WO2020148424A1

WO2020148424A1 - Magnet device

Info

Publication number: WO2020148424A1
Application number: PCT/EP2020/051120
Authority: WO
Inventors: Henrik HØYER
Original assignee: Giamag Technologies As
Priority date: 2019-01-18
Filing date: 2020-01-17
Publication date: 2020-07-23
Also published as: GB201900755D0

Abstract

A system for collecting magnetic particles from a well. The system comprises a well (20) for containing magnetic particles; a sheath (13) comprising a narrowing end (14); and a magnet device (100) removably disposed within the sheath (13). The magnet device (100) and the sheath (13) are arranged to be inserted into the well (20) to collect magnetic particles on the sheath (13). The magnet device (100) comprises a nib (130) which concentrates magnetic force at a distal end (111) of the magnet device (100). The nib (130) is disposed within the narrowing end (14) of the sheath (13).

Description

MAGNET DEVICE

Field

The invention relates to a magnet device, and particularly to a system and method for collecting magnetic particles comprising such a magnet device.

Background

Known methods of DNA molecule, RNA molecule, nucleic acids, and/or proteins analysis require collection of magnetic particles, which particles serve as vehicles for the molecules during a gathering stage of the analysis. The magnetic particles are typically gathered on a sheath about a magnet and then carried to and inserted in a solution containing the molecules for analysis. The molecules then attach to the magnetic particles (typically after a conditioning stage to mobilise them). The magnetic particles are then transferred to a further location and deposited, thereby also depositing the molecules for further analysis. An exemplary method is described herein with reference to figures 13A to 13D.

A necessary step of the method is the gathering and collection of magnetic particles onto the sheath. The efficiency of this step therefore impacts the efficiency of the overall process. Known processes are carried out using a common cylindrical magnet disposed within the sheath.

Summary

According to a first aspect of the invention there is provided a system for collecting magnetic particles from a well, comprising: a well for containing magnetic particles; a sheath comprising a narrowing end; and a magnet device removably disposed within the sheath; wherein the magnet device and the sheath are arranged to be inserted into the well to collect magnetic particles on the sheath; and wherein the magnet device comprises a nib which concentrates magnetic force at a distal end of the magnet device, and wherein the nib is disposed within the narrowing end of the sheath.

The magnet device may be an elongate device comprising a (plurality of) magnet(s) and optionally further comprising a (plurality of) magnetic element(s).

The magnet device is adapted (e.g. by its shape and/or arrangement of its constituent elements) to concentrate, shape and/or focus magnetic force at and/or about an end thereof for gathering and collecting magnetic particles using that force. The increased magnetic force at the end of the magnet device (compared to known systems) improves collection of magnetic particles on the end of the sheath.

The nib of the magnet device serves to concentrate, shape and/or focus magnetic force thereat, proximate the distal end of the magnet device and hence proximate and/or about the narrowing end of the sheath, since the nib of the magnet device is disposed within the narrowing end of the sheath. Therefore, during use when the magnet device and the sheath are inserted into the well, magnetic particles in the well will be attracted to the distal end of the magnet device (more strongly than in known systems) and will collect on the sheath at its narrowing end.

The nib of the magnet device extends outwardly from the magnet device and has a smaller cross-sectional area than that of the rest of the magnet device. That is, the nib is a smaller projecting portion of the magnet device. The width of the nib may decrease along its length. Its width may decrease linearly with distance e.g. the nib may taper. The nib may have a constant width along its length narrower than the width of the rest of the magnet device. The nib may extend along a central axis of the magnet device and may decrease in width with increasing distance along the axis. The nib may have any suitable profile. The nib may comprise any suitable projection from the magnet device e.g. any projection about which magnetic force of the magnet device is concentrated. The nib may be a tapering nib, may be rounded nib, may be a curved nib, may have concave and/or convex portions, may be a series of stepwise narrowing layers, and/or may be projection of constant width and so on.

The narrowing end of the sheath may be a smaller projecting portion of the sheath. It may be a tapering tip, may be a rounded tip, may be a curved tip, may have concave and/or convex portions, may be a series of narrowing steps and/or may be a projection of constant thickness and so on. The narrowing end of the sheath may have any suitable profile and may comprise any suitable projection from the sheath, and the cross-section of the narrowing end of the sheath may be smaller than that of the rest of the sheath. The width of the narrowing end of the sheath may decrease along its length.

The magnet device may be fittingly disposed within the sheath during use. The sheath may substantially conform to the shape of the magnet device such that no significant empty space remains inside the sheath when the magnet device is inserted therein. The walls of the sheath may have a constant thickness. The sheath may be formed of non-magnetic material, such as plastic or the like. In particular, the sheath may comprise a tapering tip, and the magnet device may comprise a tapering nib disposed within the tapering tip of the sheath.

The distal end of the magnet device is one of the ends of the magnet device. It may be understood to be the end which first encounters the well during insertion of the magnet device and sheath into the well. The nib is disposed at the distal end of the magnet device.

The magnet device may comprise a plurality of magnetically susceptible components arranged to concentrate magnetic force at a distal end of the magnet device. The magnetically susceptible components may be permanent magnets and/or may be magnetic elements susceptible to magnetic fields (e.g. magnetic metals and the like). Where magnetic elements comprise at least part of the magnet device, those magnetic elements may preferably have relatively high saturation magnetisations and/or relatively high magnetic permeabilities. The use of magnetic elements having higher saturation magnetisations and/or higher magnetic permeabilities may be preferred.

The arrangement of magnetically susceptible components of the magnet device may concentrate magnetic force at the distal end of the magnet device by various mechanisms. Particularly, the provision of a nib may serve to concentrate magnetic force thereabout.

The magnet device may comprise a plurality of permanent magnets, wherein the magnetization directions of the permanent magnets are arranged to concentrate magnetic force at the distal end of the magnet device. The magnet device may comprise any number of permanent magnets.

The plurality of permanent magnets may include at least two permanent magnets having respective magnetization directions angled relative to a central axis of the magnet device. The respective magnetisation directions of the permanent magnets may be aligned at an angle relative to the length of the magnet device (i.e. not parallel), and may be angled inwardly or outwardly (of the magnet device). The arrangement of magnetisation directions of the permanent magnets may be symmetric about the central axis of the magnet device.

The central axis of the magnet device may be defined along its length and the magnet device may be symmetric about the central axis e.g. rotationally symmetric and/or symmetric under reflection. The magnetisation directions of the permanent magnets may be orthogonal to the central axis and may be oriented directly inwards. The magnetisation directions of the permanent magnets may each be aligned between 10° to 80° to the central axis, may each be aligned between 20° to 70° to the central axis, may each be aligned between 30° to 60° to the central axis, may each be aligned between 40° to 50° to the central axis and may each be aligned about 45° to the central axis. The magnetization directions of the permanent magnets may not parallel with the central axis of the magnet device. They may be aligned having an inward or an outward component as needed to concentrate magnetic force near the distal end of the magnet device. The magnetization directions of the permanent magnets may be directed towards the central axis of the magnet device, or may be directed away from the central axis of the magnet device. The magnetization directions of the permanent magnets may all be directed towards the central axis of the magnet device, or only some of them may be.

A number of the plurality of permanent magnets may form at least a part of the nib of the magnet device. The permanent magnets may be shaped so that each provides a portion of at least a part of the nib of the magnet device so that the permanent magnets cooperate to define the nib. All of the permanent magnets may contribute to defining the nib of the magnet device, or the nib of the magnet device may be formed (at least partially) by only some of the permanent magnets. The permanent magnets may form the entirety of the nib of the magnet device.

The magnet device may comprise two permanent magnets, and may comprise only two permanent magnets. The two permanent magnets may be substantially mirror images of each other, and each of the two permanent magnets may have their magnetisation direction angled towards the other of the two permanent magnets by the same amount. That is, the magnetisation directions of the two permanent magnets may be angled with respect to the central axis of the magnet device. Each of the two permanent magnets may be shaped so as to provide at least a portion of the nib of the magnet device so the two permanent magnets cooperate to provide the entire nib.

The magnet device may comprise a magnetic element. The magnet device may form at least a part of the nib. The magnetic element may be formed of any suitable material and may be formed of any magnetically susceptible material (e.g. a magnetic metal). It may have a high magnetisation saturation and/or high magnetic permeability. The magnetic element may be disposed to provide the distal end of the magnet device. The magnetic element may form the whole of the nib, or may be relatively small with respect to the whole nib of the magnet device and may be e.g. a cylindrical disc disposed on the end of a tapered portion of the magnet device e.g. on a (plurality of) permanent magnet(s). The magnetic element may be disposed between and/or adjacent a plurality of permanent magnets as described herein. The magnetic element may not be a permanent magnet as such and may merely be an element susceptible and/or permeable to magnetic fields.

The magnet device may comprise a cylindrical magnet having its

magnetization direction aligned along (i.e. parallel to) a central axis of the magnet device. The magnetization direction of the cylindrical magnet may be oriented directly towards the distal end, or may be oriented directly away from the distal end (i.e. directly towards a proximal end). The cylindrical magnet may have a flat end orthogonal to the central axis of the magnet device and therefore may not form part of the nib of the magnet device. The nib of the magnet device may be defined by magnetically susceptible elements in addition to the cylindrical magnet. The central axis of the magnet device may be coincident with the major axis of the cylindrical magnet.

The magnet device may comprise permanent magnets in addition to the cylindrical magnet and the permanent magnets may have respective magnetisation directions angled with respect to that of cylindrical magnet. The permanent magnets may be arranged as described herein. The magnet device may comprise only two permanent magnets in addition to the cylindrical magnet. The

magnetisation directions of the permanent magnets may be angled inward to the magnet device and the magnetization direction of the cylindrical magnet may be oriented towards the distal end of the magnet device. The magnetisation directions of the permanent magnets may be angled outwardly to the magnet device and the magnetization direction of the cylindrical magnet may be oriented away from the distal end of the magnet device. The permanent magnets may be disposed at an end of the cylindrical magnet e.g. on and/or adjacent the flat end of the cylindrical magnet. The permanent magnets may modify the magnetic field generated by the cylindrical magnet so as to concentrate the magnetic force near the distal end of the magnet device.

The magnet device may comprise a magnetic element disposed on and/or adjacent the flat end of the cylindrical magnet, and the magnetic element may provide at least a portion of the nib of the magnet device. Where the magnet device comprises permanent magnets in addition to a cylindrical magnet, the magnetic element may be disposed on adjacent, and/or between the permanent magnets.

The magnet device may comprise a shaped magnet comprising a cylindrical portion and a narrowing portion, wherein the narrowing portion forms at least a part of the nib of the magnet device. The narrowing portion may form the entire nib.

The narrowing portion may be a tapering portion, may be curved, may form a rounded nib, and so on. The magnet device may comprise only a single shaped magnet wherein a portion of the single shaped magnet provides the nib of the magnet device. Alternatively the single shaped magnet may be the only permanent magnet of the magnet device and a portion thereof may provide a part of the nib and the remainder of the nib may be provided by a magnetic element.

The magnet device may comprise a central element extending along at least a portion of the central axis of the magnet device. The central element may be a permanent magnet, and/or may be a magnetic element. The central element may be a cylindrical magnet, or may be a shaped magnet e.g. with a tapering tip. The central element may therefore be any suitable magnetically susceptible element. The central element may be thinner than the magnet device and may therefore have a cross-section smaller than that of the magnet device e.g. along its entire length. The central element may form at least a portion of the nib of the magnet device. The central element may project outwardly e.g. from the rest of the magnet device and/or from other magnetically susceptible components forming at least part of the nib. The central element may comprise a tapering portion, a rounded portion, a narrowing portion, or the like. The magnet device may comprise permanent magnets disposed adjacent and/or about the central element, and the permanent magnets themselves may (or may not) provide a portion of the nib.

The magnet device may comprise shielding. The shielding may be disposed about the magnet device and/or may be disposed along at least a portion of the length of the magnet device. The shielding may therefore be disposed about what would otherwise be an outer surface of the magnet device (but for the shielding), and may be disposed proximate at least the nib. The nib of the magnet device may be exposed by the shielding. The shielding may cover all but the nib of the magnet device. The shielding may cover what would be the outer surfaces of all permanent magnets of the magnet device except for outer surfaces forming at least part of the nib. The shielding may be formed of a magnetically susceptible material e.g. metal or the like, or may be formed of material with low (or no, or negligible) magnetic susceptibility. The shielding may obstruct parts of the magnetic field of the magnet device. The shielding may be arranged to confine the magnetic field of the magnet device and help concentrate magnetic force to the region proximate the nib of the magnet device. The shielding may be arranged so as not to obstruct the magnetic field proximate the nib.

The nib of the magnet device may be adjustable. For example, the projection of the central element from the rest of the magnet device may be adjustable and e.g. thereby operable to tune the magnetic field about the nib. The shielding may be moveable relative to the nib and/or to permanent magnets of the magnet device, and may therefore be moved to affect the magnetic field about the nib. For example, the shielding may be moveable (e.g. arranged to slide) along at least a portion of the length of the magnet device to thereby expose or cover the nib and/or permanent magnets. The shielding may therefore be moveable (e.g. relative to the rest of the magnet device) to permit or obstruct the parts of the magnetic field about the device and hence to control the magnetic field about the nib.

The narrowing end of the sheath may cooperate with and substantially conform to a recess at a base of the well. During use, magnetic particles may gravitate to the recess at the base of the well, and the narrowing end of the sheath may conform to and fit into the recess of the well so as to improve collection of the magnetic particles therefrom.

The magnet device may have a substantially circular cross-section along its length, or may have a rectangular cross-section, a square cross-section, a triangular cross-section, or any suitably shaped cross-section (e.g. pentagonal, hexagonal, and so on). The cross-section can be regularly or irregularly shaped. It will be appreciated that the invention can be employed with any suitably shaped magnet device.

The invention of the first aspect provides a magnet device having a nib whereby magnetic force is concentrated near a distal end of the magnet device about the nib. Further, embodiments of the invention comprise a plurality of permanent magnets with respective magnetization directions arranged to concentrate force near the distal end of the magnet device. That is, both features provide a mechanism for concentrating or focussing magnetic force at, near, and/or about the distal end of the magnet device.

According to a second aspect of the invention there is provided a system for collecting magnetic particles from a well, comprising: a well for containing magnetic particles; a sheath; and a magnet device removably disposed within the sheath; wherein the magnet device and the sheath are arranged to be inserted into the well to collect magnetic particles on the sheath; and wherein the magnet device comprises a plurality of magnetically susceptible components whereby it is adapted to concentrate magnetic force at its distal end.

The magnetically susceptible components may be permanent magnets and/or magnetic elements or any combination thereof. The plurality of magnetically susceptible components are arranged to concentrate magnetic force at the distal end of the magnet, for example by virtue of their shape and/or by virtue of their arrangement within the magnetic device.

The magnet device may comprise a nib at the distal end whereby magnetic force is concentrated thereat. The sheath may comprise a narrowing end and the nib of the magnet device may be disposed within the narrowing end of the sheath.

The magnet device may comprise any and all of the features described above with reference to the first aspect.

According to a third aspect of the invention there is provided an elongate magnet device defining a central axis along its length, comprising a nib along the central axis, and a plurality of permanent magnets each having respective magnetization directions angled relative to that of the central axis and arranged to concentrate magnetic force at a distal end of the elongate magnet device proximate the nib.

The elongate magnet device may comprise a cylindrical magnet having its magnetisation direction aligned along (i.e. parallel to) the central axis. The plurality of permanent magnets may be disposed within the magnet device adjacent the cylindrical magnet. The plurality of permanent magnets may have respective magnetisation directions angled (e.g. inwardly or outwardly) with respect to that of the cylindrical magnet (i.e. not parallel thereto). The magnet device may comprise a magnetic element forming at least a part of the nib. The magnetic element may form the entire nib of the magnet device. Alternatively the plurality of permanent magnets may cooperate to define at least a part of the nib of the magnet device, and may define the entire nib of the magnet device. The permanent magnets may be disposed on a flat end of the cynical magnet.

The elongate magnet device may comprise any of the compatible features discussed herein with reference to the first or second aspects. The invention may provide a first plurality of wells, each for containing magnetic particles as described herein. The system may comprise a plurality of sheaths each as described herein. The system may comprise a plurality of magnet devices, each as described herein. Each magnet device may be disposed within a respective sheath, and each may be arranged to be inserted into a respective well of the first plurality of wells for collecting magnetic particles on each sheath. There may be provided the same number of wells as magnet devices in sheaths, and all of the magnet devices and sheaths may be arranged to be inserted simultaneously into respective wells of the first plurality of wells. The invention may provide a second plurality of wells and a mechanism for simultaneously inserting each of the plurality of magnet devices in respective sheaths into respective wells of the second plurality of wells. The invention may provide a third plurality of wells and a mechanism for simultaneously inserting each of the plurality of magnet devices in respective sheaths into respective wells of the third plurality of wells. There may be 24 or 96 wells in each of the plurality of wells, and 24 or 96 magnet devices and sheaths. The invention may provide a system for collecting DNA molecules, RNA molecules, nucleic acids and/or proteins and the like.

According to a fourth aspect of the invention there is provided a method of collecting magnetic particles from a well, the method comprising: providing a well containing magnetic particles; providing a sheath comprising a narrowing end; and providing a magnet device removably disposed within the sheath; providing a nib on the magnet device within the narrowing end of the sheath to concentrate magnetic force at a distal end of the magnet device; inserting the magnet device and the sheath into the well; and gathering magnetic particles at the narrowing end of the sheath proximate the nib of the magnet device.

The step of providing a nib on the magnet device may comprise

concentrating magnetic force at the nib and therefore at the distal end of the magnet device. The nib of the magnet device is arranged to concentrate magnetic force proximate the tip of the sheath.

The step of providing the magnet device may comprise providing a plurality of magnetically susceptible components and arranging the plurality of magnetically susceptible components to concentrate magnetic force at the distal end of the magnet device e.g. by virtue of their shape and/or arrangement of their

magnetization directions within the magnet device. The step of providing the magnet device may comprise providing a plurality of permanent magnets and arranging the respective magnetization directions of the permanent magnets to concentrate magnetic force at the distal end of the magnet device. The method may comprise arranging the respective magnetisation directions of the permanent magnets so they are angled inwardly to the magnet device (e.g. towards its central axis) whereby magnetic force may be concentrated at or near the distal end of the magnet device.

The step of providing the magnet device may comprise providing a cylindrical magnet having its magnetic polarisation aligned along (i.e. parallel to) its axis.

The method may comprise providing a plurality of permanent magnets forming at least part of the tapering nib and arranging the respective magnetic polarisations of each permanent magnet so that each is angled relative to that of the cylindrical magnet and arranged to concentrate magnetic force at or near the nib of the magnet device and therefore at the narrowing end of the sheath.

The step of providing the nib on the magnet device may comprise providing a magnetic element forming at least part of the nib. The magnetic element may form the entire nib.

The method may comprise comprising transferring the magnetic particles from the first well to a second well and removing the magnet device from the sheath to distance the magnetic particles from the magnet device and thereby deposit the magnetic particles in the second well.

The method may comprise using a system described herein with reference to the first and/or second aspect of the invention, or using a magnet device as described herein with reference to the third aspect of the invention.

The method may comprise collecting proteins using any of the features described herein with reference to the first, second, third, and/or fourth aspects of the invention. The method may comprise collecting DNA and/or RNA using any of the features described herein with reference to the first, second, third, and/or fourth aspects of the invention.

Viewed from another aspect, the invention provides a magnet device arranged to concentrate magnetic force at a distal end thereof, preferably for collecting magnetic particles at the distal end.

View from another aspect, the invention provides a system for collecting magnetic particles from a well, comprising: a well for containing magnetic particles; a sheath; and a magnet device removably disposed within the sheath; wherein the magnet device and the sheath are arranged to be inserted into the well to collect magnetic particles on the sheath; and wherein the magnet device is adapted to concentrate magnetic force at a distal end thereof.

Figures

Certain preferred embodiments of the invention are described in detail below by way of example only and with reference to the drawings in which:

Figure 1 shows a schematic of a cylindrical magnet typically used in known systems and methods for collecting magnetic particles from a well;

Figure 2 shows a schematic of a magnet device comprising a magnetic element forming a nib;

Figure 3 shows a schematic of a magnet device comprising a shaped permanent magnet forming a nib;

Figure 4 shows a schematic of a magnet device comprising a shaped permanent magnet and a magnetic element forming a nib;

Figure 5 shows a schematic of a magnet device comprising a plurality of permanent magnets forming a nib;

Figure 6 shows a schematic of a magnet device comprising a plurality of permanent magnets forming a nib;

Figure 7 shows a schematic of a magnet device comprising a plurality of permanent magnets and a magnetic element forming a nib;

Figure 8 shows a schematic of a magnet device comprising a plurality of permanent magnets;

Figure 9 shows a schematic of a magnet device comprising a plurality of permanent magnets forming a nib;

Figure 10 shows a schematic of a magnet device comprising a plurality of permanent magnet and a magnetic element comprising a nib;

Figure 11 shows a schematic of a magnet device comprising a plurality of permanent magnets and a magnetic element forming a nib;

Figure 12A shows the results of a simulation of magnetic force about a sheath containing a known cylindrical magnet ;

Figure 12B shows the results of a simulation of magnetic force about a sheath containing a magnet device; Figure 13A shows schematically a stage of a method of collecting magnetic particles from a well using a cylindrical magnet;

Figure 13B shows schematically another stage of the method of collecting magnetic particles comprising gather magnetic particles on a sheath;

Figure 13C shows schematically another stage of the method of collecting magnetic particles comprising transferring magnetic particles to a well;

Figure 13D shows schematically another stage of the method of collecting magnetic particles comprising depositing magnetic particles in the well of figure 13C;

Figure 14 shows a schematic of a magnet device comprising a plurality of permanent magnets and a magnetic element comprising a nib;

Figure 15 shows a schematic of a magnet device comprising a plurality of permanent magnets comprising a nib; and

Figure 16 shows a schematic of a magnet device comprising a plurality of permanent magnets and a magnetic element comprising a nib.

Description

Figures 1 to 10 each show a cross-section of a magnet device 100. In each figure, the magnet device defines a central axis A along its length. The magnet devices are all elongate along their respective central axes and may be symmetric thereabout. Magnetization directions of permanent magnets of the magnet device are indicated by arrows in the figures. These directions are not necessarily the optimal directions of magnetization. The optimal directions of magnetization depend on the exact configuration of the magnet device and the application for which the magnet device is used.

Figure 1 shows side view of a cylindrical magnet 10 used in known systems and methods for collecting magnetic particles from a well. The cylindrical magnet 10 defines a central axis A along its length, and the magnetization direction 12 of the cylindrical magnet 10 is aligned with the central axis A. The cylindrical magnet 10 has a distal end 11 at which magnetic elements are collected during use.

Figures 13A to 13D schematically show stages of a method of collecting and transferring magnetic particles 30 from a first well 20 to a second well 22 using a cylindrical magnet 10 like that of figure 1. The magnetic particles 30 are often in solution in a liquid in such a well 20. A sheath 13 is normally placed over the cylindrical magnet 10 prior to collecting magnetic particles 30, wherein the sheath 13 is largely cylindrical with a narrowing end or tip 14 at its distal end and is typically formed of plastic (see figure 13A). The tip 14 of the sheath 13 provides an empty volume adjacent the distal end 11 of the cylindrical magnet 10 when the cylindrical magnet 10 is inserted into the sheath 13. The cylindrical magnet 10 and sheath 13 are inserted into the well 20, wherein the magnetic particles 30 are attracted by the magnetic force of the cylindrical magnet 10 and consequently held to the plastic sheath 13 surrounding the cylindrical magnet 10 (see figure 13B).

The cylindrical magnet 10 and sheath 13 can then be removed from the first well 20, with the magnetic particles 30 still held to the sheath 13. The cylindrical magnet 10 and sheath 13 are transferred to a second well 22 (see figure 13C), and the cylindrical magnet 10 can then be removed from the plastic sheath 13 (see figure 13D), thereby removing the magnetic force holding the magnetic particles 30 to the sheath 13, so that the magnetic particles 30 are then released from the plastic sheath 13 into the second well 22. In this way, magnetic particles 30 are transferred from a first well 20 (where they may be e.g. in a low concentration in a large volume of liquid) to a second well 22 (where they may be e.g. in high concentration in a small volume of liquid).

Such a method is commonly used to collect and transfer products like DNA, RNA, nucleic acids and/or proteins etc. for subsequent analysis and/or purification using scientific instruments. In such cases, before depositing the magnetic particles 30 in the second well 22, the method typically comprises inserting the cylindrical magnet 10 and sheath 13 carrying the magnetic particles 30 into a well containing the DNA or the like, whereupon the DNA attaches to the magnetic particles 30. The cylindrical magnet 10 in the sheath 13, the magnetic particles 30, and the DNA attached to the magnetic particles 30 are then removed from the well, and transferred to the second well 22 as described above. Removing the cylindrical magnet 10 from the sheath 13 then deposits the magnet particles 30 - and the DNA carried thereby - into the second well 22.

The diameter of the cylindrical magnet 10 will vary from application to application, but one exemplary cylindrical magnet 10 used in the transfer of nucleic acids is about 4mm in diameter.

The inventor of the present invention has realised that improvements can be made to the known systems and methods that are typically used for collecting magnetic particles from a well. In particular, the magnetic force provided by the cylindrical magnet can be concentrated at the distal end of the magnetic device in order to improve the ability and efficiency of the magnet to collect magnetic particles at the tip of the sheath. The inventor has realised various means for doing so, some of which are illustrated in the figures and are described below.

Figure 12A shows a simulation of the magnetic force perpendicular to a surface of a cylindrical magnet 10 in a sheath 13 and therefore shown the magnetic force (e.g. magnetic capturing force) about a cylindrical magnet in a sheath 13 according to a known system. The sheath 13 comprises a tapering tip whereas the cylindrical magnet 10 comprises a flat end. The sheath 13 is sized to fittingly contain the cylindrical magnet and as such the tapering tip of the sheath 13 is empty.

An example of the effect of concentrating the magnetic forces can be seen in figure 12B. This figure shows a simulation of magnetic force perpendicular to the surface of a magnet device according to the present invention within a sheath having a narrowing end. This magnetic force is sometimes known as the magnetic capturing force. It can be seen that the magnetic force around the tapering tip of the sheath containing the magnetic device 100 is concentrated proximate a distal end 111 of the magnet device 100, and hence concentrated about the tapering tip of the sheath. The distal end 111 of the sheath and magnet device 100 is the end that in use is first inserted into a well for collecting magnetic particles thereat.

It can be seen from comparison of figures 12A and 12B that the magnet device increases magnetic force about the end of the sheath, which increase in force thereby helps improve efficiency of the system and process.

Figures 2 to 7, 9-11 , and 14-16 each show a magnet device 100 comprising a nib 130 which concentrates magnetic force thereabout proximate a distal end 111 of the magnetic device 100. The nib 130 in these embodiments has a narrower cross section than the rest of the magnet device 100 and can optionally be designed to match the geometry of a sheath that may be used with the magnet device 100 such that the nib 130 fills a portion of a narrowing end or tip that may be present in the sheath. Figure 8 shows a magnet device 100 comprising a plurality of permanent magnets 150 arranged so that their respective magnetization directions cooperate to concentrate the magnetic force at the distal end 111 of the magnet device 100.

Figure 2 shows a magnet device 100 according to the invention. The magnet device 100 defines a central axis A along its length, about which it is symmetrical. The magnet device 100 comprises a cylindrical magnet 110 having a magnetization direction 120 aligned along the central axis A. The cylindrical magnet 110 has flat ends. The magnet device 100 also comprises a nib 130 extending from the cylindrical magnet 110 and tapering with increasing length from the cylindrical magnet 110. The nib 130 has a narrower cross-section than that of the rest of the magnet device 100. The nib 130 is formed of a magnetic element 140 such as a piece of ferromagnetic metal or the like. Preferably, the magnet device 100 comprises magnetic elements 140 having higher magnetization saturations and/or higher magnetic permeabilities. The nib 130 concentrates magnetic force at the distal end 111 of the magnet device 100. When used with a sheath such as that described above in relation to the method known in the art, the nib 130 also fills at least part of the narrowing end or tip of the sheath. By concentrating the magnetic force at the distal end 111 and filling the narrowing end of the sheath, the attractive force at the distal end of the sheath is increased in comparison to the prior art. It is also possible that existing cylindrical magnets could be adapted in this way, with the addition of a nib 130 formed of a magnetic element 140 for example. Such adaptations will also be obvious in relation to other embodiments.

Figure 3 shows a magnet device 100 according to the present invention comprising a shaped magnet 150. The magnet device 100 comprises a shaped permanent magnet 150 which defines both a nib 130 at the distal end 111 of the magnet device 100, and further defines a cylindrical portion 132 of the magnet device 100. In the magnet device 100 of figure 3, the nib 130 is part of the shaped permanent magnet 150 (as opposed to being formed from a magnetic material like the embodiment of figure 2), but otherwise its shape is identical. The nib 130 serves to concentrate magnetic force proximate a distal end 111 of the magnet device 100 and fill a narrowing tip of the sheath, thereby increasing the ability and efficiency of the magnet device to collect magnetic particles at or proximate its distal end 111.

Figure 4 shows a magnet device 100 similar to the embodiment shown in figure 3 but wherein the nib 130 at the distal end 111 comprises both a portion of a (shaped) permanent magnet 150 and a magnetic element 140 in the shape of a cylindrical disc disposed on the end of the permanent magnet 150. In some applications, the diameter of the permanent magnet 150 (such as that of the embodiment shown in figure 3) may be too large to fill a tip or narrowing portion of the sheath used. Some permanent magnets may be prone to breaking and so this can limit the minimum diameter at which they can be used. Moreover, there may be size or space constraints where the magnet device is to be used. It is therefore useful to add a magnetic element 140 in order to fill space in the sheath and further enhance the focussing of the magnetic force at the distal end 111 of the magnet device 100.

Figure 5 shows a magnet device 100 comprising a cylindrical magnet 110 with a magnetization direction 120 aligned with the central axis A of the magnet device 100 and two further shaped permanent magnets 150 at the distal end 111 of the magnet device 100, wherein the nib 130 comprises a portion of the two shaped permanent magnets 150 and the two shaped permanent magnets 150 each have respective magnetization directions 180, angled towards the central axis A of the magnet device in order to focus the magnetic force of the entire magnet device 100 proximate the distal end 111. The two shaped permanent magnets 150 are symmetrical to one another about the central axis A of the magnet device 100. Again, the nib 130 takes a similar shape to that described in relation to magnet devices 100 of previous figures. In figure 5 the magnetization directions 180 of the two shaped permanent magnets 150 are about 45 and about 135 degrees respectively (with respect to horizontal). The magnetization directions of the permanent magnets 150 are each about 45 degrees from parallel with the central axis A of the magnet device 100 and both angled towards the central axis A of the magnet device 100. The optimum magnetization directions depend on the exact dimensions of the magnet device 100 and the application that it is used for. The shaped permanent magnets 150 concentrate the magnetic force at or near a distal end 111 of the magnet device 100 and in use fill a narrowing end or tip of a sheath used in conjunction with the magnet device 100.

Figure 6 shows a magnet device 100 comprising a cylindrical portion 132 and a nib 130 at a distal end 111 of the magnet device 100. The magnet device 100 comprises two shaped permanent magnets 150, with magnetization directions 120 respectively that are angled towards the central axis A of the magnet device 100 in order to focus or concentrate magnetic force at the distal end 111. The two shaped permanent magnets 150 are symmetrical to one other about the central axis of the magnet device 100. The nib 130 of the magnet device 100 takes a similar shape as that previously described but is formed from cooperation of respective portions of the two shaped permanent magnets 150. The cylindrical portion 132 is also formed from cooperation of respective portions of the shaped magnets 150. Similar to the embodiment shown in figure 5, the magnetization directions 120 of the two shaped permanent magnets 150 in this embodiment are about 45 and about 135 degrees respectively, but the optimum magnetization directions depend on the exact dimensions of the magnet device and the application that it is used for. The shaped permanent magnets 150 concentrate the magnetic force at a distal end 111 of the magnet device 100 and in use fill a possible narrowing end or tip of a sheath used in conjunction with the magnet device.

Figure 7 shows a magnet device 100 that comprises a cylindrical portion 132 with a constant diameter and a nib 130 at the distal end 111 of the magnet device 100. The cylindrical portion 132 comprises a cylindrical magnet 110 at a proximal end 170 of the magnet device 100 with a direction of magnetization 120 aligned with a central axis A of the magnet device 100 and two permanent magnets 150 symmetrical to one another about the central axis A and located towards the distal end of the magnet device 100 with directions of magnetization 180 angled towards the central axis A of the magnet device 100 in order to focus the magnetic force at the distal end 111. The nib 130 of the magnet device 100 extends from the cylindrical portion 132 and tapers with increasing length from the cylindrical portion 132 and has a narrower cross-section than that of the rest of the magnet device 100. Similar to the embodiment shown in figure 2, the nib 130 is formed of a magnetic element 140. The magnetic element 140 is disposed on the two permanent magnets 150. Preferably, the magnet device 100 comprises magnetic elements 140 having higher magnetization saturations and/or higher magnetic permeabilities. The nib 130 concentrates magnetic force at the distal end 111 of the magnet device 100 in conjunction with the two permanent magnets 150.

Figure 8 shows a magnet device comprising a plurality of magnetically susceptible components whereby the magnet device 100 is adapted to concentrate magnetic force at its distal end 111. The magnetically susceptible components may include a (plurality of) permanent magnet(s) and/or a (plurality of) magnetic element(s).

Figure 8 shows a magnet device 100 with a substantially constant diameter, for example having a circular cross-section and a cylindrical shape. The magnet device 100 comprises a cylindrical magnet 110 at a proximal end 170 (opposite the distal end 111) of the magnet device 100 with a direction of magnetization 120 aligned with a central axis A of the magnet device 100 and two permanent magnets 150 symmetrical to one another about the central axis A and located at the distal end 111 of the magnet device 100. The permanent magnets 150 have directions of magnetization 180 angled towards the central axis A of the magnet device 100.

The magnetization directions may be angled towards the central axis A by between 30 and 60 degrees inwardly to the vertical in order to focus magnetic force at the distal end 111. Particularly, the magnetization directions 180 of the two shaped permanent magnets 150 in this embodiment are about 45 either side of the central axis A (i.e. the vertical in Fig. 8) and angled inwardly towards the central axis A.

The optimum magnetization directions may depend on the exact dimensions of the magnet device 100 and the application that it is used for.

Figure 9 shows a magnet device 100 comprising a cylindrical magnet 110 with a constant diameter and a magnetization direction 120 aligned with the central axis A of the magnet device 100 and oriented directly away from the distal end 111 of the magnet device. The magnet device 100 further comprises two further shaped permanent magnets 150 at the distal end 111 of the magnet device 100, wherein the diameter of the distal end 111 of the magnet device narrows with increasing length to form a tapering nib 130 at the distal end 111 that is symmetric about the central axis A of the magnet device 100. The tapering nib 130 comprises respective portions of the two shaped permanent magnets 150 and the two shaped permanent magnets 150 each have respective magnetization directions 180, angled away from the central axis A of the magnet device 100 in order to focus the magnetic force at the distal end 111. The magnet device 100 of figure 9 is equivalent to the magnet device 100 of figure 5, but has opposite magnetization directions 120, 180. The two shaped permanent magnets 150 are symmetrical to one another about the central axis A of the magnet device 100. In figure 9 the magnetization directions 180 of the two shaped permanent magnets 150 are angled away from the central axis A by between about 30 and 60 degrees, particularly at about 225 and 315 degrees respectively (with the central axis A of the magnet device 100 at about 90 degrees and oriented vertically). The optimum magnetization directions depend on the exact dimensions of the magnet device and the application that it is used for. The shaped permanent magnets 150 concentrate the magnetic force at a distal end 111 of the magnet device 100 and in use fill a possible narrowing end or tip of a sheath used in conjunction with the magnet device 100. Magnetic force is concentrated near the distal end 111 of the magnet device by the magnetization directions of the permanent magnets 150, as well as by the tapering nib 130. Figure 10 shows a magnet device 100 comprising a cylindrical magnet 110. The cylindrical magnet 130 has a magnetisation direction 120 aligned (i.e. parallel) with a central axis A of the magnetic device 100. The magnet device also comprises two permanent magnets 150 at the distal end of the magnet device defining a nib 130. The permanent magnets 150 are symmetrical about the central axis A of the magnet device 100 and have magnetization directions angled with respect to the central axis A and the magnetization direction 120 of the cylindrical magnet 110. The nib 130 concentrates magnetic force at the distal end 111 of the magnet device 100. The magnet device 100 also comprises a magnetic element 140 forming part of the tapering nib 130 and disposed between the permanent magnets 150 and along the central axis A of the magnet device 100.

Figure 11 shows a magnet device 100 comprising a cylindrical portion 132 with a constant diameter and a tapering nip 130 which is symmetrical about the central axis A of the magnet device 100 and located at its distal end 111. The cylindrical portion 132 comprises a cylindrical magnet 110 with a constant diameter and a magnetization direction 120 aligned with the central axis A of the magnet device 100 and two further permanent magnets 150 toward the distal end 111 of the magnet device 100 that are symmetrical to one another about the central axis A. The two permanent magnets 150 each have respective magnetization directions 180, angled directly inwards towards the central axis A of the magnet device in order to focus the magnetic force at the distal end 111. The magnetization directions 180 of the permanent magnets are orthogonal to that of the cylindrical magnet 110, and are oriented directly opposite one another. The tapering nib 130 also comprises a magnetic element 140 disposed between the permanent magnets 150. The magnetic element may comprise a piece of ferromagnetic metal or the like. Preferably, the magnet device 100 comprises magnetic elements 140 having higher magnetization saturations and/or higher magnetic permeabilities. The tapering nib 130 concentrates magnetic force at the distal end 111 of the magnet device 100 in conjunction with the magnetization directions of the two permanent magnets 150.

Figure 14 shows a magnet device 100 comprising a plurality of shaped permanent magnets 150. The two shaped permanent magnets 150 shown in Fig. 14 have respective magnetization directions 180 angled inwardly towards the central axis A of the magnet device 100 in order to focus magnetic force at the distal end 111. The magnet device 100 comprises a plurality of permanent magnets 150 each providing a portion of the nib 130. For example, the magnet device 100 may comprise two permanent magnets 150, three permanent magnets 150, four permanent magnets 150, and so on, and the permanent magnets 150 may be disposed symmetrically about the central axis A of the magnet device 100. The permanent magnets 150 may be identical to each other. Each of the plurality of permanent magnets 150 has a magnetization direction 180 which may be angled with respect to the central axis A of the magnet device 100 and may thereby be arranged to concentrate magnetic force at the distal end 111. The shaped permanent magnets 150 of Fig. 14 have rounded ends providing part of the nib 130 of the magnet device 100.

The magnet device 100 of Fig. 14 also comprises a central element 160 formed by the magnetic element 140. The central element 160 is arranged along a portion of the central axis A of the magnet device 100 and projects outwardly from the rounded ends of the shaped permanent magnets 150 to provide another portion of the nib 130. The central element 160 is thinner than the rest of the magnet device 100, and therefore has a smaller cross-section (e.g. perpendicularly to central axis A) than does the rest of the magnet device 100. The central element 140 has a cylindrical portion 162 and a tapering portion 164. The central element 160 thus provides a portion of the nib 130 of the magnet device 100. Moreover, the central element 160 may make assembly of the magnet device 100 easier e.g. because the shaped permanent magnets 150 with opposing magnetization directions need not be directly adjacent each other. The magnet device 100 also comprises shielding 190 disposed about the cylindrical portion 132 of the magnet device 100. The shielding 190 covers permanent magnets (e.g. all permanent magnets) of the magnet device 100 everywhere except at the nib 130. The shielding 190 extends along a portion of the length of the magnet device 100, and is located adjacent the nib 130. The shielding 190 may be formed of magnetically susceptible material, and/or may be formed of material with low (or no) magnetic susceptibility. The shielding 190 may be metal or any suitable material. The shielding 190 may therefore obstruct magnetic fields from permanent magnets other than at the nib and hence may help to confine the magnetic field of the magnet device 100 except about the nib 130. The shielding 190 may therefore improve the efficiency with which the magnet device 100 can collect magnetic particles at the nib 130. The magnet device 100 also comprises a cylindrical magnet 110 arranged centrally within the magnet device 100 along a portion of the central axis A, and a magnetic element 142 as a lower part of the magnet device 100 (e.g. formed of a magnetically susceptible material). The magnetic element 142 may not require shielding disposed thereabout.

Figure 15 shows a magnet device 100 similar to that of Fig. 14, except that the central element 160 is a shaped permanent magnet with magnetization direction 162 parallel to the central axis A of the magnet device 100. The central element 160 therefore extends along a portion of the central axis A of the magnet device 100. It projects from the permanent magnets 150 and thereby provides a portion of the nib 130 of the magnet device 130. The permanent magnets 150 are therefore disposed about the central element 160. Any suitable number of permanent magnets 150 may be provided.

Figure 16 shows a magnet device 100 similar to that of the Fig. 14, except that the magnet device 100 of Fig. 16 comprises a cylindrical magnet 110 instead of the magnetic element 142 of Fig. 14. The magnet device 100 also comprises shielding 190 about the cylindrical magnet 110 so that only the nib 130 of the magnet device 130 is exposed by the shielding 190. The shielding 190 of the magnet device 100 thus extends the entire length except for the nib 130.

Whilst various aspects of the present invention have been described above with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined by the claims. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

Claims:

1. A system for collecting magnetic particles from a well, comprising

a well for containing magnetic particles;

a sheath comprising a narrowing end; and

a magnet device removably disposed within the sheath;

wherein the magnet device and the sheath are arranged to be inserted into the well to collect magnetic particles on the sheath; and

wherein the magnet device comprises a nib which concentrates magnetic force at a distal end of the magnet device, and wherein the nib is disposed within the narrowing end of the sheath.

2. A system as claimed in claim 1 , wherein the magnet device comprises a plurality of magnetically susceptible components arranged to concentrate magnetic force at a distal end of the magnet device.

3. A system as claimed in claim 1 or 2, wherein the magnet device comprises a plurality of permanent magnets, wherein the magnetization directions of the permanent magnets are arranged to concentrate magnetic force at the distal end of the magnet device.

4. A system as claimed in claim 3, wherein the plurality of permanent magnets include at least two permanent magnets having respective magnetization directions angled inwardly relative to a central axis of the magnet device.

5. A system as claimed in claim 3 or 4, wherein a number of the plurality of permanent magnets form at least a part of the nib of the magnet device.

6. A system as claimed in any preceding claim, wherein the magnet device comprises two permanent magnets.

7. A system as claimed in any preceding claim, wherein the magnet device comprises a magnetic element forming at least a portion of the nib.

8. A system as claimed in any preceding claim, wherein the magnet device comprises a cylindrical magnet having its magnetization direction aligned along a central axis of the magnet device.

9. A system as claimed in any preceding claim, wherein the magnet device comprises a shaped magnet comprising a cylindrical portion and a narrowing portion, wherein the narrowing portion forms at least a part of the nib.

10. A system as claimed in any preceding claim, wherein the magnet device comprises shielding.

11. A system for collecting magnetic particles from a well, comprising

a well for containing magnetic particles;

a sheath; and

a magnet device removably disposed within the sheath;

wherein the magnet device comprises a plurality of magnetically susceptible components whereby it is adapted to concentrate magnetic force at its distal end.

12. A system as claimed in claim 11 , wherein the magnetic device comprises a nib at the distal end whereby magnetic force is concentrated thereat.

13. An elongate magnet device defining a central axis along its length, comprising a nib along the central axis, and a plurality of permanent magnets each having respective magnetization directions angled relative to that of the central axis and arranged to concentrate magnetic force at a distal end of the elongate magnet device proximate the nib.

14. An elongate magnet device as claimed in claim 13, comprising a cylindrical magnet having its magnetization direction aligned along the central axis.

15. A method of collecting magnetic particles from a well, the method comprising:

providing a well containing magnetic particles; providing a sheath comprising a narrowing end; and

providing a magnet device removably disposed within the sheath;

providing a nib on the magnet device within the narrowing end of the sheath to concentrate magnetic force at a distal end of the magnet device;

inserting the magnet device and the sheath into the well; and

gathering magnetic particles at the narrowing end of the sheath proximate the nib of the magnet device.

16. A method as claimed in claim 15, wherein providing the magnet device comprises providing a plurality of magnetically susceptible components and arranging the plurality of magnetically susceptible components to concentrate magnetic force at the distal end of the magnet device.

17. A method as claimed in claim 15 or 16, wherein providing the magnet device comprises providing a plurality of permanent magnets and arranging the respective magnetization directions of the permanent magnets to concentrate magnetic force at the distal end of the magnet device.

18. A method as claimed in claim 15, 16 or 17, wherein providing the magnet device comprises providing a cylindrical magnet having its magnetic polarisation aligned along its axis.

19. A method as claimed in any of claims 15 to 18, wherein providing the nib on the magnet device comprises providing a magnetic element forming at least part of the tapering nib.

20. A method as claimed in any of claims 15 to 19, comprising transferring the magnetic particles from the first well to a second well and removing the magnet device from the sheath to distance the magnetic particles from the magnet device and thereby deposit the magnetic particles in the second well.

21. A method of collecting magnetic particles as claimed in any of claims 15 to 20, comprising using the system or any of claims 1 to 12, or using the elongate magnet device of claim 13 or 14.

22. A method of collecting proteins comprising collecting magnetic particles using a method as claimed in any of claims 15 to 21.

23. A method of collecting DNA and/or RNA comprising using a method as claimed in any of claims 15 to 22.