JP2012150098A - Chip for detecting specimen, sensor using the same, and method for detecting specimen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor for detecting a specimen contained in a droplet while suppressing decrease in sensitivity by preventing diffusion between solvents sequentially fed in different liquid interfaces.SOLUTION: A chip for detecting a specimen is used for detecting a specimen suspended in a solvent. The chip for detecting a specimen comprises: a feeding substrate having a feeding electrode for feeding the droplet of the solvent; a counter substrate facing the feeding substrate; a channel through which the droplet passes and which is formed between the feeding substrate and the counter substrate; and a fixing unit arranged in a part of the channel, and in which a ligand is immobilized. The chip detects the specimen by retaining the droplet stay at the fixing unit.

Description

  The present invention relates to a sample detection sensor for separating and detecting only a specific trace substance contained in a liquid, and more particularly to a sample detection sensor using droplets.

  Conventionally, in the environment and medical fields, various methods have been used to detect a specific substance (hereinafter referred to as a specimen) from a complex substance contained in a sample. In recent years, analyzers called Micro-TAS (Micro-Total Analysis Systems) and lab chips (Lab-on-a-Chip) have been developed.

  Patent Document 1 discloses a microchannel device including a substrate portion, a photocurable resin channel, and a light-transmitting cover substrate. An uncured resin is provided between the substrate portion and the cover substrate. There has been proposed a microchannel device in which microchannels are integrally formed by forming a channel pattern by photocuring reaction after filling. Further, Patent Document 2 proposes an enzyme immunoassay chip in which an enzyme immunoassay system for measuring a change in color by coloring a substrate solution using an enzyme as a label is integrated in a microchip. .

  In these devices, it is necessary to sequentially feed the sample and the reaction solution to the reaction unit and detection unit provided in the device, so a pump, a valve for controlling the liquid in the flow path, capillary force A liquid feeding means using the above is used.

  In addition, as a method of carrying a very small amount of liquid or droplet, a method using excitation of a surface wave (Surface Acoustic Wave) by applying a high frequency signal to the piezoelectric film, a potential difference is applied between the droplet and the substrate. Electrowetting (Electro Wetting, Electro Wetting On Dielectric) using changing the apparent wettability of the droplet to the substrate, dielectrophoresis that moves the droplet to a strong or weak electric field by an electrostatic field ( Devices using methods such as Dielectricphoresis have also been proposed. (See Patent Documents 3 and 4)

WO2003-062823 (published July 31, 2003) JP 2003-285298 A (published October 7, 2003) JP 2005-130851 A (published May 26, 2005) JP 2008-134152 A (released on June 12, 2008)

  However, when only the specimen is detected from various substances (hereinafter referred to as complex substances) contained in the sample using the devices shown in Patent Document 1 and Patent Document 2, for example, the sample flowed first Each solution diffuses at the interface between the solution and the next flowed reaction solution (liquid / liquid interface), causing a problem that the concentration of the solution changes at the interface and the specimen cannot be detected accurately. Further, since a pump for sequentially feeding the solution to the reaction unit and the detection unit provided in the device is necessary, the apparatus itself becomes large.

  On the other hand, as shown in Patent Document 3 and Patent Document 4 described above, the transport device using droplets that do not diffuse has advantages such as a small amount of a test reagent and a shortened reaction time, but the ligand is fixed. If the application is limited to the reaction or detection that does not become stable and the ligand is immobilized, there is a possibility that the transportation of the droplets is hindered.

  FIG. 13 is a diagram showing a contact angle between a droplet, a substrate, a gas, or a liquid that does not mix with the droplet. The droplet 90 includes an interfacial tension 93 between the droplet 90 and the substrate 91, an interfacial tension 94 between the droplet 90 and gas, or a liquid 92 that does not mix with the droplet, a substrate 91 and gas, or a droplet. Three forces of interfacial tension 95 between the unmixed liquids 92 are formed in balance.

  When transporting the droplet 90, it is desirable that the contact angle when electrical control is not performed is high, but the fixing unit and the detection unit constituting the specimen detection device are not in a surface state suitable for droplet transport, The surface state depends on each material. In the case where the contact angle of the fixed part or the detection part is lower than the other flow path surfaces, that is, in a surface state in which the liquid droplets easily get wet with respect to the substrate, the liquid droplet 90 tends to stay in place and is difficult to transport.

  Therefore, in order to facilitate the transport of the droplet 90, it is necessary to keep the surface of the flow path hydrophobic, but the portion where the ligand is immobilized (fixed portion) needs to react with the sample. Its surface cannot be made hydrophobic. For this reason, since the state of the fixing part facing the flow path is different from other parts that are hydrophobic, the droplet 90 cannot be smoothly transported, and the hydrophobicity of the surface of the flow path is reduced. As a result, the change in the surface state of the flow path when a voltage is applied is reduced, and the friction on the flow path surface is increased, which makes it difficult to transport the droplet 90. Under such circumstances, an effective device that uses a droplet 90 as a sample to immobilize a ligand and detect a desired analyte from a complex substance in the sample has not been put into practical use.

  The present invention has been made in view of each of the above-mentioned problems, and its purpose is to immobilize while suppressing a decrease in sensitivity while preventing diffusion between sequentially transported solutions (droplets). To provide a sample detection chip capable of detecting a sample contained in a droplet, a sensor using the same, and a sample detection method while preventing the stability of the liquid feeding from being hindered by the ligand formed is there.

  A sample detection chip according to the present invention is a sample detection chip for detecting a sample suspended in a solvent, and includes a transport substrate having a transport electrode for transporting a droplet of the solvent, A counter substrate facing the transfer substrate; a flow path formed between the substrate transfer substrate and the counter substrate through which the droplets pass; and a ligand provided in a part of the flow path Is provided, and the specimen is detected when the droplets stay in the fixed part.

  The transport electrode may be a transport electrode that changes the wettability of the droplet, and the droplet may be transported by changing the wettability of the droplet. The transport electrode may be a transport electrode that generates surface waves, and the droplets may be transported by the surface waves.

  In addition, a plurality of the transport electrodes may be provided, and each area of the transport electrodes may be larger than an area of the fixed portion. The flow path may be at least partially covered with a hydrophobic film, and the fixing portion may not be covered with the hydrophobic film. The specimen detection chip further includes droplet control means for controlling the amount of the droplet, and the droplet control means is configured such that an area where the droplet is in contact with the transfer substrate is an area of the fixed portion. The amount of the droplets may be controlled so as to be larger than that.

  A sample detection sensor according to the present invention includes any of the sample detection chips described above and a detection unit that optically detects the sample. In addition, a sample detection sensor according to the present invention may include the sample detection chip described above and at least one detection electrode that electrically detects the sample. Further, at least a part of the flow path may be covered with a hydrophobic film, and the fixing part and the detection electrode may not be covered with a hydrophobic film.

  Further, the number of the transport electrodes may be plural, and each area of the transport electrodes may be larger than the areas of the detection electrode and the fixing portion. In addition, the liquid droplet control means that includes the sample detection chip described above and is arranged on the sample detection chip has an area where the liquid droplet contacts the transport substrate, the detection electrode and the fixing unit. The amount of the droplets may be controlled so as to be larger than the area.

  The specimen detection method according to the present invention includes a step of electrically controlling a droplet of a solvent in which a specimen is suspended and conveying the inside of the flow path, and a ligand provided in a part of the flow path is immobilized. A sample detection method comprising: a step of causing the droplet to stay in a fixed portion to cause the sample to react with the ligand; and a step of detecting the sample, wherein the channel includes a droplet of the solvent. It is formed between a transfer substrate having a transfer electrode for transfer and a counter substrate facing the transfer substrate, and the area where the droplet contacts the transfer substrate is such that the fixed portion flows. The droplet is transported so as to be larger than an area facing the path.

  Further, the method may include a step of controlling the amount of the droplet. In the transporting step, the droplets may be transported by changing the wettability of the droplets. In the transporting step, the droplet may be transported by a surface wave. The specimen is electrically detected using a detection electrode, and the droplet is transported so that the area where the droplet contacts the transport substrate is larger than the area of the fixed part and the detection electrode. It is good also as a feature.

  The detection electrode may be formed of at least a working electrode and a reference electrode. The working electrode and the reference electrode may be arranged so as to be in contact with the droplet simultaneously.

  The detection electrode may be formed by a working electrode, a reference electrode, and a counter electrode. In addition, the working electrode, the reference electrode, and the counter electrode may be arranged so as to be in contact with the droplet at the same time.

  According to the specimen detection sensor of the present invention, the decrease in sensitivity is suppressed in a state where the diffusion of the solution at the interface between different solutions (droplets) that are sequentially conveyed is prevented, and the stability of the conveyance is achieved by the immobilized ligand. Can be prevented, and a sensor that can detect the specimen contained in the droplet can be realized.

1 is a cross-sectional view of a specimen detection sensor according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view of the specimen detection sensor when a droplet is sent to the specimen detection sensor according to the first embodiment. FIG. 3 is a perspective view of the sample detection sensor when a droplet is sent to the sample detection sensor according to the first embodiment. FIG. 3 is a plan view of the specimen detection sensor when a droplet is sent to the specimen detection sensor according to the first embodiment. It is the figure which showed the relationship between a droplet, the electrode for conveyance, a fixing | fixed part, and a detection electrode. It is the figure which showed the detection electrode and fixing | fixed part of a 3 electrode system. It is the flowchart which showed the procedure which detects a test substance using ELISA method. FIG. 10 is a cross-sectional view of a sample detection sensor when a droplet is sent to the sample detection sensor according to the second embodiment. FIG. 10 is a cross-sectional view of a sample detection sensor when a droplet is sent to the sample detection sensor according to the second embodiment. FIG. 9 is a cross-sectional view of a sample detection sensor when a droplet is sent to the sample detection sensor according to a third embodiment. FIG. 10 is a cross-sectional view of a sample detection sensor when a droplet is sent to the sample detection sensor according to a fourth embodiment. It is a schematic plan view of IDT. It is a figure explaining the contact angle of a droplet, a board | substrate, and gas.

  Hereinafter, embodiments of the present invention will be described. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

<Embodiment 1>
In this embodiment, a specific protein is measured by immunoassay. Here, adiponectin involved in the development of metabolic syndrome was used as the specific protein, and the concentration of the specific protein was measured by an electrochemical measurement method. However, the present invention is not limited to these configurations.

(Sensor configuration)
FIG. 1 is a cross-sectional view of a sample detection sensor 1 according to the present embodiment. In this embodiment, electrowetting is used as a method for transporting droplets. The sample detection sensor 1 includes a transport substrate 11, a transport electrode 12, a dielectric film 13, a hydrophobic film 14a, a hydrophobic film 14b, a substrate 15 having no transport electrode, a detection electrode 16, and a fixing portion 17. Is done. In the present invention, “droplet” means a liquid separated by gas or liquids having different polarities. The volume of each droplet is not particularly limited.

  For example, a glass substrate or a Si substrate can be used as the transfer substrate 11 and the substrate 15 having no transfer electrode. A plurality of transfer electrodes 12 are arranged on the transfer substrate 11, and a voltage is applied to the transfer electrodes 12 to transfer the droplets. A dielectric film 13 is formed on the transfer electrode 12. The dielectric film 13 is made of silicon nitride, silicon oxide, tantalum oxide, titanium oxide, barium titanate, or the like, and has dielectric properties.

  A hydrophobic film 14a is formed on the dielectric film 13, and a hydrophobic film 14b is formed so as to face the hydrophobic film 14a. A space between the hydrophobic film 14a and the hydrophobic film 14b is a space in which droplets are conveyed. The hydrophobic film 14a and the hydrophobic film 14b are made of, for example, a fluorine-based resin and have a low affinity for water, and the hydrophobic film 14a and the hydrophobic film 14b are close to each other even if they are the same material. Different materials may be used.

  A substrate 15 having no transfer electrode is formed on the hydrophobic film 14b. A fixed portion 17 and a detection electrode 16 are arranged on a substrate 15 that does not have a transfer electrode. The detection electrode 16 is usually composed of two electrodes, three electrodes, or a plurality of electrodes having different shapes, and the plurality of electrodes collectively function as one detection electrode 16. The detection electrode 16 can detect, for example, that a specimen is bound to a ligand described later. As the electrode material, gold, platinum or the like is mainly used. In FIG. 1, the detection electrode 16 is directly formed on the substrate 15 that does not have a transport electrode, because it is necessary to apply a resist once before the detection electrode 16 is formed. That is, when the base is the hydrophobic film 14b, there is a possibility that the resist may be repelled, so that the detection electrode 16 is formed on the substrate 15 having no transfer electrode, and thereafter, only the portion of the detection electrode 16 is removed from the hydrophobic film 14b. Is formed. A fixing part 17 is disposed on at least a part of the detection electrode 16, and a ligand that reacts with the specimen is fixed to the fixing part 17.

  FIG. 3 is a perspective view of the sample detection sensor 1 of the present embodiment, and FIG. 4 is a plan view of the sample detection sensor 1 of the present embodiment. Here, for the sake of easy understanding, the substrate 15 having no transfer electrode is omitted. The transport electrodes 12 are connected to the switches SW1, SW2, and SW3, respectively, and the voltage application state to the individual transport electrodes 12 can be controlled by turning the switches on and off. Then, the droplet 2 can be moved by controlling the voltage application state to the individual transport electrodes 12. Note that the number of switches is not particularly limited, and a necessary number can be provided.

  3 and 4, the switch SW2 is in a connected state. Here, when it is desired to move the droplet in the direction of the arrow, the switch SW2 is opened and the switch SW3 is connected. When the switch is connected, the voltage is applied until the movement of the droplet 2 is observed, and when the threshold voltage is exceeded, the droplet 2 moves to the next transport electrode. By repeating this, the droplet 2 is moved to the target location. The voltage application method is not limited to such a direct current method, and can also be performed by an alternating current method. In addition, since the wettability changes according to the potential change on the substrate electrode, the droplet 2 can be transported not only by the above-described potential application method but also by the potential change.

  5A and 5B are diagrams showing the relationship between the droplet 2 and the transport electrode 12. FIG. The shape of the transfer electrode 12 may be a shape as shown in FIG. 5B, or any other shape. In FIG. 5A, the surface 2a in which the droplet 2 is in contact with the hydrophobic film 14a, or the hydrophobic film 14b, the detection electrode 16, and the fixing portion 17, is indicated by the arrow direction shown in FIG. That is, when viewed from almost directly above, as shown in FIG. 5 (b), a plurality of transport electrodes 12 are always applied along the traveling direction of the droplet 2.

  In FIGS. 5A and 5B, the surface 2a is on the transfer electrodes 12a, 12a ′, 12b, and 12b ′. In addition, when the electrode 12 for conveyance is formed with the some electrode like the electrodes 12a and 12a 'for conveyance, this is regarded as one electrode for conveyance. Therefore, as viewed from the top of FIG. 5B, the surface 2a covers the two electrodes. As in this embodiment, by setting the transport electrode 12 and the droplet 2 in this way, the droplet 2 is transported. As a specific setting method, for example, there is a method of adjusting the amount of the droplet 2 of the sample, the size of the transfer electrode 12, and the arrangement interval of the transfer electrodes 12. A droplet control means (not shown) may be provided to control the transport amount of the droplet 2.

  The specific configuration of the droplet control unit is not particularly limited as long as it can control the transport amount of the droplet 2. For example, the droplet control means may introduce a predetermined amount of the droplet 2 into the flow path between the hydrophobic film 14a and the hydrophobic film 14b. In this case, the droplet control means may include a droplet preparation unit for forming a droplet having a predetermined volume and a pump for introducing the droplet having a predetermined volume into the flow path. It is not limited to the configuration. The volume of each droplet can be set as appropriate based on the size of the transfer electrode 12 and the arrangement interval of the transfer electrodes 12.

  Alternatively, it can be set by determining the space (height) in which the droplet 2 is transported by adjusting the arrangement of the transport substrate 11 and the substrate 15 having no transport electrode. In this case, in order to make the contact area of the droplet 2 constant, it is preferable to keep the distance between the transfer substrate 11 and the substrate 15 having no transfer electrode in the flow path constant.

  Next, the detection electrode 16 and the fixing part 17 will be described in detail. In FIG. 1, the detection electrode 16 and the fixing portion 17 are formed on the substrate 15 side that does not have the transfer electrode, but may be manufactured on the transfer substrate 11 side. Moreover, one detection electrode 16 and the fixing | fixed part 17 may be produced with respect to one flow path, and multiple may be produced. When a plurality of detection electrodes 16 and fixing parts 17 are produced, the detection electrodes 16 and the fixing parts 17 may be produced on both the substrate 15 side and the conveyance substrate 11 side that do not have the conveyance electrodes. However, it may be produced only in either one. Further, the plurality of detection electrodes 16 and the fixing portions 17 that are provided may have the same configuration or different configurations.

  Since the surface of the detection electrode 16 and the fixed part 17 (the surface facing the flow path) is not covered with the hydrophobic film 14b, the detection electrode 16 and the fixed part 17 are used to smoothly transport the droplet 2. Is preferably smaller than the transfer electrode 12. Further, the detection electrode 16 and the fixing portion 17 are preferably provided smaller than the surface 2a where the droplet 2 shown in FIG. 5A is in contact with the hydrophobic film 14a or the hydrophobic film 14b. Thereby, for example, a ligand and a specimen can be reacted efficiently.

  Here, a general electrochemical measurement method can be used as a method of detecting the specimen that has reacted with the ligand of the fixing unit 17, but the present invention is not limited to this. Electrochemical measurement methods include a two-electrode method and a three-electrode method. In the case of the two-electrode method, the working electrode and the reference electrode are used, but the three-electrode method is desirable for accurate potential measurement.

  FIG. 6A shows the detection electrode 16 and the fixing portion 17 in the case of the three-electrode system. The detection electrode 16 includes a counter electrode 161, a working electrode 162, and a reference electrode 163, which are electrochemical measurement electrodes.

  The counter electrode 161 needs to emit (or receive) electrons as fast as the working electrode 162 receives (or emits) electrons. The reference electrode 163 measures and controls the potential of the working electrode 162, and for example, an Ag / AgCl electrode can be used. The immobilization part 17 is formed by immobilizing, for example, an antibody as a ligand on the working electrode 162 by physical adsorption.

  FIG. 6B is a plan view of the three-electrode detection electrode 16 and the fixing portion 17 as viewed from the direction of the arrow in FIG. FIG. 6C is an enlarged plan view of the detection electrode 16 and the fixing portion 17. Here, in FIG. 6C, when the surfaces occupying each of the counter electrode 161, the working electrode 162, and the reference electrode 163 are a surface 164 and a surface 165, the counter electrode 161, the working electrode 162, the reference electrode 163, and the surface 164 and the surface 165 can be defined as a detection electrode region 16a. When the detection electrode 16 composed of a plurality of electrodes such as the three-electrode method or the two-electrode method as shown here is used, the detection electrode region 16a including the surface sandwiched between the electrodes has a liquid droplet 2 that is hydrophobic. It is preferable to provide a smaller size than the surface 2a in contact with the conductive film 14a or the hydrophobic film 14b. By doing so, for example, the specimen almost covers the ligand, and the specimen and the ligand can be reacted efficiently. Further, the detection electrode region 16a is preferably provided smaller than the transport electrode 12.

  Alternatively, in the case of the three-electrode system, it is desirable that the liquid droplets be arranged so that they can contact simultaneously with the working electrode, the reference electrode and the counter electrode. Note that the term “simultaneous contact” as used herein means that there is time for the droplets to contact the three electrodes of the working electrode, the reference electrode, and the counter electrode at the same time in the process of the droplets being transported in the flow path. To do.

  Further, in the case of the two-electrode system, it is desirable that at least the working electrode and the reference electrode are formed, and the droplets are arranged so that they can contact simultaneously with the working electrode and the reference electrode. Here, the simultaneous contact means that there is a time for the droplets to contact the working electrode and the reference electrode at the same time in the process in which the droplets are transported in the flow path.

(Detection procedure)
Next, a procedure for detection using an ELISA method (sandwich method) in an immunoassay using an antibody as a ligand and an antigen as a specimen will be described below.

  FIG. 7 is a flowchart showing an example of a procedure for detecting a specimen using the ELISA method. S represents each step in the flowchart. First, a ligand that is a primary antibody is immobilized on the immobilization unit 17 in advance (S71). Here, after spotting on the detection electrode 16 using a primary antibody solution (MAB 10651 manufactured by R & D System) as a ligand, it was incubated at 37 ° C. for 60 minutes, and fixed by physical adsorption. In FIG. 6, the ligand is immobilized on the working electrode 162, but the present invention is not limited to this. However, it is desirable that the fixing part 17 be close to the working electrode 162 in order to cause the electrochemical substance generated by the reaction in the fixing part 17 to undergo a redox reaction at the working electrode. In addition, a general thing can be used as a detection electrode.

  Next, blocking to prevent non-specific adsorption is performed on the entire electrochemical measurement electrode (S72). This is because the entire surface of the fixing portion 17 is not covered with the ligand antibody without a gap, and there is a gap, so it is necessary to prevent nonspecific adsorption to the gap. Here, a 1% BSA solution was used as a blocking solution, spotted in the vicinity of the detection electrode 16, and then incubated at room temperature for 60 minutes. In addition to the BSA solution, for example, casein is used as the blocking agent, but is not limited thereto. After blocking, excess blocking agent was washed with Tris buffer and washed away (S73). The solution used for washing is not limited to the Tris buffer solution, and any solution may be used as long as it does not interfere with the detection of the specimen.

  Next, since the detection method uses electrochemical measurement here, an enzyme and a substrate that generate an electrochemical substance are selected in an enzyme substrate reaction performed in a later step, and the enzyme is pre-labeled with a secondary antibody. . Here, the enzyme is not particularly limited, and a desired enzyme can be appropriately used. For example, ALP (Alkaline Phosphatase), glucose oxidase, or the like can be used as the enzyme, and pAPP (p-Aminophenyl phosphate), potassium ferricyanide, or the like can be used as the substrate for each enzyme. Is possible. Examples of the electrochemically active substance produced by the enzyme substrate reaction include pAP (paraaminophenol), potassium ferrocyanide, ferrocene, and ferrocene derivatives, or include pAP, potassium ferrocyanide, ferrocene, and ferrocene derivatives.

  In this embodiment, ALP is used as an example of an enzyme, and pAPP is used as a substrate. Next, as a sample, a droplet 2 (a droplet in which an enzyme-labeled secondary antibody is reacted with an antigen) in which an adiponectin (1065AP manufactured by R & D System) solution and an enzyme-labeled secondary antibody are mixed in advance is supplied to the fixing unit 17. The droplets 2 are removed after the transport and the primary antibody and antigen are sufficiently reacted with each other (S74).

  In the present embodiment, the specimen is detected by causing the liquid droplets to stay in the fixing unit 17. The residence time is not particularly limited as long as the residence time is long enough for the specimen and the ligand to react (for example, bind).

  In this embodiment, the antigen and the secondary antibody are mixed in advance, but they may be sequentially conveyed as separate liquids. In either case, it is possible to detect the analyte in the subsequent process, but the process can be simplified by using a droplet that has been mixed with an antigen-labeled secondary antibody in advance and then reacted. Can be

  Next, in order to wash | fix the fixing | fixed part 17, a Tris buffer solution is conveyed to the fixing | fixed part 17 as a washing | cleaning liquid, and unbound protein etc. are removed (S75). The solution used for washing is not limited to the Tris buffer, and any solution may be used as long as it does not interfere with the detection of the specimen.

  Next, the substrate solution containing the substrate solution pAPP is transported to the fixing unit 17 and reacted with the enzyme substrate (S76). Finally, the generated electrochemical substance pAP is detected by the detection electrode 16, and the dependence of the peak current value on the adiponectin concentration is measured (S77). As a method for measuring the sample amount, for example, a method in which a calibration curve is prepared in advance and the sample amount is calculated based on the standard curve is generally used.

  A desired specimen can be detected from the complex substance contained in the sample by the procedure as described above. In addition, the immobilization of a ligand and a ligand is not limited to those listed here, and known ones can be used. The ligand can be used as long as it is a substance capable of reacting (for example, binding) with a specimen. For example, in addition to the antibody used above, a peptide, DNA, aptamer, MIP (Molecular Imprinted Polymer), etc. can be used. is there.

  In addition to the physical adsorption used above, a chemical bond (for example, a covalent bond, a hydrophobic bond, an ionic bond, a hydrogen bond), a comprehensive method, or the like can be used to immobilize the ligand. In addition to the immunoassay using the antigen-antibody reaction used above, a known method such as a DNA assay using DNA hybridization can be used as a detection method for detecting the specimen, and various signals used in these methods can be used. Detection means can be used. For example, electrochemical detection method, colorimetric detection method, fluorescence detection method and the like. When an optical detection method is used for detection, it is necessary to select a transparent substrate for the substrate 15 that does not have a transport electrode. Next, detection using the fluorescence method will be described.

<Embodiment 2>
Next, Embodiment 2 in the present invention will be described. In the present embodiment, the specimen detection sensor itself does not have a detection electrode, and the specimen is detected using an external detection device or the like, or the detection section is separated from the fixed section. Is different.

  FIG. 8 is a cross-sectional view when the sample droplet 2 is fed to the specimen detection sensor 1a according to the present embodiment. In the present embodiment, electrowetting is used as a method for transporting the droplet 2. A plurality of transfer electrodes 12 are arranged on the transfer substrate 11, a dielectric film 13 and a hydrophobic film 14 a are sequentially formed thereon, and a ligand is fixed as a fixing portion 17 on the hydrophobic film 14 a. . In addition, a hydrophobic film 14b is formed on the flow path side of the substrate 15 having no transfer electrode. A droplet 2 is disposed between the transfer substrate 11 and the substrate 15 having no transfer electrode. The relationship between the droplet 2 and the transport electrode 12 is the same as that described in the first embodiment. In addition, since the portion of the fixing portion 17 does not have the hydrophobic film 14a, the fixing portion 17 is preferably provided smaller than the transport electrode 12. Furthermore, the fixing portion 17 is preferably provided smaller than the surface 2a where the droplet 2 shown in FIG. 5A is in contact with the hydrophobic film 14a or the hydrophobic film 14b. This is for efficiently reacting the ligand and the specimen. In FIG. 8, the fixing portion 17 is manufactured on the side of the transfer substrate 11, but may be manufactured on the side of the substrate 15 that does not have the transfer electrode.

  As a detection method in the detection device 26, for example, general fluorescence detection can be used. In this case, only the specific substance can be detected by putting the excitation light 31 into the droplet 2 and detecting the fluorescence 32 emitted from the droplet 2. The detection electrode 26 is not limited to the above-described configuration, and a configuration based on an electrochemical detection method, a colorimetric detection method, a fluorescence detection method, or the like can be used as appropriate.

  The immobilization part 17 is formed by immobilizing a ligand (for example, an antibody) by physical adsorption. Specifically, detection can be performed as follows using the procedure shown in FIG. 7 using an antibody as a ligand and an antigen as a specimen.

  First, a ligand that is a primary antibody is immobilized on the immobilization unit 17 in advance (S71). Next, blocking is performed to prevent nonspecific adsorption (S72). This is because not all of the fixing part 17 is covered with the ligand antibody without a gap, and there is a gap, so that it is necessary to prevent nonspecific adsorption to the gap. In addition, as a blocking agent, BSA, casein, etc. are used, for example.

  After blocking, excess blocking agent is washed away by washing (S73). Here, since the detection method uses fluorescence measurement, an enzyme and a substrate that generate a fluorescent substance are selected by an enzyme substrate reaction performed in a later step, and the enzyme is labeled in advance with a secondary antibody. Here, for example, HRP (horseradish peroxidase) is used as the enzyme, and ADHP (10-acetyl-3,7-dihydroxyphenoxyzine), QuantaBlu (registered trademark), or the like is used, but not limited thereto. For example, peroxidase (POD) or the like can be used as the enzyme, and Amplex (manufactured by Invitrogen) or the like can be used as the substrate.

  Next, a droplet 2 (a droplet in which an enzyme-labeled secondary antibody is reacted with an antigen) in which a sample solution containing an antigen as a specimen and an enzyme-labeled secondary antibody are mixed in advance is conveyed to the fixing unit 17. . After sufficiently reacting the primary antibody with the antigen for the antigen-antibody, the droplet is removed (S74). Next, in order to wash | fix the fixing | fixed part 17, a washing | cleaning liquid is conveyed to the fixing | fixed part 17, and unbound protein etc. are removed (S75). Next, the substrate solution is conveyed to the fixing unit 17 to cause an enzyme substrate reaction. If necessary, the enzyme substrate reaction may be stopped using an enzyme substrate reaction terminator at this time (S76). Finally, the fluorescent substance produced by the enzyme substrate reaction is irradiated with the excitation light 31, and the resulting fluorescence 32 is detected to measure the amount of the specimen (S77).

  In FIG. 8, the configuration is such that the excitation light 31 is emitted from the upper part of the fixed portion 17 and the fluorescence 32 is detected. However, it is of course possible to irradiate and detect the fluorescent light 32 from other than the upper part. Further, the configuration of FIG. 8 is a configuration based on fluorescence analysis, but a configuration based on general colorimetric analysis is also possible. In the case of colorimetric analysis, for example, the amount of specimen can be known from the absorbance using a chromogenic substrate OPD (o-phenylenediamine), TMB (3,3 ′, 5,5′-tetramethyl-benzidine) or the like for the HRP enzyme. it can. Alternatively, chromogenic substrates TMB, OPD, ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) can be used as an enzyme for peroxidase.

  Further, in the present embodiment, the sample detection sensor 1a has been described as having a configuration that does not include a detection unit. However, as illustrated in FIG. 9, a detection unit 16 ′ may be provided separately from the fixing unit 17. The detection means 16 ′ may be provided outside the flow path, for example, adjacent to the substrate 15 having no transfer electrode.

<Embodiment 3>
Next, Embodiment 3 in the present invention will be described. This embodiment is different from the first and second embodiments in that the transport electrodes are arranged on both upper and lower sides with the droplet 2 interposed therebetween. In this way, by using two transfer electrodes, the positive electrode and the negative electrode of the electrode do not have to be formed on one substrate, so that the substrate can be easily manufactured and the transfer electrode can be controlled. It becomes easy.

  FIG. 10 is a cross-sectional view of the sample detection sensor 1c according to the present embodiment when the sample droplet 2 is fed. In the present embodiment, electrowetting is used as a method for transporting the droplet 2. A plurality of transfer electrodes 12 are arranged on the transfer substrate 11, a dielectric film 13 and a hydrophobic film 14 a are sequentially formed thereon, and a ligand is fixed as a fixing portion 17 on the hydrophobic film 14 a. . Further, an upper electrode 120 and a hydrophobic film 14b are sequentially formed on the upper substrate 18 toward the flow path.

  A droplet 2 is disposed between the transfer substrate 11 and the upper substrate 18. The relationship between the droplet 2 and the transport electrode 12 is the same as that described in the first embodiment. Further, since there is no hydrophobic film 14 a on the surface (flow channel side) of the fixing portion 17, it is preferable to provide the fixing portion 17 smaller than the transfer electrode 12. Furthermore, the fixing portion 17 is preferably provided smaller than the surface 2a where the droplet 2 shown in FIG. 5A is in contact with the hydrophobic film 14a or the hydrophobic film 14b. This is for efficiently reacting the ligand and the specimen. The detection electrode 16 ′ is provided separately from the fixed portion 17, and can be provided outside the flow path, for example, adjacent to the upper substrate 18. In FIG. 10, the fixing portion 17 is manufactured on the transport substrate 11 side, but may be manufactured on the upper substrate 18 side.

  The voltage is applied between the transfer electrode 12 formed on the transfer substrate 11 and the upper electrode 120 formed on the upper substrate 18. The upper electrode 120 is set to the ground potential, and a voltage is applied to the transfer electrode adjacent in the direction to be transferred. The upper electrode 120 may be formed as one electrode or a plurality of electrodes.

  In FIG. 10, the switch SW2 is in a connected state. Here, to move the droplet 2 in the direction of the arrow, the switch SW2 is opened and the switch SW3 is connected. When the switch is connected, the voltage is applied until the movement of the droplet 2 is observed, and when the threshold voltage is exceeded, the droplet 2 moves to the next transport electrode. By repeating this, the droplet 2 is moved to the target location. The voltage application method is not limited to such a direct current method, and can also be performed by an alternating current method. In addition, since the wettability changes according to the potential change on the substrate electrode, the droplet 2 can be transported not only by the above-described potential application method but also by the potential change.

  In addition, the structure shown above is the structure in which the fixing portion 17 and the detection electrode 16 as shown in the first embodiment are provided at the same place, or the detection means 16 ′ described in the second embodiment is the present structure. It is applicable also to the structure detected by the detection apparatus 26 without including.

<Embodiment 4>
Next, a fourth embodiment of the present invention will be described. The present embodiment is different from the first to third embodiments in that a droplet is transported using a surface acoustic wave (Surface Acoustic Wave). By using surface waves in this way, it is not necessary to provide a plurality of electrodes in the entire flow path, and costs can be reduced. It is also possible to use a transport electrode that changes the wettability of the droplet and a transport electrode that generates surface waves.

FIG. 11 is a cross-sectional view of the sample droplet 2 fed to the specimen detection sensor 1d according to the present embodiment. A piezoelectric film 19 and a transport electrode IDT (InterDigital Transducer) 20 are formed on the transport substrate 11 to excite surface waves. The piezoelectric film 19 is made of, for example, LiNbO ₃ and has a function of deforming when an electric field is applied. When the piezoelectric film 19 is not hydrophobic, it is desirable to provide a hydrophobic film on the piezoelectric film 19.

  FIG. 12 is a plan view of the transfer electrode IDT20 as seen from the direction of the arrow in FIG. The transfer electrode IDT 20 is a comb-shaped electrode as shown in FIG. 12, and a large electrode 202 is connected to the comb-shaped small electrode 201 so that a voltage can be applied collectively. When a voltage is applied from the large electrode 202 to the small electrode 201, a surface wave is excited by the small electrode 201. When a high frequency signal is applied to the transfer electrode IDT 20 formed on the piezoelectric film 19, an electric field is generated between the electrodes, a surface acoustic wave is excited, and the surface acoustic wave propagates on the piezoelectric film 19. . When there is a droplet 2 on this propagation surface, a longitudinal wave is radiated in the droplet, and the droplet 2 can be conveyed. The piezoelectric film 19 is formed with a fixing portion 17 and a detection electrode 16, and a ligand is fixed as at least a part of the detection electrode 16 as the fixing portion 17. When the surface wave is emitted to the droplet 2, the droplet 2 is conveyed to the fixed portion 17 and the detection electrode 16. The detection method in this case can also be implemented in the same manner as in the above embodiment.

  As described above, when the ligand is immobilized by the method shown in each embodiment and the specimen detection is performed using the droplet, the stability of the liquid feeding is prevented from being hindered by the influence of the immobilized ligand. Thus, a sensor for detecting the specimen contained in the droplet could be realized.

1, 1a, 1b, 1c, 1d Specimen detection sensor 11 Transport substrate 12, 12a, 12a ', 12b, 12b' Transport electrode 120 Upper electrode 13 Dielectric film 14a, 14b Hydrophobic film 15 Transport electrode Substrate 16 Detection electrode 16 'Detection means 17 Fixed portion 18 Upper substrate 19 Piezoelectric film 20 Transport electrode IDT
26 Detection Device 31 Excitation Light 32 Fluorescence 161 Counter Electrode 162 Working Electrode 163 Reference Electrode 201 Small Electrode 202 Large Electrode SW1, SW2, SW3 Switch

Claims (20)

A sample detection chip for detecting a sample suspended in a solvent,
A transport substrate having transport electrodes for transporting the solvent droplets;
A counter substrate facing the transfer substrate;
A flow path formed between the substrate carrying substrate and the counter substrate through which the droplets pass;
Provided with a fixing portion provided in a part of the flow path, to which a ligand is fixed;
A sample detection chip, wherein the sample is detected by the liquid droplets staying in the fixed part. The transport electrode is a transport electrode for changing the wettability of the droplet,
The analyte detection chip according to claim 1, wherein the droplet is transported by changing the wettability of the droplet. The transport electrode is a transport electrode for generating surface waves,
The analyte detection chip according to claim 1, wherein the droplet is conveyed by the surface wave.   3. The sample detection chip according to claim 1, wherein a plurality of the transport electrodes are provided, and each area of the transport electrodes is larger than an area of the fixed portion. The flow path is at least partially covered with a hydrophobic membrane,
The analyte detection chip according to claim 1, wherein the fixing portion is not covered with the hydrophobic film. The sample detection chip further includes a droplet control means for controlling the amount of the droplet,
2. The droplet control unit controls the amount of the droplet so that an area where the droplet contacts the transfer substrate is larger than an area of the fixed portion. The sample detection chip according to claim 5.   A sample detection sensor comprising: the sample detection chip according to any one of claims 1 to 6; and a detection unit that optically detects the sample.   A sample detection sensor comprising: the sample detection chip according to claim 1; and at least one detection electrode for electrically detecting the sample. The flow path is at least partially covered with a hydrophobic membrane,
The sample detection sensor according to claim 8, wherein the fixed portion and the detection electrode are not covered with a hydrophobic film.   10. The sample detection sensor according to claim 8, wherein a plurality of the transport electrodes are provided, and each area of the transport electrodes is larger than an area of the detection electrode and the fixing portion. . The sample detection chip according to claim 6,
The droplet control means arranged on the sample detection chip controls the amount of the droplet so that an area where the droplet contacts the transport substrate is larger than an area of the detection electrode and the fixed portion. 9. The specimen detection sensor according to claim 8, wherein the sensor is for detecting a specimen. A step of electrically controlling a droplet of a solvent in which a specimen is suspended and transporting it in a flow path;
A step of causing the liquid droplet to stay in a fixing portion provided in a part of the flow path, where the ligand is fixed, and reacting the specimen with the ligand;
A sample detection method comprising a step of detecting the sample,
The flow path is formed between a transport substrate having a transport electrode for transporting the droplets of the solvent, and a counter substrate facing the transport substrate,
The specimen detection method, wherein the droplet is transported such that an area where the droplet contacts the transport substrate is larger than an area where the fixed portion faces the flow path.   The specimen detection method according to claim 12, comprising a step of controlling the amount of the droplet.   13. The specimen detection method according to claim 12, wherein in the transporting step, the droplet is transported by changing the wettability of the droplet.   13. The specimen detection method according to claim 12, wherein in the transporting step, the droplet is transported by a surface wave. The specimen is electrically detected using a detection electrode,
16. The liquid droplets are transported so that an area where the liquid droplets are in contact with the transport substrate is larger than an area of the fixed part and the detection electrode. 2. The specimen detection method according to 1.   The analyte detection method according to claim 16, wherein the detection electrode is formed of at least a working electrode and a reference electrode.   18. The specimen detection method according to claim 17, wherein the working electrode and the reference electrode are arranged so as to be in contact with the droplet simultaneously.   17. The specimen detection method according to 16, wherein the detection electrode is formed by a working electrode, a reference electrode, and a counter electrode.   The specimen detection method according to claim 19, wherein the working electrode, the reference electrode, and the counter electrode are arranged so as to be in contact with the droplet simultaneously.