JP2012058169A - Assay method using plasmon excitation sensor and the plasmon excitation sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assay method for performing real-time measurement during coupling reaction while having high sensitivity and accuracy, and a plasmon excitation sensor.SOLUTION: The assay method uses the plasmon excitation sensor which is provided with a metallic member, a first ligand, and a fluorescence dye precursor developer that causes coloring reaction with a fluorescence dye precursor, and the assay method and the plasmon excitation sensor have the following processes (a) to (c): process (a) for contacting analyte solution with the plasmon excitation sensor to fix the analyte; process (b) for obtaining fluorescence dye by having the fluorescence dye precursor developer react to the plasmon excitation sensor to which the analyte is fixed; and a process (c) for exciting the fluorescence dye by radiating excitation light to a metal member to measure an amount of emitted fluorescence.

Description

  The present invention relates to an assay method for detecting an analyte with high sensitivity and a plasmon excitation sensor. More specifically, the present invention relates to an assay method using a plasmon excitation sensor based on the principle of surface plasmon excitation enhanced fluorescence spectroscopy (SPFS), and the plasmon excitation sensor.

  With surface plasmon excitation enhanced fluorescence spectroscopy (SPFS), irradiation is performed by generating a close-packed wave (surface plasmon) on the surface of the metal film under the condition that the irradiated laser light is attenuated by total reflection (ATR) on the surface of the metal film. The amount of photons contained in the laser light is increased to several tens to several hundreds times (the electric field enhancement effect of surface plasmons), which allows the fluorescent dye in the vicinity of the metal film to be efficiently excited. This is a method capable of detecting a low concentration of analyte. For this reason, in order to increase the sensitivity of bioassays, research and development of plasmon excitation sensors based on the principle of SPFS and assay methods using the same have been conducted in recent years.

  As described above, in recent years, a surface plasmon enhanced fluorescence measurement method based on the principle of such surface plasmon excitation enhanced fluorescence spectroscopy (SPFS) has been developed. For example, Patent Document 1 discloses the technical disclosure thereof. .

  In SPFS, a primary antibody is generally immobilized on a substrate by providing a flow path, an analyte is captured, and then a sandwich immunoassay is performed using a fluorescently labeled secondary antibody to calculate the amount of captured antibody. Since the generated electric field enhancement effect extends to the range of about 200 nm from the surface of the metal film, not only the fluorescent dye (specific adsorption component) immobilized on the surface of the metal film via the analyte, but also the excitation light irradiation in the channel A fluorescent dye (non-specifically adsorbed component) that is not immobilized on the surface of the metal film in the region via the analyte is also excited to generate fluorescence. Fluorescence emission, which is this non-specific adsorption component, is also detected as a detection fluorescence signal. Therefore, after the completion of the binding reaction between the analyte immobilized on the metal film surface and the fluorescent dye, the non-specific adsorption component is measured prior to the measurement of the fluorescence amount. The fluorescent dye needs to be washed. In SPFS, this cleaning is generally performed. For example, Patent Documents 2 and 3 disclose a technique of a process for performing such cleaning.

  However, when such washing is performed, the non-specifically adsorbed component can be washed, but a part of the specifically adsorbed component is often washed away, which causes a problem that the S / N deteriorates. In addition, there is a problem that it is difficult to realize a rapid assay method after washing. That is, since washing is performed prior to measurement of the fluorescence amount, the fluorescence amount cannot be measured unless after washing, and real-time measurement cannot be performed during the binding reaction between the analyte and the fluorescent dye.

  As described above, washing after the binding reaction between the analyte and the fluorescent dye prior to the measurement of the fluorescence amount leads to a decrease in the detected fluorescent signal due to a decrease in the fluorescent dye for specific adsorption, and the fluorescence for this specific adsorption. Variations in the detected fluorescent signal are also caused by the amount of dye decrease. Furthermore, since the amount of fluorescence can only be measured after washing, it cannot be measured in real time during the binding reaction between the analyte and the fluorescent dye, and it takes time to measure the amount of fluorescence because there is a washing process. There is also a problem.

JP 2006-208069 A JP 2009-128012 A JP 2010-48756 A

  The present invention has been made in view of the above problems, and in an assay method using a plasmon excitation sensor, an assay method and a plasmon excitation sensor that enable real-time measurement during a binding reaction while having high sensitivity and accuracy. The purpose is to provide.

  The above object of the present invention is achieved by the following configurations.

  1. An assay method using a plasmon excitation sensor comprising a fluorescent dye precursor developer that causes a color reaction with a metal member, a first ligand, and a fluorescent dye precursor, comprising the following steps (a) to (c) An assay method characterized by the above.

Step (a): bringing an analyte solution into contact with the plasmon excitation sensor and fixing the analyte in the analyte solution to the plasmon excitation sensor;
Step (b): A fluorescent dye precursor-ligand complex having a second ligand and a fluorescent dye precursor is brought into contact with the plasmon excitation sensor to which the analyte is fixed, and the first ligand is passed through the second ligand. A step of obtaining a fluorescent dye by immobilizing the fluorescent dye precursor to the ligand and reacting with the fluorescent dye precursor developer;
Step (c): A step of exciting the fluorescent dye by irradiating the metal member with excitation light and measuring the amount of fluorescence emitted from the excited fluorescent dye.

  2. 2. The assay method according to 1 above, wherein SAM is formed on the surface of the metal member.

  3. 3. The assay method according to 2 above, wherein dextran is immobilized on the surface of the SAM.

  4). 2. The assay method according to 1 above, wherein the fluorescent dye precursor developer is fixed to the metal member.

  5. 3. The assay method according to 2 above, wherein the fluorescent dye precursor developer is fixed to the SAM.

  6). 4. The assay method according to 3 above, wherein the fluorescent dye precursor developer is fixed to the dextran.

  7). 4. The assay method according to any one of 1 to 3, wherein the fluorescent dye precursor developer is fixed to the first ligand.

  8). The assay method according to any one of 1 to 7, wherein the metal member is a metal film.

  9. The assay method according to any one of 1 to 7, wherein the metal member is a metal particle.

  10. 10. The assay method according to 9 above, wherein the plasmon excitation sensor includes a substrate, and the metal particles are dispersed on the substrate.

  11. 11. The assay method according to any one of 1 to 10, wherein the fluorescent dye precursor ligand complex is a fine particle modified with the fluorescent dye precursor and the second ligand.

  12 12. The assay method according to any one of 1 to 11, wherein the analyte solution is at least one body fluid selected from blood, serum, plasma, urine, nasal fluid, and saliva.

  13. A plasmon excitation sensor comprising a metal member, a first ligand, and a fluorescent dye precursor developer that causes a color development reaction with the fluorescent dye precursor.

  14 14. The plasmon excitation sensor according to 13, wherein a SAM is formed on the surface of the metal member.

  15. 15. The plasmon excitation sensor according to 14 above, wherein dextran is fixed to the surface of the SAM.

  16. 14. The plasmon excitation sensor according to 13, wherein the fluorescent dye precursor developer is fixed to the metal member.

  17. 15. The plasmon excitation sensor according to 14 above, wherein the fluorescent dye precursor developer is fixed to the SAM.

  18. 16. The plasmon excitation sensor as described in 15 above, wherein the fluorescent dye precursor developer is fixed to the dextran.

  19. The plasmon excitation sensor according to any one of 13 to 15, wherein the fluorescent dye precursor developer is fixed to the first ligand.

  20. The plasmon excitation sensor according to any one of 13 to 19, wherein the metal member is a metal film.

  21. The plasmon excitation sensor according to any one of 13 to 19, wherein the metal member is a metal particle.

  22. The plasmon excitation sensor according to the item 21, wherein the plasmon excitation sensor includes a substrate, and the metal particles are dispersed on the substrate.

  The present invention can provide an assay method and a plasmon excitation sensor that enable real-time measurement during a binding reaction while having high sensitivity and accuracy in an assay method using plasmon excitation.

It is a schematic diagram showing a plasmon excitation sensor and assay method according to the present invention.

  In the figure, a) is a schematic diagram of the plasmon excitation sensor 10, and b) is a part in which the fluorescent dye precursor ligand complex 20 is added and a part thereof is fixed to the first ligand 12 via the analyte 31. It is a schematic diagram. c) is a schematic diagram showing a state in which the fluorescent dye precursor 24 of the fluorescent dye precursor ligand complex 20 has reacted with the fluorescent dye precursor developer 13 to become the fluorescent dye 22. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventors of the present invention developed a color between a fluorescent dye precursor and a fluorescent dye precursor developer (hereinafter also simply referred to as a developer) in an assay method using SPFS. The above problem could be solved by using a reaction.

  That is, according to the present invention, a fluorescent dye precursor fixed to the second ligand is allowed to act on a plasmon excitation sensor including a metal member, a first ligand, and a developer, so that the fluorescent dye precursor is in the vicinity. It is characterized by causing a color development reaction with a developer to generate fluorescence and measuring the amount of fluorescence.

  Since the unreacted fluorescent dye precursor in the flow channel that did not cause a color reaction with the developer does not generate fluorescence, the electric field enhancement effect on the surface plasmon is not obtained, and the measurement of the fluorescence amount is not affected. This eliminates the need for cleaning prior to measurement. As a result, it was found that the S / N was improved as compared with the conventional assay method using SPFS using a fluorescent dye, and rapid processing was possible while having high sensitivity and accuracy. It is.

[Plasmon excitation sensor]
The plasmon excitation sensor according to the present invention includes at least a metal member, a first ligand, and a fluorescent dye precursor developer that causes a color development reaction with the fluorescent dye precursor.

  Hereinafter, an example of the plasmon excitation sensor of the present invention will be specifically described with reference to FIG.

  For example, the plasmon excitation sensor 11 according to the present invention includes a metal film 112 on a transparent substrate 111, and has a first ligand 12 and a fluorescent dye precursor developer 13 on the metal film 112.

"substrate"
In the assay method according to the present invention, when a substrate that supports the structure of the plasmon excitation sensor 11 is used, the transparent substrate 111 is preferably used. In the present invention, the transparent substrate 111 is used as the substrate because light irradiation to the metal film 112 described later is performed through this substrate.

  The transparent substrate 111 used in FIG. 1 of the present invention has at least a metal film forming plane because a metal film 112 described later is formed on the surface of the transparent substrate 111. An example of such a transparent substrate 111 is a transparent flat substrate. The transparent substrate 111 used in FIG. 1 of the present invention may further include other components such as a prism portion and a sample holding portion in addition to the metal film forming plane. The transparent substrate 111 may be an integrated structure block including a metal film forming plane, a prism portion, and a sample holding portion.

  The material of the transparent substrate 111 used in FIG. 1 of the present invention is not particularly limited as long as the object of the present invention is achieved. The material of the transparent substrate 111 may be made of, for example, glass or an optical resin such as polycarbonate (PC), polymethyl methacrylate (PMMA), or cycloolefin polymer (COP).

The transparent substrate 111 is preferably a refractive index at the d-line (588 nm) _{[n d]} is 1.40 to 2.20.

(1) Transparent flat substrate The transparent flat substrate used as an example of the transparent substrate 111 in the present invention is usually made of glass or an optical resin such as polycarbonate (PC), polymethyl methacrylate (PMMA), or cycloolefin polymer (COP). It is a transparent flat substrate made of steel.

When using a glass flat transparent substrate as a transparent substrate 111, commercially, SCHOTT AG Corp. BK7 (refractive index _{[n d]} 1.52) and LaSFN9 (refractive index _{[n d]} 1.85), ( Co.) Sumita Optical Glass manufactured K-PSFn3 (refractive index _{[n d]} 1.84), K-LaSFn17 (refractive index _{[n d]} 1.88) and K-LaSFn22 (refractive index _{[n d]} 1.90 ), and (Ltd.) S-LAL10 (refractive index made of Ohara _{[n d]} 1.72) and the like, from the viewpoint of optical properties and cleanability.

  The size (length × width) of the transparent flat substrate used as the transparent substrate 111 having the prism portion is not particularly limited, but the thickness is preferably 0.01 to 10 mm, more preferably 0.5 to 5 mm. .

  The transparent flat substrate used as the transparent substrate 111 is preferably cleaned with acid and / or plasma before the metal film 112 is formed on the surface.

  Examples of the acid cleaning treatment include a method of immersing in 0.001 to 1N hydrochloric acid for 1 to 3 hours.

  Examples of the plasma cleaning treatment include a method of immersing in a plasma dry cleaner (PDC200 manufactured by Yamato Scientific Co., Ltd.) for 0.1 to 30 minutes.

(2) Integrated Structure Block The integrated structure block used as the transparent substrate 111 in the present invention includes a metal film forming plane, a prism portion, and a sample holding portion. The integrated structure block has a structure in which the metal film forming plane and the prism portion are integrated, and the metal film forming plane is located on the light reflecting surface of the prism portion. Further, the integrated structure block has a side surface structure formed continuously so as to surround the metal film forming plane, and a recess formed by the side structure and the metal film forming plane is a sample holding portion. Is configured. That is, the metal film forming plane constitutes the bottom surface of the sample holding portion, and the side structure constitutes the side surface of the sample holding portion. Advantages of using the integrated structure block as the transparent substrate 111 in the present invention are that the plasmon excitation sensor can be easily replaced, and therefore, it is possible to increase the throughput of analyte detection, and the plane for forming the metal film. And the prism portion are integrated, the reflection of incident light at the interface between the metal film forming plane and the prism portion can be suppressed.

  This integrated structure block is usually a block made of glass or resin, but polycarbonate (PC), polymethylmethacrylate, etc., particularly for reasons such as cost and moldability (less deterioration in optical properties due to molding). A block made of an optical resin such as (PMMA) or cycloolefin polymer (COP) is suitably used for an integrated structure block. The integrated structure block used as the transparent substrate 111 can be formed by, for example, injection molding of a raw material resin, such as ZEONEX (registered trademark) 330R (refractive index 1.50) manufactured by Nippon Zeon Co., Ltd. Commercial products can also be used. Note that the size of the integrated structure block used in the present invention is not particularly limited because the metal film forming plane and the prism portion are integrated.

  Even when an integrated structure block is used as the transparent substrate 111, it is preferable to clean the surface with acid and / or plasma before forming the metal film 112 on the surface. The conditions of the acid cleaning process and the plasma cleaning process are the same as in the case of using a transparent flat substrate as the transparent substrate 111 described above.

《Metal member》
The metal member in the present invention has a role of generating surface or localized plasmon excitation by irradiation light from a light source. As the metal member, for example, a metal film or metal fine particles can be used.

  In the assay method illustrated in FIG. 1 of the present invention, a metal film 112 is provided on one surface of a transparent substrate 111. The metal film 112 has a role of generating surface plasmon excitation by light irradiated from a light source. In the present invention, the surface plasmon generated in the metal film 112 excites a fluorescent dye described later to generate fluorescence.

  The metal film 112 formed on one surface of the transparent substrate 111 is preferably made of at least one metal selected from gold, silver, aluminum, copper, and platinum, in terms of chemical stability and optical characteristics. More preferably, it consists of gold. About these metal seed | species, the form of the alloy may be sufficient, and what laminated | stacked the some metal may be sufficient. Such a metal species is preferable because it is stable against oxidation and is highly excited by surface plasmons.

  When a transparent glass substrate is used as the transparent substrate 111, a thin film of chromium, nickel chromium alloy or titanium is used in advance in order to bond the transparent glass substrate and the metal film 112 more firmly. It is preferable to form on a transparent substrate.

  Examples of methods for forming the metal film 112 and / or chromium thin film on the transparent substrate 111 include sputtering, vapor deposition (resistance heating vapor deposition, electron beam vapor deposition, etc.), electrolytic plating, electroless plating, and the like. Is mentioned. Since adjustment of the thin film forming conditions is easy, it is preferable to form the chromium thin film and / or the metal film 112 by sputtering or vapor deposition.

  The thickness of the metal film 112 is 5 to 500 nm for gold, 5 to 500 nm for silver, 5 to 500 nm for aluminum, 5 to 500 nm for copper, 5 to 500 nm for platinum, and alloys thereof. 5-500 nm is preferable. Moreover, as thickness of the thin film of chromium, a nickel chromium alloy, or titanium, 1-20 nm is preferable.

  From the viewpoint of the electric field enhancing effect, more preferable thicknesses are 20 to 70 nm for gold, 20 to 70 nm for silver, 10 to 50 nm for aluminum, 20 to 70 nm for copper, 20 to 70 nm for platinum, and those. In the case of this alloy, 10 to 70 nm is more preferable, and the thickness of the chromium, nickel chromium alloy or titanium thin film is more preferably 1 to 3 nm.

  It is preferable that the thickness of the metal film 112 be within the above range because surface plasmons are likely to be generated. In addition, as long as the metal film 112 has such a thickness, the size (vertical x horizontal) is not particularly limited.

  When metal particles are used, localized plasmon excitation can be generated, and the type of metal is not particularly limited as long as particles capable of generating plasmon excitation can be prepared, but gold, silver, the same, aluminum Platinum, zinc, or an alloy of two or more of these is preferable. The particle size of the metal particles is not particularly limited as long as localized plasmon excitation occurs, but preferably 10 to 100 nm, and a group of metal particles having an average particle size in such a range is used. It is preferable to do.

  For example, the metal particles can be used in a manner dispersed in a flow path described later, but preferably the metal particles are used in a manner dispersed in the above-described substrate.

《Dielectric spacer layer》
In the assay method described with reference to FIG. 1 of the present invention, it is desirable to form a spacer layer made of a dielectric for the purpose of preventing metal quenching of the fluorescent dye 22 by the metal film 112. The spacer layer is formed on the metal film 112 and on the other surface of the metal film 112 that is not in contact with the transparent substrate 11.

As the dielectric used for forming the spacer layer, various optically transparent inorganic substances, natural or synthetic polymers can be used. Among them, it is preferable to contain silicon dioxide (SiO ₂ ) or titanium dioxide (TiO ₂ ) because it is excellent in chemical stability, production stability and optical transparency.

  The thickness of the spacer layer made of a dielectric is usually 10 nm to 1 mm, and 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. In the assay method of the present invention, the thickness of the spacer layer is desirably 10 to 100 nm for the purpose of enhancing the electric field more effectively.

  Examples of the method for forming a spacer layer made of a dielectric 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.

<< SAM >>
A self-assembled monolayer (SAM) 113 is formed on the metal film 112 or, if necessary, the spacer layer formed on the metal film 112. In the assay method of the present invention, the analyte and fluorescent dye precursor described later were immobilized on the metal film 112 (or the spacer layer formed thereon) via the first ligand 12 and the second ligand 21 described later. In this state, the amount of fluorescence is measured. At this time, the first ligand 12 is fixed to the metal film 112 via the SAM 113. That is, the SAM 113 serves as a foundation when the first ligand 12 is fixed to the metal film 112.

  In the present invention, when the spacer layer is made of a dielectric, the SAM 113 is preferably made of a silane coupling agent. As such a silane coupling agent, any silane coupling agent having an amino group or a carboxyl group can be used. Any conventionally known one can be used without any particular limitation. When the SAM 113 is directly formed on the metal film 112, a molecule having a thiol group at the end is usually used. The SAM113 contains a single molecule, usually a carboxyalkanethiol having about 4 to 20 carbon atoms (for example, available from Dojindo Laboratories Co., Ltd., Sigma Aldrich Japan Co., etc.), particularly preferably 10- Carboxy-1-decanethiol is used. Carboxyalkanethiol having 4 to 20 carbon atoms has properties such as little optical influence of SAM13 formed using it, that is, high transparency, low refractive index, and thin film thickness. Therefore, it is preferable.

  Further, when a coating layer is formed on the SAM 113 as will be described later, an aminoalkanethiol having about 4 to 20 carbon atoms, such as 10-amino-1-decanethiol, may be used as a single molecule contained in the SAM113. Good. When a single molecule having an amino group is used in the SAM 113 as described above, a hydrophilic polymer having a carboxyl group can be used as a molecule constituting the coating layer formed on the SAM 113.

  A method for forming the SAM 113 is not particularly limited, and a conventionally known method can be used. As a specific example, an ethanol solution containing 10-carboxy-1-decanethiol (manufactured by Dojindo Laboratories) or 10-amino-1-decanethiol is used as a transparent substrate 111 on which a metal film 112 is formed. The method of immersing in the method is mentioned. In this manner, the thiol group possessed by 10-carboxy-1-decanethiol or 10-amino-1-decanethiol is bonded to the metal and immobilized, and self-assembles on the surface of the metal film to form SAM113.

<Coating layer>
In the present invention, for the purpose of facilitating the immobilization of the first ligand 12 on the plasmon excitation sensor obtained after the formation of the SAM 113 and suppressing nonspecific adsorption of the analyte to the plasmon excitation sensor, the SAM 113 is used. A coating layer made of a hydrophilic polymer such as carboxymethyldextran (CMD) or polyethylene glycol may be formed thereon.

  This coating layer can be formed by bonding a hydrophilic polymer to the SAM 113 using a conventionally known method such as an active esterification method.

《Fluorescent dye precursor developer》
In the assay method according to the present invention, the fluorescent dye precursor developer is provided on a metal film provided on a transparent substrate. The developer develops a color reaction with a fluorescent dye precursor described later.

  The developer may be formed on the metal film as a fluorescent dye precursor developer complex directly fixed to the first ligand 12 described later, or in parallel with the first ligand 12. It may be formed on a metal film. The form of the complex is the same as that of the fluorescent dye precursor ligand complex 20 described later, and is preferably a fine particle modified with the developer 13 and the first ligand 12.

  The developer can be used alone or in combination of two or more. Specific examples of the developer include phenolic substances, organic or inorganic acidic substances, and esters and salts thereof as shown below, but are not limited thereto.

  Gallic acid, salicylic acid, 4-aminosalicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropyl Dendiphenol, 1,1′-inopropylidenebis (2-chlorophenol), 4,4′-isopropylidenebis (2,6-dibromophenol), 4,4′-isopropylidenebis (2,6-dichloro) Phenol), 4,4′-isopropylidenebis (2-methylphenol), 4,4′-isopropylidenebis (2,6-dimethylphenol), 4,4-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidenebispheno 4,4′-cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol , Methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac-type phenol resin, 2,2′-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol, phloroglysin, phloroglysin carboxylic acid, 4 -Tert-octylcatechol, 2,2'-methylnebis (4-chlorophenol), 2,2'-methylnebis (4-methyl-6-tert-butylphenol), 2,2, -dihydroxydiphenyl, p-hydroxybenzoic acid ethyl, -Propyl hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid-p-chlorobenzyl, p-hydroxybenzoic acid-o-chlorobenzyl, p-hydroxybenzoic acid-p- Methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6-naphthoic acid zinc, 4-hydroxy Diphenylsulfone, 4-hydroxy-4′-chlorodiphenylsulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, 3,5-di- Tin tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, kueh Acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivative, 4-hydroxythiophenol derivative, bis (4-hydroxyphenyl) acetic acid, bis (4-hydroxyphenyl) ethyl acetate, bis ( 4-hydroxyphenyl) acetic acid n-propyl, bis (4-hydroxyphenyl) acetic acid m-butyl, bis (4-hydroxyphenyl) acetic acid phenyl, bis (4-hydroxyphenyl) acetic acid benzyl, bis (4-hydroxyphenyl) acetic acid Phenethyl, bis (3-methyl-4-hydroxyphenyl) acetic acid, methyl bis (3-methyl-4-hydroxyphenyl) acetate, n-propyl bis (3-methyl-4-hydroxyphenyl) acetate, 1,7-bis (4-hydroxyphenylthio) 3,5-dioxaheptane, 1,5-bis (4 Hydroxyphenylthio) 3-oxaheptane, dimethyl 4-hydroxyphthalate, 4-hydroxy-4′-methoxydiphenylsulfone, 4-hydroxy-4′-ethoxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4'-propoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, 4-hydroxy-4'-isobutoxydiphenylsulfone, 4-hydroxy-4-butoxydiphenylsulfone, 4-hydroxy-4 ' -Tert-butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 4-hydroxy-4'-phenoxydiphenylsulfone, 4-hydroxy-4 '-(m-methylbenzyloxy) diphenylsulfur 4-hydroxy-4 '-(p-methylbenzyloxy) diphenylsulfone, 4-hydroxy-4'-(O-methylbenzyloxy) diphenylsulfone, 4-hydroxy-4 '-(p-chlorobenzyloxy) Diphenyl sulfone and the like.

《Fluorescent dye precursor》
In the assay method according to the present invention, a fluorescent dye precursor that exhibits a color development reaction with the above-described fluorescent dye precursor developer is used.

  The fluorescent dye precursor can be used in the form of a fluorescent dye precursor molecule-ligand complex directly fixed to a second ligand described later.

  Examples of the fluorescent dye precursor include leuco dyes. The leuco dyes can be used alone or in combination of two or more, and are themselves colorless or light-colored dye precursors.

  The fluorescent dye precursor of the present invention becomes a fluorescent dye by color development reaction with a developer.

  Specific examples of fluorescent dye precursors include triphenylmethane phthalide, triallyl methane, fluorane, phenothiocyan, thiofluorane, xanthene, indophthalyl, spiropyran, azaphthalide, chrome, etc. Preferred are leuco compounds such as nopyrazole, methine, rhodamine anilinolactam, rhodamine lactam, quinazoline, diazaxanthene and bislactone. Particularly preferred are fluoran and phthalide leuco dyes. Examples of such compounds include, but are not limited to, those shown below.

  2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6- (di-n-butylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N) -Methylamino) fluorane, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-sec-butyl-N-ethylamino) fluorane, 2- Anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) Luolan, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2- Anilino-3-methyl-6- (N-ethyl-Np-toluidino) fluorane, 2-anilino-3-methyl-6- (N-methyl-Np-toluidino) fluorane, 3-diethylamino-7, 8-benzofluorane, 1,3-dimethyl-6-diethylaminofluorane, 1,3-dimethyl-6-di-n-butylaminofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7 -Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 10-diethylamino-2-ethylbenzo [1,4] Azino [3,2-b] fluorane, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4 -Azaphthalide, 3- [2,2-bis (1-ethyl-2-methyl-3-indolyl) vinyl] -3- (4-diethylaminophenyl) phthalide, 3- [1,1-bis (4-diethylaminophenyl) ) Ethylene-2-yl] -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-carboxyphthalide and the like.

<< Method of manufacturing plasmon excitation sensor chip >>
The plasmon excitation sensor chip 10 according to the present invention is obtained by forming a metal film 112 on a transparent substrate 111. Here, the SAM 113 may be formed on the metal film 112 and the plasmon excitation sensor chip 10 having the SAM 113 may be used.

[Plasmon excitation sensor]
The plasmon excitation sensor according to the present invention includes a metal member, a first ligand, and a fluorescent dye precursor developer.

  As an example of an embodiment of the plasmon excitation sensor of the present invention, a plasmon excitation sensor 11 shown in FIG. 1 has a first ligand 12 and a fluorescent dye precursor developer 13 on a metal film of the plasmon excitation sensor chip 10. It is characterized by that.

<Ligand>
In the plasmon excitation sensor 11 according to FIG. 1 of the present invention, at least a ligand is bonded to the surface of the plasmon excitation sensor chip 10 on the side where the metal film is formed. This ligand is used for the purpose of fixing the analyte 31 in the analyte solution to the plasmon excitation sensor 11.

  In the present invention, “ligand” refers to a molecule or molecular fragment that can specifically recognize (or be recognized) and bind to an analyte contained in an analyte solution. Examples of such “molecule” or “molecular fragment” include nucleic acids (DNA that may be single-stranded or double-stranded, RNA, polynucleotides, oligonucleotides, PNA (peptide nucleic acids), etc., Or nucleosides, nucleotides and their modified molecules), proteins (including polypeptides and oligopeptides), amino acids (including modified amino acids), carbohydrates (oligosaccharides, polysaccharides, sugar chains, etc.), lipids, or modifications thereof Examples include, but are not limited to, molecules and complexes.

  Examples of the “protein” include an antibody and the like, and specifically, an anti-α fetoprotein (AFP) monoclonal antibody (available from Nippon Medical Laboratory, Inc.), carcinoembryonic antigen (CEA) Monoclonal antibodies, anti-CA19-9 monoclonal antibodies, anti-PSA monoclonal antibodies and the like can be mentioned.

  In the present invention, the term “antibody” includes polyclonal antibodies or monoclonal antibodies, antibodies obtained by gene recombination, and antibody fragments.

  When an antibody is used as a ligand in the present invention, the ligand may also be used in step (b) in the assay method described later for the purpose of binding the fluorescent dye precursor 24 to the analyte 31. Therefore, in the present invention, a ligand that is immobilized in advance on the plasmon excitation sensor 11 may be referred to as a “first ligand”, and a ligand that is used in step (b) described later may be referred to as a “second ligand”.

《Ligand fixation mode》
In the plasmon excitation sensor 11 of the present invention, the mode of binding of the first ligand 12 to the plasmon excitation sensor chip 10 is not particularly limited.

  As a typical binding mode, a mode in which the first ligand 12 itself is bound to the surface of the SAM 113 or the metal film 112 can be mentioned. For example, when the SAM 113 or the metal film 112 already has the ligand-fixing binding group, the first ligand 12 can be directly bonded to the surface of the SAM 113 or the metal film 112 by a conventional method. On the other hand, when the metal film 112 does not have the ligand fixing binding group, such as when the metal film 112 is formed only from the inorganic dielectric, a silane having an appropriate ligand fixing binding group. By allowing a coupling agent to act, a ligand-fixing binding group is introduced into the metal film 112, and then the first ligand 12 is attached to the surface of the metal film 112 through the ligand-fixing binding group by a conventional method. It may be fixed. The ligand-fixing binding group introduced here is a functional group such as an amino group, a thiol group, or a carboxyl group.

  When a silane coupling agent having a ligand-fixing binding group is allowed to act, it is preferable to adjust the reaction position and concentration of the silane coupling agent as necessary.

[Assay Method]
The assay method according to the present invention is an assay method using a plasmon excitation sensor comprising a metal member, a first ligand and a fluorescent dye precursor developer, and comprises the following steps (a) to (c): Features.

Step (a): bringing an analyte solution into contact with the plasmon excitation sensor and fixing the analyte in the analyte solution to the plasmon excitation sensor;
Step (b): contacting a fluorescent dye precursor-ligand complex having a second ligand and a fluorescent dye precursor with a plasmon excitation sensor having the analyte immobilized thereon, and passing the first ligand through the second ligand A step of obtaining a fluorescent dye by fixing the fluorescent dye precursor to a ligand and reacting with the fluorescent dye precursor developer;
Step (c): A step of exciting the fluorescent dye by irradiating the metal member with excitation light and measuring the amount of fluorescence emitted from the excited fluorescent dye.

<Process (a)>
In the assay method of the present invention, step (a) is a step of bringing the analyte solution into contact with the plasmon excitation sensor described above and immobilizing the analyte in the analyte solution on the plasmon excitation sensor.

  When the analyte 31 to be measured by the assay method of the present invention is contained in the analyte solution, as shown in FIG. 1, the analyte 31 passes through the first ligand 12 and the plasmon excitation sensor 12. Fixed to.

Analyte Solution In the present invention, the “analyte solution” refers to a sample containing various analytes to be measured by the assay method of the present invention.

  The analyte solution may be any solution containing an analyte, and examples thereof include a specimen. Examples of the sample include blood (serum / plasma), urine, nasal fluid, saliva, feces, body cavity fluid (spinal fluid, ascites, pleural effusion, etc.), etc., and can be appropriately diluted in a desired solvent, buffer, etc. It may be used. Of these samples, blood, urine, nasal fluid and saliva are preferred. These may be used alone or in combination of two or more.

Analyte In the present invention, “analyte” means a molecule or molecular fragment that can specifically recognize (or recognize) and bind to the first ligand 12 immobilized on the surface of the SAM 113 or the metal film 112. . Examples of such “molecule” or “molecular fragment” include, for example, nucleic acid (DNA, RNA, polynucleotide, oligonucleotide, PNA (peptide nucleic acid), which may be single-stranded or double-stranded, or the like, or Nucleosides, nucleotides and their modified molecules), proteins (including polypeptides and oligopeptides), amino acids (including modified amino acids), carbohydrates (oligosaccharides, polysaccharides, sugar chains, etc.), lipids, or modified molecules thereof In particular, it may be a tumor marker such as AFP (α-fetoprotein), carcinoembryonic antigen, a signal transducing substance, a hormone, and the like, and is not particularly limited.

Contact In the present invention, “contact” is included in the liquid supply in a state where the flow path of the surface on which at least the first ligand 12 of the plasmon excitation sensor is immobilized is immersed in the liquid supply. It refers to bringing an object (analyte) into contact with this plasmon excitation sensor. By this “contact”, an analyte-ligand complex in which the first ligand 12 and the analyte 31 are combined is formed. In the step (a), the “contact” between the analyte solution and the plasmon excitation sensor includes an analyte solution included in the liquid circulation circulating in the flow path, and the first ligand of the plasmon excitation sensor is immobilized. An embodiment in which the plasmon excitation sensor and the alanite solution are brought into contact with each other while only the surface being immersed in the liquid feeding is preferable.

  The “channel” is a rectangular parallelepiped or a tube that can efficiently deliver a small amount of a chemical solution, and can change or circulate the solution feeding speed in order to promote the reaction. . Here, as the shape of this flow path, the vicinity of the location where the plasmon excitation sensor is installed preferably has a rectangular parallelepiped structure, and the vicinity of the location where the drug solution is delivered preferably has a tubular shape.

  As the material of the flow path, in the plasmon excitation sensor portion having a plasmon excitation sensor, a homopolymer or copolymer containing methyl methacrylate, styrene or the like as a raw material; a light-transmitting material such as polyolefin such as polyethylene, a chemical solution In the delivery part, polymers such as silicone rubber, Teflon (registered trademark), polyethylene, and polypropylene are used.

  However, for the plasmon excitation sensor unit, the flow channel structure is not necessarily made of a light-transmitting material unless the flow channel is kept in a fixed shape at the time of fluorescence measurement and the detection of fluorescence generated by plasmon excitation is not hindered. There is no need to consist only of. That is, of the flow path of the plasmon excitation sensor part, a part necessary for transmitting the fluorescence generated by plasmon excitation and guiding it to the detection part, specifically, a part including a transparent window necessary for collecting the fluorescence. However, other parts may be partially or entirely made of a chemically stable material other than the light transmissive material. When the flow path of the plasmon excitation sensor unit has a rectangular parallelepiped structure, when the surface of the plasmon excitation sensor 11 on which the SAM 113 or the metal film 112 exists is used as the bottom surface, for example, a ceiling surface at a position facing the bottom surface is The light transmitting material may be used, and the side surface may be formed of a chemically stable material other than the light transmitting material.

  Here, the other part, for example, the side surface does not necessarily need to be a rigid body as long as a certain shape is maintained at the time of fluorescence measurement, and may have an appropriate elasticity to ensure a sealing property. For example, regarding the flow path of the plasmon excitation sensor unit, the ceiling surface may be made of polymethyl methacrylate (PMMA) and the side surface may be made of silicone rubber.

  In the plasmon excitation sensor unit, from the viewpoint of increasing the contact efficiency with the analyte solution and shortening the diffusion distance, the vertical and horizontal cross sections of the channel of the plasmon excitation sensor unit are preferably independently about 100 nm to 1 mm.

  In the flow path, the position of the liquid feeding inlet for introducing the liquid feeding from the drug delivery section to the plasmon excitation sensor section and the position of the liquid feeding outlet for discharging the liquid feeding from the plasmon excitation sensor section are both obstructing the fluorescence measurement. Unless it becomes, it will not specifically limit. For example, when the flow path of the plasmon excitation sensor section has a rectangular parallelepiped structure, it is convenient to prepare the flow path for the liquid feed inlet and the liquid feed outlet on the ceiling surface. Either one or both of the liquid discharge ports may be provided on the side surface.

  The method for fixing the plasmon excitation sensor to the flow path is not particularly limited as long as the flow path is kept in a fixed shape and the fluorescence measurement is not hindered.

  As an example of such a fixing method, in a small lot (laboratory level), first, a silicone rubber having a certain thickness is formed on the surface of the plasmon excitation sensor 11 on which the SAM 113 or the metal film 112 is formed. A side structure of the flow path is formed by placing a sheet or an O-ring, and then a light-transmitting top plate (for example, a PMMA substrate) provided with a liquid feeding inlet and a liquid feeding outlet is disposed thereon. For example, a method may be used in which the ceiling surface of the flow path is formed, and then these are pressure-bonded and fixed with an appropriate fastener. At this time, if a silicone rubber sheet having an appropriate thickness and having a hole having an arbitrary shape and size is used as a material constituting the side surface structure, the inner periphery of the hole has a plasmon. Since it becomes the side structure of the flow path of an excitation sensor part, since the flow path which has a required shape and a size can be formed easily, it is preferable. For example, first, a perforated polydimethylsiloxane (PDMS) sheet having a flow path height of 0.5 mm is formed on the surface of the plasmon excitation sensor SAM 113 or metal film 112 formed on the surface of the plasmon excitation sensor. Next, a PMMA substrate provided with a liquid feeding inlet and a liquid feeding outlet in advance is placed on this polydimethylsiloxane (PDMS) sheet, and then placed. The PMMA substrate, the polydimethylsiloxane (PDMS) sheet, and the plasmon excitation sensor are pressure-bonded and fixed with a fastener such as a screw. In addition, when a silicone rubber sheet or O-ring and a light-transmitting top plate are pressure-bonded and fixed to the plasmon excitation sensor, an appropriate spacer made of a material such as silicone rubber or stainless steel is attached as necessary. You may use together.

  Also, in large lots (factory level) manufactured industrially, as a method of fixing the plasmon excitation sensor to the flow path, a gold substrate is directly formed on a plastic integrally molded product, or a separately manufactured gold substrate is fixed. Then, after the SAM and the ligand are immobilized on the gold surface, it can be manufactured by covering with a plastic integrally molded product corresponding to the top plate of the flow path. If necessary, the prism can be integrated into the flow path.

  When an integrated structure block is used as the transparent substrate 111, since a side structure has already been formed as a sample holder, a liquid feeding inlet and a liquid feeding outlet are provided on the integrated structure block. A ceiling surface of the flow path is formed by arranging a certain light transmissive top plate (for example, PMMA substrate), and then the plasmon excitation sensor is attached to the flow path by crimping them and fixing them with appropriate fasteners. Can be fixed.

  The “liquid feeding” is preferably the same as the solvent or buffer in which the analyte solution is diluted, and examples thereof include phosphate buffered saline (PBS) and Tris buffered saline (TBS). It is not limited.

  The temperature and time for circulating the liquid feed vary depending on the type of the analyte solution and are not particularly limited, but are usually 20 to 40 ° C. for 1 to 60 minutes, preferably 37 ° C. for 5 to 15 minutes, It is to circulate the liquid feeding.

  The initial concentration of the analyte contained in the analyte solution being fed is preferably 100 μg / ml to 0.0001 pg / ml.

  The total amount of liquid feeding, that is, the volume of the flow path is usually 0.0001 to 20 ml, preferably 0.01 to 1 ml.

  The flow rate of the liquid feeding is usually 1 to 30,000 μl / min, preferably 5 to 10,000 μl / min.

<Step (b)>
In the assay method of the present invention, in the step (b), the fluorescent dye precursor having the second ligand 21 and the fluorescent dye precursor 24 on the plasmon excitation sensor to which the analyte obtained in the above step (a) is fixed. The fluorescent dye precursor 24 is fixed to the first ligand 12 via the second ligand 21 and reacted with the fluorescent dye precursor developer. This is a step of obtaining a dye. Referring to FIG. 1, the fluorescent dye precursor ligand complex 20 is coupled to the plasmon excitation sensor 11 via the analyte 31. The fluorescent dye precursor exhibits a color development reaction with the fluorescent dye precursor developer, and becomes a fluorescent dye. This makes it possible to quantify the amount of analyte-ligand complex produced in the form of fluorescence emission in step (c) described below.

《Fluorescent dye precursor ligand complex》
The fluorescent dye precursor ligand complex 23 used in the present invention includes a second ligand 21 and a fluorescent dye precursor 24.

Second Ligand In the assay method of the present invention, the second ligand 21 is a ligand used for the purpose of labeling the analyte 31 with the fluorescent dye precursor 24, and may be the same as the first ligand 12. And may be different. However, when the primary antibody used as the first ligand 12 is a polyclonal antibody, the secondary antibody used as the second ligand 21 may be a monoclonal antibody or a polyclonal antibody. When is a monoclonal antibody, the secondary antibody is preferably a monoclonal antibody that recognizes an epitope that the primary antibody does not recognize, or a polyclonal antibody.

Embodiment of Complex In the present invention, the binding state of the fluorescent dye precursor ligand complex 20 is not particularly limited as long as it comprises the second ligand 21 and the fluorescent dye precursor 24. However, from the viewpoint of enabling highly sensitive measurement by binding as many fluorescent dye precursors 24 as possible to the analyte 31 immobilized on the plasmon excitation sensor 11, the fluorescent dye precursor ligand complex 20 is Desirably, the fine particles are modified with the fluorescent dye precursor 24 and the second ligand 21.

  The fine particles (hereinafter referred to as “basic fine particles”) used as the material of the modified fine particles are fine particles that can be suspended without being precipitated in the liquid feeding. Examples of such basic fine particles include hydrophobic fine particles such as latex particles and hydrophilic fine particles such as liposomes.

  Among these, the latex particles used in the present invention are granular polymer substances that can be suspended in water and insoluble in water, and can be obtained by a conventionally known method. In the present invention, the latex particles preferably have a particle size of 30 nm or more and 100 nm or less. The larger the particle size, the more fluorescent dye precursor 22 can be fixed and the emission signal is increased. However, if the particle size is too large, there is a risk that resistance will be easily received during liquid feeding. .

  Latex particles used in the present invention can be obtained in a state in which the fluorescent dye precursor 22 is previously incorporated. For example, as in the method disclosed in Japanese Patent No. 4277479, the polymer obtained by radical polymerization of a vinyl monomer having a polymerizable ethylenically unsaturated double bond and the fluorescent dye precursor 22 are placed in an organic solvent. It can be produced as latex particles containing the fluorescent dye precursor 22 by a method of dissolving (or dispersing) and removing the organic solvent after emulsification in water. As vinyl monomers having a polymerizable ethylenically unsaturated double bond used here, vinyl acetate, methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid Isononyl, dodecyl acrylate, octadecyl acrylate, 2-phenoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, dodecyl methacrylate , Octadecyl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, benzyl methacrylate, glycidyl methacrylate, phenyl methacrylate, styrene, α-methylstyrene, acrylonitrile Acetoacetoxyethyl methacrylate, glycidyl methacrylate of soybean oil fatty acid modified products: include (Blenmer G-FA manufactured by NOF Corporation) and the like. Here, a monomer having an appropriate functional group such as an amino group or a carboxyl group is mixed with the vinyl monomer having a polymerizable ethylenically unsaturated double bond and used in the latex particle to form the second ligand 21. Functional groups used for immobilization can be introduced.

  On the other hand, the liposome used in the present invention has an outer shell composed of an amphiphilic bilayer surrounding a certain volume of water or an aqueous solution, and usually has a particle size of 50 nm to 100 μm. The amphiphilic bilayer used here is usually composed of mixed lipid components such as phospholipids.

The method for producing such a liposome is not particularly limited, but from the viewpoint that the liposome surface can be efficiently modified, for example, a membrane emulsification method, a stirring emulsification method, a droplet method, a contact method pore membrane, etc. are used. In the two-stage emulsification method using the membrane emulsification method, a microchannel emulsification method and an emulsification method using a shirasu porous glass membrane (hereinafter, “SPG membrane”) are used. Preferably used. As a typical procedure,
(I) In the primary emulsification step, a W1 / O emulsion is formed by dispersing the first aqueous phase (W1) containing the mixed lipid component in an appropriate organic solvent (O) that is difficult to mix with water,
(Ii) In the subsequent secondary emulsification step, the W1 / O emulsion is dispersed in the second aqueous phase (W2) by using an appropriate emulsification method in the presence of the second mixed lipid component, whereby W1 / O / W2 Forming an emulsion,
(Iii) Thereafter, liposomes can be formed by removing the organic solvent (O) contained in the W1 / O / W2 emulsion. For example, when the membrane emulsification method is used, the W1 / O emulsion is dispersed in the second aqueous phase (W2) by using, for example, a microchannel or SPG membrane having a required pore size in the secondary emulsification step. Can do.

  The composition of the mixed lipid component used for the production of the liposome is not particularly limited, but in general, phospholipid (animal and plant derived lecithin; Glycerophospholipids, which are fatty acid esters; sphingophospholipids; derivatives thereof, and the like, and sterols (cholesterol, phytosterol, ergosterol, derivatives thereof, etc.) that contribute to the stabilization of lipid membranes. Lipids, glycols, aliphatic amines, long chain fatty acids (oleic acid, stearic acid, palmitic acid, etc.), and other compounds that impart various functions may be blended. In the present invention, neutral phospholipids such as dipalmitoyl phosphatidylcholine (DPPC), dioleyl phosphatidylcholine (DOPC), dipalmitoyl phosphatidylglycerol (DPPG) are commonly used as the phospholipid. The mixing ratio of the mixed lipid component may be appropriately adjusted according to the application while considering properties such as the stability of the lipid membrane and the behavior of the liposome in vivo.

  In addition, the second mixed lipid component can be the same component as the mixed lipid component used in the primary emulsification step, and even if it has the same composition as the mixed lipid component used in the primary emulsification step, There may be. Here, in the present invention, the second ligand 21 and the fluorescent dye precursor 24 are fixed by including a lipid component having an appropriate functional group such as an amino group or a carboxyl group in the second mixed lipid component. It is preferred to introduce possible functional groups into the liposome surface. Examples of lipid components having such an appropriate functional group include distearoyl phosphatidylethanolamine (DSPE), and a functional group is introduced via a linker moiety such as a PEG group such as DSPE-PEG-COOH. It may be.

  In the secondary emulsification step, the second aqueous phase (W2) may contain a dispersing agent such as protein, polysaccharide, and nonionic surfactant.

  With respect to the basic particles such as latex particles and liposomes thus obtained, the second ligand 21 and the fluorescent dye precursor 24 can be immobilized using a conventionally known coupling method. For example, immobilization using conventional methods such as active ester method, amine coupling, coupling method based on reaction of iodoacetamide and thiol group, and method using affinity such as biotin-streptavidin bond Can do. For the fine particles into which the fluorescent dye precursor 24 is introduced when producing the basic fine particles such as latex particles containing the fluorescent dye precursor 24, only the second ligand 21 is used in the same manner. It may be fixed by.

  The concentration of the fluorescent dye precursor-ligand complex 20 produced in this way during feeding is preferably 0.001 to 10,000 μg / ml, more preferably 1 to 1,000 μg / ml.

  The fluorescent dye precursor ligand complex 20 is fixed to the first ligand, and then undergoes a color development reaction with a neighboring fluorescent dye precursor developer to become a fluorescent dye ligand complex 23.

<Step (c)>
In the assay method of the present invention, step (c) is a step of irradiating the metallic member with excitation light to excite the fluorescent dye and measuring the amount of fluorescence emitted from the excited fluorescent dye.

  Step (c) is usually performed by detecting the fluorescence emission from the fluorescent dye 22 bound to the fluorescent dye-ligand complex 23. Specifically, the plasmon excitation sensor obtained in the step (b) is performed by irradiating the metal member with excitation light and measuring the amount of fluorescence emitted from the fluorescent dye 22.

  In the assay method illustrated in FIG. 1 of the present invention, only the fluorescent dye precursor 24 in the vicinity of the fluorescent dye precursor developer 13 immobilized on the transparent substrate 111 or the first ligand 12 causes a color development reaction. Since it changes to the fluorescent dye 22, the fluorescent dye precursor 24 that is not in the vicinity of the fluorescent dye precursor developer 13 does not change to the fluorescent dye 22, and does not emit fluorescence.

  On the other hand, the unreacted fluorochrome precursor ligand complex 20 that is not immobilized on the first ligand 12 does not emit fluorescence, so it may be suspended in the flow path, and is generally used in an assay method based on SPFS. It is not necessary to remove the unreacted fluorescent dye precursor ligand complex 20 from the flow path before the measurement in the step (c) due to the washing. From this, in the assay method of the present invention, it is possible to measure the amount of fluorescence in real time by simultaneously performing the steps (b) and (c).

  The fact that the amount of fluorescence can be measured in real time means that the amount of fluorescence emitted at the end of the reaction can be estimated from the rate of increase in the amount of fluorescence emitted from the start of the reaction. This is an advantage. Further, in the assay method based on SPFS of the present invention, the washing is performed prior to the measurement of the fluorescence amount between the step (b) and the step (c), which has conventionally been necessary to remove the unreacted fluorescent dye and the like. Since a process is not necessary, there is an advantage that measurement can be performed for a short time.

Optical System The excitation light used in the present invention is not particularly limited as long as it can cause plasmon excitation in the metal member.

  Examples of the excitation light include laser light. In laser light, it is desirable to adjust the energy and the amount of photons immediately before entering the transparent substrate through an optical filter.

  In the assay method illustrated in FIG. 1 of the present invention, surface plasmons are generated on the surface of the metal film 112 under the total reflection attenuation condition (ATR) by irradiation with laser light. Due to the electric field enhancement effect of the surface plasmon, the fluorescent dye changed from the fluorescent dye precursor to the fluorescent dye is excited by the photons increased to several tens to several hundred times the amount of irradiated photons, thereby generating fluorescence. In addition, although the photon increase amount by the electric field enhancement effect depends on the refractive index of the transparent substrate 111 and the metal species and film thickness of the metal film 112, the increase amount is usually about 10 to 20 times when the metal species is gold. .

  Examples of the “laser light” include an LD (laser diode) laser having a wavelength of 200 to 900 nm, 0.001 to 1,000 mW, a wavelength of 230 to 800 nm (the resonance wavelength is determined by the metal species used for the metal film 112), and 0. A semiconductor laser of 0.01 to 100 mW can be used.

  The “prism” is intended to allow laser light that has passed through various filters to efficiently enter the plasmon excitation sensor, and preferably has the same refractive index as that of the transparent substrate 111. In the present invention, various prisms for which total reflection conditions can be set can be selected as appropriate, and therefore, there is no particular limitation on the angle and shape. For example, a 60-degree dispersion prism may be used. Examples of such commercially available prisms include those similar to the above-mentioned commercially available “glass-made transparent flat substrate”. The prism may be incorporated in the transparent substrate 111 as a prism portion of the integrated structure block.

  Examples of the “optical filter” include a neutral density (ND) filter and a diaphragm lens. The “darkening (ND) filter” (or neutral density filter) is intended to adjust the amount of incident laser light. In particular, when a detector with a narrow dynamic range is used, it is preferable to use it for carrying out a highly accurate measurement.

  The “polarizing filter” is used to make the laser light P-polarized light that efficiently generates surface plasmons.

  “Cut filters” are external light (illumination light outside the device), excitation light (transmission component of excitation light), stray light (excitation light scattering component in various places), plasmon scattered light (originating from excitation light, plasmon A filter that removes various types of noise light such as scattered light generated by the influence of structures or deposits on the surface of the excitation sensor), autofluorescence of the enzyme fluorescent substrate, and examples thereof include interference filters and color filters. It is done.

  The “collecting lens” is intended to efficiently collect the fluorescent signal on the detector, and may be an arbitrary condensing system. As a simple condensing system, a commercially available objective lens (for example, manufactured by Nikon Corporation or Olympus Corporation) used in a microscope or the like may be used. The magnification of the objective lens is preferably 10 to 100 times.

  As the “chemiluminescence detector”, a detection system usually used for SPFS detection can be used, and a photomultiplier tube (a photomultiplier manufactured by Hamamatsu Photonics Co., Ltd.) is preferable from the viewpoint of ultrahigh sensitivity. Also, although the sensitivity is lower than these, a CCD image sensor capable of multipoint measurement is also suitable because it can be viewed as an image and noise light can be easily removed. In the assay method according to the present invention, it is possible to select a detection wavelength such that the detected chemiluminescence wavelength is shorter than the wavelength of the normal incident light and is in the wavelength region near green. There is an advantage that it is easy to perform detection using a variety of light receiving systems.

  In the assay method illustrated in FIG. 1 of the present invention, as in the assay method based on SPFS, the light source is located on the opposite side of the plasmon excitation sensor 11 with respect to the chemiluminescence detection unit, and measurement is performed under the total reflection condition. Is called.

Drive Device In the present invention, the optical system may be integrated in the form of a “drive device”. The drive apparatus of this invention is for implementing this invention using the said plasmon excitation sensor.

  The “driving device” includes at least a light source, various optical filters, a prism, a cut filter, a condenser lens, and a chemiluminescence detector. In addition, when handling an analyte solution, a cleaning liquid, etc., it is preferable to have a liquid feeding system combined with a plasmon excitation sensor. The type of liquid feeding system is not limited as long as the object of the present invention can be achieved. For example, a microchannel device connected to a liquid pump may be used.

  In addition, a surface plasmon resonance (SPR) detection unit, that is, a photodiode as a light receiving sensor dedicated to SPR, an angle variable unit for adjusting the optimum angle of SPR and SPFS (to determine total reflection attenuation (ATR) conditions with a servomotor) In addition, the angle of 30 to 85 ° can be changed by synchronizing the photodiode and the light source with a resolution of preferably 0.01 ° or more.), A computer for processing information input to the chemiluminescence detector May also be included.

  Preferred embodiments of the light source, the optical filter, the cut filter, the condensing lens, and the chemiluminescence detector are the same as those described above.

  As the “liquid feed pump”, for example, a micro pump suitable for a small amount of liquid feed, a syringe pump with high feed accuracy and low pulsation, which is preferable but cannot be circulated, a simple and excellent handleability but a small amount of liquid feed For example, a tube pump may be difficult.

  In the assay method of the present invention, a step (d) of calculating the amount of the analyte 31 contained in the analyte solution from the measurement result obtained in the step (c) may be further added.

  More specifically, a calibration curve is prepared by performing measurement with a target antigen or target antibody at a known concentration, and the target antigen amount or target antibody amount in the analyte solution to be measured based on the prepared calibration curve. Is calculated from the measurement signal.

Assay S / N
Furthermore, in the step (d), the “blank luminescence signal” measured before the step (a), the “assay luminescence signal” obtained in the step (d), and the metal substrate not modified at all are used. When the signal obtained by measuring SPFS while flowing in ultrapure water while fixing in the flow channel is defined as “initial noise”, the assay S / N represented by the following formula (1a) can be calculated:
Assay S / N = | Ia / Io | / In (1a)
(In the above formula (1a), Ia is the assay luminescence signal, Io is the blank luminescence signal, and In is the initial noise).

However, in calculating the assay S / N, instead of the above formula (1a), in practice, the “assay noise signal” when the concentration of the analyte 31 contained in the analyte solution is 0 is used as a reference. You may calculate according to following formula (1b):
Assay S / N = | Ia | / | Ian | (1b)
(In the above formula (1b), Ian is an assay noise signal, and Ia is an assay luminescence signal as in the case of the above formula (1a)).

〔kit〕
The kit according to the present invention is characterized by being used in the assay method of the present invention. In carrying out the assay method of the present invention, the first ligand 12 and the fluorescent dye precursor ligand complex 20 All necessary except for the analyte solution, for example, a primary antibody, a ligand such as an antigen (ie, the analyte 31 contained in the analyte solution is not limited to an antigen, and may be an antibody. It is preferable to include everything necessary except for the analyte solution and the secondary antibody.

  For example, the content of a specific tumor marker can be detected with high sensitivity and high accuracy by using a kit according to the present invention, blood or serum as a specimen as an alanite solution, and an antibody against the specific tumor marker. Can do. From this result, the presence of a preclinical noninvasive cancer (carcinoma in situ) that cannot be detected by palpation or the like can be predicted with high accuracy.

  Specifically, the plasmon excitation sensor chip 10 includes a solution or a diluent for dissolving or diluting the analyte; a solution used in the reaction between the plasmon excitation sensor chip 10 and the analyte; and a cleaning reagent. Furthermore, various devices or materials required for carrying out the assay method of the present invention and the above-mentioned “drive device” can be included.

  Further, the kit element may include a standard material for preparing a calibration curve, instructions, a necessary set of equipment such as a microtiter plate capable of simultaneously processing a large number of analytes, and the like.

<Synthesis of fluorescent dye precursor (3,3-bis (p-dimethylaminophenyl) -6-carboxyphthalide)>
A 100 ml three-headed flask equipped with an oil bath was sealed, and 24.6 g of dimethylaniline and 5 g of anhydrous aluminum chloride were added and stirred under a dry nitrogen stream. Further, 20 g of trimellitic anhydride was added and maintained at 170 ° C., followed by heating and stirring for 6 hours. After cooling, hydrochloric acid was added and heated to dissolve until all the contents were dissolved. 50 ml of 1M / l sodium hydroxide was dropped with a dropping funnel, and the precipitated solid was collected and recrystallized from methanol to obtain 19.6 g of the desired product. It was confirmed to be the target product by NMR and mass spectrometry.

<Labeled secondary antibody 1: Preparation of “Alexa Fluor 647” labeled anti-AFP monoclonal antibody>
An anti-alpha fetoprotein (AFP) monoclonal antibody (6D2, 2.5 mg / ml, manufactured by Mikuli Immuno Laboratory Co., Ltd.) was prepared with a commercially available Alexa Fluor 647 labeling kit (Molecular Probes), and Alexa Fluor 647 labeled anti-AFP. A monoclonal antibody solution was obtained.

  The obtained antibody solution was quantified for protein and fluorescent dye concentrations with an absorbance meter and stored at 4 ° C.

<Labeled secondary antibody 2: Preparation of “leuco dye” labeled anti-AFP monoclonal antibody>
3,3-bis (p-dimethylaminophenyl) -6-carboxyphthalide was used as a leuco body, and 2 mg of leuco body was dissolved in 1 ml of 25 mM MES (2-morpholinoethanesulfonic acid) buffer (pH 6.0). -Ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC: manufactured by Dojin Chemical Laboratory) 50 mM, N-hydroxysuccinimide (NHS: manufactured by Thermo Scientific) 50 mM activated the carboxyl group I let you. 4 ul of active leuco body is added to 100 ul (10 equivalents) of 1.4 mg / ml anti-α-fetoprotein (AFP) monoclonal antibody (6D2, manufactured by Mikuli Immuno Laboratory Co., Ltd.), and reacted at room temperature for 1 hour to produce leuco dye. Was reacted with the antibody. After the reaction, purification by centrifugal ultrafiltration (manufactured by Millipore) gave a leuco dye-labeled anti-AFP monoclonal antibody solution. The obtained antibody solution was quantified for protein and fluorescent dye concentrations with an absorbance meter and stored at 4 ° C.

<Labeled Primary Antibody: Preparation of “Developer” Labeled Anti-AFP Monoclonal Antibody>
The carboxyl group was activated by adding 50 mM EDC and 50 mM NHS to 1 ml of a 1.4 mg / ml anti-α-fetoprotein (AFP) monoclonal antibody (1D5, manufactured by Mikuli Immuno Laboratory Co., Ltd.) and 25 mM MES buffer (pH 6.0). . Using 4-aminosalicylic acid as a developer, 4 ul of 5 mM developer was added (10 equivalents) to 100 ul of the antibody solution, and the developer was allowed to react at room temperature for 1 hour to bind the developer to the antibody. After the reaction, a developer-labeled anti-AFP monoclonal antibody solution was obtained by purification by centrifugal ultrafiltration. The resulting antibody solution was quantified with an absorbance meter and stored at 4 ° C.

  The labeled antibodies used in the following examples and comparative examples were all prepared by the same method.

Example 1
(Step 1: Formation of metal film)
A glass transparent flat substrate “S-LAL 10” (manufactured by OHARA INC., Refractive index [n _d ] = 1.72) having a thickness of 1 mm was plasma-cleaned with a plasma dry cleaner. A metal film was formed on the surface of the plasma-cleaned substrate by sputtering. The thickness of the metal film was 44 to 52 nm.

(Step 2: Binding of carboxymethyldextran)
The transparent substrate obtained in the step 1 is immersed in an ethanol solution containing 1 mM of 10-amino-1-decanthiol for 12 hours or more, and SAM (Self Assembled Monolayer; Molecular film) was formed. The substrate was taken out from the ethanol solution, washed with ethanol and isopropanol, and then dried using an air gun. The obtained SAM-forming substrate was immersed in a 1 mg / ml aqueous solution of carboxymethyl dextran (manufactured by Meisei Sangyo Co., Ltd., molecular weight 5 million, substitution degree 1.08). Furthermore, 0.5 mM each of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC: manufactured by Dojin Chemical Laboratory) and N-hydroxysuccinimide (NHS: manufactured by Thermo Scientific) The mixture was reacted at room temperature for 1.5 hours, and amide coupling between the SAM at the amino group end and the carboxyl group of dextran was performed to obtain a plasmon excitation sensor precursor substrate on which carboxymethyldextran was immobilized. After completion of the reaction, 1N / l sodium hydroxide was dropped onto the substrate surface and reacted at room temperature for 30 minutes to convert the activated carboxyl group into carboxylic acid.

(Step 3: Immobilization of primary antibody)
1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC: manufactured by Dojin Chemical Laboratory), N-hydroxysuccinimide (NHS: manufactured by Thermo Scientific) 25 mM MES containing 100 mM each ( 2-Morpholinoethanesulfonic acid (buffer) buffer, 10 mM NaCl (pH 6.0) mixed solution is dropped onto a substrate on which carboxymethyldextran is fixed, reacted at room temperature for 20 minutes, and fixed on the surface of the precursor substrate incorporated in the sensor chip. The produced carboxymethyl dextran was active esterified.

  Subsequently, 4-aminosalicylic acid (developer) 0.01 mM (25 mM MES buffer, 10 mM NaCl (pH 6.0)) was added dropwise and reacted at room temperature for 30 minutes to fix 4-aminosalicylic acid to carboxymethyldextran. After completion of the reaction, 1N / l sodium hydroxide was dropped onto the substrate surface and reacted at room temperature for 30 minutes to convert the activated carboxyl group into carboxylic acid.

  Thereafter, an anti-α fetoprotein (AFP) monoclonal antibody (1D5, 1.8 mg / ml, manufactured by Mikuli Immuno Laboratory Co., Ltd.) (first ligand) was added to 25 mM MES (2- A solution obtained by diluting with morpholinoethanesulfonic acid buffer, 10 mM NaCl (pH 6.0) is dropped onto the substrate, reacted at room temperature for 30 minutes, and the first ligand is linked to the carboxymethyldextran. did.

  Finally, a 1% BSA-TBS buffer (pH 7.4) solution was dropped onto the substrate, and a blocking treatment was performed by reacting at room temperature for 40 minutes to obtain a surface plasmon excitation sensor.

(Process 4: Construction of sensor chip)
Made of polymethylmethacrylate (PMMA) having a flow path length of 7 mm and a width of 2 mm and a thickness of 2 mm for forming a measurement region on the surface of the plasmon excitation sensor substrate obtained in step 3 on which the antibody is bound. A flow path was mounted. In this PMMA channel, a hole for introducing a liquid feed (liquid feed inlet) and a hole for discharging a liquid (liquid feed outlet) are formed. A laminate of these sensor substrate and PMMA channel was crimped at the outer periphery and fixed with screws to form a sensor chip.

  A silicone rubber tube and a peristaltic pump were connected to the liquid feeding inlet and the liquid feeding outlet of the sensor chip. (Unless otherwise specified, all liquid feeding and circulation are performed using such a tube and peristaltic pump.) went).

(Step 5: Signal measurement)
First, the surface plasmon excitation sensor manufactured by the steps 1 to 4 was diluted with PBS buffer (pH 7.4) so that AFP (2.0 mg / ml solution, Acris Antibodies GmbH) was 0.1 ng / ml. The solution was allowed to flow at 5000 μl / min for 25 minutes.

  Subsequently, labeled secondary antibody 2 prepared as described above: “Fluorescent dye precursor” labeled anti-AFP monoclonal antibody (fluorescent dye precursor ligand complex) is 1% BSA-PBS so as to be 2.5 μg / ml. A solution diluted with a buffer (pH 7.4) was allowed to flow at 5000 μl / min for 5 minutes to obtain a surface plasmon excitation sensor on which the second ligand was immobilized.

  Laser light (640 nm, 40 μW) was irradiated from the back side of the surface plasmon excitation sensor to which the second ligand was fixed via a prism, and the amount of fluorescence emitted from the sensor surface was measured with a CCD. This measured value was defined as “assay luminescence signal”.

  On the other hand, with respect to another surface plasmon excitation sensor manufactured in the same manner as in Steps 1 to 4 of Example 1, AFP (2.0 mg / ml solution, Cris Antibodies GmbH) was set at 0 in the first step of Step 5 above. 1% BSA-PBS buffer (pH 7.4) containing no AFP (0 ng / ml) was used instead of the solution diluted with PBS buffer (pH 7.4) to 1 ng / ml. The amount of fluorescence was measured by the same procedure, and the measured value was defined as “assay noise signal”.

Example 2
In Example 1, a surface plasmon excitation sensor was manufactured in the same manner as in Example 1 except that Step 3 was changed as follows, and assay luminescence signal and assay noise signal were measured.

(Step 3: Immobilization of primary antibody)
1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC: manufactured by Dojin Chemical Laboratory), N-hydroxysuccinimide (NHS: manufactured by Thermo Scientific) 25 mM MES containing 100 mM each ( A 2-morpholinoethanesulfonic acid) buffer, 10 mM NaCl (pH 6.0) mixed solution was dropped onto a substrate on which dextran was fixed, reacted at room temperature for 20 minutes, and fixed on the surface of the precursor substrate incorporated in the sensor chip. Carboxymethyldextran was active esterified.

  Subsequently, a labeled primary antibody: “developer” labeled anti-AFP monoclonal antibody (developer ligand complex) was added to a 25 mM MES (2-morpholinoethanesulfonic acid) buffer, 10 mM NaCl so that the antibody was 50 μg / ml. A solution obtained by diluting with (pH 6.0) was dropped onto the substrate, reacted at room temperature for 30 minutes, and the antibody was linked to the carboxymethyldextran.

  Finally, a 1% BSA-TBS buffer (pH 7.4) solution was dropped onto the substrate, and a blocking treatment was performed by reacting at room temperature for 40 minutes to obtain a surface plasmon excitation sensor.

[Comparative Example 1]
In Example 1, a surface plasmon excitation sensor was produced in the same manner as in Example 1 except that steps 3 to 5 were changed as follows, and assay luminescence signal and assay noise signal were measured.

(Step 3: Immobilization of primary antibody)
1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC: manufactured by Dojin Chemical Laboratory), N-hydroxysuccinimide (NHS: manufactured by Thermo Scientific) 25 mM MES containing 100 mM each ( 2-Morpholinoethanesulfonic acid (buffer) buffer, 10 mM NaCl (pH 6.0) mixed solution is dropped onto a substrate on which carboxymethyldextran is fixed, reacted at room temperature for 20 minutes, and fixed on the surface of the precursor substrate incorporated in the sensor chip. The produced carboxymethyl dextran was active esterified.

  Subsequently, an anti-α fetoprotein (AFP) monoclonal antibody (1D5, 1.8 mg / ml, manufactured by Mikuli Immuno Laboratory Co., Ltd.) (first ligand) was added to 25 mM MES (2 -A solution obtained by diluting with morpholinoethanesulfonic acid buffer, 10 mM NaCl (pH 6.0) was dropped onto the substrate, reacted at room temperature for 30 minutes, and the first ligand was added to the carboxymethyldextran. Connected.

  Finally, a 1% BSA-TBS buffer (pH 7.4) solution was dropped onto the substrate, and a blocking treatment was performed by reacting at room temperature for 40 minutes to obtain a surface plasmon excitation sensor.

(Process 4: Construction of sensor chip)
Made of polymethylmethacrylate (PMMA) having a flow path length of 7 mm and a width of 2 mm and a thickness of 2 mm for forming a measurement region on the surface of the plasmon excitation sensor substrate obtained in step 3 on which the antibody is bound. A flow path was mounted. In this PMMA channel, a hole for introducing a liquid feed (liquid feed inlet) and a hole for discharging a liquid (liquid feed outlet) are formed. A laminate of these sensor substrate and PMMA channel was crimped at the outer periphery and fixed with screws to form a sensor chip.

  A silicone rubber tube and a peristaltic pump were connected to the liquid feeding inlet and the liquid feeding outlet of the sensor chip. (Unless otherwise specified, all liquid feeding and circulation are performed using such a tube and peristaltic pump.) went).

(Step 5: Signal measurement)
First, the surface plasmon excitation sensor manufactured by the steps 1 to 4 was diluted with PBS buffer (pH 7.4) so that AFP (2.0 mg / ml solution, Acris Antibodies GmbH) was 0.1 ng / ml. The solution was allowed to flow at 5000 μl / min for 25 minutes. As a washing step, a TBS solution (pH 7.4) containing 0.05% Tween 20 was allowed to flow at 5000 μl / min for 2 minutes.

  Subsequently, the labeled secondary antibody 1: “Alexa Fluor 647” labeled anti-AFP monoclonal antibody (second ligand) prepared as described above was adjusted to a concentration of 2.5 μg / ml with 1% BSA-PBS buffer (pH 7. The solution diluted in 4) was allowed to flow at 5000 μl / min for 5 minutes. As a washing step, a TBS solution (pH 7.4) containing 0.05% Tween 20 was flowed at 5000 μl / min for 2 minutes to obtain a surface plasmon excitation sensor on which the second ligand was immobilized.

  Laser light (640 nm, 40 μW) was irradiated from the back side of the surface plasmon excitation sensor to which the second ligand was fixed via a prism, and the amount of fluorescence emitted from the sensor surface was measured with a CCD. This measured value was defined as “assay luminescence signal”.

  On the other hand, with respect to another surface plasmon excitation sensor manufactured in the same manner as in steps 1 to 4 of Comparative Example 1, AFP (2.0 mg / ml solution, Acris Antibodies GmbH) was set to 0. 1% BSA-PBS buffer (pH 7.4) containing no AFP (0 ng / ml) was used instead of the solution diluted with PBS buffer (pH 7.4) to 1 ng / ml. The amount of fluorescence was measured by the same procedure, and the measured value was defined as “assay noise signal”.

[Comparative Example 2]
A surface plasmon excitation sensor was produced in the same manner as in Comparative Example 1 except that Step 5 was as described below, and assay luminescence signal and assay noise signal were measured. In Comparative Example 2, a short-time treatment was attempted without washing after the sandwich assay.

(Step 5: Signal measurement)
First, the surface plasmon excitation sensor manufactured by the steps 1 to 4 was diluted with PBS buffer (pH 7.4) so that AFP (2.0 mg / ml solution, Acris Antibodies GmbH) was 0.1 ng / ml. The solution was allowed to flow at 5000 μl / min for 25 minutes.

  Subsequently, the labeled secondary antibody 1: “Alexa Fluor 647” labeled anti-AFP monoclonal antibody (second ligand) prepared as described above was adjusted to a concentration of 2.5 μg / ml with 1% BSA-PBS buffer (pH 7. The solution diluted in 4) was allowed to flow at 5000 μl / min for 5 minutes.

  Thereafter, laser light (640 nm, 40 μW) was irradiated from the back side of the surface plasmon excitation sensor to which the second ligand was fixed via a prism, and the amount of fluorescence emitted from the sensor surface was measured with a CCD. This measured value was defined as “assay luminescence signal”.

  On the other hand, with respect to another surface plasmon excitation sensor manufactured by the steps 1 to 4, except that 1% BSA-PBS buffer (pH 7.4) containing no AFP (0 ng / ml) was flowed in the first step. Measured the amount of fluorescence by the same procedure as above, and the measured value was defined as “assay noise signal”.

  For each of the above Examples and Comparative Examples, S / N was calculated from the assay signal and blank signal according to the following formula.

  S / N = | (assay luminescence signal) | / | (assay noise signal) |

  As is clear from the results in Table 1, the assay luminescence signal was high during the assay of Comparative Example 1 and Comparative Example 2 (3 minutes passed) in which the conventional ordinary sandwich immunoassay was performed, but the assay noise signal was also high. This is because the fluorescence (non-specific adsorption) of the labeled antibody in the flow path is also detected, and as a result, S / N cannot be obtained and a significant detection accuracy cannot be obtained. Significant detection accuracy cannot be obtained unless a washing step is performed after completion of the assay as in Comparative Example 1. On the other hand, in Example 1 and Example 2 of the present invention, as can be seen from the assay noise signal, the fluorescent dye precursor and the developer are physically separated sufficiently during the assay. Fluorescence (nonspecific adsorption) is hardly detected. It can be seen that a signal corresponding to the supplemental amount of AFP is obtained and the S / N is also high. In addition, since the S / N is discriminated, even if the reaction is not performed until the end of the assay (5 minutes), for example, in Example 1 and Example 2, the significant S / N can be obtained, and it can be seen that the amount of AFP can be measured in a short time while having high sensitivity and accuracy.

  In Examples 1 and 2, the assay method of the present invention was carried out in the same manner except that the metal film was changed to metal particles. However, as shown in Examples 1 and 2 of Table 1, almost the same results can be obtained. did it.

10 Plasmon Excitation Sensor Chip 11 Plasmon Excitation Sensor 111 Transparent Substrate 112 Metal Film 113 SAM
12 First Ligand 13 Fluorescent Dye Precursor Developer 20 Fluorescent Dye Precursor Ligand Complex 21 Second Ligand 22 Fluorescent Dye 23 Fluorescent Dye Ligand Complex 24 Fluorescent Dye Precursor 31 Analyte

Claims (22)

An assay method using a plasmon excitation sensor comprising a fluorescent dye precursor developer that causes a color reaction with a metal member, a first ligand, and a fluorescent dye precursor, comprising the following steps (a) to (c) An assay method characterized by the above.
Step (a): bringing an analyte solution into contact with the plasmon excitation sensor and fixing the analyte in the analyte solution to the plasmon excitation sensor;
Step (b): A fluorescent dye precursor-ligand complex having a second ligand and a fluorescent dye precursor is brought into contact with the plasmon excitation sensor to which the analyte is fixed, and the first ligand is passed through the second ligand. A step of obtaining a fluorescent dye by immobilizing the fluorescent dye precursor to the ligand and reacting with the fluorescent dye precursor developer;
Step (c): A step of exciting the fluorescent dye by irradiating the metal member with excitation light and measuring the amount of fluorescence emitted from the excited fluorescent dye.   The assay method according to claim 1, wherein a SAM is formed on a surface of the metal member.   The assay method according to claim 2, wherein dextran is immobilized on the surface of the SAM.   The assay method according to claim 1, wherein the fluorescent dye precursor developer is fixed to the metal member.   The assay method according to claim 2, wherein the fluorescent dye precursor developer is fixed to the SAM.   The assay method according to claim 3, wherein the fluorescent dye precursor developer is fixed to the dextran.   The assay method according to any one of claims 1 to 3, wherein the fluorescent dye precursor developer is fixed to the first ligand.   The assay method according to claim 1, wherein the metal member is a metal film.   The assay method according to claim 1, wherein the metal member is a metal particle.   The assay method according to claim 9, wherein the plasmon excitation sensor includes a substrate, and the metal particles are dispersed on the substrate.   The assay method according to any one of claims 1 to 10, wherein the fluorescent dye precursor ligand complex is a fine particle modified with the fluorescent dye precursor and the second ligand.   The assay method according to any one of claims 1 to 11, wherein the analyte solution is at least one body fluid selected from blood, serum, plasma, urine, nasal fluid and saliva.   A plasmon excitation sensor comprising a metal member, a first ligand, and a fluorescent dye precursor developer that causes a color development reaction with the fluorescent dye precursor.   The plasmon excitation sensor according to claim 13, wherein a SAM is formed on a surface of the metal member.   The plasmon excitation sensor according to claim 14, wherein dextran is fixed to the surface of the SAM.   The plasmon excitation sensor according to claim 13, wherein the fluorescent dye precursor developer is fixed to the metal member.   The plasmon excitation sensor according to claim 14, wherein the fluorescent dye precursor developer is fixed to the SAM.   The plasmon excitation sensor according to claim 15, wherein the fluorescent dye precursor developer is fixed to the dextran.   The plasmon excitation sensor according to any one of claims 13 to 15, wherein the fluorescent dye precursor developer is fixed to the first ligand.   The plasmon excitation sensor according to any one of claims 13 to 19, wherein the metal member is a metal film.   The plasmon excitation sensor according to any one of claims 13 to 19, wherein the metal member is a metal particle.   The plasmon excitation sensor according to claim 21, wherein the plasmon excitation sensor includes a substrate, and the metal particles are dispersed on the substrate.

Images