Impedance measuring device and impedance measuring method

Abstract

To provide a technique that can measure the impedance of a biological specimen by using a multi-electrode array device.SOLUTION: An impedance measurement apparatus 1 comprises a measurement container 10, a plurality of first electrodes 31, a second electrode 33, a voltage application circuit 43, a current detection circuit 45, and a voltage detection circuit 47. The plurality of first electrodes 31 are arranged in array on a bottom face inside the measurement container 10. The second electrode 33 is located inside the measurement container 10. The voltage application circuit 43 applies voltage between each of the first electrodes 31 and the second electrode 33. The current detection circuit 45 detects a current flowing in each of the first electrodes 31. The voltage detection circuit 47 detects the voltage between each of the first electrodes 31 and the second electrode 33.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The subject matter disclosed in this specification relates to an impedance measurement device and an impedance measurement method.

Background Art

[0002] In the field of electrophysiology, analysis of the behavior of single or collective cell ion channels has been carried out. As ion channel analysis devices, for example, an intracellular action potential detection device using the patch clamp method and an extracellular action potential detection device using a multi-electrode array (MEA) device are known. The multi-electrode array device is disclosed, for example, in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in order to simply measure the morphological changes or cell density of cells, impedance measurement of a target biological sample (including cells and biological slices) may be performed. However, conventionally, multi-electrode array devices have only been used for detecting extracellular action potentials, and a technique for measuring the impedance of biological materials using multi-electrode array devices has not yet been established.

[0005] An object of the present invention is to provide a technique capable of measuring the impedance of biological materials using a multi-electrode array device.

Means for Solving the Problems

[0006] To solve the above problems, a first aspect is an impedance measurement device, comprisingThe liquid containing the object is placed. A measuring container, a plurality of first electrodes arranged in an array on the bottom surface inside the measuring container, a second electrode located inside the measuring container, and between each of the first electrodes and the second electrode exchange A voltage application circuit that applies a voltage; a current detection circuit that detects the current flowing through each of the first electrodes and outputs a voltage corresponding to the current; a voltage detection circuit that detects the voltage between each of the first electrodes and the second electrode; and a differential signal detection circuit that detects the difference between the AC voltage applied by the voltage application circuit and the voltage output by the current detection circuit. a calculation unit that calculates the impedance of the object based on the difference and the voltage detected by the voltage detection circuit. It is equipped with.

[0007] A second embodiment is an impedance measuring device according to the first embodiment, further comprising an electrode selection circuit that selects one first electrode from among the plurality of first electrodes to be connected to the current detection circuit.

[0009] A third aspect is an impedance measuring device according to the first or second aspect, The calculation unit described above, Based on the current detected by the current detection circuit and the voltage detected by the voltage detection circuit, The aforementioned object Calculate impedance ru.

[0010] The 4 The embodiment is an impedance measurement method, a) The liquid containing the object is placed. a) A step of applying an AC voltage between at least one of a plurality of first electrodes arranged in an array on the bottom surface of the measuring container and a second electrode located inside the measuring container; b) a step of detecting the current flowing through the first electrode while the AC voltage is applied in step a) and outputting a voltage corresponding to the current; c) a step of detecting the voltage between the first electrode and the second electrode while the AC voltage is applied in step a); d) a step of comparing the voltage output in step b) and the AC voltage applied in step a) difference The process of detecting, and e) The voltage detected by step c) and the voltage detected by step d) The aforementioned difference Based on, The aforementioned This includes the step of calculating the impedance of the object. [Effects of the Invention]

[0011] According to the impedance measurement device of the first aspect to the 3 According to the impedance measurement device of the aspect, the impedance of the object can be measured by the two-terminal method using the first electrodes arranged in an array. Furthermore, the impedance of an object can be calculated based on the phase difference between the AC voltage and the AC current.

[0012] According to the impedance measurement device of the second aspect, the impedance can be measured using one first electrode selected from among the plurality of first electrodes.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram schematically showing the configuration of the impedance measurement device according to the embodiment. [Figure 2] It is a perspective view showing the measurement container shown in FIG. 1. [Figure 3] It is a top view showing the measurement container shown in FIG. 1. [Figure 4] It is a diagram showing an equivalent circuit in the case of measuring impedance.

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the components described in this embodiment are merely examples, and are not intended to limit the scope of the present invention thereto. In the drawings, for ease of understanding, the dimensions and numbers of each part may be exaggerated or simplified as necessary.

[0016] <1. First Embodiment> FIG. 1 is a diagram schematically showing the configuration of an impedance measurement device 1 according to an embodiment. FIG. 2 is a perspective view showing the measurement container 10 shown in FIG. 1. FIG. 3 is a top view showing the measurement container 10 shown in FIG. 1. As shown in FIG. 1, the impedance measurement device 1 includes a measurement container 10 and a measurement unit 20.

[0017] The measurement container 10 is a container for measuring the impedance of the cells 9 which are the objects. A cell suspension containing the cells 9 is dropped inside the measurement container 10. As shown in FIGS. 2 and 3, the measurement container 10 has a bottom portion 11 and a side wall portion 13. The bottom portion 11 extends in a disc shape along the horizontal plane. The side wall portion 13 extends upward in a cylindrical shape from the peripheral edge of the bottom portion 11. The bottom portion 11 is an example of a "measurement plate". The upper surface of the bottom portion 11 is the bottom surface inside the measurement container 10 where the cell suspension is dropped. Note that the measurement target of the measurement container 10 is not limited to the cells 9, and may be a biological tissue slice specimen or the like.

[0018] The measurement container 10 has a plurality of first electrodes 31, a second electrode 33, a plurality of first wirings 35, and a second wiring 37. The plurality of first electrodes 31, the second electrode 33, the plurality of first wirings 35, and the second wiring 37 are located on the upper surface of the bottom portion 11 (the bottom surface inside the measurement container 10). Each of the first wirings 35 and the second wiring 37 is covered with an insulator (for example, photosensitive polyimide or the like). Each of the first electrodes 31, the second electrode 33, each of the first wirings 35, and the second wiring 37 is formed on the upper surface of the bottom portion 11, for example, by photolithography.

[0019] The plurality of first electrodes 31 are arranged in an array. The measurement container 10 is a multi-electrode array (or microelectrode array) device in which a plurality of minute first electrodes 31 are arranged in an array. In the example shown in FIGS. 1, 2, and 3, 16 first electrodes 31 are arranged in a 4-row and 4-column matrix. Note that the number and arrangement of the first electrodes 31 can be set arbitrarily. Preferably, 10 or more first electrodes 31 are arranged. The shape of the first electrode 31 is square when viewed from above. However, the shape of the first electrode 31 may be a polygon other than square or a circular shape or the like.

[0020] The second electrode 33 is located radially outward from the plurality of first electrodes 31. The plurality of first electrodes 31 and the second electrode 33 are insulated from each other. In the examples shown in Figures 1, 2, and 3, the second electrode 33 is substantially annular in shape with a portion open when viewed from above. The second electrode 33 is arranged to surround the plurality of first electrodes 31. Note that the shape of the second electrode 33 is not limited to substantially annular, but may be circular or polygonal, etc.

[0021] It is not essential that the second electrode 33 is located on the upper surface of the bottom 11. For example, the second electrode 33 may be in the shape of a stick, so that it is immersed in the liquid 91 injected into the measuring container 10.

[0022] Each first wire 35 is electrically connected to a corresponding first electrode 31. Each first wire 35 extends outward from the measuring container 10. Multiple first wires 35 extend outward through the open portion of the second electrode 33. The first wires 35 and the second electrode 33 are insulated from each other. The second wire 37 is electrically connected to the second electrode 33. The second wire 37 extends outward from the second electrode 33 from the measuring container 10. As shown in Figure 1, each first wire 35 and the second wire 37 are electrically connected to the measuring unit 20 located outside the measuring container 10.

[0023] As shown in Figure 1, the measurement unit 20 includes an electrode selection circuit 41, a voltage application circuit 43, a current detection circuit 45, a voltage detection circuit 47, a differential signal detection circuit 49, and a calculation unit 51.

[0024] The electrode selection circuit 41 is a circuit for selecting one first electrode 31 from among a plurality of first electrodes 31 to be electrically connected to the current detection circuit 45 and the voltage detection circuit 47. As shown in Figure 1, the electrode selection circuit 41 has a plurality of switches that open and close the circuits connecting each first electrode 31 to the current detection circuit 45.

[0025] The voltage application circuit 43 applies an AC voltage of a predetermined frequency between the first electrode 31, which is selected by the electrode selection circuit 41, and the second electrode 33.

[0026] The current detection circuit 45 is electrically connected to the electrode selection circuit 41. The current detection circuit 45 detects the current flowing through one of the first electrodes 31 selected by the electrode selection circuit 41.

[0027] As shown in Figure 1, the current detection circuit 45 includes an operational amplifier 451, a first resistor 453, and a second resistor 455. The non-inverting input terminal (+) of the operational amplifier 451 is electrically connected to the voltage application circuit 43. The inverting input terminal (-) of the operational amplifier 451 is electrically connected to the electrode selection circuit 41. The first resistor 453 is located between the electrode selection circuit 41 and the inverting input terminal (+) of the operational amplifier 451. One end of the second resistor 455 is connected between the output terminal of the operational amplifier 451 and the differential signal detection circuit 49. The other end of the second resistor 455 is connected between the inverting input terminal (-) of the operational amplifier 451 and the first resistor 453.

[0028] The voltage detection circuit 47 detects the voltage Vx between a first electrode 31 selected by the electrode selection circuit 41 and a second electrode 33. As shown in Figure 1, the voltage detection circuit 47 has an operational amplifier 471. The non-inverting input terminal (+) of the operational amplifier 471 is connected between the electrode selection circuit 41 and the first resistor 453 and is electrically connected to the first electrode 31 via the electrode selection circuit 41. The inverting input terminal (-) of the operational amplifier 471 is electrically connected to the second electrode 33.

[0029] The differential signal detection circuit 49 detects the phase difference between the AC voltage applied by the voltage application circuit 43 and the current detected by the current detection circuit 45. As shown in Figure 1, the differential signal detection circuit 49 has an operational amplifier 491. The non-inverting input terminal (+) of the operational amplifier 491 is connected to the output terminal of the operational amplifier 451 of the current detection circuit 45. The inverting input terminal (-) of the operational amplifier 491 is connected to the voltage application circuit 43.

[0030] The calculation unit 51 includes a storage device, a processing circuit, an input device, and an output device. The storage device consists of memory (storage medium) including, for example, a hard disk drive (HDD), random access memory (RAM), read-only memory (ROM), flash memory, volatile or non-volatile semiconductor memory, magnetic disk, flexible disk, optical disk, compact disk, minidisc, or DVD. The processing circuit consists of, for example, a central processing unit (CPU) that executes programs stored in the storage device. The input device consists of, for example, a device capable of inputting information, such as a mouse, keyboard, touch panel, or various switches. The output device consists of, for example, a device capable of outputting information, such as a display, liquid crystal display device, or lamp.

[0031] The calculation unit 51 calculates the impedance based on the voltage Vx output by the voltage detection circuit 47 and the voltage Vy output by the differential signal detection circuit 49. The procedure for calculating the impedance will be explained with reference to Figure 4.

[0032] <Impedance Calculation> Figure 4 shows the equivalent circuit when measuring impedance. When measuring the impedance of cells 9 using the measurement container 10, the measurement container 10 is placed on a horizontal stand. Then, a cell suspension is dropped onto the bottom 11 of the measurement container 10 where multiple first electrodes 31 are located. When the cell suspension dropped into the measurement container 10 is left for several minutes, multiple cells 9 settle and a cell layer is formed at the bottom 11 of the measurement container 10. After the cell layer is formed, a measurement liquid 91 (such as culture medium) is injected into the measurement container 10. Then, when the liquid 91 comes into contact with the first electrodes 31 and the second electrodes 33, the first electrodes 31 and the second electrodes 33 become conductive.

[0033] As shown in Figure 4, when the voltage application circuit 43 applies an AC voltage, an AC current i flows through the first electrode 31. The voltage detection circuit 47 detects the voltage Vx generated between the first electrode 31 and the second electrode 33. This voltage Vx is expressed by the following equation (1), where Z1 is the contact impedance of the first electrode 31, Z2 is the contact impedance of the second electrode 33, and Zx is the impedance of the object (cell 9).

[0034] Vx = (Zx + Z1 + Z2) * i ... (1)

[0035] Here, the alternating current i is expressed by the following equation (2), using the applied voltage Vs of the voltage application circuit 43 and the resistance value R1 of the first resistor 453.

[0036] i = Vs / R1 ... (2)

[0037] The voltage Vy output by the differential signal detection circuit 49 is the difference between the voltage output by the current detection circuit 45 (=R2*i) and the applied voltage Vs. That is, the voltage Vy is expressed by the following equation (3).

[0038] Vy = (R² * i) - Vs ... (3)

[0039] By measuring voltages Vx and Vy, the phase difference between their signals can be detected, allowing the combined impedance Zx+Z1+Z2 to be measured. The sum of contact impedances Z1 and Z2 is measured by performing impedance measurements in a state with only liquid 91 (i.e., without cells 9; Zx=0). The target impedance Zx is calculated by subtracting the sum of the measured contact impedances Z1 and Z2 from the combined impedance Zx+Z1+Z2.

[0040] As described above, the impedance measuring device 1 can measure the impedance of the target cell 9 by measuring the current flowing through multiple first electrodes 31, which are a multi-electrode array. This makes it possible to measure the impedance of the cell 9, as well as the conventional extracellular action potential, using the measuring container 10, which is a multi-electrode array device.

[0041] Although this invention has been described in detail, the above description is illustrative in all respects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be conceived without falling outside the scope of this invention. The components described in each of the above embodiments and variations can be combined or omitted as appropriate, as long as they do not contradict each other. [Explanation of symbols]

[0042] 1. Impedance measuring device 10 Measuring containers 11 Bottom 20 Measurement section 31 1st electrode 33 Second electrode 41 Electrode Selection Circuit 43 Voltage Application Circuit 45 Current detection circuit 47 Voltage detection circuit 49 Differential signal detection circuit 51 Calculation Section

Claims

1. An impedance measuring device, Measuring container and Multiple first electrodes are arranged in an array on the bottom surface of the measuring container in which the liquid containing the object is placed, The second electrode located inside the measuring container, A voltage application circuit that applies an AC voltage between each of the first electrode and the second electrode, A current detection circuit that detects the current flowing through each of the first electrodes and outputs a voltage corresponding to the current, A voltage detection circuit for detecting the voltage between each of the first and second electrodes, A differential signal detection circuit that detects the difference between the AC voltage applied by the voltage application circuit and the voltage output by the current detection circuit, A calculation unit calculates the impedance of the object based on the difference and the voltage detected by the voltage detection circuit, An impedance measuring device equipped with the following features.

2. An impedance measuring device according to claim 1, An impedance measuring device further comprising an electrode selection circuit that selects one first electrode from among the plurality of first electrodes to be connected to the current detection circuit.

3. An impedance measuring device according to claim 1 or claim 2, The calculation unit is an impedance measuring device that calculates the impedance of the object based on the current detected by the current detection circuit and the voltage detected by the voltage detection circuit.

4. An impedance measurement method, a) A step of applying an AC voltage between at least one of a plurality of first electrodes arranged in an array on the bottom surface of a measuring container in which a liquid containing the object is placed, and a second electrode located inside the measuring container, b) A step of detecting the current flowing through the first electrode while an AC voltage is applied by step a) above, and outputting a voltage corresponding to the current, c) A step of detecting the voltage between the first electrode and the second electrode while the AC voltage has been applied by step a), d) A step of detecting the difference between the voltage output in step b) and the AC voltage applied in step a), e) A step of calculating the impedance of the object based on the voltage detected in step c) and the difference detected in step d), An impedance measurement method, including

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