Magnetic stand and magnetic separation method

Abstract

To provide a magnetic stand excellent in separability between magnetic beads and a liquid in magnetic separation, and to provide a magnetic separation method.SOLUTION: A magnetic stand includes: a base having an insertion hole into which a container is to be inserted, the insertion hole extending along a first axis; and a magnet provided on the base and having a magnetization that applies a magnetic field to the insertion hole. The magnet is disposed such that magnetic poles thereof face directions different from that of the container. When a plane including the first axis and determined such that a normal line of the plane is orthogonal to the first axis and passes through a center of the magnet is taken as a reference plane, and the magnetization is projected onto the reference plane, an angle formed by the first axis and the magnetization projected onto the reference plane is more than 0° and 90° or less.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present invention relates to a magnetic stand and a magnetic separation method. Background Art

[0002] In recent years, demand for testing biological substances has been increasing in the fields of medical diagnosis and life science. Among biological substance testing methods, the PCR (Polymerase chain reaction) method is a method in which nucleic acids such as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are extracted, and the nucleic acids are specifically amplified and detected. In the process of testing such biological substances, it is first necessary to extract the target test substance from a sample. For the extraction of biological substances, magnetic separation methods using magnetic beads are widely used. In the magnetic separation method, magnetic beads having a function capable of carrying biological substances to be extracted are used, and biological substances are extracted by applying a magnetic field. Specifically, after dispersing magnetic beads having a carrying capacity for the target test substance on their surfaces in a dispersion medium, the obtained dispersion is mounted on a magnetic field generator such as a magnetic stand, and ON / OFF of magnetic field application is repeated multiple times. Thereby, the target test substance is extracted. Such a magnetic separation method is a method of separating and recovering magnetic beads by magnetic force, and thus enables rapid separation operations.

[0003] Furthermore, similar magnetic separation methods are used not only for extraction in PCR methods, but also in fields such as protein purification, exosome isolation, and cell isolation and extraction.

[0004] In magnetic separation methods, a magnetic stand having a function of holding a container and a function of applying a magnetic field to the container is used. For example, Patent Document 1 discloses a magnetic stand comprising a base having holding holes for inserting containers, and a permanent magnet provided on the base. In this magnetic stand, the permanent magnet is arranged such that the N pole faces the container side and the S pole faces the opposite side. Prior Art Documents Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-018692 [Overview of the project] [Problems that the invention aims to solve]

[0006] When a magnetic field is applied to a container containing magnetic beads, the magnetic beads inside the container align along the direction of the magnetic field. Therefore, when a permanent magnet is placed as described in Patent Document 1, the magnetic beads will be arranged in a needle-like pattern along the radial direction of the container. This phenomenon of magnetic beads aligning in a needle-like pattern is also called the "spike phenomenon." When the spike phenomenon occurs, the solution is more easily retained between the needle-like arranged magnetic beads. As a result, the separation between the magnetic beads and the solution decreases, and impurities are more likely to be mixed into the extracted biological material. In other words, the washing efficiency of the biological material decreases, and the purity of the extracted biological material decreases. Furthermore, even if the spike phenomenon does not occur, these problems may occur if the direction of the magnetic field is not appropriate. [Means for solving the problem]

[0007] A magnetic stand according to an application example of the present invention is A base extending along the first axis and having an insertion hole into which a container is inserted, A magnet provided on the base and having magnetization for applying a magnetic field to the insertion hole, Equipped with, The magnet is positioned such that its magnetic poles face in a direction different from that of the container. When the magnetization is projected onto a reference plane which is a plane containing the first axis and whose normal is perpendicular to the first axis and passes through the center of the magnet, The angle between the first axis and the magnetization projected onto the reference plane is, Over 60° Below 90° the law of nature, When the container is inserted into the insertion hole and the diameter of the container measured at the position where the magnet is provided is defined as 1, The width of the magnet in the direction of magnetization is 0.2 or more and 1.5 or less. It is characterized by the following:

[0008] The magnetic separation method according to an application example of the present invention is: A magnetic separation step is performed to separate the magnetic beads from the liquid by applying a magnetic field to a container containing magnetic beads and liquid, thereby fixing the magnetic beads to the inner wall of the container. A liquid discharge step in which the liquid is discharged using a liquid suction device while the magnetic beads and the liquid are separated, It has, The magnetic poles that generate the magnetic field are oriented in a different direction from the container. When the axis of the container is defined as the second axis, and magnetic field lines representing the magnetic field are projected onto a plane including the second axis, The magnetic field is set such that the angle between the projected magnetic field lines and the second axis is greater than 0° and less than or equal to 90°. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing a magnetic stand according to an embodiment. [Figure 2] Figure 1 is a cross-sectional view of the magnetic stand when it is cut in the XZ plane. [Figure 3] This is a cross-sectional view of the magnetic stand shown in Figure 1, when it is cut in the XY plane. [Figure 4] This is a step diagram illustrating a biomaterial extraction method including a magnetic separation method according to an embodiment. [Figure 5] Figure 4 is a schematic diagram illustrating the method for extracting biomaterials shown. [Figure 6] Figure 4 is a schematic diagram illustrating the method for extracting biomaterials shown. [Figure 7] This is a schematic diagram illustrating an example where the direction of the magnetic field applied to the container is set to the direction of the container (an example that does not satisfy element (a)). [Figure 8] This is a schematic diagram illustrating an example where the direction of the magnetic field applied to the container is set to the direction of the container (an example that does not satisfy element (a)). [Figure 9]It is a schematic diagram for explaining an angle θ2 formed between a second axis AX2 of a container and a projected magnetic force line Lm' when the magnetic force line Lm is projected onto a plane P2 including the second axis AX2 of the container. [Figure 10] It is a schematic diagram showing an example where an angle θ2 formed between a second axis AX2 of a container and a projected magnetic force line Lm' when the magnetic force line Lm is projected onto a plane P2 including the second axis AX2 of the container is 0° (an example not satisfying the requirement (b)). [Figure 11] It is a schematic diagram showing an example where an angle θ2 formed between a second axis AX2 of a container and a projected magnetic force line Lm' when the magnetic force line Lm is projected onto a plane P2 including the second axis AX2 of the container is 0° (an example not satisfying the requirement (b)). [Figure 12] It is a schematic diagram for explaining an angle θ1 formed between a first axis AX1 of an insertion hole of a magnetic stand and a direction of a projected magnetization M' when magnetization M of a magnet is projected onto a plane P1 including the first axis AX1 of the insertion hole of the magnetic stand. [Figure 13] It is a view of a container inserted into the insertion hole shown in FIG. 12, as seen from the magnet side. [Figure 14] It is a graph for comparing the residual liquid amount between Example 1 and each comparative example. [Figure 15] It is a graph for comparing the residual liquid amount among Examples 1 to 5.

Mode for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the magnetic stand and the magnetic separation method of the present invention will be described in detail with reference to the accompanying drawings.

[0011] 1. Magnetic Stand First, the magnetic stand according to the embodiment will be described.

[0012] Figure 1 is a perspective view showing a magnetic stand 1 according to an embodiment. In the figures of this application, the X-axis, Y-axis, and Z-axis are defined as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip side being "positive" and the base side being "negative". In the following description, for example, "X-axis direction" includes both the positive and negative directions of the X-axis. Also, in the following description, the positive side of the Z-axis may be described as "up" and the negative side of the Z-axis as "down".

[0013] Figure 2 is a cross-sectional view of the magnetic stand 1 shown in Figure 1 when cut in the XZ plane. Figure 3 is a cross-sectional view of the magnetic stand 1 shown in Figure 1 when cut in the XY plane.

[0014] The magnetic stand 1 shown in Figure 1 is a magnetic field generator that holds a container 9 such as a microtube as shown in Figure 2, and applies an external magnetic field to the sample. The magnetic stand 1 comprises a stand 11 (base) and a magnetic plate 12 having a magnet 124. By applying an external magnetic field generated from the magnet 124, magnetic beads and liquid placed inside the container 9 can be magnetically separated. Specifically, an external magnetic field is applied to the magnetic beads, fixing them to the inner wall surface of the container 9. This makes it possible to separate the solid phase magnetic beads from the liquid phase liquid.

[0015] 1.1. Stand The stand 11 shown in Figure 1 comprises an upper plate 112 and a lower plate 114, and side plates 116 and 118 that connect them to each other. The upper plate 112 and the lower plate 114 are plate-shaped, extending along the XY plane. The side plates 116 and 118 are plate-shaped, extending along the XZ plane.

[0016] The top plate 112 has multiple through holes 113. The through holes 113 penetrate the top plate 112 along the Z-axis. The through holes 113 are also arranged at predetermined intervals along the Y-axis.

[0017] The lower plate 114 is positioned below the upper plate 112 at a distance from each other and has a plurality of recesses 115. The recesses 115 open upwards. The recesses 115 are also arranged at predetermined intervals along the Y-axis. The positions of the through holes 113 and the recesses 115 coincide in the Y-axis direction. As a result, one through hole 113 and one recess 115 form a pair, which constitutes an insertion hole 13. The insertion hole 13 extends along the first axis AX1 and is a hole into which the container 9 is inserted. When the container 9 is inserted from above the through hole 113, the container 9 is held by the through hole 113 and the recesses 115. In other words, the container 9 is propped up in the insertion hole 13. This allows the orientation of the container 9 to be maintained along the first axis AX1, and the distance between the container 9 and the magnet plate 12 can be kept sufficiently close. Furthermore, because the stand 11 has a plurality of insertion holes 13, it can hold multiple containers 9 simultaneously.

[0018] The inner wall surface of the through-hole 113 shown in Figure 1 forms a continuous annular shape surrounding the first axis AX1, but is not limited to this, and may have a partially interrupted shape. Similarly, the inner wall surface of the recess 115 shown in Figure 1 also forms a continuous annular shape, but is not limited to this, and may have a partially interrupted shape. Furthermore, the recess 115 may penetrate the lower plate 114. Moreover, if the container 9 can be held in place by the through-hole 113 alone, the recess 115 may be omitted.

[0019] Furthermore, although the first axis AX1 shown in Figure 1 is parallel to the Z-axis, it may also be inclined with respect to the Z-axis.

[0020] Side plate 116 connects the Y-axis negative end of the top plate 112 to the Y-axis negative end of the bottom plate 114. Side plate 118 connects the Y-axis positive end of the top plate 112 to the Y-axis positive end of the bottom plate 114. The frame is formed by the top plate 112, bottom plate 114, side plate 116, and side plate 118.

[0021] The materials used to construct the stand 11 are not particularly limited as long as they are non-magnetic materials, but for example, resin materials such as ABS, polypropylene, and nylon, and metal materials such as aluminum alloys can be used.

[0022] 1.2. Magnetic Plate The magnet plate 12 is located on the X-axis positive side of the insertion hole 13 and is provided between the upper plate 112 and the lower plate 114. As shown in Figure 2, the magnet plate 12 comprises a back plate 122 and a magnet 124 provided inside the back plate 122.

[0023] The back plate 122 is plate-shaped and extends along the YZ plane. The back plate 122 supports multiple magnets 124. The magnets 124 are arranged at predetermined intervals along the Y axis. The positions of the magnets 124 in the Y axis direction coincide with the positions of the insertion holes 13. As a result, one insertion hole 13 is paired with one magnet 124, allowing an external magnetic field from the magnets 124 to be applied to the container 9 inserted into the insertion hole 13. Furthermore, since the back plate 122 is located between the upper plate 112 and the lower plate 114, the magnets 124 can be brought closer to the insertion holes 13. This allows the external magnetic field applied to the container 9 to be strengthened.

[0024] The magnet 124 may be an electromagnet, but it is preferable that it be a permanent magnet. This eliminates the need for a power supply for the magnetic stand 1 and makes it easier to miniaturize and lighten it. It also improves the portability of the magnetic stand 1, thus increasing the flexibility of its installation location.

[0025] Examples of permanent magnets include neodymium iron boron magnets, samarium cobalt magnets, ferrite magnets, and alnico magnets. Of these, neodymium iron boron magnets are preferred because they can generate a sufficient magnetic field even in a small size. Furthermore, it is preferable to use neodymium iron boron magnets coated with nickel plating or the like to ensure reliability over time, such as corrosion resistance.

[0026] The magnetic flux density on the surface of the magnet 124 is preferably 50 mT or more, and more preferably 200 mT or more. This increases the movement speed of the magnetic beads during magnetic separation and suppresses the detachment of the fixed magnetic beads. The surface magnetic flux density of the magnet 124 is measured, for example, with a Gauss meter using a Hall element.

[0027] The size of the magnet 124 is selected appropriately according to the size of the container 9, etc. Therefore, it is preferable that the size of the magnet 124 be set appropriately according to the size of the insertion hole 13. Specific sizes will be described later.

[0028] With the container 9 inserted into the insertion hole 13, a portion of the back plate 122 may or may not be interposed between the container 9 and the magnet 124, as shown in Figure 2.

[0029] Figures 2 and 3 show how magnetic field lines Lm generated from magnet 124 penetrate into container 9. The magnet 124 shown in Figures 2 and 3 is positioned so that its north pole points towards the negative Y-axis and its south pole points towards the positive Y-axis. As a result, the magnetic field lines Lm generated from magnet 124 contain a large number of components parallel to the XY plane, as shown in Figures 2 and 3. This external magnetic field, represented by these magnetic field lines Lm, acts on magnetic beads (not shown) housed in container 9.

[0030] 2. Method for extracting biomaterials Next, a method for extracting biomaterials, including a magnetic separation method according to the embodiment, will be described.

[0031] Figure 4 is a process diagram illustrating a biomaterial extraction method including a magnetic separation method according to an embodiment. Figures 5 and 6 are schematic diagrams illustrating the biomaterial extraction method shown in Figure 4.

[0032] The biomaterial extraction method shown in Figure 4 comprises a dissolution / adsorption step S102, a magnetic separation step S104, a liquid discharge step S106, a washing step S108, and an elution step S110. Of these, the magnetic separation step S104 and the liquid discharge step S106 constitute the magnetic separation method according to this embodiment.

[0033] The biomolecules targeted for extraction in biomolecule extraction methods include substances such as nucleic acids (DNA and RNA), proteins, various cells (such as cancer cells), peptides, and viruses. Nucleic acids may exist in biological samples such as cells and tissues, as well as in viruses and bacteria. The biomolecule extraction method shown in Figure 4 extracts such biomolecules through the steps of dissolution / adsorption, separation, washing, and elution. The extraction procedure is usually defined for each magnetic bead dispersion provided as a reagent or for each target biomolecule, and is typically clearly indicated by the provider. Such a procedure is generally referred to as an "extraction protocol."

[0034] The following describes each step in order. Note that the following explanation uses the case where the biological substance is nucleic acid as an example. Furthermore, the following explanation describes the case where the magnetic stand 1 mentioned above is used in the magnetic separation method, but it is also possible to use magnetic field generating devices other than the magnetic stand 1.

[0035] 2.1.Dissolution / adsorption process In the dissolution and adsorption process S102, first, the sample containing nucleic acids is placed in the container 9 shown in Figures 5 and 6. A dispersion containing magnetic beads 3 and a dissolution and adsorption solution are then added to this container 9. The contents of container 9 are then mixed. Since nucleic acids are usually encapsulated in the cell membrane or nucleus, the dissolution and adsorption solution first dissolves and removes the so-called outer shell of the cell membrane or nucleus, thereby extracting the nucleic acids. Subsequently, the nucleic acids are adsorbed onto the magnetic beads 3 by the adsorption action of the dissolution and adsorption solution.

[0036] As the dissolution and adsorption solution, for example, a liquid containing a chaotropic substance is used. Chaotropic substances generate chaotropic ions in aqueous solutions, reducing the interaction of water molecules and thereby destabilizing the structure, contributing to the adsorption of nucleic acids onto magnetic beads 3. Examples of chaotropic substances that exist as chaotropic ions in aqueous solutions include guanidine thiocyanate, guanidine hydrochloride, sodium iodide, potassium iodide, and sodium perchlorate. Of these, guanidine thiocyanate or guanidine hydrochloride, which have a strong protein denaturing effect, are preferably used.

[0037] The concentration of the chaotropic substance in the dissolved adsorbent solution varies depending on the chaotropic substance, but is preferably between 1.0 M and 8.0 M. In particular, when guanidine thiocyanate is used, it is preferably between 3.0 M and 5.5 M. Furthermore, when guanidine hydrochloride is used, it is preferably between 4.0 M and 7.5 M.

[0038] The soluble adsorbent may contain a surfactant. The surfactant is used to disrupt the cell membrane or denature proteins contained within the cell. While not particularly limited, examples of surfactants include polyoxyethylene sorbitan monolaurate, nonionic surfactants such as Triton-type and Tween-type surfactants, and anionic surfactants such as sodium N-lauroyl sarcosinate. Of these, nonionic surfactants are preferred. Using a nonionic surfactant suppresses the influence of ionic surfactants when analyzing nucleic acids after extraction. As a result, electrophoretic analysis becomes possible, expanding the range of analytical methods available.

[0039] The concentration of the surfactant in the dissolved adsorbent is not particularly limited, but is preferably 0.1% by mass or more and 2.0% by mass or less.

[0040] Furthermore, the soluble adsorbent may contain at least one of a reducing agent and a chelating agent. Examples of reducing agents include 2-mercaptoethanol and dithiothreitol. Examples of chelating agents include disodium ethylenediaminetetraacetate dihydrate (EDTA).

[0041] The concentration of the reducing agent in the dissolved adsorbent is not particularly limited, but is preferably 0.2 M or less. The concentration of the chelating agent in the dissolved adsorbent is not particularly limited, but is preferably 0.2 mM or less.

[0042] The pH of the dissolved adsorbent solution is not particularly limited, but it is preferably neutral, between 6 and 8. Furthermore, tris(hydroxy)aminomethane or HCl may be added as a buffer solution to adjust the pH.

[0043] In the dissolution and adsorption step S102, the contents of container 9 are stirred as needed using a vortex mixer, manual shaking, etc. The stirring time is not particularly limited, but is preferably between 5 seconds and 40 minutes.

[0044] The magnetic beads 3 are not particularly limited, and are not limited in any way other than magnetic particles that have residual magnetization and are capable of adsorbing nucleic acids. For example, the magnetic beads 3 include ferrite nanoparticles and magnetic metal particles.

[0045] Of these, magnetic metal particles are preferably used. Because magnetic metal particles have a high saturation magnetization, they can improve the movement speed of the magnetic beads 3 during magnetic separation. This makes it possible to shorten the time required for magnetic separation.

[0046] Examples of magnetic metal particle compositions include alloys with Fe as the main component (Fe-based alloys), specifically Fe-Co alloys, Fe-Ni alloys, Fe-Co-Ni alloys, Fe-Si alloys, Fe-Si-Cr alloys, and the like.

[0047] Furthermore, the metallic structure constituting the magnetic metal particles can take on various forms, such as crystalline, amorphous, and nanocrystalline structures. In particular, using an amorphous or nanocrystalline structure results in a lower coercivity Hc, thereby improving the dispersibility of the magnetic beads 3.

[0048] The magnetic beads 3 preferably have a coating layer that covers the surface of the magnetic metal particles. The coating layer has the function of capturing the biological substance to be extracted. Examples of materials that make up the coating layer include silicon oxide, as well as a composite oxide or composite of silicon and one or more oxides selected from the group consisting of Al, Ti, V, Nb, Cr, Mn, Sn, and Zr.

[0049] The average particle size of the magnetic beads 3 is preferably between 0.5 μm and 50 μm, and more preferably between 2 μm and 20 μm. This allows the magnetic beads 3 to be uniformly dispersed in the liquid and a sufficient amount of nucleic acid to be adsorbed onto the surface of the magnetic beads 3. This improves the extraction efficiency and detection accuracy of nucleic acids.

[0050] 2.2. Magnetic Separation Process In the magnetic separation step S104, an external magnetic field is applied to the magnetic beads 3 on which nucleic acids are adsorbed, causing magnetic attraction. This moves the magnetic beads 3 to the inner wall of the container 9 and fixes them in place. As a result, the solid phase magnetic beads 3 and the liquid phase can be separated. Figures 5 and 6 illustrate a state in which the magnetic beads 3 are fixed to a part of the inner wall surrounding the second axis AX2 when the container 9 is a cylindrical microtube extending along the second axis AX2.

[0051] The magnetic separation step S104 and the liquid discharge step S106, described later, are performed after the dissolution and adsorption step S102, as well as in the washing step S108 and the elution step S110, described later, as needed.

[0052] Before performing magnetic attraction, the contents of container 9 are stirred as needed. This increases the probability that nucleic acids will adsorb onto the magnetic beads 3. Stirring can be done using, for example, a vortex mixer or manual shaking.

[0053] After magnetic attraction, the container 9 may be accelerated as needed. This allows any liquid adhering to the magnetic beads 3 to be shaken off, thereby improving the accuracy of magnetic separation. The acceleration may be centrifugal acceleration. A centrifuge can be used to apply centrifugal acceleration.

[0054] In the magnetic separation step S104, as described above, a magnetic field is applied to the contents of container 9. This means that, if the magnetic field is represented by magnetic field lines Lm, the magnetic field is generated so that the magnetic field lines Lm pass through the inside of container 9, as shown in Figures 5 and 6. The density of magnetic field lines Lm represents the strength of the magnetic field. When there is a difference in the strength of the magnetic field in space, that is, the magnetic beads 3 move according to the gradient of the magnetic field strength.

[0055] In Figures 5 and 6, the magnet 124 is a magnetic field generator, and the magnetic field is stronger the closer you are to the magnetic pole of the magnet 124. Therefore, the magnetic beads 3 move toward the magnet 124 and are fixed to the inner wall near the magnet 124. In this way, as shown in Figure 5, the magnetic beads 3 and the liquid 4 can be separated. Subsequently, in the liquid discharge step S106 described later, with the magnetic beads 3 fixed to the inner wall of the container 9, the liquid 4 in the container 9 is discharged using a liquid aspirator such as a pipette.

[0056] In this embodiment, the magnetic field is set to satisfy the following two elements (a) and (b).

[0057] (a) The magnetic poles that generate the magnetic field are facing in a different direction from the container 9. (b) When magnetic field lines Lm are projected onto a plane containing the second axis AX2 of the container 9, the angle between the second axis AX2 and the projected magnetic field lines Lm is greater than 0° and less than or equal to 90°.

[0058] By satisfying these two elements (a) and (b), the problems of conventional technology can be solved. The reasons for this are explained below.

[0059] 2.2.1. Element (a) In Figures 5 and 6, the magnetic poles that generate the magnetic field are oriented in a direction different from that of the container 9. Specifically, Figures 5 and 6 illustrate a magnet 124, which is an example of a magnetic field generating device. With the magnet 124 as the reference, the container 9 is located on the negative side of the X-axis. On the other hand, Figure 5 shows the north pole of the magnet 124, which is oriented in a direction different from that of the container 9, towards the negative side of the Y-axis. Figure 6 shows the north and south poles, with the north pole oriented towards the negative side of the Y-axis and the south pole oriented towards the positive side of the Y-axis. Therefore, in Figures 5 and 6, the direction of the magnetic field is set to satisfy element (a) above. Note that a direction different from that of the container 9 means, for example, the direction in which the extension of the magnetization direction of the magnet 124 deviates from that of the container 9.

[0060] By satisfying element (a) above, the occurrence of the spike phenomenon, which is a problem of conventional technology, can be suppressed. The spike phenomenon occurs when the magnetic poles that generate the magnetic field are close to the container 9, and the magnetic field lines Lm are densely distributed. By satisfying element (a), the magnetic poles are more likely to move away from the container 9. This suppresses an increase in the density of magnetic field lines Lm passing through the container 9. As a result, the spike phenomenon becomes less likely to occur, and the separation performance in magnetic separation can be improved.

[0061] In contrast, Figures 7 and 8 are schematic diagrams showing an example where the direction of the magnetic field applied to the container 9 is set to the direction of the container 9 (an example that does not satisfy element (a) above).

[0062] In Figures 7 and 8, the magnetic poles that generate the magnetic field are oriented toward the container 9. In other words, in Figures 7 and 8, the magnetic field does not satisfy element (a) above. Specifically, in Figures 7 and 8, the north pole is oriented toward the negative X-axis, which is the direction of the container 9. As a result, the density of magnetic field lines Lm passing through the container 9 tends to be high. Consequently, the magnetic beads 3 are arranged in a needle-like pattern, and a spike phenomenon occurs.

[0063] 2.2.2.Element (b) Figure 9 is a schematic diagram illustrating the angle θ2 between the second axis AX2 of the container 9 and the projected magnetic field line Lm' when the magnetic field line Lm is projected onto a plane P2 containing the second axis AX2 of the container 9. The second axis AX2 of the container 9 refers to the axis of the cylinder when the container 9 is cylindrical. In the example shown in Figure 9, the angle θ2 is 90°. Therefore, in Figure 9, the magnetic field is set to satisfy element (b) above.

[0064] When the angle θ2 is 90°, the magnetic field lines Lm passing through the container 9 will spread along the XY plane perpendicular to the second axis AX2, as shown in Figures 5 and 6. As a result, the magnetic poles (the north and south poles of the magnet 124), which are the starting and ending points of the magnetic field lines Lm, will be located away from the container 9, according to the cross-sectional shape (ring-shaped) of the container 9 in the XY plane, as shown in Figure 6. Consequently, the distance between the contents of the container 9 and the magnetic poles will naturally increase, suppressing the occurrence of spike phenomena.

[0065] In contrast, Figures 10 and 11 are schematic diagrams showing an example where the angle θ2 between the second axis AX2 and the projected magnetic field line Lm' is 0° when the magnetic field line Lm is projected onto a plane P2 containing the second axis AX2 of the container 9 (an example that does not satisfy element (b) above).

[0066] In Figures 10 and 11, the angle θ2 is 0°, so element (b) above is not satisfied. When the angle θ2 is 0°, the magnetic field lines Lm passing through the container 9 spread along a plane containing the second axis AX2, for example, the XZ plane, as shown in Figures 10 and 11. In that case, the magnetic poles, which are the starting and ending points of the magnetic field lines Lm, tend to approach the container 9 according to the cross-sectional shape of the container 9 determined by the XZ plane, as shown in Figure 10. As a result, the distance between the contents of the container 9 and the magnetic poles naturally decreases, making it easier for spike phenomena to occur, especially near the magnetic poles.

[0067] As mentioned above, angle θ2 is not limited to 90°, but can be greater than 0° and less than or equal to 90°. Even in this case, it is possible to suppress the occurrence of the spike phenomenon compared to the case of 0°. Angle θ2 is the angle between the second axis AX2 and the projected magnetic field line Lm', and in the example of Figure 9, it is the angle that is formed on the positive side of both the Y axis and the Z axis. Angle θ2 is not limited to the angle that is formed at the position shown in Figure 9, but is defined as the angle between the second axis AX2 and the projected magnetic field line Lm' that is 90° or less. Therefore, if the angle θ2 shown in Figure 9 is greater than 90°, the acute angle adjacent to that obtuse angle should be taken as angle θ2.

[0068] The angle θ2 is preferably between 60° and 90°, and more preferably between 75° and 90°. This allows for more reliable suppression of the spike phenomenon, thereby particularly improving the separation performance in magnetic separation.

[0069] 2.2.3. The effects of elements (a) and (b) From the above, by satisfying both elements (a) and (b), it is possible to suppress the occurrence of the spike phenomenon, which is a problem of conventional technology. By suppressing the occurrence of the spike phenomenon, the separation performance in magnetic separation can be improved.

[0070] Figures 7 and 8 show a typical arrangement of magnetic beads 3 when the spike phenomenon occurs. When the spike phenomenon occurs, the magnetic beads 3 arrange themselves in a needle-like shape, making it easier for gaps to form between them. If liquid 4 enters these gaps, it becomes difficult for the liquid 4 to escape. As a result, even if the magnetic beads 3 are fixed to the inner wall of the container 9, a large amount of liquid 4 remains between the magnetic beads 3 due to surface tension (resulting in a large amount of residual liquid). Consequently, the separation efficiency between the magnetic beads 3 and the liquid 4 in magnetic separation decreases. This liquid 4 may contain, for example, chaotropic substances. The liquid 4 remaining between the magnetic beads 3 is difficult to remove with a pipette, etc., and is therefore more likely to be carried over to the washing step S108 and elution step S110 described later. As a result, the chaotropic substances may affect the nucleic acids that are ultimately extracted, potentially reducing the purity of the nucleic acids.

[0071] In contrast, when the spike phenomenon is suppressed, gaps are less likely to form between the magnetic beads 3. This improves the separation efficiency between the magnetic beads 3 and the liquid 4 during magnetic separation. As a result, high-purity nucleic acids can ultimately be extracted.

[0072] Furthermore, the magnetic beads 3, whose spike phenomenon is suppressed, tend to clump together more compactly within the container 9, as shown in Figure 6. In other words, the magnetic beads 3 that exhibit the spike phenomenon spread out significantly within the container 9, as shown in Figure 8, but such protrusion is suppressed.

[0073] The magnetic beads 3 shown in Figure 8 may interfere with the pipette or other device when discharging the liquid 4 after magnetic separation, potentially hindering the discharging operation. In contrast, the magnetic beads 3 shown in Figure 6 are less likely to interfere with the pipette or other device, thus less likely to hinder the discharging operation.

[0074] 2.2.4. Magnetic stand that generates a magnetic field satisfying elements (a) and (b) A magnetic field that satisfies the aforementioned elements (a) and (b) can be generated by the magnetic stand 1 shown in Figures 1 to 3.

[0075] Figure 12 is a schematic diagram illustrating the angle θ1 between the first axis AX1 and the projected magnetization M' when the magnetization M of the magnet 124 is projected onto a plane P1 containing the first axis AX1 of the insertion hole 13 of the magnetic stand 1. The first axis AX1 of the insertion hole 13 refers to the axis of the cylinder when the insertion hole 13 is cylindrical. In the example shown in Figure 12, the angle θ1 is 90°.

[0076] When the angle θ1 is 90°, the magnetic field lines Lm passing through the container 9 inserted into the insertion hole 13 will follow the pattern shown in Figures 5 and 6. In this case, the magnet 124 that generates these magnetic field lines Lm is positioned so that its north and south poles face in directions different from those of the container 9, as shown in Figure 12. Thus, the magnetic field applied to the container 9 by the magnetic stand 1 can satisfy element (a) above.

[0077] If the angle θ1 shown in Figure 12 is 90°, then the angle θ2 shown in Figure 9 is also 90°. Specifically, when the container 9 is inserted into the insertion hole 13, the container 9 is held such that the first axis AX1 of the insertion hole 13 and the second axis AX2 of the container 9 are approximately parallel. Therefore, the magnetic field applied to the container 9 by the magnetic stand 1 can satisfy element (b) above.

[0078] Furthermore, plane P1 is a plane that includes the first axis AX1, and as shown in Figure 12, it is a plane determined such that the normal NL is perpendicular to the first axis AX1 and passes through the center O of the magnet 124. The center O of the magnet 124 is the midpoint between the north and south poles.

[0079] Furthermore, the angle θ1 is not limited to 90°, but can be greater than 0° and less than or equal to 90°. Even in this case, it is possible to suppress the occurrence of the spike phenomenon compared to the case of 0°. Note that angle θ1 is the angle between the first axis AX1 and the projected magnetization M', and in the example of Figure 12, it is the angle that is formed on the positive side of both the Y axis and the Z axis. The angle θ1 is not limited to the angle that is formed at the position shown in Figure 12, but is defined as the angle between the first axis AX1 and the projected magnetization M' that is 90° or less. Therefore, if the angle θ1 shown in Figure 12 is greater than 90°, the acute angle adjacent to that obtuse angle should be taken as angle θ1.

[0080] The angle θ1 is preferably between 60° and 90°, and more preferably between 75° and 90°. This allows for more reliable suppression of the spike phenomenon, thereby particularly improving the separation performance in magnetic separation.

[0081] Furthermore, it is preferable that the direction of the magnetization M of the magnet 124 is parallel to the plane P1. This ensures that the distances between the two magnetic poles and the container 9 are approximately equal, preventing one of the magnetic poles from getting too close to the container 9. As a result, the occurrence of spike phenomena can be suppressed more reliably.

[0082] Figure 13 shows the container 9 inserted into the insertion hole 13 shown in Figure 12, as viewed from the magnet 124 side.

[0083] The size of the magnet 124 is set appropriately according to the size of the container 9. In Figure 13, when viewed from the normal line NL shown in Figure 12, the diameter of the container 9 at the position where the magnet 124 is installed is φ, the width of the magnet 124 is W, and the length of the magnet 124 is L. The width W of the magnet 124 is the width of the magnet 124 in the direction of magnetization M. The length L of the magnet 124 is the length of the magnet 124 in the direction perpendicular to the magnetization M.

[0084] When the diameter φ of the container 9 is 1, the relative value of the width W of the magnet 124 is preferably 0.2 or more and 1.5 or less, more preferably 0.3 or more and 1.0 or less, and even more preferably 0.4 or more and 0.8 or less. This allows for an appropriate distance between the magnetic poles of the magnet 124 and the container 9, while also ensuring the necessary volume of the magnet 124 to generate a sufficiently strong magnetic field. As a result, the occurrence of spike phenomena can be suppressed, improving the separation performance in magnetic separation, while also sufficiently increasing the movement speed of the magnetic beads 3. Furthermore, this prevents the magnet 124 from becoming unnecessarily large, enabling miniaturization and weight reduction of the magnetic stand 1. If the relative value of the width W falls below the lower limit, the volume of the magnet 124 may not be sufficiently secured, potentially resulting in insufficient surface magnetic flux density of the magnet 124. On the other hand, if the relative value of the width W exceeds the upper limit, the magnetic poles and the container 9 may be too far apart, potentially reducing the movement speed of the magnetic beads 3.

[0085] The width W of the magnet 124 is preferably 3 mm to 20 mm, and more preferably 4 mm to 12 mm.

[0086] The length L of the magnet 124 is preferably, for example, 3 mm to 40 mm, and more preferably 4 mm to 15 mm. This allows for a balance between the width W and length L while ensuring the volume of the magnet 124 necessary to generate a sufficiently strong magnetic field, thereby preventing the magnetic pole range from spreading too far in the Z-axis direction, which would increase the gaps between the magnetic beads 3 and increase the amount of residual liquid.

[0087] The thickness T of the magnet 124 is preferably, for example, 2 mm or more and 20 mm or less, and more preferably 3 mm or more and 10 mm or less.

[0088] Furthermore, the shortest distance between the magnet 124 and the container 9 is preferably 10 mm or less, and more preferably 0.5 mm or more and 6 mm or less.

[0089] 2.3.Liquid discharge process In the liquid discharge step S106, with the magnetic beads 3 fixed to the inner wall of the container 9, the liquid 4 inside the container 9 is discharged using a pipette or the like. This allows the liquid 4, which contains chaotropic substances, to be separated from the nucleic acids adsorbed on the magnetic beads 3.

[0090] 2.4. Washing Process In the washing step S108, the magnetic beads 3 on which nucleic acids are adsorbed are washed. Washing is an operation to remove impurities adsorbed on the magnetic beads 3 by bringing the magnetic beads 3 on which nucleic acids are adsorbed into contact with a washing solution and then separating them again.

[0091] Specifically, with the magnetic beads 3 fixed to the inner wall of the container 9 by an external magnetic field, the washing solution is supplied into the container 9 using a pipette or the like. Then, the magnetic beads 3 and the washing solution are stirred. This causes the washing solution to come into contact with the magnetic beads 3, and the magnetic beads 3 on which nucleic acids are adsorbed are washed. For stirring, for example, a vortex mixer or manual shaking can be used. At this time, the external magnetic field may also be temporarily removed. This disperses the magnetic beads 3 in the washing solution, thereby further improving the washing efficiency.

[0092] Next, an external magnetic field is applied to the magnetic beads 3 again to fix them to the inner wall of the container 9, and then the cleaning solution is discharged. By repeating the supply and discharge of the cleaning solution as described above one or more times, the magnetic beads 3 are cleaned, thereby accurately removing impurities other than nucleic acids.

[0093] The washing solution is not particularly limited as long as it is a liquid that does not promote the elution of nucleic acids and does not promote the binding of impurities to the magnetic beads 3. Examples include organic solvents such as ethanol, isopropyl alcohol, and acetone, or aqueous solutions thereof, and low-salt aqueous solutions. Examples of low-salt aqueous solutions include buffer solutions. The salt concentration of the low-salt aqueous solution is preferably 0.1 mM to 100 mM, and more preferably 1 mM to 50 mM. The salt used to make the buffer solution is not particularly limited, but salts such as TRIS, HEPES, PIPES, and phosphoric acid are preferably used.

[0094] The cleaning solution may contain surfactants such as Triton®, Tween®, or SDS. The cleaning solution may also contain chaotropic substances such as guanidine hydrochloride. The pH of the cleaning solution is not particularly limited.

[0095] The cleaning step S108 may be performed as needed, and may be omitted if cleaning is not required.

[0096] Furthermore, in the washing step S108, the same operations as those described above for the magnetic separation step S104 and the liquid discharge step S106, i.e., the magnetic separation method according to the embodiment, can be performed. This makes it possible to suppress the retention of a large amount of washing liquid on the fixed magnetic beads 3. As a result, it is possible to suppress the transfer of the washing liquid or its components to the elution step S110.

[0097] 2.5. Elution process In the elution step S110, nucleic acids adsorbed on the magnetic beads 3 are eluted into the elution solution. Elution is the process of transferring nucleic acids to the elution solution by bringing the magnetic beads 3, on which the nucleic acids are adsorbed, into contact with the elution solution and then separating them again.

[0098] Specifically, first, the eluent is supplied into the container 9 using a pipette or the like. Then, the magnetic beads 3 and the eluent are stirred. This allows the eluent to come into contact with the magnetic beads 3, enabling the elution of nucleic acids. For stirring, for example, a vortex mixer or manual shaking can be used. At this time, the external magnetic field may also be temporarily removed. This disperses the magnetic beads 3 in the eluent, thereby further increasing the elution efficiency.

[0099] Next, an external magnetic field is applied to the magnetic beads 3 again to fix them to the inner wall of the container 9, and then the eluate containing the dissolved nucleic acids is discharged. This allows the nucleic acids to be recovered.

[0100] The eluent is not particularly limited as long as it is a liquid that promotes the elution of nucleic acids from the magnetic beads 3 on which the nucleic acids are adsorbed. For example, in addition to water such as sterile water or pure water, an aqueous solution containing TE buffer, i.e., 10 mM Tris-HCl buffer and 1 mM EDTA, with a pH of about 8, is preferably used.

[0101] The eluate may contain surfactants such as Triton®, Tween®, and SDS. It may also contain sodium azide as a preservative.

[0102] Furthermore, in the elution step S110, the eluate may be heated. This can promote the elution of nucleic acids. The heating temperature of the eluate is not particularly limited, but is preferably 70°C to 200°C, more preferably 80°C to 150°C, and even more preferably 95°C to 125°C.

[0103] Examples of heating methods include supplying a preheated eluate or supplying an unheated eluate to a container and then heating it. The heating time is not particularly limited, but it is preferably between 30 seconds and 10 minutes.

[0104] The elution step S110 may be performed as needed, and may be omitted if, for example, the only purpose is the separation of the magnetic beads 3 and the liquid 4 in the magnetic separation step S104.

[0105] Furthermore, in the elution step S110, the same operations as those described above for the magnetic separation step S104 and the liquid discharge step S106, i.e., the magnetic separation method according to the embodiment, can be performed. This makes it possible to suppress the retention of a large amount of nucleic acid on the fixed magnetic beads 3. As a result, it is possible to suppress a decrease in the nucleic acid yield.

[0106] 3. Effects of the Embodiment As described above, the magnetic stand 1 according to the embodiment comprises a stand 11 (base) and a magnet 124. The stand 11 has an insertion hole 13 into which the container 9 is inserted. The insertion hole 13 extends along the first axis AX1. The magnet 124 is provided on the stand 11 and has a magnetization M that applies a magnetic field to the insertion hole 13.

[0107] Furthermore, the magnet 124 is positioned so that its magnetic poles face in a different direction from the container 9. Also, as shown in Figure 12, when the magnetization M is projected onto the plane P1 containing the first axis AX1 of the insertion hole 13, the angle θ1 between the first axis AX1 and the magnetization M' projected onto the plane P1 is greater than 0° and less than or equal to 90°. Note that the plane P1 is determined such that its normal vector NL is perpendicular to the first axis AX1 and passes through the center O of the magnet 124.

[0108] This configuration makes it possible to suppress the occurrence of spike phenomena in the magnetic beads 3 contained within the container 9. This prevents a large amount of liquid 4 from remaining on the magnetic beads 3 even after magnetic separation. As a result, the separation efficiency in magnetic separation can be improved. This allows for, for example, the extraction of high-purity nucleic acids in high yield when using magnetic separation to extract nucleic acids from a sample.

[0109] Furthermore, the aforementioned angle θ1 is preferably between 60° and 90°. This makes it possible to more reliably suppress the occurrence of the spike phenomenon.

[0110] Furthermore, when the diameter φ of the container 9 measured at the position where the container 9 is inserted into the insertion hole 13 and the magnet 124 is provided is set to 1, the width of the magnet 124 in the direction of magnetization M is preferably 0.2 to 1.5. This allows for an appropriate distance between the magnetic poles of the magnet 124 and the container 9, while also ensuring sufficient volume of the magnet 124 to generate a magnetic field of sufficient strength. As a result, the movement speed of the magnetic beads 3 can be sufficiently increased while suppressing the occurrence of spike phenomena and improving the separation performance in magnetic separation.

[0111] Furthermore, it is preferable that the magnet 124 is a permanent magnet. This eliminates the need for a power supply for the magnetic stand 1 and facilitates miniaturization and weight reduction. It also improves the portability of the magnetic stand 1, thus increasing the flexibility of its installation location.

[0112] Furthermore, the magnetic separation method according to this embodiment includes a magnetic separation step S104 and a liquid discharge step S106. In the magnetic separation step S104, a magnetic field is applied to a container 9 containing magnetic beads 3 and liquid 4 to fix the magnetic beads 3 to the inner wall of the container 9, thereby separating the magnetic beads 3 and the liquid 4. In the liquid discharge step S106, with the magnetic beads 3 and liquid 4 separated, the liquid 4 is discharged using a liquid suction device. The magnetic poles that generate the magnetic field are oriented in a direction different from that of the container 9. In addition, the axis of the container 9 is defined as the second axis AX2, and when magnetic field lines Lm representing the magnetic field are projected onto a plane P2 including the second axis AX2, the magnetic field is set such that the angle θ2 between the projected magnetic field lines Lm' and the second axis AX2 is greater than 0° and less than or equal to 90°.

[0113] This configuration makes it possible to suppress the occurrence of spike phenomena in the magnetic beads 3 contained within the container 9. This prevents a large amount of liquid 4 from remaining on the magnetic beads 3 even after magnetic separation. As a result, the separation efficiency in magnetic separation can be improved. This allows for, for example, the extraction of high-purity nucleic acids in high yield when using magnetic separation to extract nucleic acids from a sample.

[0114] Furthermore, the aforementioned angle θ2 is preferably between 60° and 90°. This makes it possible to more reliably suppress the occurrence of the spike phenomenon.

[0115] The magnetic stand and magnetic separation method of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited thereto. For example, the magnetic separation method of the present invention may have additional steps for any purpose added to the above embodiments. Furthermore, the magnetic stand of the present invention may have each part of the above embodiments replaced with any configuration having a similar function, or may have additional components added to the above embodiments. [Examples]

[0116] Next, specific embodiments of the present invention will be described. 4. Nucleic acid extraction by magnetic separation 4.1. Example 1 First, in the dissolution and adsorption step, 100 μL of a dispersion containing HeLa cells, 40 μL of a magnetic bead dispersion, and a dissolution and adsorption solution were placed in a container (a microtube with a diameter of φ10.5 mm) and stirred for 10 minutes using a vortex mixer. The dissolution and adsorption solution used was an aqueous solution containing guanidine hydrochloride. As magnetic beads, a coated magnetic powder comprising Fe-Al-Si-B alloy magnetic powder and a silica film covering the particle surface was used. The average particle size of the magnetic beads was 3.3 μm.

[0117] Next, as a magnetic separation step, magnetic separation (B / F separation) was performed using a magnetic stand as shown in Figures 5 and 6. Neodymium-iron-boron magnets were used for the magnetic stand. The width W of the magnet was 5 mm, the length L was 10 mm, the thickness T was 5 mm, and the shortest distance between the magnet and the container was 1 mm. Subsequently, as a liquid discharge step, the supernatant, which was the liquid phase, was discharged using a pipette.

[0118] Next, the cleaning process was carried out according to the following procedure. First, 900 μL of the first washing solution was placed in a container and stirred for 5 seconds. Next, as a magnetic separation step, magnetic separation was performed using the magnetic stand shown in Figures 5 and 6. Subsequently, as a liquid discharge step, the supernatant was discharged. These washing operations were then repeated several times.

[0119] Next, 900 μL of the second washing solution was added to the container and stirred for 5 seconds. Subsequently, magnetic separation was performed using the magnetic stand shown in Figures 5 and 6 as part of the magnetic separation process. Following this, the supernatant was discharged as part of the liquid discharge process. These washing operations were then repeated several times.

[0120] Next, the elution process was carried out according to the following procedure. First, 100 μL of sterile water, to be used as the eluate, was placed in a container and stirred for 10 minutes. Next, magnetic separation was performed using the magnetic stand shown in Figures 5 and 6. Subsequently, the supernatant was discharged as part of the liquid discharge process. In this manner, a nucleic acid extract was obtained.

[0121] 4.2. Example 2 A nucleic acid extract was obtained in the same manner as in Example 1, except that the length L of the magnet was changed to 5 mm.

[0122] 4.3. Example 3 A nucleic acid extract was obtained in the same manner as in Example 1, except that the length L of the magnet was changed to 20 mm.

[0123] 4.4. Example 4 A nucleic acid extract was obtained in the same manner as in Example 1, except that the length L of the magnet was changed to 5 mm and the width W of the magnet was changed to 10 mm.

[0124] 4.5. Example 5 A nucleic acid extract was obtained in the same manner as in Example 1, except that the width W of the magnet was changed to 10 mm.

[0125] 4.6. Comparative Example 1 Nucleic acid extract was obtained in the same manner as in the examples, except that a magnetic stand as shown in Figures 7 and 8 was used. The length of the magnet in the Z-axis direction was 10 mm, the width in the Y-axis direction was 5 mm, the thickness in the X-axis direction was 5 mm, and the shortest distance between the magnet and the container was 1 mm.

[0126] 4.7. Comparative Example 2 Nucleic acid extract was obtained in the same manner as in the examples, except that a magnetic stand as shown in Figures 10 and 11 was used. The length of the magnet in the Z-axis direction was 3 mm, the width in the Y-axis direction was 5 mm, the thickness in the X-axis direction was 4 mm, and the shortest distance between the magnet and the container was 1 mm.

[0127] 5. Evaluation of Separability in Magnetic Separation 5.1. Relationship between magnetic field direction and separability In the magnetic separation of Example 1 and each comparative example, the separation performance was evaluated using the following procedure.

[0128] First, after the cleaning process was completed, the weight of the container holding the contents was measured. These contents consisted of magnetic beads and the liquid adhering to them (residual liquid). The measured weight is referred to as the "weight after magnetic separation."

[0129] Next, the weight of the container alone and the weight of the magnetic beads placed in the container during the dissolution and adsorption process were subtracted from the weight after magnetic separation. The result of this subtraction corresponds to the weight of the remaining liquid mentioned above, and is therefore referred to as the "weight of the remaining liquid." Subsequently, the volume of the remaining liquid was calculated from the weight of the remaining liquid. This calculated result is referred to as the "amount of remaining liquid." A graph was created to compare the calculated amounts of remaining liquid in Example 1 and each comparative example. The created graph is shown in Figure 14.

[0130] As shown in Figure 14, the amount of residual liquid was significantly reduced in the magnetic separation in Example 1 compared to the magnetic separations in Comparative Examples 1 and 2. Furthermore, while the magnetic separation in Example 1 showed almost no spike phenomenon in the magnetic beads, the spike phenomenon was observed in the magnetic separations in Comparative Examples 1 and 2. Therefore, it is considered that the direction of the magnetic field generated by the magnet and the resulting spike phenomenon are related to the suppression of residual liquid volume.

[0131] 5.2. Relationship between magnet size and separability In the magnetic separations of Examples 1 to 5, the separation performance was evaluated using the following procedure.

[0132] First, the amount of residual liquid was calculated in the same manner as in 5.1. Next, a graph was created to compare the calculated amounts of residual liquid in Examples 1 to 5. The created graph is shown in Figure 15. Figure 15 also includes a table showing the sizes of the magnets used in Examples 1 to 5.

[0133] As shown in Figure 15, the amount of residual liquid was reduced in magnetic separation in Examples 1 and 2 compared to magnetic separation in Examples 3 to 5. This is thought to be due to the fact that the size of the magnets used in Examples 1 and 2 was optimized for the container (microtube with a diameter of φ10.5 mm). [Explanation of Symbols]

[0134] 1…Magnetic stand, 3…Magnetic beads, 4…Liquid, 9…Container, 11…Stand, 12…Magnet plate, 13…Insertion hole, 112…Top plate, 113…Through hole, 114…Bottom plate, 115…Recess, 116…Side plate, 118…Side plate, 122…Back plate, 124…Magnet, AX1…First axis, AX2…Second axis, L…Length, Lm…Magnetic field lines, Lm'…Projected magnetic field lines, M…Magnification, M'…Projected magnetization, NL…Normal, O…Center, P1…Plane, P2…Plane, S102…Dissolution / adsorption process, S104…Magnetic separation process, S106…Liquid discharge process, S108…Washing process, S110…Dissolution process, T…Thickness, W…Width, θ1…Angle, θ2…Angle, φ…Diameter

Claims

1. A base extending along the first axis and having an insertion hole into which a container is inserted, A magnet provided on the base and having magnetization for applying a magnetic field to the insertion hole, Equipped with, The magnet is positioned such that its magnetic poles face in a direction different from that of the container. When the magnetization is projected onto a reference plane which includes the first axis and whose normal is perpendicular to the first axis and passes through the center of the magnet, The angle between the first axis and the magnetization projected onto the reference plane is 60° or more and 90° or less. When the diameter of the container measured at the position where the magnet is provided, after the container has been inserted into the insertion hole, is defined as 1, A magnetic stand characterized in that the width of the magnet in the direction of magnetization is 0.2 or more and 1.5 or less.

2. The magnetic stand according to claim 1, wherein the magnet is a permanent magnet.

3. A magnetic separation step is performed to separate the magnetic beads from the liquid by applying a magnetic field to a container containing magnetic beads and liquid, thereby fixing the magnetic beads to the inner wall of the container. A liquid discharge step in which the liquid is discharged using a liquid suction device while the magnetic beads and the liquid are separated, It has, The magnetic poles that generate the magnetic field are oriented in a different direction from the container. When the axis of the container is defined as the second axis, and magnetic field lines representing the magnetic field are projected onto a plane including the second axis, A magnetic separation method characterized in that the magnetic field is set such that the angle between the projected magnetic field lines and the second axis is greater than 0° and less than or equal to 90°.

4. The magnetic separation method according to claim 3, wherein the angle is 60° or more and 90° or less.

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