JP2012058042A - Measurement device using element for detecting biological material and measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the number of viruses, bacteria, tissues which are measuring objects with high accuracy and high sensitivity by removing variation of background signals and individual difference.SOLUTION: An array having: a substrate; a plurality of working electrodes provided on the surface of the substrate; wiring connected to each of the plurality of electrodes and provided on the opposite side of the surface of the substrate; and a probe which captures the measuring objects on the working electrodes is used, reference solution containing a reagent which emits light by an oxidation-reduction reaction is brought into contact on the array, each connection between counter electrodes and the wiring is controlled, voltage is applied between the working electrodes and the counter electrodes, and presence/absence of the measuring objects captured by the probe is measured based on variation and difference of light intensity by introduction of a measurement sample.

Description

The present invention relates to a measuring apparatus and a measuring method capable of measuring a biological material with high accuracy and high sensitivity by performing electrical and optical measurements.

  Immunological techniques represented by antigen-antibody reaction are widely known as methods for detecting biological materials such as viruses and bacteria. For example, in recent years, detection kits based on immunochromatography and fine particle aggregation have become widespread for the purpose of simple inspection of whether or not a virus or bacteria are involved (for example, Patent Document 1). These kits are composed of a sample introduction part, a part holding a labeling antibody, and a test part for antigen detection. As the labeling substance, fine metal particles that develop color by aggregation are used. When the sample is introduced, the labeling antibody is developed together with the sample, and when the detection target is present in the sample, the labeling antibody is bound via the detection target in the test unit. At this time, coloration occurs in the test part due to the aggregation of the labeling substance, and the presence or absence of the detection target in the sample is determined from the presence or absence of the coloration. Since the operation is simple and the implementation time is a few minutes to several tens of minutes, and it can be visually judged, it is suitable as a simple inspection.

  Immunoassays are widely used as a more sensitive method for detecting biological substances using antigen-antibody reactions. Immunoassays are roughly classified into two types: detection using a labeling antibody that can be detected by an optical method, and environmental changes caused by the binding between a normal immobilized antibody and a detection target without using a labeling substance. It can be divided into methods. The former includes Enzyme-Linked ImmunoSorbent Assay (ELISA) method (for example, Non-Patent Document 1), Luminescent Oxygen Channeling Immunoassay (LOCI) method (for example, Patent Document 2), and the like. On the other hand, the latter includes latex agglutination (for example, Patent Document 3), surface plasmon resonance (SPR) (for example, Patent Document 4), crystal oscillator microbalance method (QCM) (for example, Patent Document 5), capacitance measurement ( For example, Non-Patent Document 2), impedance measurement (for example, Patent Document 6), interface potential measurement (for example, Non-Patent Document 3), and the like are included.

  In the ELISA method, an object to be detected and a labeling antibody are injected onto a substrate on which an antibody is immobilized, and after the reaction for a certain time, washing is performed to remove the free labeling antibody. Thereafter, the labeled enzyme remaining on the substrate surface is reacted with the substrate, the amount of the reaction product is optically measured, and the concentration of the detection target is obtained. In the LOCI method, microparticles A and B each having different antibodies that recognize different parts of the detection target are used. When the detection object and the fine particles A and B are mixed, the fine particles A and B are bonded via the detection object. The antibody immobilized on the microparticles A and B is modified with a labeling substance that emits light only when present in the vicinity, so that the target to be detected can be obtained without removing the microparticles that are not bound to the target to be detected. The concentration can be determined.

  In the latex agglutination method, when an object to be detected is injected into a dispersion of latex particles to which an antibody is immobilized, the optical characteristics (latest wavelength, transmission wavelength) when latex particles grow into an aggregated cluster starting from the object to be detected. Measure changes in light intensity and scattered light intensity. SPR, QCM, capacitance measurement, impedance measurement, and interface potential measurement all detect a change in a physical quantity on the surface when an object to be detected is bound to an antibody immobilized on the sensor surface. SPR detects changes in plasma resonance angle due to changes in dielectric constant, QCM detects changes in resonance frequency due to changes in mass, and capacitance, impedance, and interface potential measurements detect changes in capacitance, impedance, and interface potential, respectively. Yes.

  In addition, for the purpose of detecting one biomolecule, a technique called single molecule imaging combining a fluorescent label and a microscope has been rapidly developed in recent years (for example, Non-Patent Document 4). In single-molecule imaging, in order to perform high-sensitivity measurement, background signals are reduced and single molecules are detected by using evanescent light whose penetration depth is about half the wavelength of light.

  As a method aimed at detecting another biomolecule, a method for detecting a single biological substance by combining a plurality of microelectrodes, a field effect transistor (FET), and a charge coupled device (CCD) has been reported. (For example, Patent Document 7). In this method, a change in charge due to the binding of the detection target to the antibody immobilized on the electrode surface is detected, and it is determined that there is one biological substance when the amount of change in charge at this time exceeds a certain threshold value. The biological material is detected by performing the above.

JP-A-1-32169 EP0515194A US4250394 US4997278 US6006589 US7192752 US7022287

Immunochemistry, 1971, 8, 871-874. Anal. Chem., 1997, 69, 3651-3657. Analyst, 2002, 127, 1137-151. Nature, 1996, 380, 451-453.

In the prior art, viruses, bacteria, and cells could not be quantified in single units.
In the immunochromatography or latex agglutination method using fine particle aggregation, a change in optical properties occurs only when a plurality of fine particles are aggregated. Therefore, in principle, it was difficult to measure a single biological substance.

  In the conventional immunoassay, it was difficult to detect by one unit due to the influence of the background signal. For example, in an ELISA method using a labeling antibody, a labeling antibody that could not be removed by the washing step generates a background signal. The same applies to the LOCI method. On the other hand, for the method (SPR, QCM, capacitance measurement, impedance measurement, interface potential measurement) for detecting changes in the physical quantity of the sensor surface due to the binding of biological substances, non-specific adsorption of substances (contaminants) other than the detection target is not possible. It becomes a background signal source. In these methods, the concentration of the detection target is obtained from the correlation between the concentration of the detection target determined experimentally and the signal signal value. However, when the concentration of the detection target becomes small, the background to the signal signal value is obtained. Since the signal value ratio becomes so large that it cannot be ignored, detection in units of one is difficult. Even in the method of combining a plurality of microelectrodes with charge change, it can be said that there is a similar problem because adsorption of a foreign substance that causes charge change becomes a background signal.

  In single-molecule imaging, detection can be performed in units of one biological substance, but it does not have position resolution below the wavelength of light and is difficult to integrate below the wavelength of light. Also, since the illumination area is very small, it takes a long time to scan the entire substrate. For the above reasons, it is difficult to quantify thousands to tens of thousands of biological substances by single-molecule imaging. Moreover, since the size information is not included in the obtained information, size selectivity cannot be provided.

  The present invention provides a measuring device and a measuring method for measuring and quantifying a biological substance in units of one.

  As typical embodiments of the present invention, a substrate, a plurality of working electrodes provided on the surface of the substrate, a wiring connected to each of the plurality of electrodes and provided on the side opposite to the surface of the substrate, and a working electrode An array having a probe for capturing a measurement target, a solution contact means for contacting a reference solution containing a reagent that emits light by an oxidation-reduction reaction on the array, a counter electrode provided to contact the reference solution, By controlling the connection of each wiring, the voltage control means for controlling the voltage between the working electrode and the counter electrode, the photodetector for detecting the light from the array, and the sample contact with the solution contact means, And a calculation unit that measures the presence or absence of a measurement target captured by a probe based on measurement of light intensity detected by a photodetector.

  In addition, as a measurement method, a step of introducing a reference solution onto the above-described array, a step of introducing a sample solution onto the array, and a step of controlling the electrical connection of each of the plurality of working electrodes were connected. When the sample solution is introduced for the step of controlling the voltage application between the working electrode and the counter electrode in contact with the reference solution, the step of detecting light from the array by a photodetector, and the array into which the reference solution is introduced And a step of measuring the presence or absence of the measurement target captured by the probe based on the measurement of the light intensity when not introduced.

  Then, for each of the plurality of working electrodes, the number of captured measurement objects is counted, and the number of measurement objects in the sample is measured and quantified.

  For detection of the presence or absence of the captured measurement target, for the array into which the reference solution was introduced, a method for determining whether the change in light intensity after the introduction of the sample solution exceeded the threshold or a reference solution was introduced. For the array, a method of determining whether or not the difference in light intensity between when the sample solution is introduced and when the sample solution is not introduced exceeds a threshold value can be used.

  Alternatively, the voltage application start time to the working electrode may be synchronized with the measurement start time at the light receiving element.

  With the above-described configuration, it is possible to determine the presence / absence of one unit of the detection target by measuring the emission intensity. And the influence which the background signal which became a problem conventionally has on a measured value can be suppressed. Further, by determining the presence / absence of the detection target object, it is possible to suppress the influence of the variation in the signal change caused by the individual difference of the detection target, which has been a problem as in the past. Furthermore, by summing up the number of electrodes determined to have a detection target, the amount of detection target in the sample can be obtained. Thereby, a detection target can be quantified without using a labeling substance. In addition, by measuring the start time of voltage application to the working electrode in synchronization with the measurement start time at the light receiving element, the distance between the adjacent working electrodes can be measured individually even if it is below the position resolution of the optical microscope. Working electrodes can be distinguished.

  As described above, since the background signal and variations in individual differences can be removed for each working electrode as described above, measurement with higher accuracy and higher sensitivity than before can be performed.

The conceptual diagram which shows an example of a measuring device. An example of the flowchart of a measuring method. The conceptual diagram which shows an example of a measuring device. An example of the flowchart of a measuring method. The conceptual diagram which shows an example of the measurement cell of FIG. The conceptual diagram which shows an example of the measurement cell of FIG. The conceptual diagram which shows an example of the measurement cell of FIG. The conceptual diagram which shows an example of the measurement cell of FIG. An example of the flowchart of a measuring method. An overhead view showing an example of the element Sectional view showing an example of element The conceptual diagram at the time of fixing a probe to a working electrode. The conceptual diagram when a detection target couple | bonds with a working electrode. Sectional drawing which shows an example of an element. Figure showing the luminescence intensity of a working electrode in chronological order Sectional drawing which shows an example of the working electrode used for an element. The conceptual diagram at the time of fixing a probe to a working electrode in an example of the working electrode used for an element. The conceptual diagram when a detection target couple | bonds with a working electrode in an example of the working electrode used for an element. Sectional drawing which shows an example of the working electrode used for an element. Sectional drawing which shows an example of the working electrode used for an element. Sectional drawing which shows an example of the working electrode used for an element. The conceptual diagram at the time of fixing a probe to a working electrode in an example of the working electrode used for an element. The conceptual diagram when a detection target couple | bonds with a working electrode in an example of the working electrode used for an element. Sectional drawing which shows an example of the working electrode used for an element. Sectional drawing which shows an example of the working electrode used for an element. The figure which shows the relationship between the diameter of a working electrode, and the light emission intensity decreasing rate by the coupling | bonding of a detection target. The figure which shows the relationship between the diameter of a working electrode, and the light emission intensity decreasing rate by the coupling | bonding of a detection target when changing the height of the wall around a working electrode. The figure which shows the relationship between the diameter of a working electrode, and the light emission intensity decreasing rate by the coupling | bonding of a detection target when the ratio of the diameter of a working electrode and the diameter of a detection target is changed. The figure which shows the reaction pathway of typical electrochemiluminescence. The figure which shows the relationship between the dimensionless number (pi) in typical electrochemiluminescence, and the light emission intensity decreasing rate by the coupling | bonding of a detection target. The conceptual diagram which shows an example of an element whose adjacent working electrode space | interval is below the wavelength resolution of light. The figure which shows the relationship between the diameter of the working electrode calculated | required by experiment and calculation, and the light emission intensity decreasing rate by the coupling | bonding of a detection target, respectively. The bird's-eye view of the element which has 16 working electrodes used in experiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a conceptual diagram of an element and a measuring device using the element. This measuring apparatus includes a measuring unit 101 and a control unit 110. A reference solution 104 is placed in a container 103 formed on the element 102. The reference solution 104 contains a reagent that causes a redox reaction. As a reagent that causes this redox reaction, a reagent that emits light by electrical energy is used. A counter electrode 105 and a reference electrode 106 are arranged in the reference solution 104. Each working electrode of the element is connected to the input terminal of the multiplexer 107. Details of the element will be described later. The counter electrode 105 and the output terminal of the multiplexer 107 are connected to a potentiostat 108. The potentiostat 108 and the light receiving element 109 are connected to the control unit 110. The role of the multiplexer 107 is to connect at least one of the plurality of working electrodes on the element 102 to the potentiostat 108. The role of the potentiostat 108 is to impress a potential difference between at least one of the plurality of working electrodes on the element 102 and the counter electrode 105, and to detect photons generated on the working electrode with the light receiving element 109. As the control unit 110, for example, a personal computer (PC) as shown in FIG. 1 can be used. The PC includes a data processing device 111 and a data display device 115. The data processing device 111 includes, for example, an arithmetic device 112, a temporary storage device 113, and a nonvolatile storage device 114.

  FIG. 2 is an example of a flowchart of the measurement method. This will be described in conjunction with FIG. First, the reference solution 104 is injected into the container 103. Subsequently, light emission on each working electrode is measured by the potentiostat 108 and the light receiving element 109 while switching the connection between the input terminal and the output terminal by the multiplexer 107, and the respective light emission intensities are recorded. Thereby, the emission intensity is measured for all working electrodes on the element 102.

  Next, the sample solution is injected into the container 103. The sample solution refers to, for example, a biological sample such as a subject's blood, saliva, urine, or a solution obtained by adjusting them. It waits for a fixed time until the detection target in the sample solution is bound to the probe immobilized on the working electrode of the element 102. Subsequently, while switching the connection between the input terminal and the output terminal by the multiplexer 107, the light emission intensity is measured by the potentiostat 108 and the light receiving element 109, and each light emission intensity is recorded. Compared with the emission intensity measured before the sample solution injection, if the change in emission intensity is greater than the threshold, the counter is incremented. Thus, the presence or absence of binding of the detection target for each working electrode on the element 102 is determined, and the number of detection targets coupled on all the working electrodes on the element 102 is counted. Finally, the counter value, that is, the number of detection targets coupled on all the working electrodes on the element 102 is output.

  As a means for generating photons on the working electrode, a means for transferring electric energy from the working electrode to a reagent that causes a redox reaction may be used. An example of such means is electrochemiluminescence. Examples of the reagent necessary for electrochemiluminescence include tri (bipyridyl) ruthenium or a derivative thereof. Examples of the working electrode material necessary for electrochemiluminescence include gold, platinum, glassy carbon, and boron-doped diamond.

  Other means for generating photons include light emission using singlet oxygen. Since singlet oxygen has a very strong oxidizing power, for example, an olefin compound has a feature that it emits light when oxidized, a light emitting system can be constructed by combining singlet oxygen and such a substance. An electrode necessary for generating singlet oxygen includes a semiconductor electrode such as titanium oxide.

  As a procedure for measuring the photons generated on the working electrodes, the time for applying the voltage to each working electrode and the time for measuring the photons by the light receiving element may be synchronized. For example, after applying a voltage to one working electrode, measurement is started with the light receiving element from the time when the current value has reached a steady state, and after a certain period of time, voltage application and measurement are terminated, and the same applies to the next working electrode. There is a method to repeat the operation. By measuring in this way, light emission at each working electrode can be reliably measured in units of one electrode, and when a detection target is captured on the electrode surface, a stable change in light emission intensity can be measured. it can.

  By counting the detection target on the working electrode using the threshold value, the measurement accuracy can be improved as compared with the conventional method of measuring the amount of the detection target with one working electrode. Factors that change the emission intensity include disturbances such as non-specific adsorption of contaminants and temperature changes in addition to the binding of the detection target. In the conventional method of measuring the amount of detection target with one electrode, these disturbances reduce the measurement accuracy, but when the detection target on the working electrode is counted using a threshold, the disturbance is less than the threshold. Does not affect the count value. Therefore, by counting the detection target on the working electrode using the threshold value, the influence of disturbance can be suppressed and the measurement accuracy can be improved.

  The probe provided on the working electrode may be any substance having the ability to selectively capture the detection target. Examples of such substances include antibodies, virus recognition sites, receptors and the like having biological affinity. Another example is a positively or negatively charged substance that can bind to an object to be detected by electrostatic interaction. Another example includes an active ester group, a thiol group, and an amine group, which are functional groups that form a coordinate bond or a covalent bond with a specific functional group.

  FIG. 3 is another conceptual diagram of the measuring device. As shown in FIG. 3A, this measurement apparatus includes a measurement unit 301 and a control unit 311. In the measurement unit 301, the reference solution in the reference solution container 302 passes through the flow path 304 by the pump 303 and reaches the waste liquid container 308 through the measurement cell 307. A valve 306 is provided on the flow path 304, and the sample solution is injected into the measurement solution in the flow path by the syringe 305.

  FIG. 3B is a detailed view of the measurement cell 307, and the channel 312 is in contact with the element 313. Each working electrode on the element 313 is connected to the input terminal of the multiplexer 314. In this example, the counter electrode 315 and the reference electrode 316 are also mounted on the element 313 and are in contact with the flow path 312. The output terminal of the multiplexer 314, the counter electrode 315, and the reference electrode 316 are connected to the potentiostat 309. The role of the multiplexer 314 is to connect one of the plurality of working electrodes on the element 313 to the potentiostat 309. The role of the potentiostat 309 is to impress a potential difference between one of the plurality of working electrodes on the element 313 and the counter electrode 315, and to detect photons generated at the working electrode by the light receiving element 310.

  FIG. 4 is an example of a flowchart of a measuring method using the measuring device according to the present invention. This will be described in conjunction with FIG. First, the reference solution in the reference solution container 302 is caused to flow through the channel 304 using the pump 303. Subsequently, while switching the connection between the input terminal and the output terminal by the multiplexer 314, the light emission is measured by the potentiostat 309 and the light receiving element 310, and the respective light emission intensities are recorded. Thereby, the emission intensity is measured for all working electrodes on the element 313.

  Next, a sample solution is injected into the channel 304 and reacted in the measurement cell 307. Subsequently, while switching the connection between the input terminal and the output terminal by the multiplexer 314, the light emission is measured by the potentiostat 309 and the light receiving element 310, and the respective light emission intensities are recorded. Compared with the emission intensity measured before the sample solution injection, if the change in emission intensity is greater than the threshold, the counter is incremented. As a result, the presence or absence of binding of the detection target for each working electrode on the element 313 is determined, and the number of detection targets coupled on all the working electrodes on the element 313 is counted. Finally, the value of the counter, that is, the number of detection targets coupled on all the working electrodes on the element 313 is output.

  In the above example, the change in emission intensity of the same working electrode was examined. However, the working electrode group for reference and the working electrode group for detection were prepared on the same or different elements, and the working electrode group for reference and the detecting electrode group were detected. You may investigate the difference in the luminescence intensity of the working electrode group. In the comparison, a comparison may be made by using a plurality of the same number of working electrodes arranged at the same interval, and a working electrode for reference is identified and the identified working electrode for reference is identified. The emission of each of the detection working electrode groups may be compared.

  FIG. 5 is an overhead view showing another configuration example of the measurement cell 307 in FIG. A flow path 501 on the solution introduction side is connected to a flow path switchable valve 502, and the valve 502 is connected to a reference flow path 503 and a detection flow path 504. An element 507 facing a plurality of working electrodes is in contact with the reference channel and the detection channel, and a valve 505 that can switch the channel again is provided at the end of each channel. 506 is connected. With these valves 502 and 505, the reference solution can flow in both the reference channel 503 and the detection channel 504, and the measurement sample can flow only in the detection channel 504. Further, as shown in FIG. 5A, the arrangement of the working electrode may be the same between the element 507 facing the reference channel 503 and the element 507 facing the detection channel 504, or FIG. ), The working electrode of the reference channel 503 may be reduced to take a representative value. Further, as shown in FIGS. 5C and 5D, the element 507 may be provided separately.

  FIG. 6 is an example of a flowchart of a measuring method using the measuring device according to the present invention. This will be described in conjunction with FIG. 3 and FIG. First, the reference solution is caused to flow through the flow path 501 in the measurement cell 307. Here, the reference solution is allowed to flow through the reference channel 503 and the detection channel 504 to the channel 506. Subsequently, the switching valve 502 is switched to the detection channel side, the sample solution is caused to flow into the detection channel 504 using the syringe 305 and the pump 303, and the reaction is performed in the detection channel 504. While switching the connection between the input terminal and the output terminal by the multiplexer 314, the light emission is measured by the potentiostat 309 and the light receiving element 310, and the respective light emission intensities are recorded. Thereby, the emission intensity is measured for all working electrodes on the element 507. The emission intensity of the working electrode in the reference channel and the emission intensity in the detection channel are compared, and if the difference in emission intensity is greater than the threshold, the counter is incremented. As a result, the presence or absence of binding of the detection target for each working electrode in the detection flow path on the element 507 is determined, and the detection target combined on all the working electrodes in the detection flow path of the element 507 is determined. Count the number. Finally, the value of the counter, that is, the number of detection targets coupled on all the working electrodes on the element 507 is output. Here, the reference solution is filled in the flow path here, but if a biological sample such as blood, saliva, urine or the like diluted with the reference solution is used as the sample solution, the detection flow path is used. It is possible to omit the step of filling the reference solution with the above. Further, here, the reference channel 503 and the detection channel 504 are branched from the channel 501, but as shown in FIGS. 5E, 5F, 5G, and 5H. The flow path may be divided from the beginning. In this case, the measurement of light emission in the reference channel and the measurement of light emission in the detection channel can be performed in parallel, and the measurement time can be shortened.

  In the measurement flows of FIGS. 2, 4, and 6, it is desirable that the amount of the reference solution and the sample solution to be placed in the container or the flow path be a predetermined fixed amount. By doing in this way, it is possible to compare the detection target concentrations among a plurality of sample solutions and to obtain the absolute value of the detection target concentration. If the detection target concentration of the sample solution is high, it may be bound to almost all of the working electrodes. In that case, since the concentration cannot be estimated correctly, it becomes possible to correctly measure by reducing or diluting the amount of the sample solution. Note that the change in the value of the current flowing through the electrode may be examined instead of the change in the emission intensity.

In order to quickly replace a used element with a new element after measurement of the sample solution, it is desirable that the element be replaced as a single chip. At this time, in order to improve the convenience of circuit wiring, it is conceivable to combine an element and a multiplexer into one chip. In this way, if the element is a single chip, not only can the replacement be speeded up, but for example, if various types of probes are prepared on the working electrode, multiple items can be obtained by simply replacing the chip. It becomes possible to measure.
In the above example, the light-receiving element and the plurality of working electrodes on the element are made to correspond one-to-one with the multiplexer, and light emission is measured one by one. However, a plurality of light-receiving elements such as a CCD and a photodiode array are used. A plurality of light emission may be simultaneously measured using a device having For example, when a photomultiplier tube is used as the light receiving element, since only one light receiving element is used and processing is performed sequentially for each working electrode, the total processing time is (number of working electrodes) × (working electrode). Total processing time per electrode). For example, when a CCD or photodiode array is used as a light receiving element, since there are a plurality of light receiving elements, if a plurality of working electrodes corresponding to each light receiving element are simultaneously generated and measured, the total processing time is (Number of working electrodes corresponding to one light receiving element) × (total processing time per time). Therefore, since the number of working electrodes and the processing time are in a trade-off relationship, the light receiving element may be selected so that the total processing time is shortened depending on the case.

  In addition, the example in which the presence / absence of the detection target on the working electrode is determined using the threshold value of the emission intensity change or the difference of the emission intensity has been described. it can. For example, the time during which the substance on the working electrode has been captured can be obtained by arranging the emission intensities of one working electrode in chronological order as shown in FIG. Since the probe provided on the working electrode specifically binds to the detection target, the time during which the detection target is captured is longer than when the contaminants are captured by adsorption. Therefore, the determination accuracy can be improved by determining whether the captured substance is a detection target or a foreign substance from the substance capture time.

  If beads or liposomes are used as labels, this method is also effective for detecting proteins. A probe that binds to the detection target is selected as a probe that is immobilized on the working electrode or another probe that is immobilized on a bead or liposome. In this way, since beads and liposomes are immobilized on the working electrode via the detection target, a substance smaller than the working electrode can also be detected. Although the detection target cannot be counted in units of one, the so-called homogeneous assay becomes possible because nonspecific adsorption of the label can be suppressed and the label released in the solution is difficult to detect as a signal.

  The element will be described below. 7 to 10 are views showing an example of the element according to the present invention. FIG. 7 is an overhead view of a part of the element. A plurality of working electrodes 702 are provided on the substrate 701, and wirings 703 are connected to the individual working electrodes 702. When the working electrode is embedded in the substrate as shown in FIG. 1, there are few obstacles for the detection target to be coupled. FIG. 8 shows a cross-sectional view of the working electrode of FIG. The substrate 801 is provided with a working electrode 802, and a wiring 803 is connected to the working electrode 802.

  FIG. 9 shows a conceptual diagram when the working electrode of FIG. 8 is provided with a probe. A working electrode 902 is provided on the substrate 901, a wiring 903 is connected to the working electrode 902, and a probe 904 is provided on the working electrode 902. The probe 904 is preferably a substance capable of selectively capturing a detection target, such as an antibody, a receptor, a virus recognition site, a positively or negatively charged substance, or the like. Immobilization of the probe 904 on the working electrode 902 may be physical adsorption or chemical bonding. In addition, the same type of probe may be mounted on the plurality of electrodes, but depending on the measurement conditions, different types of probes may be fixed on the electrode by determining the range to be fixed or mixed. Good. It is desirable that the substrate 901 is modified with a substance that suppresses nonspecific adsorption, such as polyethylene glycol, in order to suppress erroneous detection due to nonspecific adsorption of impurities.

FIG. 10 is a conceptual diagram when a detection target is coupled to a working electrode provided with the probe of FIG. A working electrode 1002 is provided on the substrate 1001, a wiring 1003 is connected to the working electrode 1002, a probe 1004 is provided on the working electrode 1002, and one detection object 1005 is coupled to the probe 1004. An insulator such as SiO ₂ or Si ₃ N ₄ is used for the substrate. Although it is desirable to use gold, platinum, silver, copper or carbon for the working electrode, titanium, aluminum, chromium or the like can also be used depending on the required durability. A conductor is used for the wiring. The working electrode and the wiring may be connected by, for example, forming the working electrode after forming the wiring by using a semiconductor manufacturing process. The diameter of the wiring does not have to be smaller than the diameter of the working electrode as shown in FIG. 7, for example, the working electrode and the wiring have the same diameter (FIG. 11A), or the wiring is thicker than the diameter of the working electrode. (FIG. 11B), and the effect of the present invention can be obtained by coupling the portion exposed on the substrate surface with the detection target. The size of the working electrode may be any size that can be paired with the detection target. And by making the diameter of a working electrode into about 2 times or less of the diameter of a detection target, it can prevent that two or more detection targets couple | bond with a working electrode. On the other hand, by setting the diameter of the working electrode to be more than half of the diameter of the detection target, the change in light emission that occurs when a substance smaller than the detection target is non-specifically bound to the working electrode is reduced. Selectivity was improved.

  The detection target is a virus, bacteria, cell, or the like. Table 1 shows the approximate sizes of viruses, bacteria, and cells.

  Accordingly, the size of the working electrode is about 5 to 200 nm for viruses, about 150 nm to 16 μm for bacteria, and about 5 to 20 μm for cells according to the detection target.

  13 to 22 are conceptual diagrams showing other examples of the working electrode provided in the element. The substrate 1301 has a portion dug down by one step, and a working electrode 1302 is provided on the bottom of the dug down portion. A wiring 1303 is connected to the working electrode 1303, and a wall 1304 exists around the working electrode 1302. FIG. 14 shows a state in which the probe is immobilized on the working electrode in FIG. 13, and FIG. 15 shows a state in which the detection target is bound to the probe in FIG. FIG. 16 shows a shape in which the wall of FIG. 13 protrudes to a part of the working electrode. When the wall covers a part of the working electrode in this way, in this embodiment, the portion where the working electrode is exposed can be regarded as an effective working electrode. Therefore, since the effective size of the working electrode can be controlled by the size of the opening of the wall without reducing the size of the entire working electrode, a part of the manufacturing process is made common. It becomes possible. It is also effective when it is difficult to reduce the size of the working electrode. FIG. 17 shows an example of a shape in which the wall exists only in the vicinity of the working electrode. FIG. 18 shows an example in which the working electrode has a concave shape. FIG. 19 shows a shape in which the probe is fixed to the concave working electrode of FIG. 18, and FIG. 20 shows a state in which the detection target is bound to the probe of FIG. Here, in order to ensure that only one detection object can be combined, it is desirable that the opening diameter of the wall is not more than twice that of the detection object.

  21 and 22 show another form of FIG. 13 and FIG. Even if the wall is tapered as shown in FIG. 21, the effect of diffusion inhibition by the wall obtained in FIG. 13 can be obtained. Further, even if the working electrode is rounded and recessed as shown in FIG. 22, the effect of the concave electrode obtained in FIG. 18 can be obtained.

  In the following, the effects of taking each configuration will be described.

FIG. 23 shows the result of numerical analysis using the finite element method for the relationship between the size of the working electrode and the rate of change of the emission intensity when the state of FIG. 9 changes to the state of FIG. The working electrode is a disk having a diameter of 0.2, 1, 2, 5, 10, 25, 50, 100 μm, the detection target is a sphere having the same diameter as the working electrode, and the working electrode and the detection target are in contact. . Electrochemiluminescence is used for the light-emitting system, and typical conditions for electrochemiluminescence include tris (2,2'-bipyridyl) ruthenium (Ru (bpy) ₃ ²⁺ ) 5 mM (diffusion coefficient 590 μm ² / s), Employing tripropylamine 100 mM, applied voltage 1.2 V (reaction rate of electrode reaction 10,000 μm / s), calculating the emission intensity in the steady state, and determining the amount of change in emission intensity depending on the presence or absence of the detection target on the working electrode surface It was. As shown in FIG. 23, the emission intensity decreased due to the presence of the detection target on the surface of the working electrode, and the rate of decrease was substantially constant regardless of the diameter of the working electrode.

  FIG. 24 shows the difference in the amount of change in emission intensity depending on the presence or absence of a detection target on the surface of the working electrode when the height of the wall around the working electrode as shown in FIG. 13 is changed. The same light emitting system as that shown in FIG. 23 was used. The working electrode was a disk having a diameter of 0.2, 1, 2, 10, 20 μm, the detection target was a sphere having the same diameter as the working electrode, and the working electrode and the detection target were in contact. The detection target on the surface of the working electrode when the wall opening diameter is the same as that of the working electrode and the height of the wall is changed to 1/4, 1/2, 3/4 with respect to the radius of the detection target The amount of change in the emission intensity due to the presence or absence of was determined numerically by the finite element method in the same manner as in FIG. From FIG. 24, the decreasing rate of the emission intensity increased as the wall height increased. This is presumably because the increase in the wall height hinders the supply of reagents that cause redox to the working electrode surface. Thus, by providing a wall around each working electrode, it is possible to increase the amount of change in light emission intensity due to the presence or absence of a detection target in the vicinity of the working electrode.

  FIG. 25 shows the difference in the amount of change in emission intensity depending on the presence or absence of the detection target on the surface of the working electrode when the ratio of the diameter of the detection target to the diameter of the working electrode changes. The same light emitting system as that shown in FIG. 23 was used. The working electrode is a disk having a diameter of 0.2, 1, 2, 10, 20 μm, the detection target is a sphere, and the diameter is changed to 1, 2, 5 times the diameter of the working electrode. The amount of change in the light emission intensity depending on the presence or absence of the detection target on the surface was obtained numerically by the finite element method in the same manner as in FIG. As shown in FIG. 25, the decrease rate of the emission intensity increases as the size of the detection target with respect to the working electrode increases. This is presumably because the increase in the size of the detection target hinders the supply of a reagent that causes a redox reaction to the working electrode surface. Accordingly, if the diameter of the working electrode is made smaller than the diameter of the detection target, the determination threshold can be set higher, and therefore the selectivity can be further improved in combination with the effect of improving the selectivity by the excluded volume effect. . In addition, when determining the presence or absence of detection, an upper limit and a lower limit of the emission intensity reduction rate calculated from the information on the working electrode obtained in advance and the size of the detection target are determined, and within that range There is also a method for determining that a detection target exists if an actual measurement value is entered. By determining the determination range in this way, it is possible to suppress erroneous determination due to a foreign object larger than the detection target that is rarely non-specifically adsorbed to the working electrode.

  Hereinafter, the phenomenon shown in FIGS. 23 to 25 will be described. Here, attention is focused on electrochemiluminescence as a luminescent system, but the same argument applies to other luminescent systems via redox reactions. FIG. 26 shows a typical reaction path in electrochemiluminescence. A represents an electrochemiluminescence reagent, C represents a catalyst in an electrochemiluminescence reaction, and P represents a photon. Electrochemiluminescence occurs when the electrochemiluminescent reagent is excited by receiving electrical energy from the working electrode and releases the energy as photons in the process of returning to the ground state. In general, the reaction rate of receiving an electron from an electrode (electrode reaction) is the slowest in a series of electrochemical reactions, so that the electrochemical reaction is electrode reaction rate limiting ((1) in FIG. 26 is electrode reaction). .

  In addition, as can be seen from the reaction path of FIG. 26, the electrochemiluminescence intensity depends on the time change of the concentration of the electrochemiluminescence reagent in the electrode reaction, that is, the current value, and is proportional to the current value in the steady state. Therefore, investigating the behavior of the electrochemiluminescence intensity is equivalent to examining the behavior of the current value in the electrode reaction. Here, an electrochemical reaction via a catalyst has been exemplified, but the same argument applies to an electrochemiluminescence reaction not via a catalyst (for example, a reaction via an anion and cation anion). When the concentration of the electrochemiluminescent reagent is C, the rate of the electrode reaction is k, and the diffusion coefficient of the electrochemiluminescent reagent is D, the electrode reaction in the steady state is expressed by the following equation (1).

There are four independent variables that govern the behavior of the system, C (mol / m ³ ), k (m / s), D (m ² / s), and electrode radius d (m). From the π theorem, the dimensionless number π, which is an indicator of the electrode reaction behavior, can be derived as π = (D / k) / d. This dimensionless number π is qualitatively understood as follows. (D / k) has a dimension of length and represents how much the supply rate of the electrochemiluminescence reagent is with respect to the rate at which the electrochemical reagent is consumed in the electrode reaction. Therefore, if the ratio is normalized by taking the ratio of d to (D / k), it can be evaluated from the dimensionless number π whether the electrode reaction is electrode reaction rate limited or diffusion supply limited under certain conditions. it can.

  FIG. 27 is a diagram showing the change rate of the light emission intensity when changing from the state of FIG. 9 to the state of FIG. 10 using a dimensionless number π. When the dimensionless number π is sufficiently large, the diffusion rate is sufficiently high, so that the electrochemiluminescent reagent is sufficiently spread on the electrode surface, and the current value does not change depending on the presence or absence of the detection target on the electrode surface. On the other hand, when the dimensionless number π is sufficiently small, the reaction rate is sufficiently fast, so if there is a detection target on the electrode surface, the electrochemiluminescent reagent is consumed before reaching the gap between the working electrode and the detection target. The current value decreases. Since this reduction rate is an excluded volume effect depending on the detection target, it takes a constant value in a region where the dimensionless number is sufficiently small. 23 and 25, the reason why the reduction rate is almost constant regardless of the diameter of the electrode is that the value of the dimensionless number π is in the range of 0.001 to 0.5 in the diffusion supply rate limiting region. From the above discussion, it is considered that one of the reasons why the emission intensity decreased due to the presence of the detection target on the electrode surface is due to the diffusion inhibition of the reagent that causes the redox reaction by the detection target.

  When considering the accuracy of detection of the presence or absence of a detection target, the larger the reduction rate threshold, the better. In the case of the electrode provided with the wall shown in FIGS. 13 to 17, since the effect of the diffusion inhibition due to the presence of the detection target is amplified by the wall as shown in FIG. 24, the threshold of the reduction rate is set higher than that of the plate electrode. It can be set, and the detection accuracy can be improved.

  Considering the measurement of the emission intensity, the larger the absolute value of the emission intensity, the easier the measurement becomes. Therefore, it is desirable that the absolute value of the emission intensity is large. In the case of the concave electrode shown in FIGS. 18 to 20, in addition to the amplification effect of the reduction rate due to the walls of FIGS. Can be easily.

  The absolute value of the emission intensity can also be increased by bringing the counter electrode closer to the working electrode. For example, if the counter electrode is arranged in parallel directly above the working electrode and the distance between the counter electrode and the working electrode is reduced, the current value increases and the emission intensity also increases. In order not to lose the amount of light at the counter electrode, an electrode material transparent to light emission is preferable, and for example, an indium tin oxide (ITO) electrode is desirable. The wall and the concave electrode also have an effect of improving the selectivity with respect to the detection target. In the case of a plate electrode, if a substance larger than the detection target is adsorbed non-specifically on the electrode surface, the emission intensity changes in the same manner as the detection target, which may cause erroneous detection. However, in the electrode having a wall or the concave electrode, a substance larger than the opening diameter of the wall or the concave electrode cannot approach the electrode surface, and the selectivity to the detection target can be improved.

  In order to detect the detection object with high efficiency, it is desirable that the number of working electrodes is larger in order to increase the coupling probability. Also, the larger the number of working electrodes, the better in order to detect a detection object in a high concentration range. In order to increase the number of working electrodes while keeping the size of the entire device constant, it is necessary to increase the integration of the working electrodes, that is, to reduce the distance between the working electrodes as shown in FIG. However, when this working electrode interval is less than the resolution of the optical microscope, the adjacent working electrodes are distinguished in the method of detecting each light by detecting each working electrode on the element at the same time and the conventional optical microscope. It becomes impossible to do. Therefore, there is a trade-off relationship between high integration of the working electrode, high detection efficiency, and detection upper limit of the detection target.

  A technique of detecting each working electrode by emitting light one by one using a multiplexer is a technique for solving this trade-off. In this way, for example, by applying a voltage to each working electrode one by one and synchronizing the applied time with the time for measuring with the light receiving element, one emission of each working electrode can be observed, and the working electrode spacing is light. It is possible to distinguish between adjacent working electrodes even if the wavelength is equal to or shorter than the wavelength. By combining this method with the electrode spacing below the resolution of the optical microscope, it becomes possible to improve the detection efficiency and detect the detection target in the high concentration range.

  In addition, the combination of this method and the electrode spacing below the resolution of the optical microscope has the effect that position information below the position resolution of the optical microscope can be acquired. Since the position resolution of the optical microscope is about half of the wavelength of light (0.3 to 0.5 μm), using an element having an electrode interval less than this wavelength and this method, position information less than the wavelength of the emitted light is obtained. be able to. For example, if a flat cell is to be detected using an electrode array having a working electrode of about 100 nm and an electrode interval of about 100 nm, the surface shape of the cell can be determined with a position resolution of about 100 nm. It can be acquired.

  By detecting a detection target using an element in which two or more types of different antibodies are immobilized on one element, it is possible to detect a plurality of types of detection targets at the same time. For example, a group of working electrodes having about 10,000 working electrodes with a diameter of 100 nm to which antibodies against influenza A virus are immobilized and about 100 nm with a working electrode having a diameter of 100 nm to which antibodies against influenza B virus are immobilized, for example, for each antibody. If a sample of a patient suspected of having influenza virus is measured using an element separately provided, it is possible to simultaneously determine the disease and type of the virus. The same effect can be obtained not only for viruses but also for bacteria and cells.

FIG. 29 shows the change rate of the emission intensity depending on the size of the working electrode and the presence or absence of the detection target coupled on the working electrode. Gold electrode with a diameter of 10, 25, 100 μm as working electrode, Tris (2,2′-bipyridyl) ruthenium (Ru (bpy) ₃ ²⁺ ) 5 mM, Tripropylamine 100 mM phosphate buffer solution as electrochemiluminescence reagent Was used. Electrochemiluminescence was caused under the condition of an applied voltage of 1.2 V using a platinum electrode as a counter electrode and a saturated potassium silver chloride silver chloride electrode as a reference electrode. As a model for detection, polystyrene beads of almost the same size as the working electrode were used. The measurement with the light receiving element was started after 5 seconds had elapsed from the voltage application, and the voltage application and measurement were terminated after 2 seconds had elapsed since the start of light reception. As a result, as shown in FIG. 29, the measured value (black circle) of the change rate of the emission intensity was in good agreement with the calculated value (white circle) by the finite element method. Therefore, it can be seen that the numerical analysis by the finite element method can reproduce the actual measurement well.

Experiments were performed using 16 nm 300 nm diameter gold electrodes with an electrode interval of 300 nm as shown in FIG. 30 and 300 nm beads as detection targets. Each working electrode is numbered 1-16 for convenience. Biotin was immobilized on the gold electrode surface by chemical bonding, and streptavidin was immobilized on the bead surface by chemical bonding. A 1 μL sample containing about 500 beads was dropped on the device and reacted for 10 minutes to capture the beads on the surface of the gold electrode. Then, it wash | cleaned by the phosphate buffer solution, the fluorescence observation with the optical microscope was measured in the phosphate buffer, and the electrochemiluminescence was measured in the solution containing an electrochemiluminescence reagent. As an electrochemiluminescence reagent, tris (2,2′-bipyridyl) ruthenium (Ru (bpy) ₃ ²⁺ ) 5 mM, tripropylamine 100 mM phosphate buffer solution was used. Electrochemiluminescence was caused under the condition of an applied voltage of 1.2 V using a platinum electrode as a counter electrode and a saturated potassium silver chloride silver chloride electrode as a reference electrode.

  The same operation is applied to all working electrodes at the same time, starting the measurement with the light receiving element after 1 second from the voltage application to each working electrode and terminating the voltage application and measurement after 2 seconds from the start of light reception. The method of going and measuring was used. Here, the threshold is set to 15%, and as a result of applying a voltage to all working electrodes simultaneously, it is not possible to obtain position information as to which working electrode emits light, and to determine whether beads are captured. I couldn't. On the other hand, as a result of setting the threshold value to 15% in the procedure of FIG. 2 and applying one voltage to each working electrode, it was possible to distinguish the light emission from each working electrode.

  As a result of detecting the presence / absence of beads from the change in emission intensity of each working electrode, it was possible to distinguish that five beads were captured (in terms of electrode numbers, 1, 7, 12, 13, 14). ). Therefore, even when the adjacent working electrodes are in the range below the position resolution of the optical microscope and the individual working electrodes cannot be distinguished by the conventional method, the time for applying the voltage to each working electrode and the light receiving element are different. It was possible to distinguish individual working electrodes by measuring the time to start the measurement synchronously.

101, 301 Measuring unit 102, 313, 507 Element 103 Container 104 Solution 105, 315 Counter electrode 106, 316 Reference electrode 107, 314 Multiplexer 108, 309 Potentiostat 109, 310 Light receiving element 110, 311 Control unit 111 Data processing device 112 Operation Device 113 Temporary storage device 114 Non-volatile storage device 115 Data display device 302 Reference solution container 303 Pump 304, 312 Flow path 305 Syringe 306 Valve 307 Measurement cell 308 Waste liquid container 501 Introduction side flow path 502 Switching valve 503 Reference flow path 504 Flow path for detection 505 Switching valve 506 Discharge side flow path 701, 801, 901, 1001, 1101, 1301, 1401, 1501, 1601, 1701, 1801, 1901, 2001, 2101, 2201 , 2801 substrate 702, 802, 902, 1002, 1102, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002, 2102, 2202, 2802 working electrode 703, 803, 903, 1003, 1103, 1303, 1403 1503, 1603, 1703, 1803, 1903, 2003, 2103, 2203, 2803 Wiring 904, 1004, 1405, 1505, 1904, 2004 Immobilized probe 1005, 1506, 2005 Detection object 1304, 1404, 1504, 1604, 1704, 1104 wall

Claims (18)

A substrate, a plurality of working electrodes provided on the surface of the substrate, a wiring connected to each of the plurality of electrodes and provided on the opposite side of the surface of the substrate, and a measurement object is captured on the working electrode An array having probes;
Solution contact means for bringing a reference solution containing a reagent that emits light by oxidation-reduction reaction into contact with the array;
A counter electrode provided in contact with the reference solution;
Voltage control means for controlling each connection of the wiring to control a voltage between the working electrode and the counter electrode;
A photodetector for detecting light from the array;
A calculation unit for contacting the sample solution with the solution contact unit and measuring the presence or absence of the measurement target captured by the probe based on measurement of light intensity detected by the photodetector. A measuring device.   The measurement apparatus according to claim 1, wherein the calculation unit counts the number of the measured objects to be measured.   The measurement device according to claim 1, wherein the calculation unit stores a threshold value of a light intensity change for determining whether or not the measurement target is captured.   The measuring apparatus according to claim 1, wherein the voltage control unit selects one of the plurality of working electrodes and applies a voltage.   The measurement apparatus according to claim 1, wherein the solution contact unit is a container that holds the array on a bottom surface and holds the reference solution.   The measuring apparatus according to claim 1, wherein the solution contact means is a flow path for flowing the reference solution.   The flow path includes a first flow path through which the measurement target flows and a second flow path through which the measurement target does not flow, and the calculation unit is in contact with the first flow path. The measurement apparatus according to claim 6, wherein the measurement target is measured based on a difference in intensity between the light from the array that is in contact with the light from the array that is in contact with the second flow path.   The measuring apparatus according to claim 1, further comprising a side wall on the substrate such that the working electrode is a bottom surface.   The measurement apparatus according to claim 1, wherein an interval between the plurality of working electrodes is smaller than a wavelength resolution of light.   The measurement apparatus according to claim 1, wherein the voltage control unit applies a voltage for a certain period of time, and the calculation unit measures the time when the light intensity changes to determine whether the measurement target is captured.   The measuring apparatus according to claim 1, wherein a size of the working electrode is a size that is paired with the measurement target.   The measuring apparatus according to claim 1, wherein the size of the working electrode is not less than half and not more than twice the size of the measurement target.   The measuring apparatus according to claim 1, wherein the measurement target is any one of a cell, a bacterium, a virus, a bead, a liposome, and a protein. A substrate, a plurality of working electrodes provided on the surface of the substrate, a wiring connected to each of the plurality of electrodes and provided on the opposite side of the surface of the substrate, and a measurement object is captured on the working electrode Introducing a reference solution containing a reagent that emits light by an oxidation-reduction reaction onto an array having probes;
Introducing a sample solution onto the array;
Controlling the electrical connection of each of the plurality of working electrodes;
Controlling voltage application between the connected working electrode and the counter electrode in contact with the reference solution;
Detecting light from the array with a photodetector;
Measuring the presence or absence of the measurement target captured by the probe based on the measurement of the light intensity when the sample solution is introduced and when the sample solution is not introduced for the array into which the reference solution is introduced. Characteristic measuring method. The measurement method according to claim 14, further comprising a step of measuring presence / absence of capture of the measurement object for each of the plurality of working electrodes and counting the number of captured measurement objects.   For the array into which the reference solution has been introduced, it is determined whether or not the change in light intensity after the introduction of the sample solution exceeds a threshold, and the presence or absence of the measurement target captured by the probe is measured. The measurement method according to claim 14.   The presence or absence of the measurement target captured by the probe is measured based on a difference in light intensity between the case where the sample solution is introduced and the case where the sample solution is not introduced for the array into which the reference solution is introduced. Item 15. The measuring method according to Item 14.   The measurement method according to claim 14, wherein the measurement is performed by synchronizing the timing of the voltage application step and the step of detecting by the photodetector.

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