GB2635671A

GB2635671A - Magnetic separation apparatus for use with a multi-well plate

Info

Publication number: GB2635671A
Application number: GB2317602.7A
Authority: GB
Inventors: Gledhill David; Pardoe Reuben; Lewis Robert; Cochrane David; Michael Billington David
Original assignee: SPT Labtech Ltd
Current assignee: SPT Labtech Ltd
Priority date: 2023-11-16
Filing date: 2023-11-16
Publication date: 2025-05-28
Also published as: WO2025104451A1

Abstract

A magnetic separation apparatus 100 comprising a housing 110, a support 120 for a multi-well plate wherein the wells contain magnetic beads, an array of magnets 130 mounted on a carrier 140 beneath the support, and a drive mechanism 150 to move the carrier by raising and lowering. The support may comprise a plate, optionally flat and removably supported on the housing. The apparatus may comprise a barrier layer 160 comprising an array of hollow protrusions 164, wherein the layer may be formed from a waterproof material. Optionally the support may be removable from the housing. An induction coil (Fig. 5; 170) may be located adjacent to a lower wall 112 of the housing. The magnets may be post magnets. The mechanism may comprise a belt drive, stepper motor, cam, rack and pinion, bevel gear or worm gear, or a controller. Also disclosed is a liquid dispensing apparatus comprising the apparatus. A method using the apparatus wherein a test sample comprising a supernatant and a complex of macromolecules bond to magnetic particles is provided in wells of a multi-well plate positioned on the support, and the carrier is raised so that the array of magnets attracts the magnetic particles so that the macromolecules are separated from the supernatant.

Description

MAGNETIC SEPARATION APPARATUS FOR USE WITH A MULTI-WELL PLATE FIELD OF THE INVENTION

The present invention relates to a magnetic separation apparatus for use with a multi-well plate. The present invention relates in particular to a magnetic separation apparatus for separating magnetic particles from a test sample in a multi-well plate using an array of magnets and to related methods. Such apparatuses are applicable for use with an automated multi-syringe liquid handling device.

BACKGROUND OF THE INVENTION

Automated multi-syringe liquid handling devices are often used to dispense and aspirate liquid samples into and from a sample vessel, such as a 96 or 384 configuration well plate. In use, the well plate is supported on the instrument deck beneath a moveable pipetting head to which an array of syringes is mounted. These liquid handling devices can be used for a variety of applications, such as sample preparation for NGS library preparation or polymerase chain reaction (PCR) methods. In various types of liquid handling methods, it may be necessary to isolate macromolecules, such as nucleic acids, from a sample for further study and/or processing. As an alternative to centrifugal or vacuum separation, which can be hard to automate, the isolation and purification of macromolecule samples is often achieved using magnetic particles, such as magnetic beads. The magnetic beads are coated in a substance with which the macromolecule has affinity under certain conditions and are mixed with a liquid sample in a vessel, such as the wells of a multi-well plate. The macromolecules and magnetic particles beads form a complex and are separated from the remainder of the sample (the "supernatant") using external magnets to attract and aggregate the complexes at the side of the wells.

The supernatant is then removed, and the macromolecules are isolated from the magnetic beads and transferred for subsequent analysis. The external magnets are typically provided on a magnetic plate or magnetic separation apparatus which is positioned beneath the multi-well plate. The well plate is typically lowered towards the magnet plate to apply a magnetic field to attract the magnetic beads and raised away from the magnet plate to remove the magnetic field. These manipulation steps can increase the risk that the sample is inadvertently disturbed or spilled. Every time a well plate is manipulated or otherwise physically transferred, be it manually or in an automated process, this introduces a risk of spillage occurring, whether this is on pick up, in transit, dropping it, or placing it down again.

It is an aim of the present invention to provide an improved magnetic separation apparatus to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a magnetic separation apparatus for separating magnetic particles from a test sample in a multi-well plate, as defined in claim 1. The apparatus comprises a housing, a support for supporting a multi-well plate on the housing during use, an array of magnets mounted on a carrier beneath the support, and a drive mechanism configured to raise and lower the carrier relative to the support to vary a height position of the array of magnets. The drive mechanism is operable to hold the array of magnets stationary at a plurality of height positions including a raised position, a lowered position, and a plurality of active positions between the raised and lowered positions.

With this arrangement, the magnetic particles in the test sample -which are typically provided as magnetic beads comprising magnetic particles -can be manipulated by the array of magnets without the need to manipulate or otherwise physically transfer the multi-well plate in which the test sample is contained. This can reduce the risk that the sample is inadvertently disturbed. Furthermore, by providing a drive mechanism which is operable to hold the array of magnets stationary at a plurality of height positions including a plurality of active positions between raised and lowered positions, the magnets can be moved to any chosen height position within their limits of travel.

As will be understood, the plurality of "active" positions are positions in which the magnetic field generated by the array of magnets interacts with the contents of a well plate on the support with sufficient strength to manipulate the position of the magnetic particles. The lowered position is typically not an active position. In that position, the magnetic field generated by the array of magnets is far enough below the outer walls of the well plate such that the magnetic particles are not manipulated by the magnetic field. The lowered position can, therefore, be considered as an inactive or deactivated position. The raised position is generally an active position in addition to the plurality of active positions between the lowered and raised positions. The claimed arrangement enables the vertical position of the magnetic field, and therefore the height of the cluster of magnetic beads, to be adjusted as desired. In this manner, the position of the cluster of magnetic beads can be better adapted according to one or more of: the geometry and/or depth of the wells of the multi-well plate, the levels of liquid within the wells of the multi-well plate, and the step of the process being undertaken. For example, due to the tapered shape of the wells of a typical multi-well plate, raising the height of the cluster of magnetic beads can better pull the magnetic beads out of the way of the syringe tips as they are inserted into and removed from wells. This can help to prevent contact between the syringe tip and the magnetic beads which might otherwise lead to inadvertent re-mixing of the beads with the supernatant. Lowering the active height position of the array of magnets can enable the magnetic separation apparatus to be used in processes in which the amount of liquid in the well is low and for which the magnetic field would otherwise be above the top level of the liquid sample, preventing the complexes to be pulled from the solution. The variable active height position of the array of magnets allows the position of the magnetic beads within the wells to be tuned according to the volume of liquid in the wells and/or according to the step in the liquid handling process. For example, the claimed arrangement can allow the magnetic beads to be pulled to the bottom of each well so that they are in the direct "firing line" of the pipettes and/or in the position of most turbulence to enable more effective re-suspension or washing of the magnetic particles. This differs from known arrangements in which the magnets are either fixed in position, such that the well plate must be moved away from the magnets to lessen the interaction with the magnetic field, or moved between an inactive position and a single active position such that the magnetic field is effectively either "off" or "on" in relation to the magnetic beads and fine tuning of the position of the magnetic beads within the wells is not possible.

The support may comprise one of more surfaces of the apparatus on which the multi-well plate can be rested during use. For example, the support may comprise support surfaces which contact the periphery of the well-plate.

In one or more embodiments, the support comprises a support plate extending across an upper region of the housing, whereby the support plate comprises an array of well holes for receiving and engaging at least a lower portion of the wells of the multi-well plate during use.

As used herein, the term "engaging at least a lower portion of the wells" means that the regions of the support plate by which the well holes are defined are in frictional contact with the outer walls of the wells of the multi-well plate, preferably around the entire circumference of each well.

By engaging the wells with the well apertures, the vertical position of the multi-well plate can be established and maintained more accurately across the full extent of the well plate, i.e. across its full length and width. Often, well plates are not entirely flat due to manufacturing variations and/or distortion which can occur after manufacture. Friction between the wells and the well apertures can help to ensure that the well plate sits flat once placed in position by resisting upward movement of the wells when received in the well apertures. The well apertures can also act as an accurate datum for the well plate and this can be more effective that using contact with the plate skirt as the datum. This can increase the accuracy of syringe positioning within each well, particularly for wells located towards the centre of the well plate for which deviation in the vertical position on a conventional device due to bowing of the well-plate is typically at its greatest.

The well holes may be cavities or blind holes in an upper surface of the support plate, wherein the cavities receive the lowermost end of a respective well. The well holes may be apertures extending through the thickness of the support plate. In such embodiments, each aperture forms a ring around its associated well at a position along the height of the well.

The support plate contacts with the outer walls of the wells -generally the outer well bottoms. By engaging the outer walls of the wells, the support plate acts to flatten the well-plate supported thereon. The support plate can thus be considered as a "flattening plate".

Preferably, the support plate is flat. This can facilitate flattening of the well plate. As used herein, the terms "flattening", "flatten" and "flat" refer to a planar geometry in which any variation in vertical height across the full width and/or length of the plate, for example due to manufacturing tolerances and/or post-manufacturing deformations (i.e. bowing), is less than 100 microns, preferably less than 90 microns, 80 microns, 70 microns, 60 microns, 50 microns, 40 microns, 30 microns, 20 microns, or 10 microns.

In other embodiments, the support plate may be non-flat. In such embodiments, the array of well apertures may vary in diameter across the width and/or length of the support plate to engage with different height positions of the outer walls of the well plate and thereby counteract variations in the vertical height of the support plate so that a non-flat support plate can still act to flatten the well plate.

The support plate may be fixed to the housing. The support plate may be releasably coupled to the housing. The support plate may be removable from the housing. The support plate may be removably supported on the housing, i.e. rested on the housing. In such an arrangement, the support plate rests on the housing and may be removed simply by lifting from the housing. This avoids the need to remove any releasable fasteners before removing the support plate. By removably supporting the support plate on the housing, the support plate may be lifted from the housing together with a multi-well plate supported on the support plate. For example, to perform additional sample processing steps, such as pre-cooling or heating of a liquid sample contained in the wells. This can avoid the need to lift the well-plate from the magnetic separation apparatus and place on a separate flattening plate or heating or cooling plate before carrying out these steps. Instead, the support plate can be placed directly on a further apparatus, such as a heating plate, together with the well plate. Reducing the number of transfer steps can reduce the risk of spillage or disturbance of the sample in the wells. This transfer process can also reduce the need for human interaction which might otherwise be required to remove the well plate from the magnetic separation apparatus, for example if the well plate becomes lodged in place on the apparatus.

The support plate may be removably supported on the housing and the magnetic separation apparatus may comprise one or more locating devices for laterally positioning the support plate on the housing. With this arrangement, the one or more locating devices can form a datum by which the lateral position of the support plate, and thereby the well plate, can be correctly maintained on the housing. The one or more locating devices may comprise one or more pairs of locating devices at opposite ends of the support plate. The one or more locating devices may be integral with the support plate, and/or integral with the housing, and/or integral with an intermediate layer positioned between the support plate and the housing, and/or discrete components which are positioned in a locating recess in both the support plate and the housing. For example, the one or more locating devices may comprise a cooperatively shaped male locating device and female locating device for receiving the male locating device. The male locating device may be a stud, dowel, pin, or similar. The female locating device may be a hole, cavity or recess. In certain embodiments, the one or more locating devices comprises one or more male locating device in the form of a projection which forms an integral part of one or more components of the apparatus. For example, where the apparatus comprises a barrier layer, the one or more male locating devices may be provided as a projection formed on the surface of the barrier layer during manufacture, e.g. during injection moulding. In this manner, the locating device can be provided without requiring a hole to be formed through the barrier layer. This may help to reduce the risk of liquid flow through the barrier layer.

The support plate may be formed from any suitable material. Preferably, the support plate is formed from a metal, such as aluminium. In such embodiments, the support plate can be pre-heated or pre-cooled before being placed on the housing. Thus, the support plate can be used to control the temperature of a sample stored in one or more wells of a well plate on the support plate.

The support plate may comprise any suitable number of well holes as desired.

The array of well holes may correspond to the number and location of the wells of a multi-well plate with which the magnetic separation apparatus is intended for use. For example, the array of well holes may comprise at least 24 well holes. The array of well holes may comprise at least 96 well holes. The array of well holes may comprise at least 384 well holes. The array of well holes may comprise 24 well holes arranged in a four by six grid. The array of well holes may comprise 96 well holes arranged in an eight by twelve grid. The array of well holes may comprise 384 well holes arranged in a sixteen by twenty-four grid.

The support plate may be positioned on the housing such that the array of magnets remains beneath the support plate at one or more height positions. The support plate may be positioned on the housing such that the array of magnets remains beneath the support plate in the raised position.

In certain embodiments, the support plate comprises an array of magnet holes for receiving the array of magnets. The magnet holes may be cavities or blind holes in the underside of the support plate. The magnet holes may be apertures extending through the thickness of the support plate. In such embodiments, the array of magnets protrudes above the support plate at least when in the raised position.

The array of magnet holes may each be configured to receive a plurality of the array of magnets. For example, one or more of the magnet holes may be an elongated slot configured to receive multiple magnets in a row of the array of magnets. In certain embodiments, the array of magnet holes corresponds in number and position to the array of magnets. In such embodiments, each magnet hole is configured to receive a single magnet of the array of magnets. In other words, the array of magnet holes may match the array of magnets one-to-one.

The magnetic separation apparatus may comprise a barrier layer extending across the upper region of the housing between the support plate and the array of magnets. The barrier layer is water resistant. The barrier layer may be formed from a waterproof material. With such an arrangement, the barrier layer acts to protect the array of magnets from liquid spilled during a liquid processing or transporting operation. This can be particularly beneficial with liquid samples containing magnetic particles, which can be very difficult or impossible to separate from the array of magnets. The barrier layer can also reduce the burden and time taken to clean the apparatus after use. The barrier layer may be hydrophilic. The barrier layer may be a waterproof membrane. The barrier layer may be a waterproof membrane which prevents transmission of liquid water therethrough at a pressure of at least 0.5 cm water head for 5 minutes. The barrier layer can enable the assembly to form a watertight enclosure in which the array of magnets is housed. The assembly may form an enclosure with an P68 waterproof rating. The barrier layer may be formed from any suitable material. In certain embodiments, the barrier layer is formed from a polymer, such as a thermoplastic elastomer (TPE), polystyrene, high density polystyrene or polypropylene (PP).

The barrier layer may be fixed to the housing and/or to the support plate. In certain embodiments, the barrier layer is releasably coupled to the housing. The barrier layer may be removable from the housing. This can facilitate cleaning of the barrier layer, or replacement of the barrier layer, following use. The barrier layer may be removably supported on the housing, i.e. rested on the housing. In such an arrangement, the barrier layer rests on the housing and may be removed simply by lifting from the housing. This avoids the need to remove any releasable fasteners before removing the barrier layer.

The barrier layer may comprise an array of magnet receptacles on its underside for receiving the array of magnets at least in the raised position. The barrier layer may have sufficient thickness such that the array of magnet receptacles is defined within the thickness of the barrier layer. In certain embodiments, the barrier layer may comprise an array of hollow protrusions on its upper surface by which the array of magnet receptacles is defined. With this arrangement, the thickness of the barrier layer, and the overall height of the apparatus can be minimised.

Where the magnetic separation apparatus comprises a support plate with an array of magnet holes for receiving the array of magnets, preferably the hollow protrusions are received in the array of magnet holes. In such embodiments, the array of magnet holes and the array of hollow protrusions may have complimentary geometries. For example, the array of magnet holes and the array of hollow protrusions may each have a frustoconical shape or a cylindrical shape.

The barrier layer may extend across an opening in the upper region of the housing. In preferred embodiments, the housing comprises a top wall extending across the width of the upper region of the housing, wherein the top wall has an array of magnet apertures through which the array of magnets extends when at least in the raised position. The barrier layer may be supported from underneath by the top wall. In this manner, the barrier layer may be thinner and lighter, since it is not required to support its own weight across the width of the housing.

The barrier layer may form a seal across the upper region of the housing such that the array of magnets, the carrier, and the drive mechanism are sealed within the housing. With this arrangement, the working components of the magnetic separation apparatus can be protected from contamination or damage from spillages or leakage during use of the apparatus.

The magnetic separation apparatus may comprise an induction coil within the housing which is electrically connected to the drive mechanism. The induction coil enables the drive mechanism to be connected to a controller and/or to a power source via an inductive coupling. Thus, the magnetic separation apparatus can be provided free of external electrical connectors. Preferably, the induction coil is located adjacent to a lower wall of the housing. This can enable the induction coil to form an inductive coupling more easily with a further induction coil positioned beneath the housing, for example on a surface on which the magnetic separation apparatus is supported.

The array of magnets may comprise any suitable type of magnet. For example, the array of magnets may comprise an array of electromagnets.

Preferably, the array of magnets comprises an array of permanent magnets.

In certain embodiments, the array of magnets comprises an array of post magnets. The post magnets may have any suitable shape. Preferably, the array of post magnets are cylindrical and have a circular cross-section shape. This can help to ensure more uniform magnetic fields in the region around each post magnet and at different height positions of the array of magnets.

In certain embodiments, the array of post magnets is arranged such that each post magnet is laterally positioned in a central region between each group of four adjacent well holes in the support plate. This enables a single post magnet to be used to manipulate the magnetic particles in four wells simultaneously. This can also enable the post magnet to be raised higher in relation to the wells in comparison to arrangements in which the array of magnets comprises rows of bar magnets. This is because the central region between four adjacent wells provides a wider space envelope than the region between pairs of adjacent wells in which a bar magnet must be accommodated. This can allow the post magnets to provide a magnetic field at more height positions in the well, improving versatility.

The array of post magnets may have a substantially uniform polarity. In certain embodiments, the array of post magnets may be arranged such that at least some of the post magnets have an opposite polarity to one or more adjacent post magnets. This can enable the shape of the magnetic field to be tuned. In a preferred embodiment, the array of magnets has alternating polarity across the width and length of the array. In other words, the array of magnets may be arranged such that the polarity alternates in a checkerboard arrangement. In this manner, the polarity of each magnet is opposite to the polarity of each adjacent magnet. This has been found to enable the array of magnets to manipulate the magnetic particles into tighter, smaller clusters in relation to an equivalent uniform array. This can allow more accurate control of the position of the magnetic particles in the wells.

The magnetic separation apparatus may comprise any suitable drive mechanism. For example, the drive mechanism may comprise one of more of: a belt drive; a stepper motor; a cam mechanism; a rack and pinion mechanism; a bevel gear; and a worm gear.

The magnetic separation apparatus may comprise a controller configured to operate the drive mechanism to hold the array of magnets stationary at the plurality of height positions.

According to a second aspect of the present invention, there is provided a magnetic separation apparatus of the first aspect and a controller configured to operate the drive mechanism to hold the array of magnets stationary at the plurality of height positions. The controller may be remote from the magnetic separation apparatus and connected to the drive mechanism by any suitable means. For example, via a wired communication connection or via a wireless communication connection. The controller may be provided as part of a liquid handling device with which the magnetic separation apparatus is intended for use and/or via a remote network or remote device, such as a smart phone, tablet, computer, or similar.

According to a third aspect of the present invention, there is provided a liquid dispensing apparatus comprising a main body with a deck; a pipetting head above the deck and comprising a pipette body mounting assembly for holding an array of removable pipettes, and a dispense drive actuator assembly operable to move a plunger assembly relative to the pipette body mounting assembly along a drive axis to perform a dispensing operation; and a magnetic separation apparatus according to the first aspect, the magnetic separation apparatus being positioned on the deck.

According to a fourth aspect of the present invention, there is provided a method of separating macromolecules from a test sample in a multi-well plate, the method comprising the steps of: providing a magnetic separation apparatus according to the first aspect; placing a multi-well plate on the support; providing a test sample in at least one well of the multi-well plate, the test sample comprising a supernatant and a complex of macromolecules and magnetic particles; raising the carrier relative to the support to attract the complex to the side of the at least one well using the array of magnets and thereby separating the complex from the supernatant; removing the supernatant from the at least one well.

Optionally, the step of raising the carrier relative to the support comprises raising the carrier to a first active position to attract the complex to the side of the at least one well and subsequently raising the carrier to a second active position which is at a different height position to the first active position to move the complex along the side wall of the at least one well.

Optionally, the second active position is higher than the first active position such that the complex is moved further from a central axis of the at least one well when the carrier moves to the second active position. In this manner, the complex can be less likely to be disturbed when a syringe or pipette is inserted into the well in order to perform one or more liquid handling operations, such as removing the supernatant from the well.

As used herein, the terms "above", "upper", "low", "below", "lowest" and other similar indications of orientation refer to the normal orientation of the magnetic separation apparatus during use.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will be further described below, by way of example only, with reference to the accompanying drawings in which: FIGURE 1 is a front view of a liquid dispensing apparatus with a magnetic separation apparatus in accordance with the present invention; Figure 2 is a perspective view of a magnetic separation apparatus in accordance with the present invention; Figure 3 is an exploded perspective view of the apparatus of Figure 2; Figure 4 is a cross-sectional exploded perspective view of the apparatus of Figure 2; Figure 5 is a plan view of the drive mechanism of the apparatus of Figure 2; Figure 6 is an enlarged cross-sectional perspective view showing a plate locating means of the magnetic separation apparatus of Figure 2; Figure 7 is an enlarged cross-sectional perspective view showing a multi-well plate supported on the support plate of the apparatus of Figure 2, with the remaining components of the apparatus omitted for clarity, the cross-section being taken along the centre line of a row of well holes in the support plate; Figure 8 is an enlarged cross-sectional perspective view showing a multi-well plate supported on the support plate of the apparatus of Figure 2, the cross-section being taken along the centre line of a row of magnet holes in the support plate; and Figure 9A is a cross-sectional perspective view of part of the magnetic separation apparatus of Figure 2, with the array of magnets in the raised position; Figure 9B is a cross-sectional perspective view of part of the magnetic separation apparatus of Figure 2, with the array of magnets in the lowered position; Figure 9C is a cross-sectional perspective view of part of the magnetic separation apparatus of Figure 2, with the array of magnets in an active position between the raised and lowered positions; and Figure 10 is a flow chart of a method of separating macromolecules from a test sample in a multi-well plate in accordance with the present invention.

DETAILED DESCRIPTION

Figure 1 shows a liquid dispensing apparatus 10 for use with the magnetic separation apparatus. The liquid dispensing apparatus 10 comprises a main body 12 with a well plate receiving area, or deck, 14. The microplate receiving area 14 is has a substantially horizontal upper surface 16 arranged to receive a laboratory microplate. The receiving area 14 can be located on a height-adjustable support structure 18 which enables the height of the microplate receiving area 14 to be varied as required. The liquid dispensing apparatus 10 further includes a pipetting head 20 positioned above the microplate receiving area 14 and having a pipette body mounting assembly 22 for holding an array of removable pipettes and a dispense drive actuator assembly 24 operable to move a plunger assembly 26 relative to the pipette body mounting assembly 22 along a drive axis 28 to perform a dispensing operation. Shown beneath the pipetting head 20 and on the deck 14 is a magnetic separation apparatus 100 according to the present invention. During use, the pipetting head 10 is used to perform liquid handling operations in relation to liquid samples contained in a multi-well plate, such as a microplate, supported by the magnetic separation apparatus 100. The receiving area 14 may be configured to retain a laboratory microplate, and/or the magnetic separation apparatus 100, in a fixed position. For example, the upper surface 16 of the receiving area 14 may comprise one or more recesses (not shown) arranged to receive a microplate and to prevent lateral translation of the microplate with respect to the receiving area 14. The upper surface 16 of the deck 14 may also include an external induction coil 172 for forming an inductive coupling with an internal induction coil (see feature 170 in Figure 5) in the magnetic separation apparatus.

The inductive coupling enables power to be transmitted to the magnetic separation apparatus 100 and/or communication signals to be transmitted to and/or from the magnetic separation apparatus 100 without the need for electrical connectors extending through the wall of the magnetic separation apparatus 100.

The liquid dispensing apparatus 10 will generally be used in the orientation shown in Figure 1 to retain products in wells of the microplate by gravity. The axis marked Z in Figure 1 therefore represents an upward direction, with gravity acting in the opposite direction to retain the products in the wells of the microplate. References to upward and downward directions or to an axial direction therefore refer to movement along the axis marked Z in Figure 1, while references to lateral or transverse directions refer to movement in the directions marked X (width) and Y (depth) in Figure 1. References to vertical direction or height also therefore refer to dimensions or movement along the axis marked Z in Figure 1. The pipetting head 20 may be moveable in relation to the deck 14 to bring pipettes mounted on the pipetting head 20 into proximity with a microplate supported on the magnetic separation apparatus 100 to allow liquid to be aspirated from or dispensed into the wells of the microplate.

Figure 2 is a perspective view of the magnetic separation apparatus 100, Figure 3 is an exploded perspective view of the magnetic separation apparatus 100, and Figure 4 is a cross-sectional view of the magnetic separation apparatus 100.

With reference to Figures 2 to 4, the magnetic separation apparatus 100 comprises a housing 110, a support 120 at an upper region of the housing 110 for supporting a multi-well plate 1000 above the housing during use, an array of magnets 130 mounted on a carrier 140 beneath the support 120 and within the housing 110, and a drive mechanism 150 configured to raise and lower the carrier relative to the support to vary a height position of the array of magnets 130. The drive mechanism 150 is operable to hold the array of magnets 130 stationary at a plurality of height positions. The plurality of height positions includes a raised position, a lowered position, and a plurality of active positions between the raised and lowered positions, as discussed in relation to Figures 9A-9C.

The housing 110 has a housing base plate 112, a housing top plate 114 and housing side walls 116 by which the base plate 112 and the top plate 114 are connected to form the housing. The top plate 114 includes an array of magnet apertures 115 through which the array of magnets 130 extends from the housing.

In the illustrated embodiment, the support 120 is provided in the form of a support plate removably supported, i.e. resting, on the housing 110 and extending across the upper region of the housing 110. In this manner, the support plate 120 can be simply lifted from the housing. In other embodiments, the support 120 can be integral with the housing or fixed to the housing, for example with screws. The support plate 120 includes an array of well holes 122 for receiving and engaging at least a lower portion of the wells 1010 of the multi-well plate 1000 during use. This is discussed in relation to Figure 7. The array of well holes 122 comprises 384 well holes arranged in a sixteen by twenty-four grid. In this manner, the support plate 120 is specifically configured for use with a standard 384 microplate. However, it will be understood that the array of well holes 122 may have different configurations based on the configuration of the well plate with which the apparatus is intended for use. The support plate 120 further includes an array of magnet holes 124 for receiving the array of magnets 130. The array of magnet holes 124 corresponds in number and position to the array of magnets 130. In this manner, each magnet hole 122 receives a single magnet 130 of the array of magnets 130. In other embodiments, one or more of the magnet holes might be larger and configured to receive multiple magnets. In the illustrated embodiment, the array of well holes 122 are cavities or recesses (i.e. blind holes) formed in the upper surface of the support plate 120, wherein the array of magnet holes 124 are through holes which extend through the entire thickness of the support plate 120. However, it will be understood that the array of well holes 122 may be through holes and/or the array of magnet holes 124 may be cavities or recesses (i.e. blind holes) formed in the underside of the support plate 120. The support plate 120 also includes a pair of guide walls 126 at the periphery of the support plate 120 for locating the well plate 1000 on the support plate 120. The guide walls 126 are optional and help to prevent accidental misloading of the well plate by one or more rows.

The array of magnets 130 are mounted on a carrier 140 in the form of a carrier plate 140 located within the housing 110. The array of magnets 130 is an array of post magnets 130 which extend upwardly from the carrier plate 140. In the illustrated embodiment, array of magnets corresponds in number and position to the array of magnet holes 124 in the support plate 120 such that each magnet is received in a corresponding magnet hole 124. The array of post magnets 130 is arranged such that each post magnet 130 is laterally positioned in a central region defined between each group of four adjacent well holes 122 in the support plate 120. This enables a single post magnet 130 to be used to manipulate the magnetic particles in four wells simultaneously. This can also enable the post magnet to be raised higher in relation to the wells in comparison to arrangements in which the array of magnets comprises rows of bar magnets. This is because the central region between four adjacent wells provides a wider space envelope than the region between pairs of adjacent wells in which a bar magnet must be accommodated.

The drive mechanism 150 is located within the housing 110 and is configured to raise and lower the carrier 140 relative to the support 120 to vary a height position of the array of magnets 130. Any suitable drive mechanism may be used.

In the illustrated embodiment, the drive mechanism 150 comprises a belt drive in which a belt 152 is driven by an actuator 154 via a bevel gear 156 to raise or lower the carrier 140 along threaded support rods 158 located at the four corners of the support plate 120. The drive mechanism 150 also comprises control circuitry 155 which is electrically connected to the actuator 154 and can be used to control the operation of the drive mechanism 150.

The magnetic separation apparatus 100 further comprises a barrier layer 160 extending across the upper region of the housing 110 and located between the support plate 120 and the array of magnets 130. The barrier layer 160 is removably supported on the housing 110 and forms an intermediate layer between the housing and the support plate 120. The barrier layer 160 is formed from a waterproof material, such as polypropylene, and provides protection for the array of magnets 130 from liquid spilled onto the support plate 120. The barrier layer 160 comprises an array of magnet receptacles 162 (see also Figure 8) which are accessible from the underside 168 of the barrier layer 160 and which are defined by a corresponding array of hollow protrusions 164 on the upper surface 169 of the barrier layer 160.

Optionally, the barrier layer 160 has a downwardly extending peripheral skirt 166 by which the barrier layer 160 can seal against the side walls of the housing 110 and thereby form a seal across the upper region of the housing 110 to completely enclose the contents of the housing 110 within a sealed unit.

The multi-well plate 1000 with which the magnetic separation apparatus 100 is intended for use comprises a plurality of wells 1010 arranged in a grid and held in a frame 1020 with a downwardly extending peripheral skirt 1022. The illustrated well plate 1000 is an SBS standard 384 microplate. However, it will be understood that the apparatus 100 may be configured for use with different types of well plate, for example well plates with a different array of wells and/or well geometries.

As shown in Figure 5, the magnetic separation apparatus 100 optionally includes an internal induction coil 170 which is electrically connected to the drive mechanism 150 and is located within the housing. The internal induction coil 170 enables the drive mechanism to be connected to a controller and/or to a power source (not shown) via an inductive coupling. Thus, the magnetic separation apparatus can be provided free of external electrical connectors which extend through the walls of the housing 110. Thus, the housing 110 can remain as a sealed unit. The internal induction coil 170 is illustrated as being mounted on the base wall 112 of the housing 110. This can enable the internal induction coil 170 to form an inductive coupling more easily with an external induction coil 172 positioned beneath the housing, for example on a surface on which the magnetic separation apparatus 100 is supported (as shown schematically in Figure 1). Alternatively, the external induction coil 172 may be mounted on the external surface of the base wall 112 adjacent to the induction coil 170. However, it will be appreciated that the internal induction coil 170 and external induction coil 172 may be provided at any location.

Referring to Figure 6, the support plate 120 is removably supported on the housing 110. To facilitate correct positioning of the support plate 120 on the housing, the magnetic separation apparatus 100 includes a locating arrangement.

The locating arrangement comprises one or more locating devices. For example, one or more male locating devices and one or more corresponding female locating devices in which the male locating devices are received. In the illustrated embodiment, the locating arrangement comprises a pair of male locating devices 180 in the form of a pair of locating projections extending from the top and bottom surfaces of the barrier layer 160, and a pair of female locating devices 182 in the form of a locating cavity 182 in the surface of each of the housing 110 and the support plate 120. The locating projections 180 of formed as an integral part of the barrier layer during manufacture of the barrier layer, for example during injection moulding. The locating cavities 182 are provided at the periphery of the apparatus 100. The locating cavity 182 in the housing 110 extends into the side wall 116 of the housing 110 such that the compartment defined within the housing can remain entirely enclosed. In use, the locating projection 180 on the underside of the barrier layer 160 is inserted into the locating holes 182 in the housing 110. The support plate 120 is then be placed over the barrier layer 160 such that the locating projection 180 on the upper surface of the barrier layer 160 is received in the locating hole 182 in the underside of the support plate 120, thereby ensuring the correct lateral position of the support plate 120 on the housing 110. A single pair of locating devices 180, 182 is shown in Figure 6. However, it will be understood that further locating devices may be provided. For example, in the region of an opposite side wall of the housing 100. Although the locating projections 180 are illustrated as integral to the barrier layer 160, in other embodiments, the male locating devices may be integral with the support plate, and/or integral with the housing, and/or provided as discrete components which are inserted into the locating cavities 182 and through an aperture in the barrier layer 160.

Referring to Figure 7, the well plate 1000 is supported and engaged by the support plate 120 to form an assembly which can be removed from the magnetic separation apparatus 100 as a single unit. Each well 1010 has sidewalls 1012 which define a well volume 1014 and taper inwardly towards the curved bottom region 1016 of the well 1010. Each well 1010 has a central axis 1015. The external surface of the well 1010 is an outer wall 1018 by which the well 1010 can be engaged by the support plate 120. The well holes 122, into which the outer walls 1018 of the wells 1010 are received, are blind holes in the upper surface of the support plate 120. By providing the well holes 122 as blind holes no leakage of fluid can occur through the well holes 122 to the array of magnets below In this embodiment, the wells 1010 and well holes 122 have corresponding circular cross-sectional shapes.

The side walls of the well holes 122 frictionally engage the outer walls 1018 of the wells 1010 to resist axial movement of the wells 1010. Thus, once the plate 1000 is placed onto the support plate 120 in the correct position, the well holes resist deformation of the plate 1000 away from a planar or flat configuration. In this manner, the well holes act to ensure the correct position of the wells in relation to the pipetting head and thereby ensure accuracy of syringe positioning within each well. In this manner, the well holes 122 can act as a datum for the well plate. This can be more effective than using the skirt 1022 of the well plate 1000 as a datum, which can suffer from increased tolerance stack-up between the datum and the well positions. To assist with the provision of an accurate datum, the periphery of the support plate 120 is preferably configured such that an axial clearance exists between the underside of the skirt 1022 of the plate 1000 and the opposing surface of the support plate 120, as shown in Figure 7. In this manner, interaction between the skirt 1022 and the support plate 120 does not interfere with the correct axial positioning of the wells as defined by the well holes 122.

Referring to Figure 8, the array of hollow protrusions 164 on the upper surface 169 of the barrier layer 160 are received in the magnet holes 124 in the support plate 120 when the support plate 120 is received on the housing 110. In this embodiment, the magnet holes 124 extend through the thickness of the support plate 120 and the hollow protrusions 164 protrude through the support plate 120 such that the upper region of each protrusion 164 extends above the support plate 120. In this manner, the raised position of the array of magnets 130 relative to the wells 1010 can be increased, enabling a greater range of height positions. This is illustrated in Figure 7, in which the post magnets 130 are shown in an active position in which the top of each post is above the support plate 120. As will be appreciated, the drive mechanism is operable to hold the magnets 130 in a plurality of active height positions relative to the wells 1010 of the plate 1000, from the raised position shown in Figure 7 to a lowered position (not shown) in which the magnetic field generated by the magnets 130 is sufficiently below the wells 1010 that the array of magnets 130 can be considered as inactive. Optionally, the magnet holes 124 and the hollow protrusions 164 have one or more frustoconical regions 125, 165. These frustoconical regions form a tapering interface between the protrusions 164 and the magnet holes 124 which can facilitate assembly of the support plate by using the protrusions 164 to provide a guide for the correct locating of the support plate 120 on the housing 110. The resulting tapered walls 165 of the protrusions 164 can also facilitate manufacture of the barrier layer.

Referring to Figures 9A-9C, the magnetic separation apparatus 100 is shown in cross-section with the carrier 140 and the array of magnets 130 held in a variety of height positions. These positions are achieved by raising and lowering the carrier 140 using the drive mechanism and holding the carrier stationary with the drive mechanism to keep the magnets in the desired position.

Figure 9A shows the array of magnets in the raised position. In this position, the top of each magnet 130 is at or close to the top of its respective magnet receptacle 162 in the underside of the barrier layer 160. This is an active position in which the magnetic field produced by the array of magnets is directly adjacent to the wells 1010 and will influence the position of magnetic particles in the wells. This may be the uppermost height position to which the array of magnets may be raised during normal operation.

Figure 9B shows the array of magnets in the lowered position. In this position, the top of each magnet 130 is retracted from the top of its respective magnet receptacle 162 in the underside of the barrier layer 160 and the magnets 130 are sufficiently far below the wells 1010 that the magnetic field produced by the array of magnets is of insufficient strength to manipulate or influence the position of magnetic particles in the wells. Consequently, this can be considered an inactive, or disengaged, position. This may be the lowermost height position to which the array of magnets may be lowered during normal operation. Although the magnets are shown as extending through the apertures in the top plate and received in the lower part of the receptacles 162, it will be understood that the lowered position may equate to a different height of magnet in other embodiments.

Figure 9C shows the array of magnets in one of a plurality of active positions between the raised and lowered positions. These is just one of any number of active positions to which the drive mechanism is operable move and hold the array of magnets. In Figure 9C, the array of magnets 130 is closer to the lowered position of Figure 9B than the raised position of Figure 9A. In this position, the top of each magnet is approximately halfway down the height of its respective receptacle. In this position, the magnetic field may still influence the position of the magnetic particles within the wells and so is regarded as an active position. For example, due to position of the magnets beneath the wells, the magnetic field can be used to pull the magnetic particles to a central position in the bottom of the wells. As discussed above, this can be beneficial for washing and/or re-suspension of the magnetic particles by placing the magnetic particles directly in the path of fluid ejected from syringes inserted centrally into the wells during use of the apparatus 100.

Figure 10 illustrates a method 900 of separating macromolecules from a test sample in a multi-well plate. The method is described in relation to the magnetic separation apparatus 100 illustrated in Figures 1 to 8 and as described above. However, it will be understood that other configurations of apparatus might also be appropriate. At step 5-901, a magnetic separation apparatus 100 is provided. At step 5-902, a multi-well plate 1000 is placed on the support plate 120 of the apparatus 100 such that the wells 1010 of the plate 1000 are received in and engaged by the well holes 122 in the support plate 120 (as illustrated in Figure 7). At step 5-903, a test sample is provided in at least one of the wells 1010 of the plate 1000. The test sample includes a supernatant and a complex of macromolecules and magnetic particles. At step 5-904, the drive mechanism 150 is operated to raise the carrier 140 relative to the support plate 120 and thereby bring the post magnets 130 into position adjacent to the outer walls of the wells 1010. In this active height position, the magnetic field generated by the magnets 130 attracts the complex to the side wall of each well, thereby separating the complex from the supernatant. At step 5-905, the supernatant is removed from the well by using a pipetting head to insert an array of pipettes into the array of wells and to aspirate the liquid supernatant from the wells, leaving the complex immobilised and aggregated against the side walls of the wells. The complex can then be processed in a conventional manner. Optionally, at step 5-906 the macromolecule-bead complex is washed with a wash buffer, such as 70% ethanol. Optionally, at step 5-907, the macromolecules are isolated from the magnetic beads using an elution process in which an elution buffer is added to the complex to release the macromolecules from the magnetic beads. The macromolecules then free float in the elution buffer while the magnetic beads remain immobilised by the magnets. Optionally, at step 5-908 the supernatant formed by the elution buffer and isolated macromolecule is transferred from the well plate to a new well plate for subsequent analysis. The magnetic beads are then typically discarded as having served their purpose.

At step 5-904, the process of raising the carrier relative to the support can be carried out by raising the carrier to a first active position to attract the complex to the side of the wells 1010 and subsequently raising the carrier to a second active position which is higher than the first active position to move the complex upwardly along the side walls of the wells and further, in a radial direction, from the central axes 1015 of the wells. This can reduce the risk of dislodgement of the magnetic particles and/or the macromolecule-bead complex from the side walls of the well during operations in which an array of syringes or pipettes is moved within the wells, for example during any of steps S-905 to S-908.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. A magnetic separation apparatus for separating magnetic particles from a test sample in a multi-well plate, the magnetic separation apparatus comprising: a housing; a support for supporting a multi-well plate above the housing during use; an array of magnets mounted on a carrier beneath the support; and a drive mechanism configured to raise and lower the carrier relative to the support to vary a height position of the array of magnets, wherein the drive mechanism is operable to hold the array of magnets stationary at a plurality of height positions including a raised position, a lowered position, and a plurality of active positions between the raised and lowered positions.
2. The magnetic separation apparatus of claim 1, wherein the support comprises a support plate extending across an upper region of the housing, the support plate comprising an array of well holes for receiving and engaging at least a lower portion of the wells of the multi-well plate during use.
3. The magnetic separation apparatus of claim 2, wherein the support plate is flat.
4. The magnetic separation apparatus of claim 2 or claim 3, wherein the support plate is removably supported on the housing.
5. The magnetic separation apparatus of any of claims 2 to 4, further comprising one or more locating devices for laterally positioning the support plate on the housing.
6. The magnetic separation apparatus of any of claims 2 to 5, wherein the array of well holes comprises at least 96 well holes, optionally the array of well holes comprises at least 384 well holes, optionally the array of well holes comprises 384 well holes arranged in a sixteen by twenty-four grid.
7. The magnetic separation apparatus of any of claims 2 to 6, wherein the support plate comprises an array of magnet holes for receiving the array of magnets.
8. The magnetic separation apparatus of claim 7, wherein the array of magnet holes corresponds in number and position to the array of magnets such that each magnet hole receives a single magnet of the array of magnets.
9. The magnetic separation apparatus of any of claims 2 to 8, further comprising a barrier layer extending across the upper region of the housing between the support plate and the array of magnets.
10. The magnetic separation apparatus of claim 9, wherein the barrier layer is formed from a waterproof material.
11. The magnetic separation apparatus of claim 9 or claim 10, wherein the barrier layer is removably supported on the housing.
12. The magnetic separation apparatus of any of claims 9 to 11, wherein the barrier layer comprises an array of magnet receptacles on its underside for receiving the array of magnets at least when in the raised position.
13. The magnetic separation apparatus of claim 12, wherein the barrier layer comprises an array of hollow protrusions on its upper surface by which the array of magnet receptacles is defined.
14. The magnetic separation apparatus of any of claims 7 to 13, wherein the housing comprises a top wall extending across the width of the upper region of the housing, wherein the top wall has an array of magnet apertures through which the array of magnets extends when in the raised position.
15. The magnetic separation apparatus of any of claims 7 to 14, wherein the barrier layer forms a seal across the upper region of the housing to enclose the array of magnets and the drive mechanism within the housing.
16. The magnetic separation apparatus of any preceding claim, further comprising an induction coil which is electrically connected to the drive mechanism and is located within the housing.
17. The magnetic separation apparatus of claim 16, wherein the induction coil is located adjacent to a lower wall of the housing.
18. The magnetic separation apparatus of any preceding claim, wherein the array of magnets is an array of post magnets.
19. The magnetic separation apparatus of claim 18, wherein the array of post magnets is arranged such that each post magnet is laterally positioned in a central region between each group of four adjacent well holes in the support plate.
20. The magnetic separation apparatus of any preceding claim, wherein the drive mechanism comprises one of more of: a belt drive; a stepper motor; a cam mechanism; a rack and pinion mechanism; a bevel gear; and a worm gear.
21. The magnet separation apparatus of any preceding claim, comprising a controller configured to operate the drive mechanism to hold the array of magnets stationary at the plurality of height positions.
22. A magnetic separation system comprising the magnetic separation apparatus of any of claims 1 to 21 and a controller configured to operate the drive mechanism to hold the array of magnets stationary at the plurality of height positions.
23. A liquid dispensing apparatus comprising: a main body with a deck; a pipetting head above the deck and comprising a pipette body mounting assembly for holding an array of removable pipettes, and a dispense drive actuator assembly operable to move a plunger assembly relative to the pipette body mounting assembly along a drive axis to perform a dispensing operation; and a magnetic separation apparatus according to any of claims 1 to 21, the magnetic separation apparatus being positioned on the deck.
24. A method of separating macromolecules from a test sample in a multi-well plate, the method comprising the steps of: providing a magnetic separation apparatus according to any of claims 1 to 21; placing a multi-well plate on the support; providing a test sample in at least one well of the multi-well plate, the test sample comprising a supernatant and a complex of macromolecules and magnetic particles; raising the carrier relative to the support to attract the complex to the side of the at least one well using the array of magnets and thereby separating the complex from the supernatant; removing the supernatant from the at least one well.
25. The method of claim 24, wherein the step of raising the carrier relative to the support comprises raising the carrier to a first active position to attract the complex to the side of the at least one well and subsequently raising the carrier to a second active position which is at a different height position to the first active position to move the complex along the side wall of the at least one well.
26. The method of claim 25, wherein the second active position is higher than the first active position such that the complex is moved further from a central axis of the at least one well when the carrier moves to the second active position.