Magnetic particle separation device

Abstract

This invention provides a magnetic particle separation device that, even with sample containers of the same size as conventional ones, can ensure that the amount of magnetic powder adsorbed in the liquid is approximately the same at both the ends and the center. The magnetic particle separation device comprises multiple sample containers containing a mixture of liquid and magnetic particles, a first magnet disposed relative to each of the multiple sample containers and capable of moving independently up and down relative to the sample containers, a magnetic container covering the first magnet, and a perforated plate having holes capable of holding the multiple sample containers; at least the side portion of the perforated plate near the sample containers is made of a soft magnetic material.

Description

Technical Field

[0001] This invention relates to a magnetic particle separation device for separating magnetic particles from a liquid containing suspended magnetic particles. Background Technology

[0002] In recent years, information obtained through nucleic acid analysis, such as cancer genome screening using next-generation sequencing (NGS) systems, has been applied in various fields, including medical, clinical testing, pharmaceutical, and food industries. In this nucleic acid analysis, nucleic acid extraction from various biological samples, such as blood, tissues, and cultured cells, is an essential pretreatment step.

[0003] Nucleic acid extraction methods generally do not use harmful organic solvents such as phenol and chloroform, but rather methods based on the property of nucleic acids binding to silica in the presence of a dissociative agent or on the property of nucleic acids binding to silica in the presence of an organic solvent. Nucleic acid extraction methods utilizing these methods include nucleic acid capture chips in which a silica-containing solid phase is embedded as a nucleic acid capture carrier, and methods using magnetic microbeads (nucleic acid capture carriers) with a silica-coated surface. These methods include a nucleic acid binding step to the nucleic acid capture carrier and an elution step of eluting nucleic acids from the nucleic acid capture carrier using an elution buffer.

[0004] In methods using magnetic microbeads, after the elution step, the magnetic microbeads are recovered from the eluent using a magnet. Patent Document 1 describes a method for effectively collecting magnetic microbeads by temporarily collecting them against the wall of a container and then recovering them using a magnetic rod. In this case, it is disclosed that magnetic coupling is achieved by setting the magnetization directions of adjacent magnets to different directions, thereby suppressing the difference in magnetic flux density distribution between the end and center of the reagent container.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Publication No. 2007-520331 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In a DNA extraction and purification apparatus, multiple sample containers arranged in a crisscross pattern contain a mixture of a liquid containing DNA and surface-treated magnetic particles that adsorb DNA. The combination of magnetic rods and magnets moves independently up and down relative to the sample containers. After a stirring-based DNA adsorption reaction, during "magnetic collection" to gather magnetic particles onto the surface of the magnetic containers near the magnets, magnetic coupling between magnets is generated in the small containers with short distances between them. The magnetic flux density distribution in the liquid differs at the ends and the center of the sample containers, resulting in different adsorption amounts of magnetic powder.

[0010] In Patent Document 1, magnetic coupling was achieved by setting the magnetization directions of adjacent magnets to different directions, thereby suppressing the difference in magnetic flux density distribution between the end and central portions of the sample container. However, the end magnets have fewer adjacent magnets, resulting in a difference between the end and central portions. While using more magnets than the number of sample containers can reduce this difference, the increased space and the greater number of magnets present challenges.

[0011] The purpose of this invention is to provide a magnetic particle separation device that can make the amount of magnetic powder adsorbed in the liquid approximately the same at the end and the center, even with a sample container of the same size as in the past.

[0012] Methods for solving problems

[0013] The present invention configured to achieve the above objectives is as follows.

[0014] A magnetic particle separation device comprises a plurality of sample containers containing a mixture of liquid and magnetic particles, a first magnet disposed relative to the plurality of sample containers and capable of moving up and down independently relative to the sample containers, a magnetic body container covering the first magnet, and a perforated plate having holes capable of holding the plurality of sample containers, wherein at least the side portion of the perforated plate near the sample containers is made of soft magnetic material.

[0015] Invention Effects

[0016] A particle separation device is available that can provide approximately the same amount of magnetic powder adsorbed in the liquid at both the end and the center of the sample container, even with the same sample container size as in the past. Attached Figure Description

[0017] Figure 1 This is a perspective view of the nucleic acid extraction device of the present invention.

[0018] Figure 2 This is a perspective cross-sectional view of the nucleic acid extraction device of the present invention.

[0019] Figure 3 This is a diagram showing an example of an 8×12 column magnet container 4.

[0020] Figure 4 This is a top view of the orifice plate and the holes.

[0021] Figure 5 This is a perspective cross-sectional view of the perforated plate.

[0022] Figure 6 This is a diagram showing the location of the magnetic flux density evaluation points.

[0023] Figure 7 This is a diagram showing the difference in magnetic flux density between the end and the center of the orifice plate.

[0024] Figure 8 This is a diagram showing the state of the orifice plate after its position has changed.

[0025] Figure 9 yes Figure 8 The calculation results of the difference in magnetic flux density distribution.

[0026] Figure 10 This is a diagram showing the positions of the upper and lower ends of the orifice plate.

[0027] Figure 11 yes Figure 10 The calculation results of the difference in magnetic flux density distribution.

[0028] Figure 12 This is a diagram showing the state in which the position of the upper magnet has changed.

[0029] Figure 13 This is a diagram illustrating an embodiment using an upper magnet and a lower magnet.

[0030] Figure 14 It is a diagram showing the magnetic particle collection process using upper and lower magnets.

[0031] Figure 15 This is a diagram showing the positions of the upper and lower ends of the orifice plate.

[0032] Figure 16 yes Figure 15 The calculation results of the difference in magnetic flux density distribution.

[0033] Figure 17 This is an embodiment with a tapered hole.

[0034] Figure 18 This is an embodiment with a groove.

[0035] Figure 19 It is a diagram showing the difference in driving force caused by the presence or absence of tapered machining. Detailed Implementation

[0036] Hereinafter, embodiments of the present invention will be described using the accompanying drawings.

[0037] Example 1

[0038] Figure 1 , Figure 2 These are a perspective view and a cross-sectional perspective view of the nucleic acid extraction apparatus 100 of the present invention. The nucleic acid extraction apparatus 100 is a device for extracting nucleic acids from a sample containing nucleic acids and magnetic particles.

[0039] The nucleic acid extraction apparatus 100 includes a linear motion mechanism A1 for moving the magnetic rod 3 vertically, a linear motion mechanism A2 for moving the magnet container 4 vertically, a linear motion mechanism B for moving the sample container 1 and the orifice plate (container holding member) 2 holding the sample container 1 together horizontally, and an electric motor 101 for driving these linear motion mechanisms. The sample container 1 is held in the orifice plate (container holding member) 2, described later.

[0040] The direct-acting mechanism B moves the magnetic container 4 downwards towards the magnetic rod 3, while the direct-acting mechanism A1 moves the magnetic rod 3 up and down, thereby enabling the loading and unloading of the magnetic container 4 relative to the magnetic rod 3. Furthermore, the direct-acting mechanism B moves the sample container 1 (with the magnetic container 4 mounted on it) downwards towards the magnetic rod 3, causing the magnetic container 4 (and the magnetic rod 3) to move up and down, thereby enabling the liquid inside the sample container 1 to be stirred by the magnetic container 4.

[0041] It should be noted that in this figure, the thickness of the magnet container 4 varies, but it can also be the same thickness.

[0042] in addition, Figure 2 The nucleic acid extraction device 100 described herein includes a lower magnet 10, but the lower magnet 10 is used in Example 2 and not in Example 1. The lower magnet 10 will be described again in Example 2.

[0043] In this embodiment, the magnetic rods 3 are arranged in a horizontal row of 6, but the device can also have multiple rows of magnetic rods 3. For example, it can have 8 rows of magnetic rods 3, with 6×8=48 magnetic rods 3. With this configuration, magnetic rods 3 can be inserted into all the sample containers placed on the orifice plate 2 at the same time, and magnetic particles can be collected in all sample containers simultaneously. In this case, the magnet container 4 is also configured in a matrix shape, similar to the magnetic rods 3. Figure 3 Example of a magnet container 4 with 8×12 columns.

[0044] Next, the details of the orifice plate will be explained. Figure 4 The orifice plate 2 has 8 holes 9 arranged longitudinally and 12 holes 1 in the transverse direction for the specimen containers 1. Figure 5This is a cross-sectional perspective view of the well plate 2. The sample container 1 can be arranged side-by-side by inserting it into the hole 9 of the well plate 2. To collect only the magnetic particles 7 from the sample 6 containing suspended magnetic particles 7 in the sample container 1, a magnetic rod 3, an upper magnet 5 coupled to the magnetic rod 3, and a magnetic body container 4 (also called a magnetic shield) covering them are inserted relative to the sample container 1. A stirring-based DNA adsorption reaction is performed by moving the magnetic body container 4 up and down, followed by "magnetic collection" to collect the magnetic particles 7 onto the surface of the magnetic body container 4 near the upper magnet 5. Figure 5 In the middle, the magnetization directions of all the upper magnets 5 are the same (arranged with the N pole at the bottom in the attached figure).

[0045] The magnetic flux density evaluation point 8 in the liquid containing magnetic particles 7 was calculated by magnetic field analysis. Figure 6 The magnetic flux density at each point (shown in the diagram) will be compared. Figure 4 The results of the difference in magnetic flux density between the ends and the center of the orifice plate are shown in Figure 7 The magnetization directions of the upper magnets 5 are the same. In a "non-NN-hole plate" (NN means that the magnets are arranged side by side with N poles N poles...) without a hole plate 2 containing soft magnetic materials, a difference of 14% was found. By setting it to a "non-NS-hole plate" (meaning that the magnets are arranged side by side with N poles S poles N poles...) with magnetization directions arranged in the same way as described in Patent Document 1, the difference can be reduced to 5%. It can be seen that by using the "NN-hole plate" or "NS-hole plate" of the present invention, the difference can be further reduced to 1%.

[0046] During magnetization, the upper magnet 5 and the magnet container 4 move synchronously in the vertical direction to collect magnetic particles 7. The perforated plate 2 (also called the sample container holder) has holes for receiving the sample container. Ideally, the holes 9 should completely cover the upper magnet 5, the sample 6, and the magnetic rod 3, but the sample container 1 is generally hemispherical at the bottom and cylindrical at the top, making it difficult to design the perforated plate to cover the upper part of the sample container 1. Regarding the position of the perforated plate, it will be as follows... Figure 8 The difference in magnetic flux density between the end and the center of the sample container 1 when the 5mm thick perforated plate is positioned at the bottom, middle, and top is shown in the figure. Figure 9 .Depend on Figure 9 It can be seen that the end face of the hole does not need to completely cover the upper magnet 5 and the magnetic rod 3. Figure 8 The most effective method is to cover the front end of the magnet downwards by about 5mm, which does not affect the difference in magnetic flux density even if a perforated plate is not required on the top of the container.

[0047] Furthermore, it will be like Figure 10 The difference in magnetic flux density between the end and the center is shown when the thickness H from the front end of the magnet to the upper surface of the perforated plate is changed in 1 mm units. Figure 11Therefore, it can be seen that the upper surface of the preferred perforated plate is located about 2mm higher than the front surface of the magnet, and has a thickness of more than 7mm to the lower end of the perforated plate.

[0048] Next, Figure 12 The relationship between the sample liquid surface and the magnet position is shown. The magnetic container 4 and the upper magnet 5 can move independently relative to the sample container 1. Considering the adsorption of the main magnetic powder in the "magnet position: upper" state where the magnet container 4 descends from the front end and contacts the sample liquid surface, it can be seen that in the size design shown in the figure, the upper end face of the orifice plate is preferably 2 mm higher than the front end face of the magnet when the sample liquid surface contacts the magnet container 4, and the distance from the front end face of the magnet when the magnet container 4 is attached to the bottom surface of the sample container 1 ("magnet position: lower") is 5 mm or more.

[0049] It should be noted that since the inner and outer diameters of the sample container 1, the size of the upper magnet 5, and the amount of sample 6 are different for each device, the magnetic coupling state between the upper magnet 5 and the orifice plate 2 is also different. Therefore, the above-mentioned ideal size values ​​obviously vary depending on the device.

[0050] In addition to having holes drilled in a soft magnetic material, the perforated plate 2 can also have a lattice structure formed by assembling sheet metal plates. When using a metallic soft magnetic material, it also exhibits excellent thermal conductivity, thus also providing temperature regulation functionality. Alternatively, it can be a structure where holes are drilled in a non-magnetic material such as resin, and a cylindrical or container-shaped soft magnetic material is inserted. Because the perforated plate 2 has the effect of enhancing magnetic force or magnetic shielding, it can also be a structure that accommodates only one sample container. Soft magnetic materials include permalloy, pure iron, iron-based alloys, nickel alloys, cobalt alloys, ferrites, and resin materials containing magnetic powder, etc.

[0051] Example 2

[0052] This embodiment further includes a lower magnet 10 (also called a bottom magnet). Reuse Figure 2 The nucleic acid extraction device 100 includes a lower magnet 10. The lower magnet 10 is positioned below the sample container 1 when it moves below the magnetic rod 3. The lower magnet 10 can move up and down, for example, via a linear motion mechanism A2. When the lower magnet 10 approaches the bottom surface of the sample container 1, it can magnetize the magnetic beads on the bottom surface of the sample container 1. Various types of lower magnets 10 can be configured, such as those for large sample containers 1 and those for small sample containers 1, or a single lower magnet 10 can be used.

[0053] Figure 13This is a perspective cross-sectional view of the perforated plate when the lower magnet 10 is used. The lower magnet 10 can be driven up and down independently relative to the upper magnet 5. To promote the stirring of the sample 6 and the magnetic particles 7, the front surface of the magnet container 4 is hemispherical. However, considering ease of molding, this results in a thick wall, increasing the distance between the upper magnet 5 and the surface of the magnet container 4, thus reducing the attraction force. On the other hand, the lower magnet 10 is positioned at the bottom of the thin-walled magnet container 4, which has the advantages of high attraction force and shorter magnetization time.

[0054] use Figure 14 This describes the magnetic particle collection process using upper magnet 5 and lower magnet 10.

[0055] First, the magnetic container 4 is immersed only in the liquid containing the suspended magnetic particles 7 in the sample container 1, and the liquid is mixed by moving the magnetic container 4 up and down (1). Next, after the magnetic container 4 is raised to the surface of the liquid, the lower magnet 10 is moved upward, bringing it close to the bottom of the sample container 1. This allows the magnetic particles 7 suspended in the liquid to be collected near the lower magnet 10 (2). Next, the upper magnet 5 and the magnetic container 4 are simultaneously immersed in the liquid to magnetize the magnetic particles 7 collected by the lower magnet 10 (3). During magnetization, the magnetic container 4 can also be moved up and down in the liquid. The magnetic container 4 and the upper magnet 5 are immersed together in the liquid of another container, and then the upper magnet 5 is moved upward. By moving only the magnetic container 4 up and down in the liquid of another container, the magnetic particles 7 collected on the surface of the magnetic container 4 are suspended in the liquid of the other container (4).

[0056] In Embodiment 1, which is an implementation without using the lower magnet 10, only the upper magnet is used for magnetization. In contrast, in Embodiment 2, the lower magnet 10 is used to temporarily collect the magnetic particles 7 in one place, and the collected magnetic particles 7 can be directly collected using the upper magnet 5. Therefore, the magnetization time is shorter than in Embodiment 1, i.e., productivity is higher. On the other hand, in Embodiment 2, since a mechanism for moving the lower magnet 10 up and down and the lower magnet 10 itself are used, the cost is higher compared to the device in Embodiment 1, and the device may also be slightly larger. Preferably, the choice between using only the upper magnet 5 or also using the lower magnet 10 is appropriate, depending on the required magnetization performance of the device.

[0057] Next, use Figure 15 This section explains the optimal plate thickness for the perforated plate when using magnet 10. For example... Figure 15As shown, if we consider that the main adsorption force is generated when the front end of the upper magnet 5 enters the magnet container 4 and contacts the liquid surface of the sample 6, or when the lower magnet 10 is close to the bottom of the sample 6 by about 10 mm, then it is preferable that the front end of the upper magnet 5 is more than 2 mm away from the front end of the magnet container 4 and the liquid surface of the sample 6 when the upper end of the orifice plate 2 is in contact with the liquid surface of the sample 6, and the lower end of the orifice plate 2 is more than 2 mm below the position when the lower magnet 10 is 10 mm away from the bottom of the sample 6. Figure 16 This represents the analytical results of the difference in magnetic flux density between the ends and the center when the distance between the end faces of the upper and lower magnets is 5mm, with the center of the plate thickness set at the center of the ends of the upper and lower magnets. It can be seen that the difference in magnetic flux density is minimized when the plate thickness is 9mm or more, and repeating the setting of 2mm or more for each magnet is sufficient.

[0058] Example 3

[0059] When using a perforated plate 2 containing a soft magnetic material as in Examples 1 and 2, and bringing the magnet close to or away from the perforated plate 2, the magnetic force increases sharply when a certain distance is formed between the perforated plate 2 and the magnet. This results in an increased load on the drive source (electric motor, etc.) used to drive the magnetic rod 3, etc. As a countermeasure, a method such as... Figure 17 , Figure 18 As shown, soft magnetic materials and tapered holes with gradually decreasing magnetic force and grooves of varying depths are provided at the (bottom) end of the perforated plate 2. The angle and shape of the tapered portion can also be varied in each hole to shift the position of the load peak (phase shift), thus reducing the total load.

[0060] Figure 17 The narrowing of the upper conical boundary 11 and the lower conical boundary 12 relative to the specimen container 1 corresponds to the upper and lower end faces of the orifice plate shown in Embodiments 1 and 2, and is the range that minimizes the difference in magnetic flux density between the ends and the center. Similarly, Figure 18 The area between the upper groove end 13 and the lower groove end 14 corresponds to the upper surface and lower surface of the perforated plate in Embodiments 1 and 2, and is the range that minimizes the difference in magnetic flux density between the end and the center.

[0061] Figure 19 This represents the magnetic force generated between the magnet and the perforated plate 2 at various locations. It can be seen that by performing tapered machining, the peak position of the magnetic force becomes smaller compared to the case without machining, and... Figure 19 The integral values ​​in the graph, showing the total force (energy) required to drive the vehicle, also decrease.

[0062] Explanation of reference numerals in the attached figures

[0063] 1: Specimen container, 2: Well plate, 3: Magnetic rod, 4: Magnet container, 5: Upper magnet, 6: Specimen, 7: Magnetic particle, 9: Well, 10: Lower magnet.

Claims

1. A magnetic particle separation device, characterized in that, have: Multiple sample containers containing a mixture of liquid and magnetic particles. A first magnet, which is disposed relative to each of the plurality of sample containers, is capable of moving independently up and down relative to the sample containers. A magnetic container that covers the first magnet, and A perforated plate having orifices capable of holding a plurality of said specimen containers; At least the side portion of the perforated plate near the specimen container is made of a soft magnetic material.

2. The magnetic particle separation device according to claim 1, characterized in that, The soft magnetic material forms a magnetic circuit between the plurality of specimen containers.

3. The magnetic particle separation device according to claim 1, characterized in that, The plurality of first magnets are configured such that all of them are magnetic poles facing the same direction.

4. The magnetic particle separation device according to claim 3, characterized in that, The device includes a second magnet that can be disposed at the bottom of the opening capable of holding a plurality of said specimen containers, the magnetic poles of the second magnet being configured to face the same direction as the magnetic poles of the first magnet.

5. The magnetic particle separation device according to any one of claims 1 to 4, characterized in that, The hole has a tapered portion whose diameter increases toward the opening or a groove of varying depth.

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