Nucleic acid extraction device and nucleic acid extraction method

Abstract

The purpose of the present invention is to provide a technique whereby stirring or elution can be effectively performed even when the amount of a specimen solution containing a nucleic acid and magnetic particles is large and the amount of eluted solution is small. The nucleic acid extraction device according to the present invention comprises a thick first magnetic bar protective jacket and a thin second magnetic bar protective jacket, a sample is stirred using the first magnetic bar protective jacket, and after the first magnetic bar protective jacket is replaced with the second magnetic bar protective jacket, a magnetic bar is inserted into the second magnetic bar protective jacket, thereby extracting nucleic acid from the sample. The magnetic particles in the sample are recovered (fig. 4).

Description

Technical Field

[0001] The present invention relates to a technique for extracting nucleic acid from a sample containing nucleic acid and magnetic particles. Background Art

[0002] In recent years, information obtained from nucleic acid analysis, such as cancer genome analysis using next-generation sequencing (NGS) systems, has been applied in various fields, including medicine, clinical testing, the pharmaceutical industry, and the food industry. Extraction of nucleic acids from various biological samples, such as blood, tissue, and cultured cells, is essential preprocessing for this nucleic acid analysis.

[0003] Nucleic acid extraction methods are not methods that use harmful organic solvents such as phenol or chloroform. Instead, they are generally based on the property of nucleic acids binding to silica in the presence of a chaotropic agent, or methods based on the property of nucleic acids binding to silica in the presence of an organic solvent. Using these methods, nucleic acid extraction methods using nucleic acid capture needles with a built-in solid phase containing silica as a nucleic acid capture carrier and methods using magnetic beads (nucleic acid capture carriers) with a surface covered with silica have been reported. These methods include a step of binding the nucleic acid to the nucleic acid capture carrier and an elution step of eluting the nucleic acid from the nucleic acid capture carrier using an elution solution.

[0004] In methods using magnetic beads, after the elution step, the magnetic beads are recovered from the eluate using a magnet. As an example, the eluate containing the magnetic beads is drawn into a dispensing needle, where the magnetic beads are retained in the needle using a magnet, and only the eluate is expelled from the needle. Another example involves inserting a rod-shaped magnet (optionally covered with a cover) into the eluate containing the magnetic beads to recover the magnetic beads from the eluate.

[0005] Patent Document 1 describes a method for effectively collecting magnetic beads by temporarily collecting them on the wall of a container and then recovering them using a magnetic rod. Patent Document 2 describes an example of extracting nucleic acids from a large liquid volume (2 mL) of a specimen using a coarse magnetic comb and a fine magnetic comb according to the steps shown in Figure 23. Patent Document 3 describes a technique for capturing and collecting magnetic substances from a liquid containing a magnetic substance, not by performing the capture and collection on the side of the container containing the specimen, but by using a dispenser that sucks and discharges the liquid containing the magnetic substance. Prior art literature Patent Literature

[0006] Patent Document 1: US6020211 Patent Document 2: US2022 / 0176369A1 Patent Document 3: Japanese Patent No. 3115501 Summary of the Invention Technical problem to be solved by the invention

[0007] In recent years, the amount of liquid of the specimen (sample liquid) to be measured has increased, while on the other hand, the amount of liquid of the eluent for eluting nucleic acids from the specimen has sometimes decreased compared to the past. This is to concentrate the eluent and strive to bring the eluent as a whole into the subsequent process. When the amount of eluted liquid is small relative to the amount of specimen input, in order to recover the small amount of eluent in the method of using a dispenser to attract and discharge the liquid containing the magnetic body, it is necessary to use a dispensing needle with a thinner inner diameter. However, this makes it easy for the magnetic beads that are increased to effectively recover nucleic acids from a large amount of specimen solution to become clogged. On the other hand, in the method of using a magnetic bar, if a thick magnetic bar is used, the stirring efficiency will be reduced in the process of stirring a small amount of eluent, and if a thin magnetic bar is used, it will be difficult to stir a large amount of specimen solution.

[0008] Patent Document 1 only describes the use of a small magnetic rod when handling a large amount of sample, so it is believed that the above-mentioned technical problems associated with the magnetic rod exist. In other words, it is believed that the document does not envision the stirring of a large amount of liquid added to a container larger than the outer diameter of the magnetic rod, or the collection of magnetic beads from a large amount of liquid.

[0009] As shown in Figure 23 of Patent Document 2, if elution is first performed with a thick magnetic rod protective cover and then with a thin magnetic rod protective cover, the adsorption (magnetic collection) and elution of DNA and magnetic particles will be performed twice, respectively, so the recovery rate of DNA will be reduced. This is because the adsorption rate of DNA on magnetic particles is not 100%, and the elution rate is not 100%. In addition, there is a technical problem that the recovery rate is reduced by repeated adsorption and elution. For example, when the recovery rate is 80%, the recovery rate after repeated 2 times will become 80% × 80% = 64%. In addition, since the adsorption and elution of DNA and magnetic particles are performed twice, it also takes a lot of time.

[0010] Patent Document 3 uses a dispenser to suck and discharge a liquid containing a magnetic substance, and therefore is considered to have the above-mentioned technical problems associated with the dispensing needle.

[0011] The present invention has been made in view of the above technical problems, and an object of the present invention is to provide a technique for efficiently performing stirring or elution even when the volume of a sample solution containing nucleic acid and magnetic particles is large and the volume of elution liquid is small. Technical means for solving technical problems

[0012] The nucleic acid extraction device involved in the present invention includes a thick first magnetic rod protective cover and a thin second magnetic rod protective cover. The first magnetic rod protective cover is used to stir the sample. After the first magnetic rod protective cover is replaced with the second magnetic rod protective cover, the magnetic rod is inserted into the second magnetic rod protective cover, thereby recovering the magnetic particles in the sample. Effects of the Invention

[0013] The nucleic acid extraction device according to the present invention can effectively perform stirring or elution even when the amount of the sample solution containing nucleic acids and magnetic particles is large and the amount of elution liquid is small. Other problems, structures, advantages, etc. of the present invention will be further clarified by the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1A This figure explains the technical problems that occur when using a thick magnetic rod protective cover. Figure 1B This figure explains the technical problems that occur when using a thin magnetic rod protective cover. Figure 2 This is a perspective view of the nucleic acid extraction device 1 according to the first embodiment. Figure 3 It is a side view of the inside of the nucleic acid extraction device 1 . Figure 4 It is a diagram illustrating the process of extracting nucleic acid from a sample by the nucleic acid extraction apparatus 1 . Figure 5 This is a diagram illustrating the process of extracting nucleic acid from a sample by the nucleic acid extraction apparatus 1 according to the second embodiment. Figure 6 This is a diagram illustrating the process of extracting nucleic acid from a sample by the nucleic acid extraction apparatus 1 according to the third embodiment. DETAILED DESCRIPTION

[0015] <Technical Issues Regarding Existing Technologies> The technical problems of the prior art will be described first, and then the embodiments of the present invention will be described. The technical problems of Patent Document 2 have been described above, so specific examples of Patent Documents 1 and 3 will be described here.

[0016] As disclosed in Patent Document 3, the method of sucking and discharging a liquid containing a magnetic substance using a dispenser has the following technical problems. When the amount of elution liquid is small relative to the amount of sample input, the proportion of eluent attached to the magnetic beads increases, making it difficult to recover the eluent. Since the amount of eluent is relatively small, the relative proportion of attached eluent increases accordingly. When the amount of eluent is small and a dispenser is used to aspirate or discharge the liquid, the inner diameter of the dispenser needle may be too large, causing only air to pass through and preventing stirring. Due to the above reasons, a smaller inner diameter dispensing needle is required to recover a smaller amount of eluate. However, in this case, the magnetic beads are more likely to clog. This is especially true when the amount of sample input increases, as more magnetic beads are needed to effectively capture nucleic acids, which can lead to increased clogging.

[0017] As disclosed in Patent Document 2, the method using a magnetic bar has the following technical problems. As the amount of sample loaded increases, use a thicker magnetic bar cover (a cover that protects the magnetic bar) to facilitate stirring. This excessive size relative to the relatively small amount of eluent used during elution reduces stirring efficiency. Furthermore, the relatively large size of the magnetic bar cover relative to the relatively small volume of eluent increases the proportion of eluent adhering to the cover, reducing eluent recovery efficiency. On the other hand, if a small magnetic rod protective cover is used, a swirling flow cannot be generated in a large amount of sample solution, making stirring difficult (a new mechanism is required for stirring). In addition, the magnetic field collection efficiency is reduced.

[0018] Figure 1A This figure illustrates the technical problems that arise when using a thick magnetic rod protective cover. Since the magnetic rod protective cover is larger than the volume of the eluent, the stirring efficiency is low. If the up and down movement of the magnetic rod protective cover is increased to fully stir the eluent, the amount of eluent attached to the side of the magnetic rod protective cover will increase, and the recovery efficiency of the eluent will decrease. Therefore, in the method of using a magnetic rod, it is not desirable to use a thick magnetic rod protective cover. Figure 1A Such a thick magnetic rod protective cover.

[0019] Figure 1B This diagram illustrates the technical issues associated with using a thin magnetic rod cover. Using a thin magnetic rod cover makes it difficult to stir large amounts of sample solution, necessitating the use of a mechanism other than the magnetic rod cover. Furthermore, since the magnetic rod is as thin as the magnetic rod cover, the efficiency of magnetic bead recovery is reduced.

[0020] <Implementation Method 1> Figure 2 This is a perspective view of a nucleic acid extraction device 1 according to Embodiment 1 of the present invention. Nucleic acid extraction device 1 is a device for extracting nucleic acid from a sample containing nucleic acid and magnetic particles. Nucleic acid extraction device 1 includes an X-axis module 11, a Z-axis module 12 (a mechanism for moving the magnetic rod protective cover and magnetic rod), magnetic rod protective covers 131 and 132, and a bottom magnet 14 (described later).

[0021] The X-axis module 11 includes a container 111 for storing a sample and a container holding mechanism 112 for holding the container 111. The X-axis module 11 can move the container 111 and the container holding mechanism 112 in the horizontal direction (X-axis direction).

[0022] The Z-axis module 12 includes a magnetic rod 121, which can move the magnetic rod 121 up and down in the vertical direction (Z-axis direction). The Z-axis module 12 also includes a mechanism that can load and unload magnetic rod protective covers 131 and 132 relative to the magnetic rod 121. As a result, the magnetic rod protective covers 131 and 132 can be replaced, as described later. The X-axis module 11 moves the magnetic rod protective cover 131 or 132 below the magnetic rod 121, and the Z-axis module 12 moves the magnetic rod 121 up and down, thereby enabling the magnetic rod protective cover 131 or 132 to be loaded and unloaded relative to the magnetic rod 121. In addition, the X-axis module 11 moves the container 111 below the magnetic rod 121 (with the magnetic rod protective cover installed), causing the magnetic rod 121 to move up and down, thereby enabling the liquid in the container 111 to be stirred using the magnetic rod protective cover.

[0023] Magnetic rod protection cover 131 is with Figure 1B The magnetic rod protection cover 132 is the same as the thin magnetic rod protection cover described in Figure 1A 131 is a member similar to the thick magnetic rod protective cover described in . That is, the diameter of the magnetic rod protective cover 131 is smaller than the diameter of the magnetic rod protective cover 132. The magnetic rod protective cover 131 does not have to be thin as a whole. At least, the diameter of the part of the magnetic rod protective cover 131 immersed in the sample is smaller than the diameter of the part of the magnetic rod protective cover 132 immersed in the sample. Two types of magnetic rod protective covers are shown here, and for example, a third type of magnetic rod protective cover can be arranged at the position marked 133, and they can be selected according to the liquid volume of the specimen or the container. Figure 2 The third type of protective cover is shown as being attached to the magnetic bar 121 .

[0024] Figure 3 1 is a side view of the inside of the nucleic acid extraction device 1. The container holding mechanism 112 holds a plurality of containers 111. For example, a plurality of containers 111 such as a container 111 holding a sample solution and a container 111 holding a reagent are held.

[0025] The magnetic bar protection cover 132 is preferably placed closer to the container 111 than the magnetic bar protection cover 131. On the other hand, if the magnetic bar protection cover 131 is placed closer to the container 111, the magnetic bar protection cover 132 will pass over the magnetic bar protection cover 131 in the steps described later, and droplets may fall from the magnetic bar protection cover 132 and contaminate the magnetic bar protection cover 131.

[0026] The nucleic acid extraction device 1 also includes a bottom magnet 14. The bottom magnet 14 is configured to be located below the container 111 when the container 111 moves below the magnetic rod 121. The bottom magnet 14 can be moved up and down by, for example, the Z-axis module 12. When the bottom magnet 14 is close to the bottom surface of the container 111, the magnetic beads can be collected on the bottom surface of the container 111. The bottom magnet 14 can be configured in multiple types, such as the bottom magnet used for the large container 111 and the bottom magnet used for the small container 111, or only one bottom magnet 14 can be used.

[0027] Figure 4 This is a diagram illustrating the process of extracting nucleic acid from a sample by the nucleic acid extraction device 1. Figure 4 Each step.

[0028] (1) Addition of magnetic beads: Magnetic beads (magnetic particles) are added to a large amount of sample solution (specimen: whole blood, plasma, serum, etc.). In addition, a reagent that promotes the binding of the biomaterial to be captured (DNA or antibodies, etc.) to the magnetic beads is added as needed.

[0029] (2) Stirring: Use the magnetic rod protective cover 132 (a thick magnetic rod protective cover) to stir the sample solution to bind the magnetic beads to the biological substance. For example, the magnetic rod protective cover 132 is moved up and down in the sample solution using the Z-axis module 12. After the magnetic beads and biological substance are fully bound, proceed to the next step.

[0030] (3.1) Magnetic collection: Insert the magnetic rod 121 into the magnetic rod protective cover 132. The diameter of the magnetic rod 121 is approximately the same as the diameter of the magnetic rod protective cover 131 (thin magnetic rod protective cover). By moving the magnetic rod protective cover 132 with the magnetic rod 121 inserted therein, for example, up and down, the sample solution is stirred and the magnetic beads are captured. By using a thick magnetic rod protective cover, a higher stirring effect can be obtained. More preferably, by moving the magnetic rod 121 up and down while moving the bottom magnet 14 close to the wall (bottom) of the container, the magnetic beads can be captured at both the container wall (bottom) and the magnetic rod 121, thereby improving the capture efficiency. Then, after bringing the magnetic rod 121 close to the container wall (bottom), only the magnetic rod 121 is removed from the magnetic rod protective cover 132, and then the magnetic rod protective cover 132 is pulled up from the sample solution. In this way, the magnetic beads are collected at the bottom of the container.

[0031] (3.2) Magnetism Collection: Insert the magnetic bar 121 into the magnetic bar protection cover 131 (a thin magnetic bar protection cover) and bring the magnetic bar protection cover 131 close to the bottom of the container. In this state, if the bottom magnet 14 is removed from the bottom of the container, the magnetic beads will be collected around the magnetic bar protection cover 131.

[0032] (4) Washing: Wash the magnetic beads bound to the nucleic acid to remove non-specific binding substances from the nucleic acid capture carrier. In the magnetic collection process (3.1-3.2), since the magnetic beads are collected on the magnetic rod protective cover 131, the magnetic beads can be washed in a container smaller than the sample container for accommodating a large number of specimens or in a container with a shape that matches the shape of the magnetic rod protective cover 131. By using a small container or a container shape that matches the shape of the magnetic rod protective cover 131, washing can be performed with a smaller amount of washing liquid, which is inexpensive. Figure 4The container shown in step (4) is the washing liquid container and is held by the container holding mechanism 112. After washing the magnetic rod protective cover 131 and the magnetic beads, the alcohol component is dried to prevent the washing liquid from being mixed into the nucleic acid elution solution in the next step. Regardless of the drying method used, the alcohol component is evaporated by allowing the magnetic rod protective cover 131, into which the magnetic rod 121 is inserted, to stand by or move up and down above the washing container.

[0033] (4) Washing: Supplement 1: The container, amount of washing solution, and number of washes suitable for washing can also be determined according to the purpose. This is not limited to the washing process, and the same can be said for the subsequent elution process. For example, since the magnetic beads and the magnetic rod protective cover 131 are washed in the washing process, the bottom shape of the container is a round bottom or other structure, which makes it easy for the solution to flow. In the elution process, since the nucleic acid is eluted with a smaller amount of elution solution, a small container inner diameter close to the outer diameter of the magnetic rod protective cover 131 is used, similar to the washing solution container.

[0034] (4) Washing: Supplement 2: The washing reagent is not particularly limited. For example, any reagent can be used as long as it can remove the reagent or impurities added in step 1 from the nucleic acid capture carrier while maintaining the binding of the nucleic acid to the nucleic acid capture carrier. For example, organic compounds such as lower alcohols or low molecular weight ketones can be used. As the washing reagent, ethanol, isopropanol, etc. can be used, and ethanol with a concentration of 70% or more is particularly preferred.

[0035] (5) Elute the nucleic acid bound to the magnetic beads from the magnetic beads. Specifically, the magnetic rod protective cover 131 that captures the magnetic beads bound to the nucleic acid is immersed in a container containing a nucleic acid eluent and stirred by moving up and down. In this way, the nucleic acid is recovered into the nucleic acid eluent. The magnetic rod 121 can also be pulled out from the magnetic rod protective cover 131 during stirring. In this case, after stirring, the magnetic rod 121 is inserted into the magnetic rod protective cover 131 again, and the magnetic beads are collected, and then the magnetic rod protective cover 131 is pulled up. The container containing the nucleic acid eluent can be smaller than the washing container. In this way, the efficiency of the magnetic rod protective cover 131 in stirring the nucleic acid eluent can be improved. Figure 4 The container shown in step (5) is the nucleic acid elution liquid container, which is held on the container holding mechanism 112.

[0036] <Implementation 1: Summary> The nucleic acid extraction device 1 involved in this embodiment 1 uses a thick magnetic rod protective cover (magnetic rod protective cover 132) to facilitate stirring even when the amount of sample input increases. On the other hand, a "thin magnetic rod protective cover + thin magnetic rod" is used for a smaller amount of liquid during elution. As a result, high-concentration nucleic acids can be recovered without reducing the stirring efficiency. In addition, the amount of smaller elution droplets attached to the magnetic rod protective cover is also limited, and the recovery efficiency of the elution liquid will not be reduced. In other words, by using the nucleic acid extraction device 1, the magnetic beads and the nucleic acid eluent can be reliably stirred, so that all (or most) of the nucleic acids are eluted from the magnetic beads, and high-concentration nucleic acids can be dissolved.

[0037] <Implementation Method 2> Figure 5 This diagram illustrates the process of extracting nucleic acid from a sample using nucleic acid extraction apparatus 1 according to Embodiment 2 of the present invention. The difference from Embodiment 1 is the magnetic collection step 3.1. In Step 3.1, instead of inserting magnetic bar 121 into magnetic bar protective cover 132, magnetic beads can be collected simply by placing bottom magnet 14 at the bottom of the sample container. The rest of the process is the same as in Embodiment 1. Figure 5 Compared to the process of embodiment 1, the efficiency of collecting magnetic beads in step 3.1 may be lower in the process shown. On the other hand, since the frequency of driving the magnetic rod 121 is reduced, the wear of the magnetic rod 121 (and the Z-axis module 12) can be suppressed. If the suppression of wear is more important, the process of embodiment 2 is useful. In addition, due to the presence of the bottom magnet 14, the efficiency of magnetic collection is improved, so the structure of the magnetic rod 121 can be made into a structure dedicated to the washing or elution process in the later process with less liquid (for example, a thinner structure).

[0038] <Implementation Method 3> Figure 6 This figure illustrates the process of extracting nucleic acid from a sample using the nucleic acid extraction device 1 according to Embodiment 3 of the present invention. The difference from Embodiment 1 is the magnetic collection step 3.1. In Step 3.1, the magnetic bar 121 is not inserted into the magnetic bar protective cover 132, and the bottom magnet 14 is not used. Instead, the magnetic bar 121 is brought close to the side of the sample container. During this time, the solution is stirred using the thick magnetic bar protective cover, and magnetic beads are collected on the inner side of the container near the magnetic bar 121.

[0039] Steps 3.2 and thereafter are the same as those in Embodiment 1, but since the magnetic beads accumulate on the side of the sample container, the magnetic rod protection cover 131 (and the magnetic rod 121 inserted therein) needs to be moved closer to the side of the container.

[0040] Figure 6The process shown may take longer than the first embodiment to collect magnetism, but has the advantage of not requiring a new magnet other than the magnetic bar (i.e., bottom magnet 14) to be installed at the bottom of the sample container. This allows the bottom magnet 14 and its movement control mechanism to be omitted.

[0041] <Implementation Method 4> In the above embodiment, the switching between the magnetic rod protective cover 132 and 131 does not necessarily need to be implemented in the magnetic collection steps 3.1 to 3.2, and can also be implemented in the washing process. At this time, the magnetic rod protective cover 132 (thick magnetic rod protective cover) is used to collect the magnetic beads, and the magnetic rod protective cover 132 holding the magnetic beads is washed. After washing, the bottom magnet 14 is used to collect the magnetic beads attached to the magnetic rod protective cover 132 to the bottom surface of the container. The magnetic rod protective cover 131 and the magnetic rod 121 are used to collect the magnetic beads on the bottom surface of the container again. The following is the same as embodiment 1. The above steps differ from embodiment 1 in that the magnetic rod protective cover 132 is replaced with 131 after washing. In this step, the washing container and the elution container are larger than those in embodiment 1, but the degree of freedom in the timing of replacing the magnetic rod protective cover is higher than that in embodiment 1.

[0042] Similarly, the step of replacing the magnetic rod protective cover after washing can also be used in the steps of embodiment 2. In the magnetic collection step 3.1, the magnetic rod protective cover 132 (thick magnetic rod protective cover) is used to collect the magnetic beads temporarily collected on the bottom surface of the container, and the magnetic rod protective cover 132 that retains the magnetic beads is washed. After washing, the bottom magnet 14 is used to collect the magnetic beads attached to the magnetic rod protective cover 132 to the bottom surface of the container. The magnetic rod protective cover 131 and the magnetic rod 121 are used to collect the magnetic beads on the bottom surface of the container again. The rest is the same as embodiment 1.

[0043] <Regarding Modifications of the Invention> In the above embodiment, the nucleic acid extracted from the sample can be used in a subsequent analysis step. Analysis using the nucleic acid solution is not particularly limited, and examples thereof include sequence analysis using a next-generation sequencer, DNA microarray, electrophoresis, and high-performance liquid chromatography-mass spectrometry.

[0044] In the above embodiment, an example is described in which nucleic acid is used as a target substance, attached to magnetic beads and extracted. However, even when other target substances are attached to magnetic beads and recovered, the same device structure and extraction process as the nucleic acid extraction device 1 can be used as long as the composition of the sample solution or eluent is appropriately changed according to the target substance. Label Description

[0045] 1: Nucleic acid extraction device 121 magnetic bar 131: Magnetic rod protective cover 132: Magnetic rod protective cover 14: Bottom magnet.

Claims

1. A nucleic acid extraction device for extracting nucleic acid from a sample containing nucleic acid and magnetic particles, the nucleic acid extraction device comprising: a first magnetic rod protective cover, which stirs the sample; a second magnetic rod protective cover, the second magnetic rod protective cover having an area thinner than a portion of the first magnetic rod protective cover immersed in the sample; a magnetic bar, which can be inserted into the first magnetic bar protective cover and the second magnetic bar protective cover respectively; as well as a mechanism that moves the first magnetic bar protective cover, the second magnetic bar protective cover, and the magnetic bar, The mechanism uses the first magnetic rod protective cover to stir the sample, After the stirring, the mechanism replaces the first magnetic rod protective cover with the second magnetic rod protective cover, and then immerses the area in the sample. The mechanism inserts the magnetic bar into the second magnetic bar protective cover immersed in the sample, The mechanism extracts the magnetic particles attached to the second magnetic rod protective cover and the nucleic acid attached to the magnetic particles from the sample by using the magnetic force of the magnetic rod by pulling the second magnetic rod protective cover into which the magnetic rod is inserted from the sample.

2. The nucleic acid extraction device according to claim 1, wherein The nucleic acid extraction device further includes a magnet, which can be arranged on the bottom surface of the container containing the sample. The mechanism moves the magnet to the bottom surface of the container after the stirring. When the magnet is disposed on the bottom surface of the container, the mechanism collects the magnetic particles to the bottom surface of the container by inserting the magnetic bar into the first magnetic bar protective cover so that the magnetic bar is close to the bottom surface of the first magnetic bar protective cover. The mechanism removes the magnetic bar from the first magnetic bar protective cover, and then removes the first magnetic bar protective cover from the sample, and then replaces the first magnetic bar protective cover with the second magnetic bar protective cover by immersing the second magnetic bar protective cover in the sample. The mechanism pulls the second magnetic bar protection cover away from the sample after removing the magnet from the bottom surface of the container.

3. The nucleic acid extraction device according to claim 1, wherein The nucleic acid extraction device further includes a magnet, which is arranged on the bottom surface of the container containing the sample. The mechanism does not insert the magnetic bar into the first magnetic bar protective cover, but moves the magnet to the bottom surface of the container, thereby collecting the magnetic particles to the bottom surface of the container. The mechanism does not insert the magnetic bar into the first magnetic bar protective cover, but replaces the first magnetic bar protective cover with the second magnetic bar protective cover. The mechanism pulls the second magnetic bar protection cover away from the sample after removing the magnet from the bottom surface of the container.

4. The nucleic acid extraction device according to claim 1, wherein After or during the stirring, the mechanism brings the magnetic bar close to the side of the container containing the sample, thereby collecting the magnetic particles on the side of the container. The mechanism replaces the first magnetic bar protection cover with the second magnetic bar protection cover after the magnetic bar is brought close to the container.

5. The nucleic acid extraction device according to claim 1, wherein The nucleic acid extraction device further includes a magnet, which is arranged on the bottom surface of the container containing the sample. The mechanism moves the magnet to the bottom surface of the container after the stirring. When the magnet is disposed on the bottom surface of the container, the mechanism collects the magnetic particles to the bottom surface of the container by inserting the magnetic bar into the first magnetic bar protective cover and bringing the magnetic bar close to the bottom surface of the first magnetic bar protective cover. The mechanism washes the magnetic particles by providing a washing liquid to the first magnetic rod protective cover to which the magnetic particles are attached. After the washing, when the magnet is arranged on the bottom surface of the container, the mechanism moves the first magnetic bar protection cover into which the magnetic bar is inserted close to the bottom surface of the container. The mechanism removes the magnetic bar from the first magnetic bar protection cover, further removes the first magnetic bar protection cover from the sample, and then replaces the first magnetic bar protection cover with the second magnetic bar protection cover by immersing the second magnetic bar protection cover in the sample.

6. The nucleic acid extraction device according to claim 1, wherein The nucleic acid extraction device further includes a magnet, which is arranged on the bottom surface of the container containing the sample. After the stirring, the mechanism does not insert the magnetic bar into the first magnetic bar protective cover, but moves the magnet to the bottom surface of the container, thereby collecting the magnetic particles to the bottom surface of the container. The mechanism washes the magnetic particles by providing a washing liquid to the first magnetic rod protective cover to which the magnetic particles are attached. After the washing, when the magnet is arranged on the bottom surface of the container, the mechanism moves the first magnetic bar protection cover into which the magnetic bar is inserted close to the bottom surface of the container. The mechanism removes the magnetic bar from the first magnetic bar protection cover, further removes the first magnetic bar protection cover from the sample, and then replaces the first magnetic bar protection cover with the second magnetic bar protection cover by immersing the second magnetic bar protection cover in the sample.

7. The nucleic acid extraction device according to claim 1, wherein The maximum diameter of the region of the second magnetic bar protection cover is smaller than the diameter of a portion of the first magnetic bar protection cover that is immersed in the sample.

8. The nucleic acid extraction device according to claim 1, wherein The nucleic acid extraction device also includes a holding table on which a container for containing the sample is placed. When the first magnetic rod protective cover and the second magnetic rod protective cover are not immersed in the sample, the first magnetic rod protective cover is arranged at a position closer to the holding table than the second magnetic rod protective cover.

9. The nucleic acid extraction device according to claim 1, wherein The mechanism washes the magnetic particles by providing a washing liquid to the second magnetic rod protective cover to which the magnetic particles are attached. After the washing, the mechanism recovers the nucleic acid into the nucleic acid elution solution by providing the nucleic acid elution solution to the second magnetic rod protective cover.

10. The nucleic acid extraction device according to claim 9, wherein The nucleic acid extraction device further includes a washing liquid container for storing the washing liquid. The washing liquid container has a volume of the washing liquid that can be stored in it that is smaller than a volume of the sample that can be stored in the sample container.

11. The nucleic acid extraction device according to claim 9, wherein The nucleic acid extraction device further comprises a nucleic acid eluent container, which contains the nucleic acid eluent. The volume of the nucleic acid elution solution that can be accommodated in the nucleic acid elution solution container is smaller than the volume of the sample that can be accommodated in the sample container that accommodates the sample.

12. A method for extracting nucleic acid from a sample containing nucleic acid and magnetic particles, the method comprising: a step of stirring the sample using a first magnetic rod protective cover for stirring the sample; After the stirring, replacing the first magnetic rod protective cover with a second magnetic rod protective cover having an area narrower than the portion of the first magnetic rod protective cover immersed in the sample, and immersing the second magnetic rod protective cover in the sample; inserting a magnetic bar into the second magnetic bar protective cover immersed in the sample; as well as The second magnetic rod protective cover is pulled up from the sample, and the magnetic force of the magnetic rod is utilized to extract the magnetic particles attached to the second magnetic rod protective cover and the nucleic acid attached to the magnetic particles from the sample.

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