FI121322B - Use of a device for separating microparticles - Google Patents

Description

Use of a device for separating microparticles

Technical field

The invention relates to the separation of magnetic particles from a mixture containing them. The invention can be used in a variety of applications, particularly in the fields of biotechnology, biochemistry and biomedicine.

10 Technology Background

In many applications, magnetic microparticles are used as a solid phase to bind biomaterial. Microparticles have the advantage of having a large solid phase surface area and short diffusion distances. Microparticles generally have a size between 0.05 and 10 μηι, 15 and are available in a variety of materials and pre-activated for many applications. The magnetic particles can be moved by the magnet.

In the currently used magnetic particle separation methods, the reaction vessel is positioned in a magnetic field so that the particles accumulate in a so-called pellet at the bottom of the vessel 20. The particle-free liquid is then decanted or aspirated. However, the removal of liquid from the container must be done very carefully so as not to remove the particles at the same time.

WO 86/06493 proposes a method for immunoassays, in which magnetic particles and the labeled complex adhered thereto are separated from the liquid by a magnetic rod and then subjected to measurement. The tip of the rod has a solid magnet and a removable cover that adheres to the outer surface. After separation, the cover is best covered with another cover before measurement. After the measurement, the shields with their particles are removed and discarded, and 30 new shields are removed for new separation. According to the publication, the magnet can also be an electromagnet, whereby the magnetic field can be removed if desired.

WO 87/05536 proposes a device for separating magnetic particles having a rod movable in a vertical drill and a mag-35 rivet at its lower end. The device is introduced into the particle-containing fluid in a magnetic down position, whereupon the particles accumulate at the end of the rod. When the magnet is released to the up position, the particles may release from the rod. In this way, particles can be collected and transferred from one fluid to another.

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However, the proposed magnetic particle separation devices and methods are poorly suited for applications where the particles need to be collected from a large volume and transported to a substantially smaller size.

5 Description of the Invention

General description

The use of claim 1 and the method of claim 5 to 10 have now been invented. Certain preferred embodiments of the invention are set forth in the other claims.

The device according to the invention has an elongated cover and a movable rod having a single magnet magnet in the longitudinal direction of the cover. The rod magnet has a pi-15 to a ratio of thickness to at least about 2: 1, preferably at least about 3: 1, and most preferably at least about 12: 1. Both the intensity and the gradient of the resulting magnetic field are strongest at the end of the rod, and when the magnet is in its down position, particles from the alloy accumulate at the very tip of the shield. From the tip of the shield, the particles can be released several times to a smaller volume of the original blend.

Preferably, the rod magnet consists of a permanent magnet and a ferromagnetic arm extending thereto.

25 The rod magnet is best long so that the top of its dipole is always above the surface of the alloy. If particles need to be collected from the alloy column higher than the dipole, care must be taken to first collect the particles from the top of the statue so that the top of the dipole is always above the particles.

When the upper end of the magnet may be above the alloy, a more efficient magnet relative to the volume of the alloy can be used, which speeds up and facilitates collection.

The device according to the invention has a strong magnetic field parallel to the shield tip. This is particularly advantageous when the particles are collected from another particle concentration obtained first by other means. A further advantage is that a high adhesive force is obtained just at the tip from which the adhesion of the liquid particularly tends to release the particles as the cap is lifted from the liquid.

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It is advantageous to have a sharp downward projection at the tip of the guard. This minimizes the amount of liquid remaining in the tip. Typically, the tip is conical. For transferring particles into very small containers, the tip is best shaped as a concave surface.

5

When a ferromagnetic arm is used in the magnet, the magnet and the magnetized arm work together as a long rod magnet. The arm obliterates the gradient of the upper pole of the field so that the upper pole does not collect particles. This also gives a long pole magnet at a cheaper price. However, with a ferromagnetic arm, it is advantageous to use a relatively long magnet (e.g., about 1.5 to 10 times the thickness). The length of the magnet is best selected so as to obtain the given magnet. Maximum internal permanent field strength for the magnet.

The connection between the magnet and its arm is best done so that the arm and the magnet 15 are slightly spaced apart. This avoids the formation of strong gradients that may collect at the junction.

The rod magnet may be, for example, circular or rectangular in cross-section. For both manufacture and use, a circular shape is best. In this case, for example, he has no effect on the rotation of the magnet about its axis. In principle, the rod can also be curved, for example to simplify the movement mechanisms.

The shape of the cover over the rod can always vary depending on the intended use. Normally a circular shape is the most advantageous both in manufacture and use. For added strength, the cap can be tapered, which also facilitates injection molding. The cover is preferably made of polypropylene.

Most preferably, the invention is applicable to particles having a size of about 1 to 10 µm.

BRIEF DESCRIPTION OF THE DRAWINGS Some preferred embodiments of the invention will now be described by way of example. In the drawings of the description - Figure 1 shows a separating device according to the invention, 4 - Figure 2 shows the use of the device of Figure 1 to collect particles from a suspension, - Figure 3 shows the use of the device of Figure 1 to release the collected particles Figure 5 illustrates the use of a third device for collecting particles from a small amount of liquid, and Figure 6 uses the device of Figure 5 to release the collected particles into a small amount of liquid.

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eXAMPLES

The separating rod of Fig. 1 has an elongated guard 1 and a bore 2 therein. There is a flange 3 at the top of the frame to facilitate gripping.

The bore 2 has a loose magnetic rod 4. It has a vertical rod magnet 5 at its lower end and a ferromagnetic arm 6 as an extension of the magnet above it.

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The lower end of the shield has a concave surface with a tapered pointed tip 8. The length of the tip corresponds approximately to the width of the lower end of the shield.

Figure 2 shows a collection of particles from a test tube where they are dispersed in suspension part 9. The separating rod is moved in a curved manner from top to bottom in the test tube. In this way, the particles are collected at the tip into an annular mass 10. When the magnet 5 is held at the lower end of the bore 2, the particles remain at the tip. To release the particles, the magnet is raised.

Tip 8 is particularly well suited for transferring particles to a very small vessel, such as a so-called. HLA plate well 11 (Figure 3). The tip is slightly longer than the well height.

As the tip is inserted into the well, the surface of the liquid therein rises upwardly along the tip surface due to surface tension 35. The edge of the moving liquid surface sweeps particles from the tip to the liquid. Moving the rod can enhance the detachment. Similarly, as the tip is lifted from the well, the surface of the fluid moves as an intact well toward the sharp end of the tip. In this way, the liquid and its particles are completely removed from the tip.

Preferably, the particles are separated from the liquid by first concentrating them in vessel 5 at one point, where they are then collected by means of a rod. Concentration can be accomplished by allowing the particles to sediment by gravity, centrifuging, or drawing the particles by magnetic field onto the vessel wall.

Figure 4 illustrates the picking of particles from a tube of a test tube into a vertical strip 9 first by means of a magnet 10 by swiping the strip along the rod tip to cause the particles to adhere to the tip 10 of the rod guard 1. It is suitable for transferring particles to containers where the tip can be properly inserted into the liquid.

15 The ratio of the length of the magnet 5 to the diameter is about 10: 1 and the ratio of the length of the arm to the length of the magnet is about 5: 1. The arm is slightly wider than the magnet and the upper end of the magnet is embedded in the lower end of the arm about 2 times its diameter.

Figures 5 and 6 show a separation means in which the magnetic rod 4 'has only a permanent magnet 51 coated with a suitable protective layer without a ferromagnetic arm. The upper end of the shield 11 has a double flange gripping member 3 'from which the device can be easily controlled, for example, in automatic separation or analysis equipment. The length to diameter ratio of the magnet is about 7: 1. The tip of the shield is a relatively blunt cone (cone height about 1/3 of its width).

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Figure 5 shows the particle separation relative to the separator rod from a relatively narrow vessel (the inside diameter of the vessel is about 70% of the rod diameter) and a relatively small amount of liquid. The lower line 11 represents the free liquid surface and the upper line 12 the liquid surface when the separation means is inserted into the liquid. The magnetic particles ke-30 wrap up at the tip of the shield to mass 10, which can be released back into a relatively small amount of liquid (Figure 6).

The device of Figures 5 and 6 is suitable for use, for example, in wells of microtiter plates having a diameter of about 7 mm.

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Claims (6)

Use of a device for separating magnetic microparticles from a mixture containing particles having a particle size of 0.05 to 10 μιη, used as solid 5 phases for binding biomaterial, characterized in that the device comprises: - an elongated cap (1; Γ) having an upper end and a lower end; having a tip, - a recess (2) from the top to the bottom of the shield, - a longitudinal rod magnet (4; 4 ') having a length to thickness ratio of at least about 2: 1, preferably at least, to collect particles from the mixture at the very tip of the shield. about 3: 1. Use according to claim 1, characterized in that the magnetic rod (4) has a magnet (5) at its lower end and a ferromagnetic arm (6) attached at its upper end. Use according to claim 1 or 2, characterized in that the ratio of the length of the magnetic bar (4) to the thickness is at least about 12: 1. Use according to claim 2 or 3, characterized in that the upper end of the magnet (5) and the lower end of the arm (6) are nested. 20 5. A method for separating magnetic microparticles from a mixture containing particles having a particle size of 0.05 to 10 μηι and used as a solid phase for binding biomaterial, characterized in that a separating means having an elongated cap (1; Γ) is inserted into the mixture. a lower end having a tip, a recess (2) protected from the upper end to a lower end, a longitudinal rod magnet (4; 4 ') movable in the recess, having a length to thickness ratio of at least about 2: 1, preferably at least about 3; : 1. Method according to Claim 5, characterized in that the separating means is inserted into the alloy so that the upper end of the magnetic rod stays above the alloy surface.