WO2015155799A1 - 表面プラズモン増強蛍光測定装置および表面プラズモン増強蛍光測定方法 - Google Patents
表面プラズモン増強蛍光測定装置および表面プラズモン増強蛍光測定方法 Download PDFInfo
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Definitions
- the present invention relates to a surface plasmon enhanced fluorescence measuring apparatus and a surface plasmon enhanced fluorescence measuring method for detecting the presence or amount of a substance to be detected contained in a specimen using surface plasmon resonance.
- SPFS surface plasmon excitation enhanced fluorescence spectroscopy
- SPR surface plasmon resonance
- a capture body for example, a primary antibody
- a capture body that can specifically bind to the substance to be detected is immobilized on the metal film to form a reaction field for specifically capturing the substance to be detected.
- the target substance bound to the reaction field is labeled with the fluorescent substance.
- the fluorescent substance that labels the substance to be detected is excited by the electric field enhanced by SPR and emits fluorescence. Therefore, the presence or amount of the substance to be detected can be detected by detecting fluorescence.
- SPFS a fluorescent substance is excited by an electric field enhanced by SPR, so that a substance to be detected can be detected with high sensitivity.
- PC-SPFS is roughly classified into prism coupling (PC) -SPFS and lattice coupling (GC) -SPFS by means of coupling (coupling) excitation light and surface plasmons.
- PC-SPFS utilizes a prism having a metal film formed on one surface. In this method, the excitation light is totally reflected at the interface between the prism and the metal film, thereby coupling the excitation light and the surface plasmon.
- PC-SPFS is the mainstream method at present, but because of the use of prisms and the large incident angle of excitation light on the metal film, PC-SPFS is problematic in terms of miniaturization of the measuring device. have.
- GC-SPFS couples excitation light and surface plasmon using a diffraction grating (see Patent Document 1 and Non-Patent Document 1). Since the GC-SPFS does not use a prism and the incident angle of the excitation light with respect to the diffraction grating is small, the measuring apparatus can be made smaller than the PC-SPFS.
- GC-SPFS has the advantage that the measuring device can be made smaller than PC-SPFS, but research on GC-SPFS has not progressed compared to research on PC-SPFS. Therefore, there is room for improvement in detection sensitivity in the measurement apparatus and measurement method using GC-SPFS.
- An object of the present invention is to provide a measuring apparatus and a measuring method using GC-SPFS, which can detect a substance to be detected with higher sensitivity.
- a surface plasmon enhanced fluorescence measurement device includes a metal film on which a diffraction grating is formed, a capturing body fixed to the diffraction grating, and a capturing body.
- a surface plasmon-enhanced fluorescence measuring apparatus that detects the presence or amount of a substance to be detected by attaching a chip having a substance to be detected that is bound with a fluorescent substance and irradiating the diffraction grating with excitation light.
- a light source that irradiates the diffraction grating with the excitation light, and linearly polarized light is extracted from the fluorescence emitted from the fluorescent material.
- a polarizer, and a light detection unit that detects the light of the linearly polarized light extracted by the polarizer.
- the surface plasmon enhanced fluorescence measurement method uses a fluorescent material that labels a target substance to emit fluorescence that is excited by an electric field based on surface plasmon resonance.
- a surface plasmon enhanced fluorescence measurement method for detecting the presence or amount of a substance to be detected by detecting a metal film having a diffraction grating formed thereon, a capture body immobilized on the diffraction grating, and the capture body And a second step of irradiating the diffraction grating with excitation light so that surface plasmon resonance occurs in the diffraction grating.
- a substance to be detected can be detected with higher sensitivity in a measuring apparatus and a measuring method using GC-SPFS.
- a substance to be detected can be detected in real time.
- FIG. 1 is a schematic diagram showing a configuration of a surface plasmon enhanced fluorescence measuring apparatus (hereinafter referred to as “SPFS apparatus”) according to Embodiments 1 and 2.
- SPFS apparatus surface plasmon enhanced fluorescence measuring apparatus
- FIG. 3A is a diagram schematically illustrating a first aspect of the chip according to the first and second embodiments
- FIG. 3B schematically illustrates a second aspect of the chip according to the first and second embodiments.
- FIG. FIG. 4 is a flowchart showing the operation of the SPFS apparatus according to the first embodiment.
- 5A and 5B are schematic views showing a procedure for measuring the fluorescence intensity.
- FIG. 6 is a graph for explaining the difference value (signal value).
- FIG. 1 is a schematic diagram showing a configuration of a surface plasmon enhanced fluorescence measuring apparatus (hereinafter referred to as “SPFS apparatus”) according to Embodiments 1 and 2.
- FIG. 3A is a diagram schematically illustrating a first aspect of the
- FIG. 7 is a flowchart showing the operation of the SPFS apparatus according to the second embodiment.
- 8A and 8B are graphs showing examples of results when the fluorescence intensity is measured in real time.
- FIG. 9 is a schematic diagram illustrating a configuration of another example of the SPFS apparatus according to the first and second embodiments.
- 10A and 10B are schematic diagrams showing the procedure of the reference experiment.
- FIG. 11 is a graph showing the measurement results of the reference experiment.
- FIG. 1 is a schematic diagram showing a configuration of a surface plasmon enhanced fluorescence measurement apparatus (SPFS apparatus) 100 according to Embodiment 1 of the present invention.
- SPFS apparatus surface plasmon enhanced fluorescence measurement apparatus
- the SPFS apparatus 100 includes an excitation light irradiation unit 110, a fluorescence detection unit 120, and a control unit 130.
- the SPFS device 100 is used in a state where the chip 200 is mounted on a chip holder (not shown). Therefore, the chip 200 will be described first, and then the SPFS device 100 will be described.
- the chip 200 includes a substrate 210 and a metal film 220 formed on the substrate 210.
- a diffraction grating 230 is formed on the metal film 220.
- a capture body (for example, a primary antibody) is immobilized on the diffraction grating 230, and the surface of the diffraction grating 230 also functions as a reaction field for binding the capture body and the substance to be detected. In FIG. 1, the capturing body and the substance to be detected are omitted.
- the substrate 210 is a support member for the metal film 220.
- the material of the substrate 210 is not particularly limited as long as it has mechanical strength capable of supporting the metal film 220.
- Examples of the material of the substrate 210 include inorganic materials such as glass, quartz, and silicon, and resins such as polymethyl methacrylate, polycarbonate, polystyrene, and polyolefin.
- the metal film 220 is disposed on the substrate 210. As described above, the diffraction grating 230 is formed on the metal film 220. When the metal film 220 is irradiated with light, surface plasmons generated in the metal film 220 and evanescent waves generated by the diffraction grating 230 are combined to generate surface plasmon resonance.
- the material of the metal film 220 is not particularly limited as long as it is a metal that generates surface plasmons. Examples of the material of the metal film 220 include gold, silver, copper, aluminum, and alloys thereof.
- a method for forming the metal film 220 is not particularly limited. Examples of the method for forming the metal film 220 include sputtering, vapor deposition, and plating.
- the thickness of the metal film 220 is not particularly limited. The thickness of the metal film 220 is, for example, 30 to 500 nm, and preferably 100 to 300 nm.
- the diffraction grating 230 generates an evanescent wave when the metal film 220 is irradiated with light.
- the shape of the diffraction grating 230 is not particularly limited as long as an evanescent wave can be generated.
- the diffraction grating 230 may be a one-dimensional diffraction grating as shown in FIG. 2A or a two-dimensional diffraction grating as shown in FIG. 2B.
- a plurality of ridges parallel to each other are formed on the surface of the metal film 220 at a predetermined interval.
- convex portions having a predetermined shape are periodically arranged on the surface of the metal film 220.
- Examples of the arrangement of the convex portions include a square lattice, a triangular (hexagonal) lattice, and the like.
- Examples of the cross-sectional shape of the diffraction grating 230 include a rectangular wave shape, a sine wave shape, a sawtooth shape, and the like.
- the optical axis of the excitation light ⁇ described later is parallel to the xz plane.
- the formation method of the diffraction grating 230 is not particularly limited.
- the metal film 220 may be provided with an uneven shape.
- the metal film 220 may be formed over the substrate 210 that has been previously provided with an uneven shape.
- the metal film 220 including the diffraction grating 230 can be formed.
- a capturing body for capturing a substance to be detected is immobilized.
- the capturing body specifically binds to the substance to be detected.
- the capturing body is fixed substantially uniformly on the surface of the diffraction grating 230.
- the type of capturing body is not particularly limited as long as it can capture the substance to be detected.
- the capturing body is an antibody (primary antibody) or a fragment thereof specific to the substance to be detected, an enzyme that can specifically bind to the substance to be detected, or the like.
- the method for immobilizing the capturing body is not particularly limited.
- a self-assembled monomolecular film hereinafter referred to as “SAM”
- a polymer film to which a capturing body is bonded may be formed on the diffraction grating 230.
- SAMs include films formed with substituted aliphatic thiols such as HOOC— (CH 2 ) 11 —SH.
- the material constituting the polymer film include polyethylene glycol and MPC polymer.
- a polymer having a reactive group that can be bound to the capturing body may be fixed to the diffraction grating 230, and the capturing body may be bound to the polymer.
- the excitation light ⁇ is applied to the metal film 220 (diffraction grating 230) at a predetermined incident angle ⁇ 1 .
- the surface plasmon generated in the metal film 220 and the evanescent wave generated by the diffraction grating 230 are combined to generate SPR.
- the fluorescent substance is excited by the enhanced electric field formed by SPR, and fluorescent ⁇ is emitted.
- fluorescence ⁇ is emitted with directivity in a specific direction. For example, the emission angle ⁇ 2 of the fluorescence ⁇ is approximated by 2 ⁇ 1 . Note that almost no reflected light ⁇ of the excitation light ⁇ is generated.
- the diffraction grating 230 comes into contact with a liquid such as a buffer solution for operations such as reaction and washing. Therefore, normally, the diffraction grating 230 is arrange
- the diffraction grating 230 may be disposed on the inner surface (e.g., the bottom surface) of a well containing liquid as shown in FIG. 3A or continuously supplied with liquid as shown in FIG. 3B. It may be disposed on the inner surface (for example, the bottom surface) of the flow path (flow cell).
- the chip 200 shown in FIG. 3B includes, for example, in addition to a general measurement of a target substance (non-real time measurement), another molecule (a target to be detected) with respect to a molecule (captured body) immobilized on the surface of the metal film 220. It is also suitable for analysis of reaction constants of substances) (real-time measurement; see Embodiment Mode 2).
- the excitation light irradiation unit 110 irradiates the metal film 220 (diffraction grating 230) of the chip 200 with excitation light ⁇ having a constant wavelength and light amount. At this time, the excitation light irradiation unit 110 emits p-polarized light with respect to the surface of the metal film 220 so that diffracted light that can be combined with the surface plasmons in the metal film 220 is generated in the metal film 220 (diffraction grating 230). Irradiate.
- the optical axis of the excitation light ⁇ is along the arrangement direction of the periodic structure in the diffraction grating 230 (the x-axis direction in FIGS. 2A and 2B).
- the optical axis of the excitation light ⁇ is xz. It is parallel to the plane (see FIG. 1). Since the excitation light ⁇ is p-polarized light with respect to the surface of the metal film 220, the vibration direction of the electric field of the excitation light ⁇ is in the xz plane including the optical axis of the excitation light ⁇ and the normal to the surface of the metal film 220. Parallel.
- the excitation light irradiation unit 110 has at least a light source 112.
- the excitation light irradiation unit 110 may further include a collimating lens, an excitation light filter, and the like.
- the light source 112 emits excitation light ⁇ toward the diffraction grating 230 of the chip 200.
- the light source 112 is a laser diode.
- the type of the light source 112 is not particularly limited, and may not be a laser diode. Examples of the light source 112 include a light emitting diode, a mercury lamp, and other laser light sources.
- a collimating lens (not shown) is disposed between the light source 112 and the chip 200 and collimates the excitation light ⁇ emitted from the light source 112.
- the excitation light ⁇ emitted from the laser diode (light source 112) has a flat outline shape even when collimated. Therefore, the laser diode is held in a predetermined posture so that the shape of the irradiation spot on the surface of the metal film 220 is substantially circular.
- the size of the irradiation spot is preferably about 1 mm ⁇ , for example.
- the excitation light filter (not shown) is arranged between the light source 112 and the chip 200 and tunes the excitation light ⁇ emitted from the light source 112.
- Excitation light filters include, for example, bandpass filters and linear polarizing filters. Since the excitation light ⁇ from the laser diode (light source 112) has a slight wavelength distribution width, the bandpass filter turns the excitation light ⁇ from the laser diode into narrowband light having only the center wavelength. In addition, since the excitation light ⁇ from the laser diode (light source 112) is not completely linearly polarized light, the linear polarization filter converts the excitation light ⁇ from the laser diode into completely linearly polarized light.
- the excitation light filter may include a half-wave plate that adjusts the polarization direction of the excitation light ⁇ so that p-polarized light is incident on the metal film 220.
- the incident angle ⁇ 1 (see FIG. 1) of the excitation light ⁇ with respect to the metal film 220 is such that the intensity of the enhanced electric field formed by the SPR is the strongest, and as a result, the angle at which the intensity of the fluorescent ⁇ from the fluorescent material is the strongest.
- the incident angle ⁇ 1 of the excitation light ⁇ is appropriately selected according to the pitch of the diffraction grating 230, the wavelength of the excitation light ⁇ , the type of metal constituting the metal film 220, and the like.
- the pitch of the diffraction grating is preferably about 400 nm, for example.
- the SPFS apparatus 100 adjusts the incident angle ⁇ 1 by relatively rotating the optical axis of the excitation light ⁇ and the chip 200. It is preferable to have a first angle adjustment unit (not shown).
- the first angle adjustment unit may rotate the excitation light irradiation unit 110 or the chip 200 around the intersection between the optical axis of the excitation light ⁇ and the metal film 220.
- the fluorescence detection unit 120 is arranged with respect to the excitation light irradiation unit 110 so as to sandwich a straight line passing through the intersection of the optical axis of the excitation light ⁇ and the metal film 220 and perpendicular to the surface of the metal film 220. Yes.
- the fluorescence detection unit 120 detects fluorescence ⁇ emitted from the fluorescent material on the diffraction grating 230 (reaction field).
- the fluorescence detection unit 120 includes at least a polarizer 122 and a light detection unit 124.
- the fluorescence detection unit 120 may further include a condenser lens group, an aperture stop, a fluorescence filter, and the like.
- the polarizer 122 is disposed between the chip 200 and the light detection unit 124 and extracts linearly polarized light from the fluorescence ⁇ emitted from the fluorescent material.
- the polarizer 122 is a polarizing plate.
- the polarizer 122 is held so as to be able to rotate in a plane perpendicular to the traveling direction of the fluorescence ⁇ from the metal film 220 toward the light detection unit 124.
- the polarizer 122 is the first in the range where the angle of the oscillation direction of the electric field from the fluorescence ⁇ to the plane (xz plane) including the normal to the surface of the metal film 220 and the optical axis of the excitation light ⁇ is 0 ⁇ 30 °. And second light within the range of 90 ⁇ 30 ° in the direction of vibration of the electric field with respect to the plane (xz plane) are taken out simultaneously or at different times.
- the polarizer 122 extracts, from the fluorescence ⁇ , p-polarized light whose angle of vibration direction of the electric field with respect to the plane (xz plane) is 0 ° as the first light, and the electric field of the electric field with respect to the plane (xz plane).
- the s-polarized light having an oscillation direction angle of 90 ° is taken out as the second light simultaneously or at different times.
- the first light for example, p-polarized light
- the second light for example, s-polarized light
- the first light is light including a signal component to be detected and a noise component
- the second light is light mainly composed of a noise component.
- the type of the polarizer 122 is not particularly limited as long as linearly polarized light having a predetermined polarization direction can be extracted, and may not be a polarizing plate.
- Examples of the polarizer 122 include a polarizing prism, a liquid crystal filter, and other polarizing filters.
- the light detection unit 124 detects the linearly polarized light extracted by the polarizer 122 and detects a fluorescent image on the metal film 220.
- the light detection unit 124 detects the first light and the second light, respectively.
- the light detection unit 124 is a photomultiplier tube having high sensitivity and a high SN ratio.
- the light detection unit 124 may be an avalanche photodiode (APD), a photodiode (PD), a CCD image sensor, or the like.
- the condensing lens group (not shown) is disposed between the chip 200 and the light detection unit 124 and constitutes a conjugate optical system that is not easily affected by stray light.
- the condenser lens group forms a fluorescent image on the metal film 220 on the light receiving surface of the light detection unit 124.
- Fluorescent filter (not shown) is disposed between the chip 200 and the light detection unit 124.
- the fluorescence filter includes, for example, a cut filter and a neutral density (ND) filter, and removes noise components other than the fluorescence ⁇ (for example, excitation light ⁇ and external light) from the light reaching the light detection unit 124, The amount of light reaching the detection unit 124 is adjusted.
- ND neutral density
- the fluorescence ⁇ is emitted from the diffraction grating 230 (reaction field) with directivity in a specific direction. Therefore, the angle of the optical axis of the fluorescence detection unit 120 with respect to the normal of the surface of the metal film 220 is preferably an angle (fluorescence peak angle) at which the intensity of the fluorescence ⁇ is maximized. Therefore, the SPFS device 100 has a second angle adjustment unit (not shown) that adjusts the angle of the optical axis of the fluorescence detection unit 120 by relatively rotating the optical axis of the fluorescence detection unit 120 and the chip 200. Is preferred. For example, the second angle adjustment unit may rotate the fluorescence detection unit 120 or the chip 200 around the intersection between the optical axis of the fluorescence detection unit 120 and the metal film 220.
- the control unit 130 includes an excitation light irradiation unit 110 (light source 112), a fluorescence detection unit 120 (polarizer 122 and a light detection unit 124), an angle adjustment unit (first angle adjustment unit) of the excitation light irradiation unit 110 and the fluorescence detection unit 120. And the operation of the second angle adjusting unit).
- the control unit 130 also functions as a processing unit that processes an output signal (detection result) from the light detection unit 124.
- the control unit 130 is, for example, a computer that executes software.
- FIG. 4 is a flowchart illustrating an example of an operation procedure of the SPFS apparatus 100.
- a primary antibody is immobilized on the metal film 220 as a capturing body.
- a secondary antibody labeled with a fluorescent substance is used as a capturing body used for fluorescent labeling.
- step S10 preparation for measurement is performed (step S10). Specifically, the chip 200 is prepared, and the chip 200 is installed at a predetermined position of the SPFS device 100. Further, when a humectant is present on the metal film 220 of the chip 200, the humectant is removed by washing the metal film 220 so that the primary antibody can appropriately capture the substance to be detected.
- the detection target substance in the specimen is reacted with the primary antibody (primary reaction, step S20).
- a specimen is provided on the metal film 220, and the specimen and the primary antibody are brought into contact with each other.
- the metal film 220 is washed with a buffer solution or the like to remove substances that have not bound to the primary antibody.
- the specimen include body fluids such as blood, serum, plasma, urine, nasal fluid, saliva, semen, and diluted solutions thereof.
- substances to be detected include nucleic acids (such as DNA and RNA), proteins (such as polypeptides and oligopeptides), amino acids, carbohydrates, lipids, and modified molecules thereof.
- the detection target substance bound to the primary antibody is labeled with a fluorescent substance (secondary reaction, step S30).
- a fluorescent labeling solution containing a secondary antibody labeled with a fluorescent substance is provided on the metal film 220, and the detection target substance bound to the primary antibody is brought into contact with the fluorescent labeling liquid.
- the fluorescent labeling solution is, for example, a buffer solution containing a secondary antibody labeled with a fluorescent substance.
- the SPFS device 100 can detect the detection target substance without removing the free secondary antibody.
- the order of the primary reaction and the secondary reaction is not limited to this.
- a liquid containing these complexes may be provided on the metal film 220 after the substance to be detected is bound to the secondary antibody.
- the specimen and the fluorescent labeling solution may be provided on the metal film 220 at the same time.
- the excitation light ⁇ is irradiated onto the metal film 220, and the intensity of the first light (for example, p-polarized light) contained in the fluorescence ⁇ emitted from the fluorescent material is measured (step S40).
- the control unit 130 causes the light source 112 to emit the excitation light ⁇ .
- the control unit 130 causes the light detection unit 124 to detect the intensity of the fluorescence ⁇ from the metal film 220.
- the control unit 130 adjusts the rotation angle of the polarizer 122 so that only the first light (p-polarized light in the drawing) included in the fluorescence ⁇ can be transmitted.
- the light detection unit 124 outputs the measurement result (output Op) to the control unit (processing unit) 130.
- the fluorescence ⁇ (signal component) emitted from the fluorescent substance that labels the detection target substance has p-polarized light or a polarization angle with respect to the surface of the metal film 220.
- the light is close to the p-polarized light. Therefore, the signal component passes through the polarizer 122 and reaches the light detection unit 124.
- the fluorescence ⁇ (noise component) emitted from the fluorescent material floating on the metal film 220 is randomly polarized light. Therefore, part of the noise component (light having the same polarization angle as the signal component) also passes through the polarizer 122 and reaches the light detection unit 124.
- the measurement result (output Op) of this step includes a signal component and a noise component.
- the excitation light ⁇ is irradiated onto the metal film 220, and the intensity of the second light (for example, s-polarized light) contained in the fluorescence ⁇ emitted from the fluorescent material is measured (step S50).
- the control unit 130 causes the light source 112 to emit the excitation light ⁇ .
- the control unit 130 causes the light detection unit 124 to detect the intensity of the fluorescence ⁇ from the metal film 220.
- the control unit 130 adjusts the rotation angle of the polarizer 122 so that only the second light (s-polarized light in the drawing) included in the fluorescence ⁇ can be transmitted.
- the light detection unit 124 outputs the measurement result (output Os) to the control unit (processing unit) 130.
- the fluorescence ⁇ (noise component) emitted from the fluorescent substance floating on the metal film 220 is randomly polarized light. Accordingly, part of the noise component passes through the polarizer 122 and reaches the light detection unit 124 also in this step. As a result, the measurement result (output Os) of this step mainly consists of noise components.
- the order of the first light measurement (step S40) and the second light measurement (step S50) is not limited to this.
- the intensity of the first light may be measured.
- control unit (processing unit) 130 analyzes the output signals (outputs Op and Os) from the light detection unit 124, and analyzes the presence of the detected substance or the amount of the detected substance (step S60). Specifically, as illustrated in FIG. 6, the control unit (processing unit) 130 calculates a difference value between the output Op and the output Os to obtain a signal value.
- the output Op is mainly composed of a signal component and a noise component
- the output Os is mainly composed of a noise component. Therefore, a signal value from which the noise component has been removed can be obtained by calculating a difference value between them. it can.
- the presence of the substance to be detected or the amount of the substance to be detected in the sample can be detected.
- the SPFS device 100 can detect only the signal component by utilizing the difference in polarization characteristics of the signal component and the noise component, and thus has higher sensitivity than the conventional SPFS device. It is possible to detect the substance to be detected.
- the SPFS device 100 can remove the noise component contained in the fluorescence ⁇ , it is not necessary to remove the free secondary antibody after the secondary reaction (step S30). Detection of a detection substance can be performed.
- the chip 200 is irradiated with the excitation light ⁇ from the metal film 220 side
- the chip 200 may be irradiated with the excitation light ⁇ from the substrate 210 side.
- the SPFS device 100 ′ according to the second embodiment has the same configuration as the SPFS device 100 according to the first embodiment, and differs from the SPFS device 100 according to the first embodiment in that real-time measurement is performed. Therefore, the description of the configuration of the SPFS apparatus is omitted, and only the operation procedure is described.
- the SPFS device 100 ′ continuously irradiates the diffraction grating 230 with the excitation light ⁇ , continuously extracts linearly polarized light from the fluorescence ⁇ emitted from the fluorescent material, and the linearly polarized light. Detect light continuously.
- continuous includes not only continuous operation but also intermittent operation. Therefore, “continuously irradiating the excitation light” means irradiating the excitation light ⁇ at an appropriate time and frequency capable of detecting a change with time of the substance to be detected.
- Continuous extracting linearly-polarized light means that linearly-polarized light is continuously extracted from the fluorescence ⁇ at an appropriate time and frequency at which a change in the substance to be detected over time can be detected.
- Continuous detecting linearly polarized light means detecting linearly polarized light from the fluorescence ⁇ at an appropriate time and frequency at which a change in the substance to be detected over time can be detected.
- the continuous irradiation with the excitation light ⁇ may be continuous irradiation with the excitation light ⁇ , or may be intermittent irradiation with the excitation light ⁇ .
- the continuous irradiation of the excitation light ⁇ is an intermittent irradiation of the excitation light ⁇ .
- the irradiation interval of the excitation light ⁇ may be constant or indefinite (arbitrary). Further, the irradiation interval of the excitation light ⁇ may be automatically determined based on a certain condition such as automatic calculation by a program, may be determined empirically by a preliminary experiment, etc. It may be arbitrarily determined by.
- the irradiation interval of the excitation light may be determined according to the detection result of the fluorescence intensity. For example, when the fluorescence intensity detection value is small, the excitation light irradiation interval may be shortened, and when the fluorescence intensity detection value is large, the excitation light irradiation interval may be lengthened. In addition, when the change in the fluorescence intensity detection value with time is large, the excitation light irradiation interval is shortened, and when the change in the fluorescence intensity detection value with time is small, the excitation light irradiation interval. May be longer.
- Such adjustment of the excitation light irradiation interval can be performed, for example, by appropriately setting a threshold value related to the fluorescence intensity detection value and performing feedback control based on the fluorescence intensity detection value.
- Such adjustment of the excitation light irradiation interval is preferable from the viewpoint of more precisely observing a change with time of the substance to be detected.
- FIG. 7 is a flowchart illustrating an example of an operation procedure of the SPFS apparatus 100 ′ according to the second embodiment.
- a primary antibody is immobilized on the metal film 220 as a capturing body.
- a secondary antibody labeled with a fluorescent substance is used as a capturing body used for fluorescent labeling.
- step S110 preparation for measurement is performed (step S110). Specifically, the chip 200 is prepared, and the chip 200 is installed at a predetermined position of the SPFS device 100 ′. Similar to the first embodiment, the metal film 220 is cleaned as necessary.
- the detection target substance in the specimen is reacted with the primary antibody (primary reaction, step S120). Specifically, a specimen is provided on the metal film 220, and the specimen and the primary antibody are brought into contact with each other. When a substance to be detected exists in the sample, at least a part of the substance to be detected binds to the primary antibody. Thereafter, the metal film 220 is washed with a buffer solution or the like to remove substances that have not bound to the primary antibody.
- the target substance bound to the primary antibody is labeled with a fluorescent substance (secondary reaction, step S130).
- a fluorescent labeling solution containing a secondary antibody labeled with a fluorescent substance is provided on the metal film 220, and the detection target substance bound to the primary antibody is brought into contact with the fluorescent labeling liquid.
- the fluorescent labeling solution is, for example, a buffer solution containing a secondary antibody labeled with a fluorescent substance.
- the SPFS device 100 ′ can measure the substance to be detected without removing the free secondary antibody.
- the order of the primary reaction and the secondary reaction is not limited to this.
- a liquid containing these complexes may be provided on the metal film 220 after the substance to be detected is bound to the secondary antibody.
- the specimen and the fluorescent labeling solution may be provided on the metal film 220 at the same time.
- the intensity of the first light (for example, p-polarized light) included in the fluorescence ⁇ emitted from the fluorescent material is measured while irradiating the excitation light ⁇ on the metal film 220 (step S140), While irradiating the metal film 220, the intensity of the second light (for example, s-polarized light) contained in the fluorescence ⁇ emitted from the fluorescent material is measured (step S150), and the intensity of the first light is measured. And the measurement of the intensity of the second light are repeated a predetermined number of times (step S160). Thereby, the measurement of the intensity of the first light and the measurement of the intensity of the second light are alternately repeated a plurality of times, and the measurement value of the first light intensity and the measurement value of the second light intensity are Each is obtained continuously (intermittently).
- the intensity of the first light for example, p-polarized light
- the intensity of the second light for example, s-polarized light
- step S140 the control unit 130 causes the light source 112 to emit the excitation light ⁇ continuously or intermittently (that is, “continuously”) at a predetermined interval.
- the “predetermined interval” is, for example, an interval for changing (adjusting) the rotation angle of the polarizer 122 described later.
- the control unit 130 causes the light detection unit 124 to continuously detect the intensity of the fluorescence ⁇ from the metal film 220.
- the timing of continuous detection of the intensity of the fluorescence ⁇ may be synchronized with the timing of irradiation of the excitation light ⁇ with time, or may be different. At this time, as shown in FIG.
- control unit 130 adjusts the rotation angle of the polarizer 122 so that only the first light (p-polarized light in the drawing) included in the fluorescence ⁇ can be transmitted.
- the light detection unit 124 outputs the measurement result (output Op) to the control unit (processing unit) 130.
- the fluorescence ⁇ (signal component) emitted from the fluorescent substance that labels the detection target substance passes through the polarizer 122 and reaches the light detection unit 124.
- part of the fluorescence ⁇ (noise component) emitted from the fluorescent substance floating on the metal film 220 also passes through the polarizer 122 and is detected by the light detection unit 124.
- the measurement result (output Op) of this step includes a signal component and a noise component.
- step S150 the control unit 130 causes the light source 112 to continue to emit the excitation light ⁇ .
- the control unit 130 causes the light detection unit 124 to continuously detect the intensity of the fluorescence ⁇ from the metal film 220.
- the control unit 130 adjusts the rotation angle of the polarizer 122 so that only the second light (s-polarized light in the drawing) included in the fluorescence ⁇ can be transmitted.
- the light detection unit 124 outputs the measurement result (output Os) to the control unit (processing unit) 130.
- step S50 of the first embodiment a part of the fluorescence ⁇ (noise component) emitted from the fluorescent material floating on the metal film 220 is transmitted through the polarizer 122 also in this step. It reaches the light detection unit 124.
- the measurement result (output Os) of this step mainly consists of noise components.
- the order of the first light measurement (step S140) and the second light measurement (step S150) is not limited to this.
- the intensity of the first light may be measured.
- step S160 for example, the control unit 130 counts the number of times the second light is measured (s-polarized light measurement number Cs). If Cs has not reached a set value (for example, N times), the rotation of the polarizer 122 is performed. The angle is adjusted again to the angle for detecting the first light, and the process returns to step S140 to measure the intensity of the first light.
- Cs s-polarized light measurement number
- control unit 130 analyzes the output signals (outputs Op and Os) from the light detection unit 124 to determine the presence of the detected substance or the amount of the detected substance. Analyze (step S170).
- the control unit (processing unit) 130 determines the intensity of the first light measured in step S140 and the intensity of the second light measured in step S150 immediately after that. For each set, a difference value between the output Op and the output Os is calculated to obtain a signal value. Therefore, when the intensity of the first light and the intensity of the second light are continuously measured, a signal value is calculated for each set of the detected value of the first light intensity and the detected value of the second light intensity. Is done. That is, a signal value that changes with time is calculated. Also, by performing steps S140 to S160 and step S170 in parallel, it is possible to calculate a signal value that changes over time in real time.
- FIG. 8A shows that the fluorescence intensity of the signal component and the fluorescence intensity of the signal component over time when a fluorescent labeling solution containing a fluorescent substance is provided on the metal film 220 at a general concentration (for example, several hundred pM to 1 ⁇ M). It is a graph which shows a change.
- FIG. 8B shows changes over time in the fluorescence intensity of the signal component and the fluorescence intensity of the signal component when a fluorescent labeling solution containing a fluorescent substance at a low concentration (for example, 100 fM to several hundred pM) is provided on the metal film 220. It is a graph to show.
- the intensities of the first light and the second light are measured in a state where a fluorescent labeling solution (free secondary antibody) is present on the metal film 220.
- a black circle ( ⁇ ) represents the fluorescence intensity (output Os) of the noise component
- a black triangle ( ⁇ ) represents the fluorescence intensity of the signal component (difference value between the output Op and output Os).
- the presence of the substance to be detected in the sample or the amount of the substance to be detected can be measured in real time.
- the SPFS device 100 ′ can detect only the signal component in real time using the difference in polarization characteristics of the signal component and the noise component, and thus is equivalent to the conventional SPFS device.
- the substance to be detected can be measured in real time with high sensitivity.
- the SPFS device 100 ′ can remove the noise component contained in the fluorescence ⁇ , it is not necessary to remove the free secondary antibody after the secondary reaction (step S130).
- the substance to be detected can be measured.
- the measurement method according to the present embodiment can detect substances such as lectins that have a weak affinity and are difficult to detect by a normal sandwich assay. Further, even when using a specimen with a lot of contaminants such as serum, it is possible to distinguish the intensity of the fluorescence derived from the detected substance captured on the diffraction grating 230 from the intensity of the fluorescence derived from the contaminant. Therefore, a measurement result that does not substantially reflect the influence of noise due to impurities can be obtained while the measurement is highly accurate.
- a detected substance in an unpurified sample such as a crude product obtained by biosynthesis of a new biological substance or an original sample collected in a clinical test can be obtained with high accuracy. It is possible to measure easily over time.
- the SPFS device 300 shown in FIG. 9 may be used instead of the SPFS device 100 (100 ′) shown in FIG.
- the SPFS apparatus 300 is configured in the same manner as the SPFS apparatus 100 except that the SPFS apparatus 300 further includes a half mirror 321, a polarizer 322, and a light detection unit 324.
- the half mirror 321 is disposed on the optical path of the fluorescence ⁇ between the diffraction grating 230 and the polarizer 122.
- the photodetector 324 is disposed on the optical path (reflected optical path) of the fluorescence ⁇ reflected by the half mirror 321, and the polarizer 322 is disposed on the reflected optical path between the half mirror 321 and the photodetector 324.
- the rotation angle of the polarizer 122 is adjusted (or fixed) so as to pass the first light (for example, p-polarized light), and the rotation angle of the polarizer 322 is the second light (for example, s-polarized light). ) Is adjusted (or fixed) to pass.
- a polarization beam splitter may be used.
- Both the photodetectors 124 and 324 continuously detect the intensity of the first light and the intensity of the second light. Therefore, when the light source 112 continuously emits the excitation light ⁇ , the photodetectors 124 and 324 continuously detect the intensity of the first light and the intensity of the second light, respectively. From the viewpoint of preventing excessive fading of the fluorescence ⁇ , when the light source 112 intermittently irradiates the excitation light ⁇ at a predetermined interval, the photodetector 124 intermittently detects the intensity of the first light and detects the light. The device 324 intermittently detects the intensity of the second light. That is, the intensity of the first light and the intensity of the second light are simultaneously detected at the same interval as the irradiation interval of the excitation light ⁇ .
- the SPFS device 100 (100 ′) has only one polarizer 122 and one photodetector 124, it is advantageous for downsizing of the device.
- the SPFS device 300 has the first light and the second light. It is advantageous for real-time SPFS measurement with higher temporal resolution.
- a first fluorescent substance (allophycocyanin, absorption wavelength: 650 nm, fluorescence wavelength 661 nm) indicated by a white star in the figure was immobilized on a diffraction grating 230 of a metal film.
- the first fluorescent substance simulates a fluorescent substance that labels a substance to be detected in GC-SPFS.
- excitation light ⁇ (wavelength 640 nm) was irradiated to the diffraction grating 230 at a predetermined incident angle, and the intensity of the fluorescence ⁇ was measured by the light detection unit 124 while rotating the polarizer (polarizing plate) 122.
- the buffer solution present on the diffraction grating 230 is omitted.
- a buffer solution containing the second fluorescent material (AlexaFluor 647, absorption wavelength: 647 nm, fluorescence wavelength 665 nm) indicated by a black star in the figure is formed on the diffraction grating 230 of the metal film.
- the second fluorescent material simulates a fluorescent material floating on the metal film, which is a noise source in GC-SPFS.
- the diffraction grating 230 was irradiated with excitation light ⁇ (wavelength 640 nm) at the same incident angle as the previous time, and the intensity of the fluorescence ⁇ was measured by the light detection unit 124 while rotating the polarizer (polarizing plate) 122.
- the buffer solution existing on the diffraction grating 230 is omitted except for the second fluorescent material.
- the actual particle size of the fluorescent material is generally about several nm.
- FIG. 11 is a graph showing the measurement results of fluorescence intensity.
- the alternate long and short dash line is a curve showing the relationship between the rotation angle of the polarizer and the fluorescence intensity when only the first fluorescent material is present (see FIG. 10A).
- the broken line is a curve showing the relationship between the rotation angle of the polarizer and the fluorescence intensity when the second fluorescent material is present in addition to the first fluorescent material (see FIG. 10B).
- the solid line is a curve showing the relationship between the rotation angle of the polarizer and the difference value between these two measured values.
- the rotation angle of the polarizer is an angle with respect to a plane including the normal to the surface of the metal film 220 and the optical axis of the excitation light ⁇ . For example, when the rotation angle of the polarizer is 0 °, p-polarized light is detected, and when the rotation angle of the polarizer is ⁇ 90 °, s-polarized light is detected.
- the fluorescence (signal component) derived from the first fluorescent material is mainly p-polarized light.
- the fluorescence intensity increases uniformly regardless of the rotation angle of the polarizer. This is considered to be due to the addition of fluorescence (noise component) derived from the second fluorescent material. Therefore, when looking at the solid line indicating these difference values, it can be seen that the fluorescence (noise component) derived from the second fluorescent material is randomly polarized.
- the noise component is almost included by subtracting the detection result of the s-polarized component from the detection result of the p-polarized component.
- the value of no signal component can be calculated.
- the surface plasmon enhanced fluorescence measuring apparatus and the surface plasmon enhanced fluorescence measuring method according to the present invention can measure a substance to be detected with high reliability, and are useful for clinical examinations, for example.
- the surface plasmon enhanced fluorescence measuring apparatus and the surface plasmon enhanced fluorescence measuring method according to the present invention can measure a substance to be detected with high reliability in real time without cleaning the metal film surface after providing a fluorescent labeling solution or the like. You can also Therefore, not only the measurement time can be shortened, but also it is expected to contribute to the development, spread and development of a very simple quantitative immunoassay system.
- SPFS device Surface plasmon enhanced fluorescence measuring device
- Excitation light irradiation unit 112
- Light source 120
- Fluorescence detection unit 122,322 Polarizer 124,324
- Photodetection part 130
- Control part (processing part) 200 chip 210 substrate 220 metal film 230 diffraction grating 321 half mirror ⁇ excitation light ⁇ fluorescence ⁇ reflected light
Abstract
Description
図1は、本発明の実施の形態1に係る表面プラズモン増強蛍光測定装置(SPFS装置)100の構成を示す模式図である。
実施の形態2に係るSPFS装置100’は、実施の形態1に係るSPFS装置100と同じ構成であり、リアルタイム測定を行う点で実施の形態1に係るSPFS装置100と異なる。そこで、SPFS装置の構成については説明を省略し、動作手順についてのみ説明する。
本実験では、GC-SPFSを利用する測定装置および測定方法において、金属膜上で励起された蛍光物質から放出された蛍光(被検出物質の存在または量を示すシグナル成分)と、液体中に浮遊している蛍光物質から放出された蛍光(ノイズ成分)の偏光特性を調べた結果を示す。
110 励起光照射ユニット
112 光源
120 蛍光検出ユニット
122,322 偏光子
124,324 光検出部
130 制御部(処理部)
200 チップ
210 基板
220 金属膜
230 回折格子
321 ハーフミラー
α 励起光
β 蛍光
γ 反射光
Claims (8)
- 回折格子を形成された金属膜と、前記回折格子に固定化された捕捉体と、前記捕捉体に結合した、蛍光物質で標識された被検出物質とを有するチップを装着され、励起光を前記回折格子に照射することで、被検出物質の存在またはその量を検出する表面プラズモン増強蛍光測定装置であって、
増強された電場により前記蛍光物質を励起して蛍光を放出させるために、前記励起光を前記回折格子に照射する光源と、
前記蛍光物質から放出された蛍光から直線偏光の光を取り出す偏光子と、
前記偏光子により取り出された前記直線偏光の光を検出する光検出部と、
を有する、表面プラズモン増強蛍光測定装置。 - 前記光検出部による検出値を処理する処理部をさらに有し、
前記偏光子は、前記蛍光物質から放出された蛍光から、前記金属膜の表面に対する法線と前記励起光の光軸とを含む平面に対する電界の振動方向の角度が0±30°の範囲内の第1の光および前記平面に対する電界の振動方向の角度が90±30°の範囲内の第2の光を同時または異時に取り出し、
前記光検出部は、前記第1の光および前記第2の光をそれぞれ検出し、
前記処理部は、前記第1の光の検出値と前記第2の光の検出値との差分値を算出する、
請求項1に記載の表面プラズモン増強蛍光測定装置。 - 前記第1の光は、前記金属膜の表面に対するp偏光の光であり、
前記第2の光は、前記金属膜の表面に対するs偏光の光である、
請求項2に記載の表面プラズモン増強蛍光測定装置。 - 被検出物質を標識する蛍光物質が、表面プラズモン共鳴に基づく電場により励起されて発した蛍光を検出して、被検出物質の存在またはその量を検出する表面プラズモン増強蛍光測定方法であって、
回折格子を形成された金属膜と、前記回折格子に固定化された捕捉体と、前記捕捉体に結合した、蛍光物質で標識された被検出物質とを有するチップを準備する第1の工程と、
前記回折格子において表面プラズモン共鳴が発生するように、前記回折格子に励起光を照射する第2の工程と、
前記蛍光物質から放出された蛍光から直線偏光の光を取り出す第3の工程と、
前記直線偏光の光を検出する第4の工程と、
を含む、表面プラズモン増強蛍光測定方法。 - 前記第4の工程で得られた検出値を処理する第5の工程をさらに含み、
前記第3の工程では、前記蛍光物質から放出された蛍光から、前記金属膜の表面に対する法線と前記励起光の光軸とを含む平面に対する電界の振動方向の角度が0±30°の範囲内の第1の光および前記平面に対する電界の振動方向の角度が90±30°の範囲内の第2の光を同時または異時に取り出し、
前記第4の工程では、前記第1の光および前記第2の光をそれぞれ検出し、
前記第5の工程では、前記第1の光の検出値と前記第2の光の検出値との差分値を算出する、
請求項4に記載の表面プラズモン増強蛍光測定方法。 - 前記第2の工程では、前記回折格子に励起光を継続して照射し、
前記第3の工程では、前記直線偏光の光を継続して取り出し、
前記第4の工程では、前記直線偏光の光を継続して検出する、
請求項4に記載の表面プラズモン増強蛍光測定方法。 - 前記第4の工程で得られた検出値を処理する第5の工程をさらに含み、
前記第3の工程では、前記蛍光物質から放出された蛍光から、前記金属膜の表面に対する法線と前記励起光の光軸とを含む平面に対する電界の振動方向の角度が0±30°の範囲内の第1の光および前記平面に対する電界の振動方向の角度が90±30°の範囲内の第2の光を継続して同時または異時に取り出し、
前記第4の工程では、前記第1の光および前記第2の光をそれぞれ継続して検出し、
前記第5の工程では、前記第1の光の検出値と前記第2の光の検出値との差分値を算出する、
請求項6に記載の表面プラズモン増強蛍光測定方法。 - 前記第1の光は、前記金属膜の表面に対するp偏光の光であり、
前記第2の光は、前記金属膜の表面に対するs偏光の光である、
請求項5または請求項7に記載の表面プラズモン増強蛍光測定方法。
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