JP7339655B2 - SPR sensor chip and SPR sensor - Google Patents

Description

The present invention relates to an SPR sensor chip and an SPR sensor.

The principle of operation of a sensor (SPR sensor) using the surface plasmon resonance (SPR) method is as follows. For example, in the case of an SPR sensor in which a metal film is provided on the surface of a prism, light is made incident on the metal film via the prism to generate an evanescent wave in the vicinity of the metal film. Surface plasmons are generated on the surface of the metal film by the incidence of light. When a predetermined resonance condition is met, the evanescent wave and the surface plasmon resonate (that is, surface plasmon resonance occurs), and the amount of light reflected at the interface between the prism and the metal film is reduced. The angle of incidence at the interface between the prism and the metal film when the amount of reflected light is the minimum value is called the resonance angle. Resonance conditions in surface plasmon resonance include, for example, the incident angle of light, the wavelength of light, the dielectric constant of the medium surrounding the metal film, and the like.

Patent Document 1 discloses a prism formed of a dielectric, a metal film provided on the surface of the prism, and a surface of the metal film opposite to the surface in contact with the prism, and included in the sample. A measuring device is disclosed that includes a sensitive film that specifically adsorbs a substance to be detected. This measurement device analyzes a sample by measuring the amount of light reflected by the metal film while changing the incident angle of the light incident on the interface between the prism and the metal film. The dielectric constant of the sensitive film as a medium surrounding the metal film changes when it absorbs the substance to be detected. The resonance angle changes when the dielectric constant of the sensitive film changes. By detecting the change in this resonance angle, the detection target substance can be detected.

Japanese Unexamined Patent Application Publication No. 2011-180110

However, in the measuring device described in Patent Document 1, since the detection target is detected by the change in the dielectric constant, it is difficult to discriminate between a plurality of detection target substances with a small difference in dielectric constant. For example, when objectively evaluating the taste of food, it is highly necessary to quantify sodium ions (Na ⁺ ), potassium ions (K ⁺ ), and calcium ions (Ca ²⁺ ) contained in the food. Small difference in dielectric constant. Therefore, it has been desired to realize a sensor capable of distinguishing a detection target substance having a small difference in dielectric constant by using the SPR method.

SUMMARY OF THE INVENTION An object of the present invention is to provide an SPR sensor chip and an SPR sensor that can determine the types and concentrations of a plurality of substances to be detected contained in a sample.

An SPR sensor chip according to the present invention includes a dielectric that transmits light, and a second dielectric that is provided on the surface of the dielectric and induces surface plasmon resonance when the light is incident on a first interface with the dielectric. and a metal film provided at a position different from the first metal film on the surface of the dielectric, and causing surface plasmon resonance when the light is incident on a second interface with the dielectric. a first sensitive film provided on the first metal film and specifically adsorbing a plurality of substances to be detected; provided on the second metal film, and a second sensitive film that specifically adsorbs the plurality of substances to be detected at an adsorption rate different from that of the first sensitive film.

The SPR sensor according to the present invention comprises the above SPR sensor chip, a light source that emits the light to be incident on the SPR sensor chip, an SPR response detection unit that detects the surface plasmon resonance response, and the SPR response detection unit. an analysis unit that analyzes the types and concentrations of the plurality of detection target substances adsorbed on the first sensitive film and the second sensitive film by performing principal component analysis based on detection results. .

According to the present invention, the types and concentrations of a plurality of substances to be detected contained in a sample can be determined.

1 is an explanatory diagram showing an SPR sensor chip embodying the present invention; FIG. 1 is an explanatory diagram showing an example of an SPR sensor embodying the present invention; FIG. FIG. 3 is an explanatory diagram for explaining the relationship between the amount of reflected light and the incident angle; FIG. 4 is an explanatory diagram for explaining the relationship between the amount of reflected light and time when the incident angle of light is fixed at the resonance angle; FIG. 10 is an explanatory diagram showing an SPR sensor chip of a second embodiment; FIG. 5 is an explanatory diagram showing an example of an SPR sensor according to a second embodiment; 4 is a graph showing results of measurement of resonance angles in water using Nafion. 4 is a graph showing results of measurement of resonance angles in water using Flemion. It is a graph showing the measurement results of the amount of reflected light in samples of various concentrations using Nafion, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the CaCl ₂ aqueous solution. indicates Fig. 3 is a graph showing the measurement results of the amount of reflected light in samples of various concentrations using Flemion, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the _CaCl2 aqueous solution. indicates It is a graph showing the results of fitting the experimental values when using Nafion, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the _CaCl2 aqueous solution. . FIG. 10 is a graph showing the results of fitting experimental values when using Flemion, where (a) is the measurement result of NaCl aqueous solution, (b) is the measurement result of KCl aqueous solution, and (c) is the measurement result of CaCl ₂ aqueous solution. . It is a graph which shows the analysis result which performed the principal component analysis.

[First embodiment]
In FIG. 1, an SPR (Surface Plasmon Resonance) sensor chip 10 embodying the present invention is used for an SPR sensor that detects the types and concentrations of a plurality of substances to be detected using the SPR method. A plurality of substances to be detected differ from each other in adsorption speed with respect to a first sensitive film 14 and a second sensitive film 15, which will be described later. Substances to be detected are, for example, ions or sugars. Ions include cations and anions. Examples of cations include sodium ions (Na ⁺ ), potassium ions (K ⁺ ), calcium ions (Ca ²⁺ ), magnesium ions (Mg ²⁺ ), and the like. Examples of anions include chloride ions (Cl ⁻ ). Na ⁺ , K ⁺ , Ca ²⁺ and the like are ions that constitute tastants. A tastant refers to a chemical substance that humans and animals can perceive as taste, and includes types such as saltiness, sourness, sweetness, bitterness, and umami. Sugars include, for example, glucose, fructose, sucrose, lactose and the like. FIG. 1 is a cross-sectional view of the SPR sensor chip 10 taken along an XZ plane perpendicular to the Y direction in the XYZ directions (X, Y, and Z directions are orthogonal to each other).

The SPR sensor chip 10 includes a dielectric 11 , a first metal film 12 , a second metal film 13 , a first sensitive film 14 and a second sensitive film 15 . The configuration of the SPR sensor chip 10 shown in FIG. 1 is an example and is not intended to limit the present invention. The number of the first metal film 12, the second metal film 13, the first sensitive film 14, and the second sensitive film 15 is one each in this embodiment, but is not limited to this and can be changed as appropriate. can do.

In this embodiment, the SPR sensor chip 10 further includes a sample placement section 19 in which a sample 18 containing a plurality of substances to be detected is placed. A sample placement portion 19 is provided on the surface 11 a of the dielectric 11 . The sample placing portion 19 is formed in a frame shape. Although the material of the sample placing portion 19 is not particularly limited, for example, ABS resin, photo-curing resin, silicon (Si), or the like is used. The liquid sample 18 is filled inside the sample placing portion 19 . A first metal film 12 , a second metal film 13 , a first sensitive film 14 and a second sensitive film 15 are provided on the surface 11 a of the dielectric 11 inside the sample placement portion 19 . Note that the sample placing portion 19 is not necessarily provided if the sample can be placed so as to cover the surfaces of the first sensitive film 14 and the second sensitive film 15. For example, the first sensitive film 14 and the second sensitive film This can be omitted by placing the sample droplets on the surface of 15 . For example, by placing a hydrophobic film around the first sensitive film 14 and around the second sensitive film 15, the surface tension of the liquid can be used to hold the sample in a droplet state.

Dielectric 11 has a front surface 11a and a back surface 11b. A sample 18 containing a plurality of substances to be detected contacts the surface 11a. Light L emitted by a light source 31, which will be described later, is incident on the rear surface 11b. The dielectric 11 is made of a material that allows the light L to pass therethrough. Various kinds of light can be used as the light L, and for example, light in the wavelength range from visible light to infrared light can be applied. If the light L is infrared light (with a wavelength range of approximately 1 μm to 10 μm), silicon can be used as the material of the dielectric 11 . When the light L is light in the wavelength range from visible light to near-infrared light (the wavelength range is approximately 380 nm or more and 2.5 μm or less), the material of the dielectric 11 may be glass, light-transmitting resin, or the like. can be used. Optical glass such as BK7 can be used as the glass. As the light-transmitting resin, polyethylene, polypropylene, ABS resin, polyamide, polycarbonate, or the like can be used. In this embodiment, the dielectric 11 is made of silicon and the light L is infrared light.

Dielectric 11 has plate 22 and prism 23 . The surface of plate 22 constitutes surface 11 a of dielectric 11 . In this embodiment, the plate 22 is made of a material that forms a Schottky barrier at the interface with the first metal film 12 and the interface with the second metal film 13 . For example, the plate 22 is made of n-type silicon doped with P (phosphorus). A prism 23 is provided on the back surface of the plate 22 . That is, the front surface of the prism 23 is in contact with the rear surface of the plate 22 , and the rear surface of the prism 23 constitutes the rear surface 11 b of the dielectric 11 . The prism 23 is formed in a columnar shape. The cross-sectional shape of the prism 23 along the XZ plane is triangular, trapezoidal, semicircular, or elliptical, for example. In FIG. 1, the cross-sectional shape of the prism 23 is a right triangle.

A first metal film 12 is provided on the surface 11 a of the dielectric 11 . The first metal film 12 is made of gold (Au), silver (Ag), copper (Cu), or the like. The first metal film 12 is formed by vapor deposition, for example. The thickness of the first metal film 12 is not particularly limited, but is, for example, 50 nm to 200 nm. The thickness direction of the first metal film 12 coincides with the Z direction in FIG. In this embodiment, the first metal film 12 is Schottky-junctioned with the dielectric 11 made of silicon. A Schottky barrier is formed at the first interface 24 between the first metal film 12 and the dielectric 11 .

The second metal film 13 is provided on the surface 11 a of the dielectric 11 at a different position from the first metal film 12 . In FIG. 1, the second metal film 13 is arranged apart from the first metal film 12 in the X direction. That is, the first metal film 12 and the second metal film 13 are arranged with a predetermined distance therebetween. The second metal film 13 is made of Au, Ag, Cu, or the like. The second metal film 13 is formed by vapor deposition, for example. The thickness of the second metal film 13 is not particularly limited, but is, for example, 50 nm to 200 nm. The thickness direction of the second metal film 13 coincides with the Z direction in FIG. In this embodiment, the second metal film 13 is Schottky-junctioned with the dielectric 11 made of silicon. A Schottky barrier is formed at the second interface 25 between the second metal film 13 and the dielectric 11 .

In this embodiment, an insulating film for electrically insulating the first metal film 12 and the second metal film 13 is provided between the first metal film 12 and the second metal film 13 in the dielectric 11 . A section (not shown) is provided. The isolation can be formed, for example, by controlling the doping concentration in the pn junction of silicon.

A first sensitive film 14 is provided on the first metal film 12 . The first sensitive film 14 specifically adsorbs multiple detection target substances contained in the sample 18 . The dielectric constant of the first sensitive film 14 changes due to the adsorption of the substance to be detected. The thickness of the first sensitive film 14 is appropriately set according to the wavelength of the light L used. It is desirable that the upper limit of the thickness of the first sensitive film 14 is approximately the same as the wavelength of the light L. Examples of the first sensitive membrane 14 include an ion exchange membrane that adsorbs ions and a boronic acid membrane that has a phenylboronic acid compound that adsorbs sugars.

Examples of ion exchange membranes include Nafion (registered trademark: manufactured by DuPont) represented by the following chemical formula (1) and Flemion (registered trademark: manufactured by Asahi Glass Co., Ltd.) represented by the following chemical formula (2). Nafion and Flemion are types of cation exchange membranes that adsorb cations.

As the boronic acid film, a film in which the surface of a substrate made of polymer or the like is coated with a phenylboronic acid compound represented by the following chemical formula (3) or (4) is used.

A second sensitive film 15 is provided on the second metal film 13 . In FIG. 1, the second sensitive film 15 is arranged apart from the first sensitive film 14 in the X direction. That is, the first sensitive film 14 and the second sensitive film 15 are arranged with a predetermined distance therebetween. The second sensitive film 15 specifically adsorbs a plurality of substances to be detected contained in the sample 18 at an adsorption speed different from that of the first sensitive film 14 . The dielectric constant of the second sensitive film 15 changes due to adsorption of the substance to be detected. The thickness of the second sensitive film 15 is appropriately set according to the wavelength of the light L used. It is desirable that the upper limit of the thickness of the second sensitive film 15 is approximately the same as the wavelength of the light L. An example of the second sensitive membrane 15 is an ion exchange membrane or a boronic acid membrane different from the first sensitive membrane 14 . For example, when Flemion is used as the first sensitive film 14 , Nafion is used as the second sensitive film 15 .

In this embodiment, the SPR sensor chip 10 further comprises two electrodes 27 electrically connected to the first metal film 12 and the second metal film 13 respectively. Each electrode 27 is provided on the surface 11 a of the dielectric 11 , that is, the surface of the plate 22 in this embodiment, but may be provided on the back surface or the side surface of the plate 22 . In FIG. 1, only one of the two electrodes 27 is shown, and the other electrode is hidden in the Y direction. Each electrode 27 is made of, for example, aluminum (Al). Each electrode 27 is in ohmic contact with dielectric 11 . The first metal film 12, the second metal film 13, and the two electrodes 27 are connected via wiring (not shown). A current detector 33, which will be described later, is connected to this wiring.

In the SPR sensor chip 10, the light L (infrared light) incident on the back surface 11b of the dielectric 11 passes through the dielectric 11 made of silicon and reaches the front surface 11a of the dielectric 11 at an angle exceeding the critical angle. is totally reflected at the first interface 24 and at the second interface 25 . As a result, an evanescent wave is generated between the first interface 24 and the second interface 25, and the free electrons of the metals of the first metal film 12 and the second metal film 13 obtain energy from the evanescent wave. An SPR, which is a compressional wave of electrons, is induced. Free electrons of the metals of the first metal film 12 and the second metal film 13 are excited by the energy of the light L, overcome the Schottky barrier and diffuse into the dielectric 11 . Holes inside the dielectric 11 diffuse into the first metal film 12 and the second metal film 13 in response to the diffusion of the free electrons. As a result, a first current flows between the first metal film 12 and the dielectric 11 and a second current flows between the second metal film 13 and the dielectric 11 . The first current and the second current are detected by a current detector 33, which will be described later. In addition, since the energy of the light L is deprived by the induction of the SPR, the first reflected light amount of the light L totally reflected at the first interface 24 decreases, and the second reflected light amount of the light L reflected at the second interface 25 decreases. The amount of reflected light is reduced.

When the sample 18 contacts the first sensitive film 14 and the second sensitive film 15, and a plurality of detection target substances contained in the sample 18 are adsorbed to the first sensitive film 14 and the second sensitive film 15, The dielectric constants of the first sensitive film 14 and the second sensitive film 15 change, and the resonance condition in SPR changes. As a result, the free electrons of the metals of the first metal film 12 and the second metal film 13 receive less energy from the light L, so that their movements change. In this embodiment, the SPR sensor chip 10 enables the taste sensor 30 as an SPR sensor, which will be described later, to detect a change in movement of free electrons as a change in current value. Further, by changing the resonance condition in SPR, the first reflected light amount of the light L totally reflected at the first interface 24 between the first metal film 12 and the dielectric 11 and the second metal film 13 The second reflected light amount of the light L totally reflected at the second interface 25 with the dielectric 11 changes.

In FIG. 2, a taste sensor 30, which is an example of an SPR sensor, uses the SPR sensor chip 10 to detect tastants as substances to be detected. The configuration of the taste sensor 30 shown in FIG. 2 is an example, and is not intended to limit the present invention. In the present embodiment, the taste sensor 30 uses Flemion as the first sensitive film 14 of the SPR sensor chip 10 and Nafion as the second sensitive film 15 to detect ions contained in the sample 18 as the substance to be detected. is Na ⁺ , K ⁺ , or Ca ²⁺ , and the concentration of each ion is detected. This taste sensor 30 can be used to objectively evaluate the taste of food.

In addition to the SPR sensor chip 10 , the taste sensor 30 further includes a light source 31 , an incident angle adjusting mechanism 32 , a current detector 33 and a controller 34 .

The light source 31 emits light L to be incident on the back surface 11 b of the dielectric 11 of the SPR sensor chip 10 . The light source 31 is composed of, for example, a light-emitting element, a lens, a mirror, and the like (not shown). For example, an LD (Laser Diode) or an LED (Light Emitting Diode) is used as the light emitting element. The wavelength range of the light L emitted by the light source 31 is the wavelength range that passes through the dielectric 11 . In this embodiment, the light L emitted by the light source 31 is infrared light.

The incident angle adjusting mechanism 32 adjusts the incident angle of the light L incident on the SPR sensor chip 10 . The incident angle is the angle with respect to the direction perpendicular to the surface 11 a of the dielectric 11 . The incident angle adjustment mechanism 32 can be configured to be able to adjust the incident angle, for example, by rotating a lens or mirror (not shown). Incidentally, the incident angle adjustment mechanism 32 may be configured to be able to adjust the incident angle using a rotating stage (not shown) that rotates the SPR sensor chip 10 and the light source 31 .

The current detection unit 33 detects a first current value, which is a current value of a first current flowing between the first metal film 12 and the dielectric 11 , and a current value between the second metal film 13 and the dielectric 11 . and a second current value, which is the current value of the second current flowing through. The current detector 33 is electrically connected to the controller 34 , generates a detection signal corresponding to the detected first current value and the second current value, and outputs the signal to the controller 34 . When the substance to be detected specifically binds to the first sensitive film 14 and the second sensitive film 15 and the dielectric constant of the first sensitive film 14 and the second sensitive film 15 changes, the first metal Free electrons of the metals of the film 12 and the second metal film 13 change their movements as the energy received from the light L changes. The current detector 33 detects changes in the movement of free electrons as changes in current value. For example, when the incident angle of the light L deviates from the resonance angle at which the first reflected light amount is minimized, the energy received by the free electrons of the metal of the first metal film 12 from the light L decreases, and the free electrons Since the movement becomes smaller, the first current value detected by the current detection section 33 decreases. When the incident angle of the light L deviates from the resonance angle at which the second reflected light quantity is minimized, the second current value detected by the current detector 33 decreases. In this way, changes in the movement of free electrons appear as changes in the current value, so the current value can be used as a surface plasmon resonance response (hereinafter referred to as SPR response). That is, the current detector 33 detects a current value as an SPR response, and functions as an SPR response detector that electrically detects the SPR response.

Further, when the incident angle of the light L deviates from the resonance angle, the first current value and the second current value decrease as described above, while the first reflected light amount and the second reflected light amount increase. do. As described above, there is a certain correlation between the current value and the amount of reflected light, such that the current value decreases and the amount of reflected light increases when the incident angle of the light L deviates from the resonance angle. For example, a table defining the above correlation is stored in advance in the control unit 34, and the amount of reflected light is obtained based on the correlation in the table stored in the control unit 34 and the current value detected by the current detection unit 33. be able to. That is, the current value can be converted into the amount of reflected light using the above correlation. In this embodiment, the current value is converted into the amount of reflected light, and the converted amount of reflected light is used as a parameter to perform principal component analysis, which will be described later. Principal component analysis may be performed using the current value as a parameter without converting the current value into the amount of reflected light.

The control section 34 is electrically connected to the SPR sensor chip 10 , the light source 31 , the incident angle adjustment mechanism 32 , the current detection section 33 and the like, and controls each section of the taste sensor 30 . For example, the control unit 34 controls the lighting and extinguishing of the light source 31 and the amount of light L emitted. The controller 34 drives the incident angle adjusting mechanism 32 to adjust the incident angle of the light L with respect to the SPR sensor chip 10 .

Based on the detection result of the SPR response detected by the SPR response detection unit, the control unit 34 performs principal component analysis to determine the type of substance to be detected adsorbed on the first sensitive film 14 and the second sensitive film 15. and an analysis unit 35 for analyzing the concentration. In this embodiment, the analysis unit 35 calculates the first reflected light amount and the second reflected light amount based on the first current value and the second current value detected by the current detection unit 33 as the SPR response detection unit. are obtained, and principal component analysis is performed using the obtained first reflected light amount and second reflected light amount as parameters.

An example of the analysis method of the analysis unit will be described below. In the following explanation, the analysis of the first sensitive film and the analysis of the second sensitive film will be explained without distinguishing between them, but the respective analysis methods are the same.

Based on the SPR response detection result detected by the SPR response detection section, the analysis section detects the incident angle at which the amount of reflected light is the minimum, that is, the resonance angle. Specifically, the analysis unit calculates the resonance angle θ _SPR when water is in contact with the surface of the dielectric and the resonance angle θ _SPR +Δθ(t) when the sample is in contact with the surface of the dielectric. to detect

FIG. 3 is an explanatory diagram for explaining the relationship between the amount of reflected light and the angle of incidence. In FIG. 3, the horizontal axis is the incident angle, and the vertical axis is the amount of reflected light. FIG. 3 is a graph plotting the results of detecting the amount of reflected light at each incident angle while changing the incident angle with respect to the SPR sensor chip embodying the present invention. Reference numeral 37 denotes the response curve when the dielectric surface is in contact with water, and reference numeral 38 denotes the response curve when the dielectric surface is in contact with the sample. It can be confirmed from FIG. 3 that the response curve 38 moves to the right on the paper surface with respect to the response curve 37 .

At an angle θ ₀ that is about 0.1° smaller than the resonance angle θ _SPR , the change in the amount of reflected light from the sample with respect to the amount of reflected light from water is defined as the amount of change in reflected light amount I(t). In FIG. 3, the amount of change I(t) in the amount of reflected light is indicated by an arrow. From FIG. 3, it can be confirmed that the amount of reflected light at the angle θ ₀ is larger in the case of the sample than in the case of water. That is, in the case of the sample, the amount of reflected light increases more than in the case of water.

In FIG. 3, assuming that the response curve 38 of the sample is parallel to the response curve 37 of water, the amount of reflected light measured at the angle θ ₀ on the sample is the angle θ ₀ -Δθ(t ) is equal to the amount of reflected light measured by Therefore, if the dip portion (that is, the resonance angle portion) is represented by R(θ) and the resonance angle shift amount is Δθ(t), the amount of change in the amount of reflected light I(t) is given by the following formula (1): is represented by The amount of change I(t) in the amount of reflected light is used for fitting, which will be described later.

R(θ) is represented by the following formula (2) using an error function.

In Equation (2), a is the resonance angle after a sufficient amount of time has passed, b is an arbitrary constant, and c is the amount of change over time in the amount of reflected light. The values of a, b, and c in Equation (2) differ depending on the type of sensitive film, the thickness of the sensitive film, and the concentration of the sample.

FIG. 4 is an explanatory diagram for explaining the relationship between the amount of reflected light and time when the incident angle of the light L is fixed at the resonance angle. In FIG. 4, the horizontal axis is time, and the vertical axis is the amount of reflected light. FIG. 4 is a graph plotting the amount of reflected light detected each time a predetermined time elapses.

The analysis unit obtains the amount of change I(t) in the amount of reflected light based on the resonance angle θ _SPR in water and the resonance angle θ _SPR +Δθ(t) in the sample. It is considered that the movement amount Δθ(t) of the resonance angle behaves differently depending on the concentration of the substance to be detected. The amount of movement Δθ(t) of the resonance angle can be expressed by the following formula (3) based on the Gompertz equation. In Equation (3), R'(θ ₀ ) indicates the slope at angle θ ₀ in the dip portion of the equation.

A in Equation (3) is given by Equation (4) below. c in Equation (3) is given by Equation (5) below.

Then, the value of A and the value of c are obtained as parameters used for principal component analysis by fitting with the amount of change I(t) in the amount of reflected light shown in Equation (1). A indicates the amount of movement of the resonance angle after a sufficient amount of time has passed. c indicates the slope at t=0 in the graph (see FIG. 4) showing the change in the amount of reflected light. Since the slope varies depending on its magnitude, it is obtained as −log ₁₀ c, which is the logarithm of c. Principal component analysis is performed using the obtained value of A and the value of −log ₁₀ c as parameters.

As described above, the taste sensor 30 as an SPR sensor performs principal component analysis based on the detection result (current value) of the SPR response detected by the SPR response detection unit (current detection unit 33), thereby detecting a plurality of detection values. It is possible to analyze the type and concentration of target substances.

[Second embodiment]
In the second embodiment, the dielectric is made of glass, the amount of visible light totally reflected at the interface between the dielectric and the metal film is detected, and principal component analysis is performed based on the detected reflected light amount. be. Parts using the same components as those of the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

5, the SPR sensor chip 50 includes a dielectric 51, a first metal film 12, a second metal film 13, a first sensitive film 14, and a second sensitive film 15. As shown in FIG. The configuration of the SPR sensor chip 50 shown in FIG. 5 is an example and is not intended to limit the present invention.

Dielectric 51 has a front surface 51a and a back surface 51b. A sample 18 containing a plurality of substances to be detected contacts the surface 51a. Visible light as light L emitted by a light source 61, which will be described later, is incident on the rear surface 51b. The material of the dielectric 51 is glass, light-transmitting resin, or the like, and BK7 is used in this embodiment.

Dielectric 51 has plate 52 and prism 53 . The surface of plate 52 constitutes surface 51 a of dielectric 51 . A prism 53 is provided on the back surface of the plate 52 . That is, the front surface of the prism 53 is in contact with the rear surface of the plate 52 , and the rear surface of the prism 53 constitutes the rear surface 51 b of the dielectric 51 . The prism 53 is formed in a columnar shape. In FIG. 5, the cross-sectional shape of the prism 53 along the XZ plane is an isosceles right triangle.

In the SPR sensor chip 50, the light L (visible light) incident on the back surface 51b of the dielectric 51 passes through the dielectric 51 made of BK7 and reaches the surface 51a of the dielectric 51 at an angle exceeding the critical angle. When incident, the light is totally reflected at the first interface 54 between the first metal film 12 and the dielectric 51, and is reflected at the second interface between the second metal film 13 and the dielectric 51. Total reflection occurs at the interface 55 . As a result, an evanescent wave is generated between the first interface 54 and the second interface 55, and the free electrons of the metals of the first metal film 12 and the second metal film 13 obtain energy from the evanescent wave. An SPR, which is a compressional wave of electrons, is induced. Since the energy of the light L is deprived by the induction of the SPR, the first reflected light amount of the light L totally reflected at the first interface 54 is reduced, and the second reflected light amount of the light L reflected at the second interface 55 is reduced. decreases.

When the sample 18 contacts the first sensitive film 14 and the second sensitive film 15, and a plurality of detection target substances contained in the sample 18 are adsorbed to the first sensitive film 14 and the second sensitive film 15, The dielectric constants of the first sensitive film 14 and the second sensitive film 15 change, and the resonance condition in SPR changes. As a result, the first reflected light amount of the light L totally reflected at the first interface 54 between the first metal film 12 and the dielectric 51 and the second interface between the second metal film 13 and the dielectric 51 The second reflected light amount of the light L totally reflected at 55 changes. In this embodiment, the SPR sensor chip 50 enables the taste sensor 60 as an SPR sensor, which will be described later, to detect a first reflected light amount and a second reflected light amount.

In FIG. 6, a taste sensor 60, which is an example of an SPR sensor, uses an SPR sensor chip 50 to detect tastants as substances to be detected. The configuration of the taste sensor 60 shown in FIG. 6 is an example and is not intended to limit the present invention. In the present embodiment, the taste sensor 60 uses Flemion as the first sensitive film 14 of the SPR sensor chip 50 and Nafion as the second sensitive film 15 so that the ions as the substance to be detected contained in the sample 18 can be detected. is Na ⁺ , K ⁺ , or Ca ²⁺ , and the concentration of each ion is detected. This taste sensor 60 can be used to objectively evaluate the taste of food.

In addition to the SPR sensor chip 50 , the taste sensor 60 further includes a light source 61 , an incident angle adjustment mechanism 32 , a light detection section 63 and a control section 64 . The light source 61 has the same configuration as the light source 31 of the first embodiment except that the light L is visible light.

The light detection unit 63 detects the light amount (first reflected light amount) of the light L reflected at the first interface 54, which is the interface between the first metal film 12 and the dielectric 51, and The amount of light L reflected at the second interface 55 between the film 13 and the dielectric 51 (second reflected light amount) is detected. The photodetector 63 detects the amount of the first reflected light and the amount of the second reflected light as the SPR response, and functions as an SPR response detector that optically detects the SPR response.

The light detection section 63 has a first photosensor 67 that detects a first amount of reflected light and a second photosensor 68 that detects a second amount of reflected light. PD (Photo Diode), for example, is used for the first optical sensor 67 and the second optical sensor 68 . The first optical sensor 67 and the second optical sensor 68 are not limited to PDs, and may be CCD (Charge Coupled Device) image sensors, CMOS (Complementary Metal-Oxide Semiconductor) image sensors, or the like. The first optical sensor 67 and the second optical sensor 68 are electrically connected to the control unit 64, which will be described later, using wiring (not shown). The first photosensor 67 outputs a reflected light detection signal corresponding to the first amount of reflected light to the controller 64 . The second photosensor 68 outputs a reflected light detection signal corresponding to the second amount of reflected light to the controller 64 .

Although the first optical sensor 67 and the second optical sensor 68 are arranged outside the SPR sensor chip 50 in this embodiment, they may be arranged inside the SPR sensor chip 50 . The first optical sensor 67 is appropriately arranged at a position capable of detecting the first amount of reflected light, and the second optical sensor 68 is appropriately arranged at a position capable of detecting the second amount of reflected light.

The first optical sensor 67 and the second optical sensor 68 output each reflected light detection signal to the control section 64 each time a predetermined time elapses. This allows the taste sensor 60 to measure changes over time in the first reflected light amount and the second reflected light amount.

The controller 64 is electrically connected to the SPR sensor chip 50 , the light source 61 , the incident angle adjustment mechanism 32 , the light detector 63 and the like, and controls each part of the taste sensor 60 . For example, the control unit 64 controls the lighting and extinguishing of the light source 61 and the amount of light L emitted. The controller 64 drives the incident angle adjusting mechanism 32 to adjust the incident angle of the light L with respect to the SPR sensor chip 50 .

Based on the detection result of the SPR response detected by the SPR response detection unit, the control unit 64 performs principal component analysis to determine the type of substance to be detected adsorbed on the first sensitive film 14 and the second sensitive film 15. and an analysis unit 65 for analyzing the concentration. In this embodiment, the analysis unit 65 performs principal component analysis using the first reflected light amount and the second reflected light amount detected by the light detection unit 63 as the SPR response detection unit as parameters. The analysis method of the analysis unit 65 is the same as the analysis method of the analysis unit 35 of the first embodiment, so the explanation is omitted.

As described above, the taste sensor 60 as an SPR sensor detects the principal component based on the SPR response detection results (the first reflected light amount and the second reflected light amount) detected by the SPR response detection unit (light detection unit 63). By performing analysis, it is possible to analyze the types and concentrations of a plurality of substances to be detected.

A sample was actually prepared, and it was verified that the type and concentration of the substance to be detected could be analyzed. Flemion was used as the first sensitive film 14 . Nafion was used as the second sensitive film 15 . The thickness of Flemion and the thickness of Nafion were set to 0.6 μm. As sample 18, NaCl aqueous solution, KCl aqueous solution, and CaCl ₂ aqueous solution were used. The concentrations of sample 18 were 1.7 mM, 3.4 mM, 8.5 mM, 17 mM and 34 mM. M=mol/L. The values of a, b, and c in the above formula (2) are a = 0.100, b = -2.73, c = 75.4, and d = 0.310 for Nafion, and for Flemion In the case a=0.157, b=-2.22, c=75.4 and d=0.238.

In the SPR sensor used in the verification experiment, a metal film made of gold is provided on the surface of a dielectric made of BK7, and Flemion or Nafion is provided as a sensitive film on this metal film. Verification experiments were conducted separately using an SPR sensor in which Flemion is provided on a metal film and an SPR sensor in which Nafion is provided on a metal film. The dielectric is composed of a plate and a prism whose cross-sectional shape is an isosceles right triangle. The thickness of the metal film was set to 50 nm. The incident angle of light incident on the back surface of the dielectric was changed from 68.75° to 106.05°, and the amount of reflected light at each incident angle was measured. The angle of incidence is the angle with respect to the direction perpendicular to the surface of the dielectric. The amount of change in the incident angle was about 2.5×10 ⁻⁴ degrees. The amount of reflected light was measured with an oscilloscope with a sampling frequency of 20 kHz.

FIG. 7 is a graph showing measurement results of resonance angles in water using Nafion. FIG. 8 is a graph showing measurement results of resonance angles in water using Flemion. 7 and 8, the horizontal axis is the incident angle, and the vertical axis is the amount of reflected light. In FIGS. 7 and 8, the difference in density of the sample 18 is represented by the difference in line type. In FIG. 7, it was confirmed that the amount of reflected light was minimized when the incident angle was 75.80°. In FIG. 8, it was confirmed that the amount of reflected light was minimized when the incident angle was 75.92°.

FIG. 9 is a graph showing measurement results of measuring the amount of reflected light in samples 18 of various concentrations using Nafion. In FIG. 9, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the CaCl ₂ aqueous solution. FIG. 10 is a graph showing the measurement results of measuring the amount of reflected light in samples 18 of various densities using Flemion. In FIG. 10, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the CaCl ₂ aqueous solution. 9 and 10, the horizontal axis is time, and the vertical axis is the amount of reflected light. In FIGS. 9 and 10, the difference in density of the sample 18 is represented by the difference in line type.

FIG. 11 is a graph showing the result of fitting the measured value obtained using Nafion with the variation I(t) of the amount of reflected light shown in Equation (1). In FIG. 11, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the CaCl ₂ aqueous solution. FIG. 12 is a graph showing the results of fitting the measured values obtained using the Flemion with Equation (1). In FIG. 12, (a) is the measurement result of the NaCl aqueous solution, (b) is the measurement result of the KCl aqueous solution, and (c) is the measurement result of the CaCl ₂ aqueous solution. In FIGS. 11 and 12, the difference in density of the sample 18 is represented by the difference in line type.

By the fitting described above, the value of A and the value of −log ₁₀ c were obtained as parameters used for principal component analysis. The parameters are shown in Table 1 below.

FIG. 13 is a graph showing analysis results of principal component analysis based on each parameter shown in Table 1. FIG. In FIG. 13, the horizontal axis is the first principal component and the vertical axis is the second principal component. In FIG. 13, the difference in concentration of sample 18 is represented by the difference in markers. From FIG. 13, sodium ions (denoted as Na), potassium ions (denoted as K), and calcium ions (denoted as Ca) could be distinguished. Moreover, the difference in the concentration of each ion could also be distinguished.

The present invention is not limited to the above embodiments, and can be appropriately modified within the scope of the present invention.

The SPR sensor chips 10 and 50 each have one first sensitive film 14 and one second sensitive film 15, and the plurality of first sensitive films 14 and the plurality of second sensitive films 15 are provided. may be provided. The plurality of first sensitive films 14 and the plurality of second sensitive films 15 can be arranged on the XY plane in FIG. 1 or FIG. The plurality of first sensitive films 14 and the plurality of second sensitive films 15 may be alternately arranged. An area for arranging the plurality of first sensitive films 14 and an area for arranging the plurality of second sensitive films 15 may be separately provided.

In the SPR sensor chip 10 including the plurality of first sensitive films 14 and the plurality of second sensitive films 15, the SPR response is a plurality of first current values corresponding to the plurality of first sensitive films 14, A plurality of second current values corresponding to the plurality of second sensitive films 15 are detected. For this reason, for example, an average value of a plurality of first current values and an average value of a plurality of second current values are obtained, and principal component analysis is performed based on each average value, thereby analyzing the substance to be detected. Accuracy can be improved.

In the SPR sensor chip 50 including the plurality of first sensitive films 14 and the plurality of second sensitive films 15, the SPR response is a plurality of first reflected light amounts corresponding to the plurality of first sensitive films 14, A plurality of second reflected light amounts corresponding to the plurality of second sensitive films 15 are detected. For this reason, for example, an average value of a plurality of first reflected light intensities and an average value of a plurality of second reflected light intensities are obtained, and principal component analysis is performed based on each average value to analyze the substance to be detected. Accuracy can be improved.

The SPR sensor chips 10 and 50 have two types of sensitive films, the first sensitive film 14 and the second sensitive film 15, but may have three or more types of sensitive films. For example, in addition to the first sensitive film 14 and the second sensitive film 15, a third sensitive film that adsorbs a substance to be detected that is different from the first sensitive film 14 and the second sensitive film 15 is used for SPR. The sensor chips 10, 50 may be constructed. For example, when Flemion is used as the first sensitive film 14 and Nafion is used as the second sensitive film 15, a boronic acid film can be used as the third sensitive film. By using a plurality of sensitive films that adsorb different substances to be detected, it is possible to increase the types of substances to be analyzed that can be analyzed.

Taste sensor 60 as an SPR sensor may further include a beam splitter between light source 61 and SPR sensor chip 50 . The beam splitter guides part of the light L incident from the light source 61 to the SPR sensor chip 50 and guides the remaining part of the light to a light receiving element such as a PD (not shown). The light receiving element is electrically connected to the control section 64 and outputs a detection signal to the control section 64 according to the amount of light incident from the beam splitter. The control unit 64 controls the light emission amount of the light source 31 based on the detection signal input from the light receiving element.

Reference Signs List 10, 50 SPR sensor chip 11, 51 dielectric 11a, 51a front surface 11b, 51b rear surface 12 first metal film 13 second metal film 14 first sensitive film 15 second sensitive film 18 sample 24, 54 first interface 25, 55 second interface 30, 60 taste sensor (SPR sensor)
31, 61 light source 32 incident angle adjusting mechanism 34, 64 controller 35, 65 analyzer L light (infrared light, visible light)

Claims (4)

a dielectric that transmits light;
a first metal film provided on the surface of the dielectric and inducing surface plasmon resonance when the light is incident on a first interface with the dielectric;
a second metal provided at a position different from the first metal film on the surface of the dielectric and inducing surface plasmon resonance when the light is incident on a second interface with the dielectric; a membrane;
a first sensitive film provided on the first metal film and specifically adsorbing a plurality of substances to be detected;
A SPR sensor chip, comprising: a second sensitive film provided on the second metal film and specifically adsorbing the plurality of substances to be detected at an adsorption speed different from that of the first sensitive film. The SPR sensor chip according to claim 1;
a light source that emits the light to be incident on the SPR sensor chip;
an SPR response detection unit that detects the surface plasmon resonance response;
By performing principal component analysis based on the detection result of the SPR response detection unit, the types and concentrations of the plurality of substances to be detected adsorbed on the first sensitive film and the second sensitive film are analyzed. An SPR sensor comprising: an analyzer for performing; the dielectric of the SPR sensor chip is made of silicon,
the light emitted by the light source is infrared light;
The SPR response detection section detects a first current value of a first current flowing between the first metal film and the dielectric and a first current value flowing between the second metal film and the dielectric. detecting a second current value of the current of 2;
3. The SPR sensor according to claim 2, wherein said analysis unit performs said principal component analysis based on said first current value and said second current value. the dielectric of the SPR sensor chip is made of glass,
The light emitted by the light source is light in a wavelength range from visible light to near-infrared light,
The SPR response detection unit detects a first reflected light amount of the light totally reflected at the first interface and a second reflected light amount of the light totally reflected at the second interface,
3. The SPR sensor according to claim 2, wherein the analysis unit performs the principal component analysis based on the first reflected light amount and the second reflected light amount.

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