Magnetic detection device for living cells

Abstract

We provide a biological cell magnetic detection device. [Solution] The present invention provides an nT meter in which the tip diameter of the sensor element is 15 μm or less, which is comparable to the size of a cell (20 μm), and is configured with a grid sensor with a diameter of 5 mm to match the size of a cell body (several millimeters). This allows the device to detect minute magnetic fields of 0.1 nT to 50 nT emitted from cells, contributing to the study of cell body activity.

Description

Technical Field

[0001] It is widely practiced to attach electrodes to the body for measurement for the health of the body and diagnose it as an electrocardiograph, electroencephalograph, etc. Further, in order to grasp information inside the body in more detail, attempts have been made to measure using a highly sensitive magnetic sensor and measure and diagnose magnetocardiogram and magnetoencephalogram.

[0002] In the field of basic medical research, an electrode is inserted into the cell body, and the potential waveform emitted by the cell is measured to study the activity of the cell body. An electric current flows due to the change in the potential of the cell body, generating a magnetic field. It is known from Non-Patent Document 1 that the magnetic field change and the potential change correspond (Figure 1), and the development of a living cell magnetic detection device capable of non-contact measurement is expected. Cells are about 20 μm in size, and cell bodies are about several millimeters in size. In order to detect a micro magnetic field in the nT level emitted from the cell body, the development of a small-sized and highly sensitive magnetic sensor (hereinafter referred to as an nT sensor) is expected. Here, it is preferable that the magnetic field emitted by the entire cell body and specific cells that strongly emit a magnetic field therein can be identified and measured.

[0003] In Patent Document 1 and Non-Patent Document 1, using a magnetic sensor with an element length of 10 mm (the magnetic sensor used in this case is a MI sensor), the element is arranged parallel to a container in which the cell body is placed in the longitudinal direction (Figure 2), and biomagnetism is measured, and it has been reported that the magnetic signal and the electrical signal correspond. The magnetic field signal emitted by the entire cell body can be measured, but the cells that strongly emit a magnetic field and their positions cannot be identified. Also, the distance between the cell body placed in the container and the sensor is as large as 0.6 mm to 1 mm, and it is difficult to accurately measure the magnetic field emitted by the cell body.

[0004] Patent Document 2 describes a method in which the element length is 2 mm or less (the magnetic sensor used in this case is a GSR sensor), and the sensor is arranged parallel to the cell body (Figure 3), maintaining a distance of 0.3 mm or less to increase measurement sensitivity. The invention involves arranging the elements in a grid pattern to measure the magnetic field emitted by the entire cell body, and then identifying cells that emit a strong magnetic field through image processing. However, because the elements are arranged parallel to the bottom of the container, it is difficult to identify specific cells of about 20 μm. Shortening the length of the elements reduces the sensitivity of the nT sensor, so this arrangement has its limitations.

[0005] However, Patent Document 2 discloses a structure in which the element and the bottom of the container are arranged vertically (Figure 4). The specification includes a comment that this structure is also possible, but no further information is provided. Judging from the specification and the provided figure, the thickness of the bottom of the container is estimated to be 160 μm, the sensor covering is 80 μm, and the gap between the tip of the element and the tip of the sensor is 60 μm, for a total of 300 μm. This distance matches the 300 μm or less stated in the claims. Assuming the magnetic wire is 1 mm long, and the measurement position of the element is considered to be at the center, it is an additional 500 μm away from the bottom, resulting in a total distance of 800 μm. Therefore, it is anticipated that the magnetic field cannot be measured accurately.

[0006] Patent Document 3 describes a method in which the amorphous magnetic wire is replaced with a Co-based alloy to improve the sensitivity of the sensor. However, in the present invention, it is preferable to employ a small, highly sensitive sensor with the best possible performance.

[0007] Based on the above, it is difficult to detect magnetic fields emitted by cells of about 20 μm in size and cell bodies of several millimeters in size with current technology. This invention solves this problem by taking an already developed and commercially available nT sensor as a basis and devising the arrangement of the nT sensor and the positional relationship between the cell body and the sensor element. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2011-89894 [Patent Document 2] Patent No. 7329783 [Patent Document 3] Patent No. 7474968 [Non-patent literature]

[0009] [Non-Patent Document 1] Shinsuke Nakayama, Tsuyoshi Uchiyama nature SCINTIFIC REP0RTS pp1~9 (06.March,2015) [Overview of the project] [Problems that the invention aims to solve]

[0010] The inventors considered the possibility of placing the magnetic wire, which is the magnetosensitive element of the nT sensor (hereinafter abbreviated as "sensor"), perpendicular to the bottom of the container, taking into account a diameter of 5 μm and a length of 1 mm, in order to detect the magnetic field emitted by a 20 μm-sized cell, and investigated its feasibility. The expected problems in this case are: The first challenge is the relationship between the distance between the cell body and the sensor tip. The magnetic field emitted by the cell body attenuates in proportion to the square of the distance. The goal is to investigate what the optimal distance between the cell and the sensor element should be.

[0011] The second challenge is that the sensor calculates its detection power by comparing the magnetic field at the center of the sensor element's length with the sensor output voltage to create a calibration curve of magnetic field strength and sensor output voltage. If the sensor element is arranged vertically, the distance between the center of the element and the cell body increases, which is expected to reduce the magnetic field strength to be measured and worsen the measurement accuracy. Therefore, the relationship between the length of the sensor element and the sensor's detection force is understood, and the sensor length is determined accordingly.

[0012] The third challenge is to devise a device that, once it is confirmed that biomagnetism can be detected with a single sensor element, can arrange these elements in a grid to determine the magnetic field distribution emitted from the cell body and identify cells that emit a strong magnetic field. [Means for solving the problem]

[0013] The inventors fabricated prototypes of GSR sensor-type nT sensors using Co alloy amorphous wire, varying the length of the sensor element from 1 mm to 10 mm, and measured the magnetic field emitted from cell bodies ranging in size from 1 mm to 20 mm. As shown in Figure 5, the results indicate that increasing the distance from the cell to the sensor element significantly reduces the strength of the measured magnetic field. To maintain high accuracy, the distance between the two must be kept at least 100 μm or less.

[0014] Based on the above research results, the inventors devised a container with a bottom thickness of 100 μm or less in order to minimize the distance between the two.

[0015] Furthermore, the magnetic wire, which acts as the magnetometer, was made longer to the tip of the sensor element (Figure 6), and the sensor element was positioned at the tip of the nT sensor (Figure 7). This made it possible for the tip of the magnetic wire to come into contact with the bottom of the container, and the distance between them became only the thickness of the bottom of the container. Furthermore, since Co-based alloys have excellent corrosion resistance, the tip of the magnetic wire can be left exposed. This solved the first problem.

[0016] Regarding the second issue, the nT sensor measures the magnetic field at the center of the sensor element and uses that value as the nT sensor's measurement. If the length of the sensor element is 1 mm, the center of the sensor element will be 0.5 mm away from the bottom of the container, which raises concerns that the measurement value will decrease significantly and high accuracy may not be obtainable.

[0017] Therefore, the length of the sensor element was changed from 1 mm to 10 mm, and the sensor element was brought into contact with the bottom of the container for measurement. As a result, when the length was 2 mm or less, it was found that the magnetic field at the bottom of the container and the measured value were almost the same (line (a) in Fig. 8). For comparison, assuming that the magnetic field at the center of the sensor element was measured, the value shown by line (b) in Fig. 8 should be obtained, but the actual measured value was much larger than that. That is, it was discovered that by bringing the sensor element into contact with the bottom of the container and using a sensor element with a length of 2 mm or less, when measuring the magnetic field by contacting the bottom of the container vertically, the measurement can be performed with the magnetic field strength at the contact point. This confirmed the superiority of vertically applying the sensor element to the bottom of the container and measuring in the vertical direction.

[0018] Regarding the third problem, since the coil width of the sensor element is about 40 μm, theoretically it is possible to arrange the sensor elements at an interval of 0.1 mm or more. For the element grid, the principle confirmation type ranges from arranging one sensor element to vertically contact the center of the bottom of the container (Fig. 9), increasing the grid size to 3.5 mm × 3.5 mm, and increasing the number to 2 × 2, 3 × 3, 4 × 4, etc., up to a maximum of 20 × 20 (Fig. 10). The more the number of grid elements increases, the more accurate the identification of the magnetic field measurement distribution emitted by the cell body and the specific cells emitting a strong magnetic field becomes.

[0019] The present invention is an apparatus (Fig. 11) realized by setting the diameter of the magnetic wire of the sensor element of the GSR sensor type nT sensor to 15 μm or less, the length to 2 mm, arranging the end of the magnetic wire at the end of the sensor, arranging the sensor element vertically with respect to the bottom of the container, setting the thickness of the bottom of the container to 0.1 mm or less, and minimizing the distance between the cell body and the end of the sensor element as much as possible. Furthermore, it is an apparatus capable of arranging the sensor elements in a grid pattern, grasping the magnetic field emitted from the entire cell body, and identifying cells emitting a strong magnetic field from the entire cell body.

Effect of the Invention

[0020] According to the present invention, it becomes possible to measure the biomagnetic field emitted from the cell body. Compared with the current method of inserting an electrode to examine the activity of the cell body, the present invention is non-contact, so the examination can be significantly simplified. Furthermore, it is also possible to identify cells with a size of 20 μm that emit a stronger magnetic field. It is considered to be a particularly effective device in basic research in the medical field that studies the activity of cells.

Brief Description of the Drawings

[0021] [Figure 1] It is a diagram showing that the potential change and the magnetic field change correspond. [Figure 2] It is a diagram showing a parallel arrangement with a magnetic sensor composed of a cell body and a sensor element with a length of 10 mm. [Figure 3] It is a diagram showing the parallel arrangement of the sensor elements of the magnetic microscope. [Figure 4] It is a diagram showing the vertical arrangement of the sensor elements of the magnetic microscope. [Figure 5] It is a diagram showing the influence of the distance between the cell and the sensor element on the strength of the magnetic field. [Figure 6] It is a diagram showing a magnetic wire arranged at the tip of the sensor element. [Figure 7] It is a diagram showing that the sensor element is arranged in contact with the bottom of the container. [Figure 8] It is a diagram showing the influence of the length of the sensor element on the measured magnetic field. [Figure 9] It is a diagram showing one sensor element arranged in contact with the center of the bottom of the container. [Figure 10] It is a diagram showing a plurality of sensor elements (grid elements) arranged in a grid pattern in contact with the center of the bottom of the container. [Figure 11] It is a conceptual diagram of a living cell magnetic detection device.

Best Mode for Carrying Out the Invention

[0022] The living cell magnetic detection device of the present invention comprises a container part for containing the cell body and a micro magnetic field measurement device, The container portion consists of a non-magnetic container for holding the cell bodies and a container fixing portion for fixing the container. The container has a cylindrical mortar shape, with the tip of the mortar having a diameter of 5 mm or less, and the thickness of the bottom of the tip being 0.1 mm or less. The aforementioned minute magnetic field measuring device consists of an nT sensor having a detection force of 1 nT or less, the magnetic material of the sensor element of the nT sensor is made of a Co-based amorphous magnetic wire, its size is 15 μm or less in diameter and 2 mm or less in length, and the tip of the magnetic material is positioned at the tip of the nT sensor. The nT sensor, consisting of the aforementioned sensor elements, is installed in an nT sensor fixing part located below the container. The nT sensor fixing portion includes a position adjustment portion for adjusting the position between the sensor element and the tip of the container, The position adjustment unit comprises an angle adjustment mechanism that adjusts the perpendicularity so that the length direction of the sensor element and the bottom surface of the container face each other perpendicularly, and a position adjustment mechanism that adjusts the position of the sensor element and the position of the tip of the container using XY axis (center) and Z axis (distance) movement devices. It is characterized by detecting magnetic signals emitted from cell bodies.

[0023] Furthermore, the nT sensor is characterized in that its sensor element consists of a plurality of grid elements.

[0024] Furthermore, each device is characterized by being made of a non-magnetic material.

[0025] The biological cell magnetic detection device will be described in detail below, primarily using Figure 11. The biological cell magnetic detection device 3 consists of a container section 31 for holding cell bodies and a micro-magnetic field measuring device 32 located below the container section 31.

[0026] <Container part> The container part 41 consists of a non-magnetic container 411 and a container fixing part 312 that fixes the container 411. The container 411 contains a cell body 4110 which is an aggregate of living cells (hereinafter referred to as cells) and its culture solution 4111. The container fixing part 412 fixes the container 411 so that it does not move during measurement by the micro magnetic field measurement device 42.

[0027] As illustrated in FIGS. 9 to 11, the shape of the container 411 is a cylindrical mortar shape with a wide upper part and a constricted tip and a small bottom. This is to facilitate putting the cell body 4110 and the culture solution 4111 into the container and to concentrate the cell body 4110 for measurement at the center of the bottom of the tip. Therefore, the size of the cylindrical mortar-shaped container 411 is preferably about 10 mm to 15 mm in diameter at the upper part and 5 mm or less in diameter at the tip. The thickness of the bottom of the tip is 0.1 mm or less. In this way, a cell body 3110 of about several millimeters exists on the bottom with a thickness of 0.1 mm or less. The material of the container 411 includes non-magnetic metal materials typified by SUS304, organic materials such as plastics and hard vinyl.

[0028] <Micro magnetic field measurement device> The micro magnetic field measurement device 42 consists of an nT sensor 421 and an nT sensor fixing part 422 that fixes the nT sensor 421. The nT sensor 421 has a detection output of 1 nT or less, and the magneto-sensitive body of the sensor element 4211 of the nT sensor 421 is made of a Co-based amorphous magnetic wire. The diameter of the magnetic wire is 15 μm or less, preferably 2 μm to 10 μm. Its length is 2 mm or less, preferably 0.5 mm to 1.8 mm. The coil pitch is from 0.5 μm to 3 μm. The number of coil turns is from 80 to 1000. This is because when using one sensor element 3211 or when forming a grid element, the diameter and length of the magnetic wire are determined corresponding to the number of grid elements. The tip of the magneto-sensitive body is arranged at the tip of the nT sensor 421 which is the tip of the sensor element 4211.

[0029] <nT sensor fixing part> The nT sensor fixing section 422 is installed below the container 41 and fixes the nT sensor 421, which consists of a sensor element 4211. It also includes a position adjustment section 422 for adjusting the position between the sensor element 4211 and the tip of the container 411.

[0030] <Position adjustment section> The position adjustment unit 422 consists of an angle adjustment mechanism 4221 and a position adjustment mechanism 4222. The angle adjustment mechanism 4221 is a mechanism that adjusts the perpendicularity so that the length of the sensor element 4211 and the bottom surface of the container 41 are perpendicular to each other. By setting the angle to a right angle, the magnetic signal emitted from the cell body 4110 can be detected with high precision. The position adjustment mechanism 4222 is a mechanism that moves the position of the sensor element 4211 and the position of the tip of the container 41 to the center of the container using the XY axes, and adjusts the tip of the element to contact or by a minute amount using a Z-axis (distance) movement device. The cell body 4110 is located on the bottom of the container 31, and the sensor element 4211 is in contact with it, separated by a bottom less than 0.1 mm thick.

[0031] This allows for the detection of magnetic signals from the tip of a magnetic wire less than 15 μm in diameter, which is the magnetosensitive element of the sensor element 4211, and from a single cell 4110 that is several millimeters in size and comprises a cell body 4110, with a size of 20 μm. From the magnetic signals of each cell, the magnetic field measurement distribution of the cell body 4110 can be obtained. Furthermore, it is possible to identify cells that emit strong magnetic fields from the entire cell body. Furthermore, by using the grid-like arrangement of sensor elements 4211, the magnetic field measurement distribution emitted by cell bodies and the identification of specific cells emitting strong magnetic fields can be performed quickly, easily, and accurately.

[0032] The performance of the micromagnetic field detection device of the present invention allows for the measurement of minute magnetic fields of 0.1 nT to 50 nT emitted by cell bodies several millimeters in size, and enables non-contact measurement of the activity level of cell bodies.

[0033] As mentioned above, since we are measuring the minute magnetic field of biological cells, it goes without saying that not only must the container be non-magnetic, but each device and component must also be made of non-magnetic material. [Examples]

[0034] The biomagnetic detection device and detection results of this embodiment are as follows. The container is a cylindrical mortar-shaped container made of vinyl resin, with a diameter of 12 mm at the cylindrical part, an overall height of 18 mm, a diameter of 4 mm at the tip of the mortar, and a thickness of 0.05 μm at the bottom. The container fixing section is made of rigid plastic material, with a diameter of 30 mm and a height of 15 mm. A cylindrical, mortar-shaped hole is formed in the center to secure the container. The container is inserted and fixed into this hole. The nT sensor in the micromagnetic field measuring device has a detection force of 0.2 nT. The sensor element uses a Co-based amorphous magnetic wire as its magnetic sensor material, with a diameter of 5 μm and a length of 1 mm. The nT sensor fixing section is installed below the container and is equipped with a position adjustment section consisting of an angle adjustment mechanism and a position adjustment mechanism, which fixes the nT sensor. Furthermore, the container fixing part and the nT sensor fixing part are assembled using a non-magnetic jig.

[0035] When cell bodies measuring 2.0 mm in size, consisting of cells ranging from 15 μm to 20 μm in size, were placed in the container of this biomagnetic detection device along with a culture medium, magnetic signals emitted from the cell bodies were detected. By processing these magnetic signals, it was possible to determine the magnetic field measurement distribution emitted by the cell bodies and identify specific cells that emitted strong magnetic fields. [Industrial applicability]

[0036] Considering the advantages of non-contact cell magnetic detection compared to conventional methods such as electropalpation, which involves inserting electrodes and observing changes in electrical potential, it is expected that this method will be widely used in basic research in medical settings. [Explanation of Symbols]

[0037] 1: Sensor element 12: Magnetic element (magnetic wire) 2: Sensor device 20: Cell body 201:Culture solution 202:Bottom of container 21: Sensor element 22: nT sensor 23: Wiring on the circuit board 3:1 sensor element 31: Container 311: Bottom of the container 32: Sensor element 4: Magnetic detection device for living cells 41: Container part 411: Container 4110: Cell body 4111:Culture solution 412: Container fixing part 42: Micromagnetic field measuring device 421: nT sensor 4211: Sensor element 422:Position adjustment section 4221: Angle adjustment mechanism 4222:Position adjustment mechanism

Claims

1. In a biological cell magnetic field detection device comprising a container for holding cell bodies and a micromagnetic field measuring device, The container portion consists of a non-magnetic container for holding the cell bodies and a container fixing portion for fixing the container. The container has a cylindrical mortar-like shape, with the tip of the mortar having a diameter of 5 mm or less, and the thickness of the bottom of the tip being 0.1 mm or less. The aforementioned minute magnetic field measuring device consists of an nT sensor having a detection force of 1 nT or less, the magnetic material of the sensor element of the nT sensor is made of a Co-based amorphous magnetic wire, its size is 15 μm or less in diameter and 2 mm or less in length, and the tip of the magnetic material is positioned at the tip of the nT sensor. The nT sensor, consisting of the aforementioned sensor elements, is installed in an nT sensor fixing part located below the container. The nT sensor fixing portion includes a position adjustment portion for adjusting the position between the sensor element and the tip of the container. The position adjustment unit comprises an angle adjustment mechanism that adjusts the perpendicularity so that the length direction of the sensor element and the bottom surface of the container face each other perpendicularly, and a position adjustment mechanism that adjusts the position of the sensor element and the position of the tip of the container using XY axis (center) and Z axis (distance) movement devices. A biological cell magnetic field detection device characterized by detecting magnetic signals emitted from cell bodies.

2. In claim 1, A biological cell magnetic detection device characterized in that the sensor element of the nT sensor consists of a plurality of grid elements.

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