody is labeled with the secondary antibody.
- the fluorescent antibody method using a fluorescent label as the secondary antibody and the radioimmunoassay using a label with a radioactive substance are widely implemented. Has been.
- lectins are known as proteins that bind to sugar chains, other than those produced by immunological methods. Lectins usually have two or more sugar binding sites per molecule.
- a protein or the like contained in a biological sample has a sugar chain, and there is a method in which a lectin that specifically recognizes a sugar chain of an antigen to be measured is used instead of a secondary antibody in an immunoassay method. Proposed.
- biological samples such as blood (serum and plasma) contain various proteins, lipids, and other contaminants in addition to the antigen to be measured.
- these contaminants are primary antibodies.
- a solid phase layer solid phase support
- a fluorescent label binds to this contaminant.
- the present invention relates to a method for measuring the amount of a compound having a sugar chain in a biological sample using an immunoassay by a sandwich method using a labeled lectin. It is an object to provide a measurement method suitable for obtaining an accurate amount.
- a ligand (sandwich method) is also used to capture contaminants having a sugar chain such as glycoprotein or glycolipid other than the target compound present in the biological sample.
- Primary antibody and a ligand are non-specifically bound to a solid phase layer (solid phase support) (hereinafter referred to as a ligand) for immobilizing a ligand on a support (such as a well).
- a solid phase layer solid phase support
- the labeled lectin also binds to the sugar chain of the contaminant non-specifically bound to the ligand etc., which causes noise. (See FIG. 1).
- the present inventors examined by focusing on the recognition range and binding strength of lectins to sugar chains. That is, by adding a sugar chain compound that competes (crosses) with the sugar chain of the contaminant in the biological sample for binding to the labeled lectin, the sugar chain of the contaminant bound to the labeled lectin is dissociated at a certain rate. The dissociated labeled lectin and the added sugar chain compound bind to each other, and as a result, it is found that the labeled lectin that is bound to impurities non-specifically bound to a ligand or the like can be released, thereby completing the present invention. (See FIG. 2).
- the competition between the sugar chain of the measurement target compound bound to the labeled lectin and the added sugar chain compound is within a certain range, and the signal intensity derived from the measurement target compound is secured. Therefore, it was found that the dissociation constant between the sugar chain compound to be added and the labeled lectin is preferably within a certain range, and the present invention has been completed.
- the measurement method of the present invention is as follows.
- a measurement method comprising adding a sugar chain compound that competes (crosses) with contaminants in a biological sample in binding to a labeled lectin.
- a measurement method suitable for obtaining an accurate amount of protein can be provided.
- FIG. 1 is a conceptual diagram showing an outline of noise generation derived from impurities in a biological sample in the conventional sandwich method.
- the sugar chain of the contaminants nonspecifically bound to the ligand, the solid phase layer, etc. and the labeled lectin bind to each other, which causes noise.
- FIG. 2 is a conceptual diagram showing an outline of the competition (crossing) between the sugar chain compound added in the present invention and the sugar chain of the contaminant in the biological sample in the binding with the labeled lectin.
- the sugar chains of contaminants bound to the labeled lectin are dissociated at a certain rate, and the dissociated labeled lectin and the added sugar chain compound are bound.
- FIG. 3 is a conceptual diagram showing an outline in which SAM and a solid phase layer are formed on the support surface and a ligand is solid phased on the solid phase layer as an example of SPFS.
- the present invention is a method for measuring the amount of a measurement target compound having a sugar chain in a biological sample.
- the biological sample to be measured is not particularly limited, and examples thereof include human and animal blood, serum, plasma, urine, spinal fluid, saliva, cells, tissues and organs, and preparations thereof (for example, biopsy specimens).
- blood, serum and plasma that may contain cancer antigens and tumor markers are suitable as biological samples to be measured.
- Liquid samples such as blood, serum, plasma, urine, spinal fluid, and saliva can be used by diluting with an appropriate buffer as necessary.
- solid samples such as cells, tissues, organs and the like can be used by adding an appropriate buffer and homogenizing the suspension or its supernatant as it is or after further dilution.
- a labeled lectin is used as a labeling substance for the sandwich method.
- the labeled lectin recognizes and binds to a specific sugar chain. Therefore, the compound to be measured in the present invention needs to have a sugar chain.
- Such a measurement target compound is a compound having a sugar chain and binding to a ligand (measurement target compound capturing substance of the sandwich method).
- measurement target compounds include glycoproteins, glycolipids, modified molecules and complexes thereof, and preferable measurement target compounds include prostate specific antigen (prostate specific antigen, PSA) and the like.
- PSA prostate specific antigen
- tumor markers for example, CA19-9, Forssman antigen, T antigen, Tn antigen, serial T antigen, etc.
- an immunoassay method based on the sandwich method is used in the present invention, but the method may be a commonly used method and is not particularly limited.
- Ligand substance capture substance for sandwich method
- the ligand to be used in the present invention specifically recognizes and binds the measurement target compound, and the sugar chain of the measurement target compound by the labeled lectin as the sandwich-method labeling substance. It is a substance that does not interfere with recognition.
- the ligand is not particularly limited as long as it is a substance suitable as a substance that captures the measurement target compound. For example, an antibody, an aptamer, a synthetic peptide, or the like can be used.
- a monoclonal antibody against the compound to be measured is suitable.
- an antibody monoclonal antibody or the like
- an anti-human PSA antibody may be used.
- the above-mentioned ligand means a substance that specifically captures a compound to be measured, and includes not only a complete antibody but also any antibody fragment or derivative.
- Fab, Fab ′ 2 , CDR, humanized antibody Various antibodies such as functional antibodies and single chain antibodies (ScFv) are also included.
- a receptor is a protein that exists in a cell, specifically recognizes various physiologically active substances, and transmits and expresses its action.
- a receptor is a steroid or thyroid hormone that can freely pass through the plasma membrane.
- intracellular receptors that specifically bind to vitamins A and D (ie, nuclear receptors), cell surface receptors that specifically bind to peptide hormones, growth factors, cytokines or catecholamines that cannot freely pass through the plasma membrane There is a body, etc.
- the ligand is usually immobilized (immobilized) on a support (solid phase). That is, the measurement target compound is captured on the support through the immobilized ligand.
- the support for immobilizing the ligand examples include insoluble polysaccharides such as agarose and cellulose, synthetic resins such as silicon resins, polystyrene resins, polyacrylamide resins, nylon resins, and polycarbonate resins, and insoluble supports such as glass.
- the body can be mentioned.
- These supports are used in the form of beads (mainly spherical), plates (mainly planar) and the like.
- a column filled with magnetic beads, resin beads, or the like can be used.
- a multiwell plate 96-well multiwell plate or the like
- a biosensor chip, or the like can be used.
- the binding between the ligand and the support can be performed by a commonly used method such as chemical bonding or physical adsorption. All of these supports can be used commercially.
- (A) Immobilization of a ligand using a solid phased layer The solid phase immobilization of a ligand on a support can be performed by providing a solid phased layer on the surface of the support on which a ligand is solidified.
- the solid phase layer is a layer having a three-dimensional structure for solid phase immobilizing the ligand on the support surface.
- This “three-dimensional structure” means that the solid phase of the ligand is not limited to the two-dimensional surface of the support (or the surface of the “sensor substrate” (and its vicinity) when SPFS is used), and is released from the surface. This means the structure of a solid phase layer that can be expanded to a three-dimensional space (see FIG. 3).
- the solid phase layer may be provided directly on the surface of the support, or a SAM described later may be provided on the surface of the support, and the solid phase layer may be provided thereon.
- Such solid phase layers include glucose, carboxymethylated glucose, vinyl esters, acrylic esters, methacrylic esters, olefins, styrenes, crotonic esters, itaconic diesters, maleic diesters.
- the polymer comprises a polymer composed of at least one monomer selected from the group consisting of monomers included in each of the monomers, fumaric acid diesters, allyl compounds, vinyl ethers and vinyl ketones, Hydrophilic polymers such as dextran and dextran derivatives and vinyl esters, acrylic esters, methacrylic esters, olefins, styrenes, crotonic esters, itaconic diesters, maleic diesters, fumaric diesters ⁇ A It is more preferable to include a hydrophobic polymer composed of hydrophobic monomers included in each of the above compounds, vinyl ethers and vinyl ketones, and dextran such as carboxymethyl dextran (CMD) is biocompatible and non-specific It is particularly suitable from the standpoint of suppressing the general adsorption reaction and high hydrophilicity.
- CMD carboxymethyl dextran
- the molecular weight of CMD is preferably 1 kDa or more and 5,000 kDa or less, and more preferably 4 kDa or more and 1,000 kDa or less.
- the solid phase layer (for example, one comprising dextran or a dextran derivative) preferably has a density of less than 2 ng / mm 2 .
- the density of the solid phase layer can be appropriately adjusted according to the type of polymer used. It is preferable that the above-mentioned polymer is immobilized on the SAM described later within such a density range because the assay signal is stabilized and increased when the plasmon sensor is used in the assay method. .
- the density of “Sensor Chip CM5” manufactured by Biacore Life Sciences was 2 ng / mm 2 . This density was estimated to be 2 ng / mm 2 as a result of measuring an average of 2000 RU in the measurement signal obtained by the SPR measuring instrument manufactured by Biacore Life Science, using this CM5 substrate and the gold film only substrate. Is.
- the average thickness of the solid phase layer is preferably 3 nm or more and 80 nm or less. This film thickness can be measured using an atomic force microscope (AFM) or the like. When the average film thickness of the solid phase layer is within such a range, it is preferable that the signal of the assay is stabilized and increased when the plasmon sensor is used in the assay method.
- CMD carboxymethyl dextran
- Carboxymethyldextran preferably has a molecular weight of 1 kDa to 5,000 kDa, carboxymethyldextran as described above is 0.01 mg / mL to 100 mg / mL and N-hydroxysuccinimide (NHS) is 0.01 mM to 300 mM.
- a substrate in which a transparent support, a metal thin film, and SAM are laminated in this order on MES buffered saline [MES] containing 0.01 mM to 500 mM of water-soluble carbodiimide (WSC) is 0.2 hours to 3.0 hours. It is immersed below, and carboxymethyl dextran can be fixed to SAM.
- MES buffered saline [MES] containing 0.01 mM to 500 mM of water-soluble carbodiimide (WSC) is 0.2 hours to 3.0 hours. It is immersed below, and carboxymethyl dextran can be fixed to SAM.
- the density of the obtained solid phase layer can be adjusted by the number of reaction points (the number of SAM functional groups), the ionic strength and pH of the reaction solution, and the WSC concentration relative to the number of carboxyl groups of the carboxymethyldextran molecule.
- the average film thickness of the solid phase layer can be adjusted by the molecular weight of carboxymethyldextran and the reaction time.
- a known chemical bond reaction can be used, and in particular, a chemical bond reaction used when modifying an antibody can be applied.
- a carboxyl group possessed by a polymer having a reactive functional group such as carboxymethyldextran [CMD] in the solid phase layer is converted to a water-soluble carbodiimide [WSC] (for example, 1-ethyl-3- (3-dimethylaminopropyl).
- WSC water-soluble carbodiimide
- EDC 1-ethyl-3- (3-dimethylaminopropyl.
- NHS N-hydroxysuccinimide
- the SAM is formed on the surface on which the ligand of the support is immobilized, as a scaffold for immobilizing the ligand, preferably the immobilized layer.
- a surface on which a ligand of a metal thin film is immobilized for the purpose of preventing metal quenching of a fluorescent molecule when a plasmon sensor is used in a sandwich assay ( The other surface not in contact with the transparent support).
- carboxyalkanethiol having about 4 to 20 carbon atoms for example, available from Dojindo Laboratories Co., Ltd., Sigma-Aldrich Sakai Japan Co., Ltd.
- 10-carboxyl -1-decanethiol is used.
- Carboxyalkanethiol having 4 to 20 carbon atoms has properties such as little optical influence of SAM formed using it, that is, high transparency, low refractive index, and thin film thickness. Therefore, it is preferable.
- a method for forming such a SAM is not particularly limited, and a conventionally known method can be used. Below, the case of the measuring method using SPFS is demonstrated to an example.
- 10-carboxy-1- Examples include a method of immersing in an ethanol solution containing decanethiol (manufactured by Dojindo Laboratories). In this way, the thiol group of 10-carboxy-1-decanethiol binds to the metal and is immobilized, and self-assembles on the surface of the thin gold film to form a SAM.
- a “spacer layer made of a dielectric material” may be formed before forming the SAM.
- an ethoxy group or a silanol group (Si—OH) is obtained by hydrolysis)
- the silane coupling agent is not particularly limited as long as it has a methoxy group and has a reactive group such as an amino group, a glycidyl group, or a carboxyl group at the other end, and a conventionally known silane coupling agent can be used.
- a method for forming such a SAM is not particularly limited, and a conventionally known method can be used.
- the dielectric used for forming such a “spacer layer made of a dielectric” various optically transparent inorganic substances, natural or synthetic polymers can be used. Among them, since it is excellent in chemical stability, manufacturing stability and optical transparency, it contains silicon dioxide (SiO 2 ), titanium dioxide (TiO 2 ) or aluminum oxide (Al 2 O 3 ). preferable.
- the thickness of the spacer layer made of a dielectric is usually 10 nm to 1 mm, and is preferably 30 nm or less, more preferably 10 to 20 nm from the viewpoint of resonance angle stability. On the other hand, it is preferably 200 nm to 1 mm from the viewpoint of electric field enhancement, and more preferably 400 nm to 1,600 nm from the stability of the effect of electric field enhancement.
- Examples of the method for forming a spacer layer made of a dielectric material include a sputtering method, an electron beam evaporation method, a thermal evaporation method, a formation method by a chemical reaction using a material such as polysilazane, or an application with a spin coater.
- the ligand can be immobilized on the SAM by providing a solid phase layer or directly on the SAM.
- a lectin binds to a specific sugar chain according to its type with high binding ability, but may bind to another sugar chain with low binding ability. Therefore, the labeled lectin used in the present invention binds to the sugar chain of the measurement target compound with a high binding ability in order to enhance the noise reduction effect due to the addition of the sugar chain compound described later, while the measurement target compound in the biological sample. It is preferable to use a lectin that binds with a weak binding ability to the sugar chain of other contaminants such as glycoproteins and glycolipids.
- A Lectins belonging to various molecular families obtained from animals, plants, fungi, bacteria, viruses, etc., that is, “R-type lectins” related to ricin B chain found in all living worlds including bacteria
- B Calnexin calreticulin”, which exists in all eukaryotes and is involved in glycoprotein folding
- C C-type lectin” requiring calcium, which contains a large amount of typical lectins such as “selectin” and “collectin” widely present in multicellular animals
- D "Galectins” that are widely distributed in the animal kingdom and show specificity for galactose
- E leguminous lectins” that form a large family in the plant legumes
- F “L-type lectin” which has structural similarity to this and is involved in transport into animal cells
- G P-type lectin” that binds to mannose 6-phosphate involved in intracellular transport of
- lectin examples include ACA (sennin clectin), BPL (purple lectin lectin), ConA (Tatami bean lectin), DBA (horsegram lectin), DSA (saturated stag bean lectin), ECA (deigo bean).
- the lectin is complexed (bound) with the label to form a labeled lectin.
- a label known to those skilled in the art such as a fluorescent dye, an enzyme / coenzyme, a chemiluminescent substance, and a radioactive substance, can be used.
- fluorescent dyes examples include fluorescein family fluorescent dyes (Integrated DNA Technologies), polyhalofluorescein family fluorescent dyes (Applied Biosystems Japan), and hexachlorofluorescein family fluorescent dyes (Applied Biosystems Japan). ), Coumarin Family Fluorescent Dye (Invitrogen), Rhodamine Family Fluorescent Dye (GE Healthcare Biosciences), Cyanine Family Fluorescent Dye, Indian Carbocyanine Family Fluorescent Dye , Oxazine family fluorescent dyes, thiazine family fluorescent dyes, squaraine family fluorescent dyes, chelated lanthanide family fluorescent dyes, BODIPY® family fluorescent dyes (in vitro Gen), naphthalenesulfonic acid family fluorescent dye, pyrene family fluorescent dye, triphenylmethane family fluorescent dye, AlexaAFluor (registered trademark) dye series (Invitrogen Corporation) and other organic fluorescent dyes Is mentioned.
- rare earth complex fluorescent dyes such as Eu and Tb (for example, ATBTA-Eu 3+ ), blue fluorescent protein (BFP), cyan fluorescent protein (CFP), green fluorescent protein (GFP), yellow fluorescent protein (YFP),
- BFP blue fluorescent protein
- CFP cyan fluorescent protein
- GFP green fluorescent protein
- YFP yellow fluorescent protein
- fluorescent dyes include fluorescent proteins typified by red fluorescent protein (DsRed) or Allophycocyanin (APC; LyoFlogen (registered trademark)), and fluorescent fine particles such as latex and silica.
- the maximum fluorescence wavelength is set in the near infrared region, such as Cy5 and Alexa Fluor 647. It is desirable to use a fluorescent dye having the same.
- the radioactive substance a radioisotope (such as 32 P, 14 C, 125 I , 3 H, 131 I) can be mentioned.
- sugar chain compound In general, the binding between a lectin and a sugar chain is an equilibrium reaction, and the binding force is considered to be weaker than the binding between an antibody and an antigen. Moreover, the specificity of the sugar chain in the binding between the lectin and the sugar chain is lower than the specificity of the antigen in the binding between the antibody and the antigen. Therefore, in the sandwich method using a labeled lectin, another sugar chain compound is added after the addition of the labeled lectin, and the sugar chain compound competes (crosses) with contaminants bound to the labeled lectin in an equilibrium reaction. Is possible.
- the sugar chain compound competes (crosses) with the contaminant in the binding between the contaminant such as glycoprotein and glycolipid and the labeled lectin.
- the contaminant such as glycoprotein and glycolipid and the labeled lectin.
- part of the contaminants bound to the labeled lectin is dissociated, and the dissociated labeled lectin and the added sugar chain compound are bound.
- the labeled lectin that has been captured on the solid phase through the contaminants non-specifically bound to the ligand or the like is released.
- the labeled lectin released from the solid phase and bound to the sugar chain compound is removed by washing or other methods to reduce noise derived from impurities in the sandwich method (see FIG. 2).
- the sugar chain compound by adding the sugar chain compound, the sugar chain compound also competes (crosses) with the measurement target compound bound to the labeled lectin, and the labeled lectin bound to the measurement target compound also dissociates, resulting in the origin of the measurement target compound.
- the signal may also decrease.
- the dissociation constant between the sugar chain compound added in the present invention and the labeled lectin is preferably within a certain range.
- the sugar chain compound added in the present invention is a sugar chain compound that competes (crosses) with impurities in the biological sample in binding to the labeled lectin. More preferably, the sugar chain compound added in the present invention is such that x is a dissociation constant between the sugar chain compound to be added and the labeled lectin, and a is a dissociation constant between the measurement target compound and the labeled lectin, and x is in a range of x> a. It is.
- the S / N may not be sufficiently increased as compared with the case where the sugar chain compound is not added. Therefore, in such a case, it is preferable to add a compound having a sugar chain different from the sugar chain compound (such as CMD) contained in the solid phase layer.
- a compound having a sugar chain different from the sugar chain compound such as CMD
- sugar chain compound competing (crossing) with impurities in the biological sample As described above, the sugar chain compound added in the present invention competes (crosses) with the impurities in the biological sample in binding to the labeled lectin. It is a sugar chain compound.
- “competition (crossing)” is synonymous with competition in general competitive inhibition or the like, and when a lectin is used as a receptor, a substance and another substance are reversibly bound at the same binding site. A relationship that competes and joins. That is, it includes not only competition in which the binding site is accurately recognized and bound at the molecular level, but also competition that occurs between sugar chains that bind to the same binding region of the lectin.
- glycoproteins and glycolipids can be considered.
- a sugar chain compound that competes with at least a part of the entire contaminant that binds to the labeled lectin in the biological sample, even if the competitive relationship with the individual contaminants in the biological sample is unknown. If available, it can be used. However, competition in binding with the labeled lectin may also occur between the added sugar chain compound and the compound to be measured.
- the sugar chain compound to be added in the present invention is examined by the actual sandwich method measurement system for the reduction of noise derived from contaminants and the decrease of the signal derived from the compound to be measured, and the noise reduction effect rather than the signal reduction effect. You need to choose the one that is big.
- An example of a method for selecting a sugar chain compound to be added in the present invention is as follows (see Examples).
- (I) In a sandwich assay system using a labeled lectin, a sugar chain compound is added to a biological sample to compete with impurities bound to the labeled lectin, and the released labeled lectin and the added sugar chain compound The signal intensity from which the conjugate has been removed is measured (that is, the total of “noise (N) derived from contaminants” and “signal (s) derived from the measurement target compound” after competition (hereinafter simply referred to as noise (N)).
- the sugar chain compound to be added preferably has an S / N ratio of 3 or more, more preferably 4 or more.
- the addition of the standard product of the measurement target compound (ii) needs to be within the concentration range of the measurement target compound in the actual measurement.
- the standard product is added excessively, the signal intensity derived from the standard product increases, and the S / N increases even if there is a lot of competition between the standard product and the added sugar chain compound.
- the addition amount of the standard product is too small, the S / N ratio becomes small even if the sugar chain compound is effective in competing with impurities. Therefore, in order to appropriately grasp the effect of the competition of the sugar chain compound in the actual measurement, the concentration of the standard product (ii) needs to be within the range of the measurement target compound in the actual measurement.
- requiring said S / N may use the biological sample used for an actual measurement, and the measurement object compound is contained in the biological sample considered that the contained impurities are substantially the same.
- a biological sample that has not been obtained for example, a normal human pooled serum that is commercially available may be used.
- the preferred sugar chain compound to be added in the present invention is the dissociation constant x of the sugar chain compound to be added and the labeled lectin, and the compound to be measured and the labeled lectin.
- x is in the range of x> a, where a is the dissociation constant.
- the dissociation constant is defined as follows.
- the binding between the sugar chain compound (A) and the lectin (B) is a reversible reaction, and the following equation is established in an equilibrium state ([A] is the concentration of the sugar chain compound (mol / L), [B] is the lectin concentration). Concentration (mol / L), [AB] is the concentration of the conjugate of sugar chain compound and lectin (mol / L)).
- the sugar chain compound to be added in the present invention is preferably one in which competition with the measurement target compound is suppressed as much as possible in binding with the labeled lectin and competition with impurities is sufficiently generated.
- a range of> a is preferred.
- sugar chain compounds to be added in the present invention are as shown in Table 1 according to the compound to be measured and the labeled lectin.
- Addition of sugar chain compound The addition of the sugar chain compound can be performed after adding the labeled lectin and washing the unreacted labeled lectin, or can be performed simultaneously with the addition of the labeled lectin.
- the sugar chain of the measurement target compound captured on the support (solid phase) through the ligand and the sugar chain of contaminants non-specifically bound to the ligand, etc.
- the labeled lectin is already bound, and it is considered that there is no free labeled lectin.
- the addition amount of the sugar chain compound may be such that a necessary amount is obtained so that a noise reduction effect derived from impurities can be obtained. .
- the measurement method used in the present invention is not particularly limited as long as it can measure the signal emitted from the labeled lectin, and can be performed according to a method known to those skilled in the art suitable for each labeled substance. For example, when detecting a lectin labeled with a radioactive substance, it can be measured by liquid scintillation or RIA. When detecting a lectin labeled with a fluorescent dye, it can be measured with a luminometer, an SPFS measuring instrument or the like.
- a chemical change of the substrate by the enzyme for example, color development, fluorescence, chemiluminescence, etc., can be measured after adding a substrate corresponding to the labeled enzyme.
- the surface plasmon-excited fluorescence spectroscopy (SPFS) method SPFS
- SPFS surface plasmon-excited fluorescence spectroscopy
- ATR total reflection attenuation
- the measurement member can have any configuration of a flow path and a well, and a sensor chip, a reaction layer, an SPFS system, an SPFS measurement device, and the like can be used.
- the following steps (1) to (6) may be performed in order. (1) introducing a biological sample into a measurement vessel (well, flow path, etc.) in which a ligand capable of binding to the measurement target compound is solid-phased and binding the measurement target compound to the ligand; (2) adding a labeled lectin into the measurement container of step (1), and binding the labeled lectin to a sugar chain of the compound to be measured; (3) A step of washing the inside of the measurement container in step (2) using, for example, a phosphate buffer to remove unbound labeled lectin, (4) The step of adding the sugar chain compound of the present invention in the measurement container of step (3) and causing the added sugar chain compound to compete with the sugar chain of the foreign substance already bound to the labeled lectin, (5) The step of washing the inside of the measurement container in step (4) using, for example, a phosphate buffer,
- a standard sample of a measurement target compound is added to a commercially available biological sample (blood, etc.), the above process is performed to create a calibration curve, and the signal intensity obtained from the biological sample to be measured is applied.
- the concentration of the measurement target compound in the biological sample to be measured can be known.
- the addition of the labeled lectin in the above step (2) and the addition of the sugar chain compound in the step (4) are performed simultaneously, the washing in the step (3) is omitted, and the unbound label is obtained by washing in the step (5).
- a conjugate of the lectin and the labeled lectin released from the solid phase and the sugar chain compound may be simultaneously removed.
- LNCaP culture supernatant LNCaP Human prostate adenocarcinoma cell line
- PSA concentration is adjusted after centrifugation. Measured by ELISA and stored at -80 ° C.
- the substrate thus obtained was immersed in 10 mL of 10-carboxy-1-decanethiol ethanol solution adjusted to 25 mg / mL for 24 hours to form SAM on the surface of the gold thin film.
- the substrate was taken out of the ethanol solution, washed sequentially with ethanol and isopropanol, and then dried using an air gun.
- pH 7.4 MES containing 1 mg / mL of carboxymethyldextran (CMD) having a molecular weight of 500,000, 0.5 mM of N-hydroxysuccinimide (NHS), and 1 mM of water-soluble carbodiimide (WSC).
- CMD carboxymethyldextran
- NHS N-hydroxysuccinimide
- WSC water-soluble carbodiimide
- An unreacted succinic acid ester is obtained by immersing a support in which SAM is formed in buffered saline (MES) (ionic strength: 10 mM) for 1 hour, immobilizing CMD in SAM, and immersing in 1N NaOH aqueous solution for 30 minutes.
- MES buffered saline
- a flow path is formed on the substrate by providing a 0.5 mm thick sheet-like silicon rubber spacer having a hole of 2 mm ⁇ 14 mm on this surface, and a 2 mm thick poly-silicone is formed so as to cover the substrate from the outside of the flow path.
- a methyl methacrylate plate was placed and pressure bonded, and the flow path and the polymethyl methacrylate plate were fixed with screws.
- Washing step Washing was performed by circulating TBS containing 0.05% by weight of Tween 20 for 10 minutes.
- blank fluorescence is used as a light source
- a laser light source is used
- a laser beam having a wavelength of 635 nm is adjusted with an optical filter (Sigma Koki Co., Ltd.) to adjust the amount of photons.
- Detection step 5 mL of PBS containing the fluorescently labeled lectin (1 ng / mL) prepared in (1-1) above is added, circulated for 20 minutes, and then the solution is switched to a TBS solution containing 0.05% by weight of Tween20. After 20 minutes, a signal was acquired by a CCD image sensor (manufactured by Texas Instruments). As a result of this measurement, the signal (S) obtained from the experiment in which the LNCaP culture supernatant was added was 18000, and the signal (N) obtained from the experiment in which the LNCaP culture supernatant was not added was 8900. The S / N ratio was calculated as 2.
- galactosylceramide ( ⁇ -Galactosylceramide) (manufactured by Funakoshi), 2'-fucosyl-D-lactose (manufactured by Sigma), galactosyl diglyceride (manufactured by Sigma), Fuc-2-Chol (International Publication WO2008 / 081686) Synthesis according to the description, see the following structural formula) or Man-2-Chol (synthesized according to the description of International Publication WO2008 / 081686, see the following structural formula) at a concentration of 0.1% by weight in PBS solution for 10 minutes.
- the ⁇ line represents that the anomeric position of the sugar is ⁇ -form and / or ⁇ -form.
- the synthesized sugar chain compound is a mixture of ⁇ -form and ⁇ -form, and the sugar structure is a mixture of D-form and L-form.
- Ligand (measurement compound capture substance) 2 Compound to be measured having sugar chain 3 Contaminant having sugar chain in biological sample 4 Sugar chain recognized by labeled lectin 5 Sugar chain not recognized by labeled lectin 6 Solid phase immobilization layer (ligand is immobilized on support) CMD etc.) 7 Support (Microplate well, SPFS transparent support, metal thin film, etc.) 7a Metal thin film 7b Transparent support (prism) 8 Labeled lectin 9 Sugar chain compound added in the present invention 10 Solid phase layer (carboxymethyldextran (CMD)) 11 SAM
Abstract
Description
標識レクチンを用いたサンドイッチ法による免疫測定法(リガンドとして、抗体以外の測定対象化合物捕捉物質を用いる場合を含む)を用いて生体試料中の糖鎖を有する測定対象化合物の量を測定する方法であって、標識レクチンとの結合において生体試料中の夾雑物と競合(交差)する糖鎖化合物を添加する測定方法。
1.測定対象化合物
(1)生体試料
本発明は、生体試料中の糖鎖を有する測定対象化合物の量を測定する方法である。測定する生体試料は特に制限はなく、例えば、ヒトや動物の血液、血清、血漿、尿、髄液、唾液、細胞、組織及び器官及びこれらの調整物(例えば、生検標本)が挙げられる。特に、癌抗原、腫瘍マーカーを含む可能性のある血液、血清及び血漿は測定する生体試料として好適である。
本発明では、サンドイッチ法の標識物質として標識レクチンを用いる。標識レクチンは特定の糖鎖を認識して結合する。従って、本発明における測定対象化合物は糖鎖を有する必要がある。
本発明では、サンドイッチ法による免疫測定法を使用するが、その方法は通常用いられている方法で良く、特に制限はされない。
(1)リガンド(サンドイッチ法の測定対象化合物捕捉物質)
本発明で使用するリガンド(サンドイッチ法の測定対象化合物捕捉物質)は、測定対象化合物を特異的に認識して結合し、かつ、サンドイッチ法の標識物質としての標識レクチンによる測定対象化合物の糖鎖の認識を妨げない物質である。測定対象化合物を捕捉する物質として適切な物質であればリガンドは特に制限されないが、例えば、抗体、アプタマー、合成ペプチド等を用いることができる。特に、測定対象化合物に対するモノクローナル抗体が好適である。癌抗原、腫瘍マーカー等を測定対象化合物とする場合は、その抗原に特異的に結合する抗体(モノクローナル抗体等)をリガンドとして用いることが適切である。例えば、ヒトPSA(前立腺特異抗原)を測定対象化合物とする場合は、抗ヒトPSA抗体を用いればよい。
サンドイッチ法においては、通常、リガンドは支持体(固相)に固相化(固定化)して用いられる。すなわち、測定対象化合物は固相化されたリガンドを通して、支持体上に捕捉される。
リガンドと支持体との結合は、化学結合や物理的な吸着などの通常用いられる方法により行うことができる。これらの支持体はすべて市販のものが好適に使用できる。
支持体へのリガンドの固相化は、支持体のリガンドを固相化する面に固相化層を設けて行うこともできる。
このような固相化層は、グルコース,カルボキシメチル化グルコース,ならびにビニルエステル類,アクリル酸エステル類,メタクリル酸エステル類,オレフィン類,スチレン類,クロトン酸エステル類,イタコン酸ジエステル類,マレイン酸ジエステル類,フマル酸ジエステル類,アリル化合物類,ビニルエーテル類およびビニルケトン類それぞれに包含される単量体からなる群より選択される少なくとも1種の単量体から構成される高分子を含むことが好ましく、デキストランおよびデキストラン誘導体などの親水性高分子ならびにビニルエステル類,アクリル酸エステル類,メタクリル酸エステル類,オレフィン類,スチレン類,クロトン酸エステル類,イタコン酸ジエステル類,マレイン酸ジエステル類,フマル酸ジエステル類,アリル化合物類,ビニルエーテル類およびビニルケトン類それぞれに包含される疎水性単量体から構成される疎水性高分子を含むことがより好ましく、カルボキシメチルデキストラン(CMD)などのデキストランが生体親和性、非特異的な吸着反応の抑制性、高い親水性の観点から特に好適である。
SPFSを用いた測定法の場合、固相化層(例えば、デキストランまたはデキストラン誘導体からなるもの)は、その密度として2ng/mm2未満を有することが好ましい。固相化層の密度は、用いる高分子の種類に応じて適宜調整することができる。上記高分子が後述するSAMに、このような密度の範囲内で固相化されていると、プラズモンセンサをアッセイ法に用いた場合に、アッセイのシグナルが安定化し、かつ増加するため好適である。なお、Biacoreライフサイエンス社製「Sensor Chip CM5」の密度は2ng/mm2であった。この密度は、このCM5基板および金膜のみの基板を用いて、Biacoreライフサイエンス社製のSPR測定機器により得られた測定シグナルにおいて、平均2000RUを測定した結果、2ng/mm2と見積もられたものである。
支持体へのリガンドの固相化は、支持体のリガンドを固相化する面にSAM(Self-Assembled Monolayer:自己組織化単分子膜)を設けて行うこともできる。
以下に、SPFSを用いた測定法の場合を例に説明する。
このような「誘電体からなるスペーサ層」の形成に用いられる誘電体としては、光学的に透明な各種無機物、天然または合成ポリマーを用いることもできる。その中で、化学的安定性、製造安定性および光学的透明性に優れていることから、二酸化ケイ素(SiO2),二酸化チタン(TiO2)または酸化アルミニウム(Al2O3)を含むことが好ましい。
SAMを形成した場合は、リガンドは、SAM上に固相化層を設けて、又はSAM上に直接、固定化することができる。
本発明では、上記2.(2)でリガンドを通して支持体(固相)上に捕捉された測定対象化合物を標識するために、標識レクチンが用いられる。
(a)動植物,真菌,細菌,ウイルスなどから得られる様々な分子家系に属するレクチン、すなわち、細菌を含むすべての生物界で見出されるリシンB鎖関連の「R型レクチン」、
(b)真核生物全般に存在し糖タンパク質のフォールディングに関与する「カルネキシン・カルレティキュリン」、
(c)多細胞動物に広く存在する「セレクチン」,「コレクチン」等代表的なレクチンを多く含むカルシウム要求性の「C型レクチン」、
(d)動物界に広く分布しガラクトースに特異性を示す「ガレクチン」、
(e)植物豆科で大きな家系を形成する「豆科レクチン」、
(f)これと構造類似性を有し動物細胞内輸送に関わる「L型レクチン」、
(g)リソソーム酵素の細胞内輸送に関わるマンノース6-リン酸結合性の「P型レクチン」、
(h)グリコサミノグリカンをはじめとする酸性糖鎖に結合する「アネキシン」、及び
(i)免疫グロブリン超家系に属し「シグレック」を含む「I型レクチン」等
が挙げられる。
標識体としては、蛍光色素、酵素・補酵素、化学発光物質、放射性物質等の当業者に公知の標識体を用いることができる。
放射性物質としては、ラジオアイソトープ(32P、14C、125I、3H、131Iなど)が挙げられる。
一般に、レクチンと糖鎖との結合は平衡反応であり、抗体と抗原の結合に比べて結合力は弱いとされている。また、レクチンと糖鎖との結合における糖鎖の特異性は、抗体と抗原との結合における抗原の特異性に比べて低い。従って、標識レクチンを用いたサンドイッチ法では、標識レクチンの添加後に別の糖鎖化合物を添加して、平衡反応で標識レクチンと結合している夾雑物に糖鎖化合物を競合(交差)させることが可能である。
更に好ましくは、本発明で添加する糖鎖化合物は、添加する糖鎖化合物と標識レクチンの解離定数をx、測定対象化合物と標識レクチンの解離定数をaとした場合、xがx>aの範囲である。
前記のように、本発明で添加する糖鎖化合物は、標識レクチンとの結合において生体試料中の夾雑物と競合(交差)する糖鎖化合物である。本発明で「競合(交差)」とは、一般的な競合阻害等における競合と同義であり、レクチンを受容体とした場合に、その同じ結合部位で、ある物質と他の物質が可逆的に競合して結合する関係をいう。つまり、結合部位を分子レベルで正確に認識して結合している競合に限らず、レクチンの同じ結合領域に結合する糖鎖間で起こる競合も含んでいる。
(i)標識レクチンを用いたサンドイッチ法の測定系で、生体試料に糖鎖化合物を添加して標識レクチンと結合している夾雑物と競合させ、遊離した標識レクチンと添加した糖鎖化合物との結合体を除去したシグナル強度を測定する(すなわち、競合後の「夾雑物由来のノイズ(N)」と「測定対象化合物由来のシグナル(s)」の合計(以下、単にノイズ(N)という)の強度を測定する)、及び
(ii)測定対象化合物の標準品を生体試料に添加した上で糖鎖化合物を添加し、上記(i)と同様にしてシグナル強度を測定する(すなわち、競合後の「標準品由来のシグナル(S)」、「夾雑物由来のノイズ(N)」及び「測定対象化合物由来のシグナル(s)」の合計(以下、単にシグナル(S)という)の強度を測定する)を測定する。そして、「S」/「N」の比が、その測定の目的に応じた程度に大きいものを添加する糖鎖化合物として選べばよい。例えば、後述の実施例の生体試料、測定対象化合物及び標識レクチンの場合には、添加する糖鎖化合物としては、S/Nの比が3以上が好ましく4以上が更に好ましい。
前記のように、本発明で添加する好ましい糖鎖化合物は、添加する糖鎖化合物と標識レクチンの解離定数をx、測定対象化合物と標識レクチンの解離定数をaとした場合、xがx>aの範囲である糖鎖化合物である。
糖鎖化合物(A)とレクチン(B)との結合は可逆反応であり、平衡状態では次の式が成り立つ([A]は糖鎖化合物の濃度(mol/L)、[B]はレクチンの濃度(mol/L)、[A-B]は糖鎖化合物とレクチンの結合体の濃度(mol/L))。
本発明で添加する糖鎖化合物の好ましい例は、測定対象化合物及び標識レクチンに応じて、表1の通りである。
糖鎖化合物の添加は、標識レクチンを添加し、未反応の標識レクチンを洗浄した後に行うことができ、また、標識レクチンの添加と同時に行うこともできる。
本発明の測定法では、リガンド及び測定対象化合物を通して支持体(固相)に捕捉された標識レクチンの発するシグナルの強度を測定する。
本発明の測定方法を用いた生体試料中の測定対象化合物は、例えば次の(1)~(6)の工程を順に実施すればよい。
(1)測定対象化合物との結合能を有するリガンドが固相化された測定容器(ウエル、流路等)に生体試料を導入し、測定対象化合物をリガンドに結合させる工程、
(2)工程(1)の測定容器内に標識レクチンを添加し、標識レクチンを測定対象化合物の糖鎖と結合させる工程、
(3)工程(2)の測定容器内を、例えばリン酸バッファー等を用いて洗浄し、未結合の標識レクチンを除去する工程、
(4)工程(3)の測定容器内に本発明の糖鎖化合物を添加し、既に標識レクチンと結合している夾雑物の糖鎖と添加した糖鎖化合物とを競合させる工程、
(5)工程(4)の測定容器内を、例えばリン酸バッファー等を用いて洗浄し、支持体(固相)から遊離した標識レクチンと添加した糖鎖化合物との結合体を除去する工程、及び
(6)工程(5)の測定容器内の標識レクチンが発するシグナルを測定する工程。
(1-1)TJA-IIレクチンの蛍光標識化
TJA-IIレクチン〔Trichosanthes japonica Lectin〕(生化学工業(株))を、Alexa Fluor(商標名)647 タンパク質ラベリングキット(インビトロゲン社)を用いて蛍光標識化した。手順は該キットに添付のプロトコールに従った。未反応レクチンや未反応蛍光等を除去するため、限外濾過膜(日本ミリポア(株)製)を用いて反応物を精製し、Alexa Fluor 647標識TJA-II溶液を得た。得られた蛍光標識化TJA-IIレクチンの溶液はタンパク定量後、4℃で保存した。
β-N-アセチルガラクトサミン残基が発現したPSAを産生するLNCaP(Human prostate adenocarcinoma cell line)を培養し、上清を回収し、遠心分離後にPSA濃度をELISAにて測定し、-80℃で保存した。
厚さ1mmのガラス製の透明平面基板「S-LAL10」((株)オハラ製、屈折率〔nd〕=1.72)を、プラズマドライクリーナー「PDC200」(ヤマト科学(株)製)でプラズマ洗浄した。プラズマ洗浄された該基板の片面に、まずクロム薄膜をスパッタリング法により形成し、さらにその表面に金薄膜をスパッタリング法により形成した。このクロム薄膜の厚さは1~3nm、金薄膜の厚さは44~52nmであった。
抗原添加工程:作成した1枚のセンサーチップには、送液をPBSに代え、LNCaP培養上清を市販血清(コージンバイオ社)で希釈し、PSA濃度が1.0ng/mLとなる溶液を0.5mL添加し、25分間循環させた。作成したもう1枚のセンサーチップには、NCaP培養上清を添加していない市販血清(コージンバイオ社)を添加し25分間循環させた。
(a) 生体試料として市販血清(コージンバイオ社)、測定対象化合物としてPSA、リガンドとして抗PSAモノクローナル抗体、標識レクチンとしてノダフジレクチン(WFA)(Vector社製)等を使用した場合、及び
(b) 生体試料として市販血清(コージンバイオ社)、測定対象化合物としてα-フェトプロテイン(AFP)(AFP;2.0mg/mL溶液;Acris Antibodies GmbH社製)、リガンドとして抗AFPモノクローナル抗体(クローン1D5;1.8mg/mL;ミクリ免疫研究所(株)製)、標識レクチンとしてレンズマメレクチン(LCA)(Vector社製)、ヒイロチャワンダケレクチン(SSA)(J-OIL MILLS社製)等を使用した場合についても、上記と同様に実験を行い、S/Nを求めた。上記(b)の場合、上記(1-3)のセンサーチップの作製におけるSAM上の一次抗体の固相化では、流路に、抗AFPモノクローナル抗体溶液2.5mL(抗AFPモノクローナル抗体濃度を50μ/mLに調整)を30分間循環送液した。また、上記(1-4)の抗原添加工程では、1枚のセンサーチップには、AFP濃度が3.0ng/mLとなる溶液(AFPを市販血清で希釈)を0.5mL添加し、25分間循環させた。
これらの結果は、表2に示す。
上記1の検出工程で、蛍光標識化レクチンを含むPBSを添加し、Tween20を含むTBS溶液を送液して洗浄した後に、糖鎖化合物として、ガラクトシルセラミド(α-Galactosylceramide)(フナコシ社製)、2′-フコシル-D-ラクトース(2′-Fucosyl-D-lactose)(シグマ社製)、ガラクトシルジグリセリド(Galactosyl diglyceride)(シグマ社製)、Fuc-2-Chol(国際公開WO2008/081686号公報の記載に従って合成、下記構造式参照)又はMan-2-Chol(国際公開WO2008/081686号公報の記載に従って合成、下記構造式参照)を濃度0.1重量%で含むPBS溶液を10分送液し、標識レクチンと結合している市販血清中の夾雑物と添加した糖鎖化合物を競合させた。次いでTween20を含むTBS溶液を送液して洗浄した。これ以外は上記1と同様に実験し、S/Nを算出した。結果は表2に示す。
2 糖鎖を有する測定対象化合物
3 生体試料中の糖鎖を有する夾雑物
4 標識レクチンが認識する糖鎖
5 標識レクチンが認識しない糖鎖
6 固相化層(リガンドを支持体に固相化するためのCMD等)
7 支持体(マイクロプレートのウエル、SPFSの透明支持体・金属薄膜、等)
7a 金属薄膜
7b 透明支持体(プリズム)
8 標識レクチン
9 本発明で添加する糖鎖化合物
10 固相化層(カルボキシメチルデキストラン(CMD))
11 SAM
Claims (6)
- 標識レクチンを用いたサンドイッチ法による免疫測定法(リガンドとして、抗体以外の測定対象化合物捕捉物質を用いる場合を含む)を用いて生体試料中の糖鎖を有する測定対象化合物の量を測定する方法であって、標識レクチンとの結合において生体試料中の夾雑物と競合(交差)する糖鎖化合物を添加する測定方法。
- 添加する糖鎖化合物と標識レクチンの解離定数をx、測定対象化合物と標識レクチンの解離定数をaとした場合、xがx>aの範囲である請求項1に記載の測定方法。
- 測定する生体試料中の糖鎖を有する化合物が、腫瘍マーカーである請求項1又は2に記載の測定方法。
- 測定対象化合物、標識レクチン及び添加する糖鎖化合物の組合せが次の(1)~(4)のいずれかである請求項1~3のいずれか1項に記載の測定方法。
(1)測定対象化合物が前立腺特異抗原(PSA)であり、標識レクチンがキカラスウリレクチン(TJA-II)であり、添加する糖鎖化合物がフコース誘導体又はガラクトース誘導体である。
(2)測定対象化合物が前立腺特異抗原(PSA)であり、標識レクチンがノダフジレクチン(WFA)であり、添加する糖鎖化合物がフコース誘導体である。
(3)測定対象化合物がα-フェトプロテイン(AFP)であり、標識レクチンがレンズマメレクチン(LCA)であり、添加する糖鎖化合物がマンノース誘導体である。
(4)測定対象化合物がα-フェトプロテイン(AFP)であり、標識レクチンがヒイロチャワンダケレクチン(SSA)であり、添加する糖鎖化合物がフコース誘導体ある。 - リガンド(測定対象化合物捕捉物質)を支持体に固相化するための固相化層が糖鎖化合物を含むものであり、当該糖鎖化合物と異なる糖鎖化合物を添加する請求項1~4のいずれか一つに記載の測定方法。
- 標識レクチンが発する蛍光を表面プラズモン励起増強蛍光分光法(SPFS)で測定する請求項1~5のいずれか一つに記載の測定方法。
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