Magnetic susceptibility measuring device and magnetic susceptibility measuring method

Abstract

This magnetic susceptibility measurement device measures the magnetic susceptibility of a magnetic particle-containing object to be measured (1), and comprises: a probe (10) with which a signal transmission line is formed, wherein the object to be measured is disposed in proximity to or in contact with the signal transmission line such that the direction of an axis of easy magnetization of the object to be measured assumes a direction orthogonal to the signal transmission line; a first magnetic field application unit (40) for applying a magnetic field in the direction of the axis of easy magnetization of the object to be measured; a second magnetic field application unit (50) for applying a magnetic field in the direction of an axis of hard magnetization that is orthogonal to the direction of the axis of easy magnetization of the object to be measured; a signal measurement instrument (20) that measures the signal transmitted by the signal transmission line when a magnetic field is being applied by both the first magnetic field application unit and the second magnetic field application unit; and a calculation processing means (30) that determines the magnetic susceptibility of the object to be measured on the basis of the signal measured by the signal measurement instrument.

Description

[Technical Field]

[0001] The present invention relates to a magnetic susceptibility measuring device and a magnetic susceptibility measuring method for measuring the magnetic susceptibility of an object to be measured, which includes an aggregate of magnetic particles. [Background technology]

[0002] The measurement of the magnetic susceptibility of magnetic nanoparticles with respect to radio frequencies (RF) has been widely studied. (For example, Non-Patent Documents 1, 2, and 3).

[0003] These magnetic nanoparticles are so-called nano-sized magnetic particles, and are expected to have applications such as magnetic hyperthermia (magnetic thermotherapy), which is attracting attention as a treatment for cancer, and immunological tests for detecting biomolecules such as disease-derived proteins and pathogens.

[0004] This magnetic thermotherapy method utilizes the fact that cancerous tissue is more sensitive to heat than normal tissue, allowing for the selective necrosis or degeneration of cancerous tissue. To achieve this, magnetic particles, such as magnetic nanoparticles, are injected into the body, and an external alternating magnetic field is applied to locally heat the magnetic particles absorbed by the body, thereby selectively killing only the cancerous tissue.

[0005] Non-patent document 4, based on the inventors' research, discloses a constant-temperature heating control method for heating magnetic nanoparticles injected into a living organism by applying an alternating magnetic field in animal experiments. This method precisely controls the applied magnetic field to maintain a constant temperature without overshooting or fluctuations at the target temperature.

[0006] Furthermore, immunoassay tests that detect biomolecules such as disease-derived proteins and pathogens utilize the antigen-antibody reaction, in which the antigen and antibody specifically bind to the substance to be detected. The antibody is labeled with a substance called a marker, and the amount of antigen is measured by detecting the signal from the marker of the antibody bound to the antigen. Magnetic immunoassay, which uses magnetic methods to detect the substance to be detected, is a method that uses magnetic particles and magnetic sensors to detect the antigen-antibody reaction. Magnetic particles (hereinafter referred to as magnetic markers) are attached to the antibody to label it, and the degree of binding to the antigen, the substance to be detected, is detected by a magnetic sensor using the magnetic signal from the magnetic marker by utilizing the differences in Brownian relaxation properties of the magnetic markers.

[0007] Furthermore, Patent Documents 1 and 2 disclose a magnetic field measuring device that detects an antigen, which is the substance to be measured, by utilizing Brownian relaxation, which is achieved by rotating a sample containing a magnetic marker (magnetic nanoparticles) using a rotation mechanism and switching the magnetic field at each rotation period, as proposed by the inventor of the present invention. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-194305 [Patent Document 2] Japanese Patent Publication No. 2020-159871 [Non-patent literature]

[0009] [Non-Patent Document 1] BKKunar, V. Veerakumar and K. Lingam, Journal of Applied Physics, vol. 105 (2009) [Non-Patent Document 2] M. Jadav, SP Bhatnagar, IEEE Transactions on Magnetics, vol, 56, p.1-8 (2020) [Non-Patent Document 3] PC Fannin, I. Malaescu and CNMarin, The European Physical Journal E, vol. 27, p.145-148 (2008) [Non-Patent Document 4] A. Shikano, L. Tonthat, and S. Yabukami, IEEJ Trans. Electr.Electron. Eng., 16, 807-809 (2021) [Overview of the project] [Problems that the invention aims to solve]

[0010] In magnetic methods using magnetic particles as exemplified above, optimizing the magnetic properties of aggregated magnetic particles can yield greater benefits, such as improved heating efficiency in magnetic thermotherapy and improved measurement sensitivity in magnetic immunoassay. The inventors of this application have now developed a method for measuring the magnetic susceptibility of magnetic particles in order to control their magnetic properties, particularly their magnetic susceptibility.

[0011] Therefore, the object of the present invention is to provide a magnetic susceptibility measuring device and a magnetic susceptibility measuring method that can measure the magnetic susceptibility of an object to be measured, which includes an aggregate of magnetic particles. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a magnetic susceptibility measuring device for measuring the magnetic susceptibility of an object to be measured containing magnetic particles, characterized by comprising: a probe in which a signal transmission line is formed and the object to be measured is positioned close to or in contact with the signal transmission line such that the easy magnetization axis direction of the object to be measured is perpendicular to the signal transmission line; a first magnetic field application unit for applying a magnetic field in the direction of the easy magnetization axis of the object to be measured; a second magnetic field application unit for applying a magnetic field in the direction of the hard magnetization axis direction perpendicular to the easy magnetization axis direction of the object to be measured; a signal measuring instrument for measuring a signal transmitted through the signal transmission line when a magnetic field is applied by both the first and second magnetic field application units; and a calculation processing means for determining the magnetic susceptibility of the object to be measured based on the signal measured by the signal measuring instrument.

[0013] The present invention provides a method for measuring the magnetic susceptibility of an object to be measured that includes magnetic particles, comprising the steps of: positioning the object to be measured in close proximity to or in contact with a probe on which a signal transmission line is formed, such that the easy magnetization axis direction of the object to be measured is perpendicular to the signal transmission line; applying a magnetic field in the direction of the easy magnetization axis of the object to be measured using a first magnetic field application means; applying a magnetic field in the direction of the easy magnetization axis of the object to be measured using a second magnetic field application means in the direction of the hard magnetization axis perpendicular to the easy magnetization axis of the object to be measured; measuring a signal transmitted through the signal transmission line using a signal measuring instrument while magnetic fields are applied by both the first and second magnetic field application means; and determining the magnetic susceptibility of the object to be measured based on the signal measured by the signal measuring instrument using a calculation processing means.

[0014] Further, the present invention provides a magnetic susceptibility control method for controlling the magnetic susceptibility of a measurement object containing magnetic particles. The magnetic susceptibility control method includes: a step in which a first magnetic field applying means magnetizes the measurement object in the direction of the easy magnetization axis of the measurement object; a step in which a second magnetic field applying means applies a magnetic field in the direction of the hard magnetization axis orthogonal to the direction of the easy magnetization axis of the measurement object; and a step in which a control means controls to change the magnetic susceptibility of the measurement object by varying the strength of the magnetic field applied by the second magnetic field applying means.

Effects of the Invention

[0015] According to the present invention, the magnetic susceptibility of a measurement object containing magnetic particles can be measured. Further, the magnetic susceptibility of a measurement object containing magnetic particles can be made variable, and the magnetic susceptibility can be controlled.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram showing a schematic configuration example of a magnetic susceptibility measurement apparatus in an embodiment of the present invention. [Figure 2] It is a diagram showing a schematic configuration example of a magnetic susceptibility measurement apparatus in an embodiment of the present invention. [Figure 3] It is a diagram showing a configuration example of the probe 10. [Figure 4] It is a diagram showing a state in which the measurement object 1 is arranged on the probe 10. [Figure 5] It is a flowchart showing the procedure of a magnetic susceptibility measurement method in an embodiment of the present invention. [Figure 6] It is a diagram showing an example of a measurement result of the magnetic susceptibility κ. [Figure 7] It is a diagram showing an example of a measurement result of the magnetic susceptibility κ. [Figure 8] It is a diagram showing an example of a measurement result obtained by applying the magnetic susceptibility measurement method in the present embodiment to magnetic immunoassay. [Figure 9] It is a diagram showing another example of a measurement result obtained by applying the magnetic susceptibility measurement method in the present embodiment to magnetic immunoassay. [Figure 10]Figure 9 shows a graph illustrating the relationship between magnetic susceptibility κ and ferromagnetic resonance frequency (FMR) in a magnetic susceptibility measurement. [Figure 11] This diagram shows the schematic configuration of the measuring device used to perform the measurement example shown in the reference example. [Figure 12] This figure shows an example of measurement results (part 1) from a reference example. [Figure 13] This figure shows an example of measurement results (part 2) from a reference example. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the drawings. However, these embodiments do not limit the technical scope of the present invention.

[0018] Figures 1 and 2 show schematic configuration examples of a magnetic susceptibility measuring device according to an embodiment of the present invention, with Figure 2 being a more graphical representation of the functional block diagram in Figure 1.

[0019] The magnetic susceptibility measuring device according to an embodiment of the present invention comprises a detection probe 10 positioned in contact with or close to the object to be measured 1, a network analyzer 20 which is a signal measuring instrument, a processing unit (for example, a computer device such as a personal computer) 30 which performs predetermined calculation processing such as numerical analysis processing, a coil 40 for easy magnetization axis which applies a DC magnetic field in the direction of the easy magnetization axis of the object to be measured 1, and a coil 50 for hard magnetization axis which applies a DC magnetic field in the direction of the hard magnetization axis which is perpendicular to the easy magnetization axis.

[0020] The probe 10 is positioned to be in contact with or in close proximity to the object under test 1, which contains an aggregate of magnetic particles, and is connected to a network analyzer (e.g., Agilent Technologies N5227A) 20 via a signal cable (e.g., coaxial cable) 3. The network analyzer 20, which is a current source, supplies a high-frequency current signal to determine the transmission coefficient (S) of the object under test 1. 21The magnetic susceptibility of the object to be measured 1 is determined by a predetermined numerical analysis process. A magnet (magnetic field application unit) 40 consisting of a solenoid coil (electromagnetic coil) whose current is controlled is used to apply a magnetic field to the object to be measured 1.

[0021] The arithmetic processing unit 30 functions as an arithmetic processing means for determining the magnetic susceptibility of the object to be measured 1, and executes a predetermined arithmetic processing program for calculating the magnetic susceptibility. The arithmetic processing unit 30 also functions as a control means for controlling the magnetic susceptibility by changing the strength of the DC magnetic field applied by the coil 50 for the hard-to-magnetize shaft.

[0022] The coil 40 for the easy magnetization axis is an electromagnetic coil that supplies a DC magnetic field to magnetize the magnetic particles contained in the object to be measured 1, which is placed on the probe 10, in the direction of the easy magnetization axis.

[0023] The hard-to-magnetize axis coil 50 is an electromagnetic coil that applies a DC magnetic field in the direction of the hard-to-magnetize axis to the magnetic particles contained in the object to be measured 1, which is placed on the probe 10. Figure 2 shows the power supplies for the easy-to-magnetize axis coil 40 and the hard-to-magnetize axis coil 50, respectively.

[0024] Figure 3 shows examples of the configuration of the probe 10, where Figure 3(a) shows the configuration of the probe 10 in the first configuration example, and Figure 3(b) shows the configuration of the probe 10 in the second configuration example. The first configuration example of the probe 10 shown in Figure 3(a) comprises a microstrip conductor 11, a flexible substrate 12, a fluororesin substrate 13, a ground conductor 14, and a pair of connectors 15 connected to both ends of the microstrip conductor 11. The microstrip conductor 11 is made of ethylene The material is processed into a straight microstrip line by ching. The microstrip conductor 11 and the flexible substrate 12 are integrally fixed by chemical or thermal treatment. The ground conductor 14 is formed from, for example, copper foil. The configuration in which the dielectric flexible substrate 12 and the fluororesin substrate 13 are sandwiched between the microstrip conductor 11 and the ground conductor 14 forms a microstrip line.

[0025] The second configuration example of the probe 10 shown in Figure 3(b) comprises a microstrip conductor 11, a flexible substrate (sheet) 12, a ground conductor 14, and a pair of connectors 15 connected to both ends of the microstrip conductor 11. The connectors 15 connect to the signal cable 3 (Figures 1 and 2). The microstrip conductor 11 and the flexible substrate 12 are integrally fixed by chemical or thermal treatment. In the second configuration example, the fluororesin substrate 13 from the first configuration example in Figure 3(a) is omitted, and the flexible substrate 12 is pressed against the ground conductor 14, which has a planar structure and a curved structure. The inside of the ground conductor 14 is shown transparently for illustrative purposes, but in reality it is made of a metallic material such as copper. The microstrip conductor 11 is processed by etching. The microstrip conductor 11 consists of a central straight-shaped portion 11a and curved-shaped portions 11b on both sides. The ends of the microstrip conductor 11 are electrically connected to the connectors 15. The microstrip conductor 11 has a characteristic impedance matched to 50Ω in both its linear portion 11a and curved portion 11b. Similar to the first configuration example, the configuration in which the dielectric flexible substrate 12 is sandwiched between the microstrip conductor 11 and the ground conductor 14 forms a microstrip line.

[0026] The microstrip conductor 11 extends into the ground conductor 14 through an opening 14a provided in the ground conductor 14 and is connected to the connector 15 on the opposite side. Regardless of the shape of the object to be measured 1, measurement is possible without the object to be measured 1 coming into contact with the connector 15 or the signal cable 3 (Figure 1) connected to it.

[0027] Figure 4 shows the state in which the object to be measured 1 is placed on the probe 10. The object to be measured 1 is an aggregate of magnetic particles enclosed in a microtube 1a (for example, a 5 μL size, about 5 mm in length), which is a slender cylindrical container. The magnetic particles are, for example, magnetic nanoparticles with a particle size of nanoscale (for example, φ200 nm), and exist in an aggregated state in the solution inside the microtube 1a. For example, by bringing a permanent magnet close to the microtube 1a, the magnetic particles dispersed inside the microtube 1 are attracted to the permanent magnet, creating an aggregated state of magnetic particles.

[0028] As shown in the figure, the elongated cylindrical microtube 1a is positioned in close proximity to or in contact with the microstrip conductor 11, with its orientation perpendicular to the direction in which the microstrip conductor 11 extends. Since the length direction of the microtube 1a is the easy magnetization axis direction of the magnetic particles contained within it, by positioning the microtube 1a perpendicular to the microstrip conductor 11, the direction perpendicular to the microstrip conductor 11 becomes the easy magnetization axis direction, and the magnetic field Heasy in the easy magnetization axis direction by the easy magnetization axis coil 40 When applied, the aggregate of magnetic particles becomes magnetized in the direction of its easy magnetization axis.

[0029] With the magnetic particles magnetized in the direction of the easy magnetization axis, a magnetic field Hhard in the direction of the hard magnetization axis perpendicular to it is then applied by the hard magnetization axis coil 50 to change the magnetic susceptibility of the magnetic particles. Measure.

[0030] Figure 5 is a flowchart showing the procedure for measuring magnetic susceptibility in an embodiment of the present invention.

[0031] The object to be measured 1, which contains an aggregate of magnetic particles inside a microtube 1a, is placed on the microstrip conductor 11 of the probe 10 (S100). As described above, the microtube 1a is The length direction is oriented perpendicular to the direction in which the microstrip conductor 11 extends, and the easy magnetization axis direction is perpendicular to the direction in which the microstrip conductor 11 extends.

[0032] A DC magnetic field Heasy is applied to the object to be measured 1 in the direction of the easy magnetization axis by the easy magnetization axis coil 40. The magnetic particles of the object to be measured 1 are magnetized in the direction of the easy magnetization axis (S102). The strength of the DC magnetic field applied in the direction of the easy magnetization axis is, for example, 0.135 [T].

[0033] With the Heasy DC magnetic field applied in the direction of the easy magnetization axis by the easy magnetization axis coil 40, Next, the magnetization-hard axis coil 50 applies a magnetic field Hhard to the object under measurement 1 in the direction of the magnetization-hard axis, which is the direction in which the microstrip conductor 11 extends, and the signal measuring instrument (network) Calibrate the 20 (Caliber analyzer) (S104). Specifically, the coil for the hard magnetization axis. A relatively strong DC magnetic field Hhard (e.g., 0.4 [T]) is applied using the 50 to magnetically saturate the object under test 1, and the network analyzer 20 is calibrated. This removes the electrical length of the probe 10 and coaxial cable 3, the DC impedance of the object under test 1, non-magnetic signals, etc. This calibration makes it possible to perform measurements based on the state in which a predetermined magnetic field is applied to the object under test.

[0034] A DC magnetic field Hhard is applied by the coil 50 for the hard-to-magnetize shaft, and the coil 40 for the easy-to-magnetize shaft and the magnet The transmission coefficient (S) of a high-frequency current signal when a magnetic field is applied by both coils 50 for hard-to-transform shafts. 21 ) is measured (S106). Preferably, with a constant DC magnetic field Heasy applied in the direction of the easy magnetization axis by the easy magnetization axis coil 40, the hard magnetization axis coil 50 is applied By changing the strength of the magnetic field Hhard in the direction of the magnetization hard axis, the transmission of high-frequency current signals according to their frequency is controlled. Coefficient (S 21Measure (S 21 ). The transmission coefficient (S

[0035] ) corresponding to the change in magnetic susceptibility according to the behavior in which the magnetization that was oriented in the easy magnetization axis direction in magnetic anisotropy rotates in the hard magnetization axis direction due to the magnetic field Hhard applied by the hard magnetization axis coil 50 can be measured. 21 Based on the measured transmission coefficient (S 21 ), the magnetic susceptibility is obtained by arithmetic processing. In the arithmetic processing for obtaining the magnetic susceptibility, first, according to the following equation (1), the transmission coefficient (S

[0036] Z = 100(1 - S 21 ) / S 21 ···(1)

[0037] Specifically, in S104, a strong magnetic field is applied by the hard magnetization axis coil 50, and the transmission coefficient (S 21 ) measured by saturating the measurement object 1 is used as the background, and the transmission coefficient (S 21 ) at this time is used as the reference signal. Next, the strength of the magnetic field applied by the hard magnetization axis coil 50 is changed, and the transmission coefficient (S 21 ) is measured. The transmission coefficient (S 21 ) at this time reflects the magnetic characteristics due to the magnetic field applied to the measurement object 1, and the impedance Z reflecting the rotation of the magnetization of the magnetic particles in the measurement object 1 can be obtained from the strength of the magnetic field Heasy applied in the easy magnetization axis direction and the magnetic field Hhard applied in the hard magnetization axis direction orthogonal to it. Fur thermore, based on the obtained impedance Z, the magnetic susceptibility κ is obtained (S110).

[0038] In the impedance Z, the real part is the loss component (resistance component) R of the measurement object 1, and the imaginary part is the product ωL of the inductance component of the measurement object 1 and the angular frequency ω. The inductance component L corresponds to the real part (κ') of the magnetic susceptibility κ of the measurement object 1, and the resistance component R corresponds to the imaginary part (κ'') of the magnetic susceptibility κ of the measurement object 1. The magnetic susceptibility (complex number) κ of the measurement object 1 is expressed by the following equation (2).

[0039] κ = κ' - jκ'' ···(2)

[0040] Figures 6 and 7 show examples of the measured magnetic susceptibility κ. Figure 6 shows the frequency dependence of the magnetic susceptibility κ when the strength of the magnetic field applied in the hard magnetization axis direction is varied. Figure 6(a) shows the value of the real part (κ') of the magnetic susceptibility κ, and Figure 6(b) shows the value of the imaginary part (κ''). Figure 7 shows the magnetic susceptibility κ in Figure 6 as a function of the magnetic field strength applied in the direction of the hard magnetization axis.

[0041] In the measurement results examples shown in Figures 6 and 7, the value of the magnetic susceptibility κ on the vertical axis is the relative value of the magnetic susceptibility κ (au), which is simply obtained by dividing the impedance Z by the frequency f. Furthermore, the absolute value of the magnetic susceptibility κ can be determined by performing a known electromagnetic field analysis (e.g., finite element method analysis) and obtaining table data in advance regarding the relationship between magnetic susceptibility and inductance. The table data of magnetic susceptibility and inductance is obtained by finite element method analysis, where the inductance L when the magnetic susceptibility κ is changed is calculated using Maxwell's formula. This can be calculated using equations. The computer device 30 calculates the relationship between magnetic susceptibility and inductance using table data calculations and stores it as data.

[0042] Figure 6 shows the magnetic susceptibility κ when the strength of the magnetic field applied in the hard magnetization axis direction is varied (including the case where no magnetic field is applied in the hard magnetization axis direction (0.0T)). Specifically, the magnetic susceptibility κ is shown. Examples of magnetic susceptibility κ are given for magnetic field strength (magnetic flux density) in the hard-to-transform axis direction of 0.0T (no magnetic field applied), 0.1T, 0.05T, 0.1T, 0.15T, and 0.2T. In these example measurement results, the magnetic susceptibility κ also changes depending on the strength of the applied magnetic field, and in particular, the magnetic susceptibility κ is large when the magnetic field strength is approximately 0.1T and 0.15T. A tendency for the magnetic susceptibility to increase was observed, and in particular, the magnetic susceptibility κ was maximized at 0.1T. This is because, since the strength of the magnetic field applied in the direction of the easy magnetization axis is 0.135T, the case where the strengths of the magnetic fields applied in the directions of the mutually orthogonal easy magnetization axis and the hard magnetization axis are approximately equal corresponds to an anisotropic magnetic field, and it is thought that the magnetic susceptibility κ is approximately maximized.

[0043] Figure 7 is a graph plotting the maximum value of the magnetic susceptibility κ shown in Figure 6. Both the real part (κ') and the imaginary part (κ'') of the magnetic susceptibility κ are compared to the case where no magnetic field is applied in the direction of the hard magnetization axis. In comparison, applying a magnetic field in the direction of the hard magnetization axis increases the magnetic susceptibility κ, and changing the strength of the magnetic field in the direction of the hard magnetization axis also changes the magnetic susceptibility κ. This suggests that the magnetic susceptibility κ can be controlled by changing the strength of the magnetic field.

[0044] By increasing the magnetic susceptibility of the object being measured 1, which is a magnetic particle, for example, by increasing the real part (κ') of the magnetic susceptibility κ, the signal strength of the magnetic field of the object being measured 1 increases, which is the detection sensitivity. An improvement in sensitivity can be obtained. For example, in magnetic immunoassay, it contributes to improving the detection sensitivity of signals from magnetic markers (magnetic particles) of antibodies bound to antigens. Also, for example, when the imaginary part (κ'') of the magnetic susceptibility κ increases, the loss (resistivity) of the object being measured increases, and since this loss is converted into heat, it contributes to improving the heating efficiency of magnetic particles in magnetic thermotherapy, for example.

[0045] As described above, the magnetic susceptibility of magnetic particles can be measured by applying magnetic fields in two directions: the easy magnetization axis and the hard magnetization axis. Furthermore, by changing the magnetic field applied in the hard magnetization axis direction, the magnetic susceptibility of magnetic particles that changes in accordance with the strength of the magnetic field in the hard magnetization axis direction can be measured. Moreover, by applying magnetic fields in two directions—the easy magnetization axis and the hard magnetization axis—the magnetic anisotropy of magnetic particles can be controlled by changing the strength of the magnetic field in the hard magnetization axis direction, making the magnetic susceptibility of magnetic particles variable, and in particular, controlling it to increase the magnetic susceptibility.

[0046] Specifically, when applying magnetic particles to magnetic thermotherapy or magnetic immunoassay, a method for controlling the magnetic susceptibility of these magnetic particles (especially aggregates of magnetic particles) involves first magnetizing the target magnetic particles in the direction of easy magnetization, then applying a magnetic field in the direction of hard magnetization, and varying the strength of the magnetic field in the hard magnetization direction to change the magnetic susceptibility of the magnetic particles. This method improves the magnetic properties of the magnetic particles, providing useful and advantageous technological advancements in application fields of magnetic particles, such as improving the heating efficiency of magnetic particles in magnetic thermotherapy and improving the detection sensitivity of magnetic particles as magnetic markers in magnetic immunoassay.

[0047] Figure 8 shows an example of measurement results when the magnetic susceptibility measurement method in this embodiment is applied to a magnetic immunoassay. This is an experiment of the biotin-avidin reaction similar to the antigen-antibody reaction, in which magnetic particles (magnetic nanoparticles with a diameter of φ200 nm) are used as magnetic markers for avidin addition, and Figure 8(a) shows the magnetic susceptibility before the reaction of biotin, the detected substance that binds to din, and Figure 8(b) shows the magnetic susceptibility after the reaction. The graphs represent the frequency dependence of the magnetic susceptibility κ (its imaginary part κ'') of the measured substance, which is contained in aggregates of the magnetic particles, before and after the reaction, as measured by the magnetic susceptibility measurement method of this embodiment.

[0048] Figure 8 shows the magnetic susceptibility κ (and its imaginary part κ'') when the strength of the magnetic field applied in the hard magnetization axis direction is varied (including the case where no magnetic field is applied in the hard magnetization axis direction (0.0T)). Specifically, examples of magnetic susceptibility κ are given for magnetic field strength (magnetic flux density) in the hard magnetization axis direction of 0.0T (no magnetic field applied), 0.1T, 0.05T, 0.1T, 0.15T, and 0.2T. In this example of measurement results, it can be confirmed that the ferromagnetic resonance (FMR) frequency at which the magnetic susceptibility is maximized shifts depending on the strength of the applied magnetic field in the hard magnetization axis direction, and furthermore, before and after the reaction, the peak value decreases, its sharpness decreases, and its half width widens. As illustrated in Figure 8, for example, the full width at half maximum (FWHM) of the peak value before and after the reaction at an applied magnetic field of 0.1 T more than doubles, and this change in FWHM makes it possible to detect the substance to be detected. This is thought to be due to the substance to be detected binding to magnetic particles, which widens the spacing between magnetic particles and reduces the uniformity of the magnetic moment. The FWHM of the measured peak value of the magnetic susceptibility is used to detect the substance to be detected (antigen, biotin) in the antigen-antibody reaction or biotin-avidin reaction.

[0049] Figure 9 shows another example of measurement results for magnetic immunoassay, applying the susceptibility measurement method in this embodiment. This is an experiment to detect the protein GDF15 by antigen-antibody reaction. Furthermore, magnetic particles (50 nm magnetic nanoparticles) were used as magnetic markers for the antibody, and the sample to be measured contained aggregates of magnetic particles formed by reacting the antibody with the detectable protein GDF15. The graph below shows the frequency dependence of the magnetic susceptibility κ of the object being measured, as measured by the magnetic susceptibility measurement method in this embodiment. Figure 9(a) shows the real part (κ') of the magnetic susceptibility κ, and Figure 9(b) shows the frequency dependence of the magnetic susceptibility κ. This indicates the value of the imaginary part (κ''). Note that the protein GDF15 is used in the diagnosis of mitochondrial diseases. It is a protein.

[0050] Furthermore, Figure 10 shows the relationship between the magnetic susceptibility κ and the ferromagnetic resonance frequency (FMR) in the magnetic susceptibility measurement shown in Figure 9. This is a graph showing the relationship between the magnetic field Hhard applied in the direction of the hard magnetization axis, and which corresponds to the strength of the magnetic field Hhard in the direction of the hard magnetization axis. A graph showing the ferromagnetic resonance frequency (FMR) at which the magnetic susceptibility κ (and its imaginary part κ'') reaches its peak value. be.

[0051] Figure 9 shows the magnetic susceptibility κ when the strength of the magnetic field applied in the hard magnetization axis direction is varied (including the case where no magnetic field is applied in the hard magnetization axis direction (0.0T)). Specifically, the magnetic susceptibility κ is shown. Examples of magnetic susceptibility κ are shown for magnetic field strengths (magnetic flux density) in the hard-to-magnetize axis direction of 0.0T (no magnetic field applied), 0.1T, 0.05T, 0.1T, 0.15T, and 0.2T. In this example of measurement results, although it is difficult to determine from the visual inspection in Figure 9 alone, the ferromagnetic resonance (FMR) frequency at which the magnetic susceptibility is maximized shifts depending on the strength of the applied magnetic field in the hard-to-magnetize axis direction, and a graph plotting the ferromagnetic resonance frequencies corresponding to the magnetic field strength is shown in Figure 10.

[0052] Figure 10 shows the magnetic susceptibility of an object containing magnetic particles bound to the protein GDF15. The ferromagnetic resonance frequency of the - value is indicated by the symbol ▲, and represents the state when protein GDF15 is not bound. The ferromagnetic resonance frequency of the peak magnetic susceptibility of the object being measured, which contains magnetic particles, is indicated by the symbol ●. Generally, as the applied magnetic field is increased, the ferromagnetic resonance frequency increases before and after the binding of protein GDF15 (reaction). It can be confirmed that there is a shift (before and after). As can be seen from Figure 10, for example, the amount of shift in the ferromagnetic resonance frequency at applied magnetic fields of 0.15T and 0.2T is large, and this frequency shift This makes it possible to detect GDF15 as the target substance.

[0053] In the embodiments of the present invention described above, a method for measuring the magnetic susceptibility of magnetic particles was explained. Since the magnetic susceptibility has the relationship shown in equation (3) below with respect to the permeability of magnetic particles, the magnetic susceptibility κ can be converted to the permeability (relative permeability) μ, and can be considered substantially the same as measuring the permeability μ.

[0054] κ = μ - 1 ... (3) (μ: relative permeability)

[0055] The signal transmission line configured in the probe 10 is not limited to the microstrip line shown in the above-described configuration example, but may also be configured using, for example, a coplanar line or a coaxial line. Furthermore, regarding the imparting of magnetic anisotropy to magnetic particles, it is not limited to the case where magnetic particles are aggregated in a container that is long in one direction, such as a microtube, to impart magnetic anisotropy (shape anisotropy) to the magnetic particles in the longitudinal direction, but may also be used, for example, by using flattened magnetic particles (shape that is long in one direction) in which each particle itself possesses magnetic anisotropy.

[0056] [Reference example] Below, we describe an example of measurement using another measurement method to which the measurement technique of the present invention can be applied, as a reference example to which the present invention can be applied. The measurement example using the measurement method in this reference example is an experiment to detect the protein GDF15 by antigen-antibody reaction, and magnetic particles (magnetic nanoparticles) are used as magnetic markers for the antibody. Using particles, the protein GDF15, which is the substance to be measured (antigen) that binds to the antibody, is reacted with a magnetic field. A magnetic field is applied to a sample containing aggregates of crystalline particles, and the magnetization is detected by a magnetic field sensor to measure the amount (concentration) of the substance being measured (protein GDF15).

[0057] Figure 11 shows the schematic configuration of a measuring device for performing the measurement example in the reference example. The measuring device consists of a rotating mechanism (rotor) that rotates a container containing a sample including magnetic particles and an object to be measured that can bond with the magnetic particles, and a mechanism that reverses the direction of the magnetic field with each rotation in synchronization with the rotation period of the container. The system comprises a magnetic field generating means that applies a switching magnetic field to a sample inside a container, a magnetic field sensor positioned at a distance from the magnetic field generating means that detects a signal corresponding to the magnetic field emitted from the sample contained in the rotating container, and a signal processing means that processes the detected signal.

[0058] The magnetic field generating means comprises an excitation coil (drive coil) and a signal generator. Before the container rotates, a permanent magnet (yoke) is brought close to the bottom of the container to condense the sample, and a magnetic field is applied to switch the direction of the magnetic field from that state, and the magnetic field from the sample is detected by a magnetic field sensor. For example, the yoke and the excitation coil are arranged concentrically. Preferably, with each rotation of the container by the rotating mechanism, the magnetic field generating means applies a magnetic field such that the strength of the magnetic field increases in steps. The signal processing means comprises a signal processing circuit such as an A / D converter and a computer device such as a personal computer (PC). The detailed configuration of this measuring device and The operation is disclosed, for example, in Japanese Patent Publication No. 2020-159871 (Patent Document 2 above), which includes the inventor of the present application as an inventor.

[0059] Figure 12 shows the measurement results (part 1) of a measurement example in a reference case. The measurement results (part 1) are the results of a measurement experiment in which an antibody was generated by conjugating a primary antibody (Anti-GDF15 monoclonal) with magnetic nanoparticles (Nanomag-D, average particle size 250 nmφ) to which Protein A was added, and then reacted with antigens (protein GDF15) at concentrations of 0 ng / ml, 0.1 ng / ml, 1.0 ng / ml, and 10 ng / ml using the apparatus configuration exemplified in Figure 11. Figure 12(a) shows the relationship between the number of rotations of the container (applied voltage increases with each rotation) and the output voltage of the magnetic field sensor, and Figure 12(b) shows the relationship between the concentration of protein GDF15 determined based on the measurement results in Figure 12(a) and the output voltage of the magnetic field sensor. This shows the relationship between pressures.

[0060] Figure 13 shows the measurement results (part 2) of a reference example. The measurement results (part 2) show the generation of antibodies by conjugating a primary antibody (Anti-GDF15 monoclonal) to magnetic nanoparticles (Nanomag-D, average particle size 250 nmφ) with Protein A added, and antibodies by conjugating a secondary antibody (Anti-GDF15 polyclonal) to magnetic nanoparticles (Nanomag-D, average particle size 50 nmφ) with Protein A added. After generating two types of antibodies, the following measurement results were obtained from an antigen-antibody reaction experiment using the apparatus configuration illustrated in Figure 11, where the two types of antibodies were reacted with antigens (protein GDF15) at concentrations of 0 ng / ml, 1.0 ng / ml, 10 ng / ml, and 100 ng / ml. Figure 13(a) shows the relationship between the number of rotations of the container (applied voltage increases with each rotation) and the output voltage of the magnetic field sensor, and Figure 13(b) shows the relationship between the concentration of protein GDF15 and the output voltage of the magnetic field sensor, which can be determined based on the measurement results in Figure 13(a). vinegar.

[0061] In both the measurement results shown in Figure 12 (Part 1) and the measurement results shown in Figure 13 (Part 2), the output voltage (magnetic signal) of the magnetic field sensor increases as the applied magnetic field increases (because the applied magnetic field increases as the number of rotations increases), and the degree of increase in the magnetic signal is greater as the concentration of protein GDF15 increases. This became clear. From this, as shown in Figures 12(b) and 13(b), the concentration (amount) of protein GDF15 can be determined by the magnitude of the magnetic field being detected.

[0062] Comparing measurement result (1) and measurement result (2), the error bars for each measurement value in the graph in Figure 13 are smaller compared to the graph in Figure 12. In the case of measurement result 2, which uses two types of antibodies, the magnetic signal is increased compared to measurement result 1, and the detection sensitivity and detection accuracy are improved.

[0063] Furthermore, this measurement revealed that, when the antigen is a protein, the magnetic signal output increases as the antigen concentration increases, as shown in Figures 12 and 13. This is the opposite physical phenomenon to the phenomenon disclosed in, for example, Japanese Patent Application Publication No. 2020-159871, namely, the phenomenon in magnetic immunoassay where, when the substance to be measured (antigen) is bacteria, the magnetic signal output tends to decrease as the antigen concentration increases.

[0064] The reason why the output trend of the magnetic signal changes depending on the type of antigen is presumed to depend on the size of the antigen. Specifically, in the case of proteins, which are smaller in size compared to bacteria, it is presumed that even if the concentration of protein increases, the magnetic bonding between magnetic nanoparticles is not weakened because the size of the protein is relatively small in the aggregates of proteins bound to magnetic nanoparticles, and the magnetic signal output also increases, suggesting that the protein has an effect of promoting the aggregation of magnetic nanoparticles. On the other hand, in the case of bacteria, which are larger in size than proteins, the relatively large size of the bacteria increases the distance between magnetic nanoparticles in the aggregates of bacteria bound to magnetic nanoparticles, weakening the magnetic bonding between the magnetic nanoparticles. Therefore, it is presumed that as the concentration of bacteria increases, the magnetic signal output decreases. From the measurement examples in the above reference examples, it is possible to obtain the knowledge that the output trend of the magnetic signal differs depending on the size of the antigen. Furthermore, the measurement examples in the above reference examples can also be similarly performed by applying the magnetic susceptibility measuring device and magnetic susceptibility measuring method of the present invention corresponding to Figures 1 to 10 to measure the magnetization of the object to be measured.

[0065] The present invention is not limited to the embodiments described above, and of course, design changes that do not depart from the spirit of the invention, including various modifications and alterations that can be conceived by a person with ordinary skill in the art of the present invention, are also included in the present invention. [Explanation of Symbols]

[0066] 1: Object under measurement, 1a: Microtube, 3: Cable, 10: Probe, 11: Microstrip conductor, 12: Flexible substrate, 13: Fluoropolymer substrate, 14: Ground conductor, 15: Connector, 20: Signal measuring instrument, 30: Computer device, 40: Coil for easily magnetized axis, 50: Coil for hard-to-magnetize axis

Claims

1. In a magnetic susceptibility measuring device for measuring the magnetic susceptibility of an object containing magnetic particles, A probe is positioned such that a signal transmission line is formed and the easy magnetization axis of the object to be measured is perpendicular to the signal transmission line, and the object to be measured is positioned close to or in contact with the signal transmission line. A first magnetic field application unit for applying a magnetic field in the direction of the easy magnetization axis of the object to be measured, A second magnetic field application unit for applying a magnetic field in the direction of the hard magnetization axis perpendicular to the easy magnetization axis of the object to be measured, A signal measuring instrument for measuring a signal transmitted through the signal transmission line when a magnetic field is applied by both the first magnetic field application unit and the second magnetic field application unit, A magnetic susceptibility measuring device comprising a calculation processing means for determining the magnetic susceptibility of an object to be measured based on the signal measured by the signal measuring instrument.

2. The magnetic susceptibility measuring device according to claim 1, characterized in that the signal measuring device measures the signal transmitted through the signal transmission line when the magnetic field applied by the first magnetic field application unit is kept constant and the strength of the magnetic field applied by the second magnetic field application unit is changed.

3. The magnetic susceptibility measuring device according to claim 1, characterized in that the signal transmission line is a microstrip line.

4. In a method for measuring the magnetic susceptibility of an object containing magnetic particles, A step of positioning the object to be measured in close proximity to or in contact with a probe on which a signal transmission line has been formed, wherein the object to be measured is positioned in close proximity to or in contact with the signal transmission line such that the easy magnetization axis direction of the object to be measured is perpendicular to the signal transmission line, The first magnetic field application means applies a magnetic field in the direction of the easy magnetization axis of the object to be measured, The process involves applying a magnetic field to the object to be measured in the direction of the hard magnetization axis perpendicular to the easy magnetization axis direction using a second magnetic field application means, A step of measuring the signal transmitted through the signal transmission line in a state in which a magnetic field is applied by both the first magnetic field application means and the second magnetic field application means using a signal measuring instrument, A method for measuring magnetic susceptibility, characterized by comprising the step of determining the magnetic susceptibility of an object to be measured based on the signal measured by the signal measuring instrument using a calculation processing means.

5. The magnetic susceptibility measurement method according to claim 4, characterized in that, in the step of measuring the signal, the magnetic field provided by the first magnetic field applying means is kept constant, and the signal transmitted through the signal transmission line is measured when the strength of the magnetic field applied by the second magnetic field applying means is changed.

6. The magnetic susceptibility measurement method according to claim 4, characterized in that, in the step of determining the magnetic susceptibility, the magnetic susceptibility corresponding to a predetermined frequency band is determined, and further, the object to be detected coupled with magnetic particles contained in the object to be measured is detected using the peak value of the magnetic susceptibility in the predetermined frequency band.

7. The magnetic susceptibility measurement method according to claim 4, characterized in that, in the step of determining the magnetic susceptibility, the magnetic susceptibility corresponding to a predetermined frequency band is determined, and further, based on the frequency at which the magnetic susceptibility peaks, a detectable object coupled with magnetic particles contained in the object to be measured is detected.

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