Magnetic particle transfer device

Liquid purification or separation – Processes – Using magnetic force

Patent

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Details

210222, 436526, B01D 3506

Patent

active

059421240

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to the separation of magnetic particles from a composition containing them and the transferring of them to a liquid. The invention can be used in different applications, especially in the fields of biotechnology, biochemistry, and biomedicine.


BACKGROUND OF THE INVENTION

Magnetic microparticles are used as a solid phase in various applications to bind biomaterial. One advantage of microparticles is the large area of the solid phase and short diffusion lengths. The size of microparticles is generally 0.05-10 .mu.m and they are available in different materials and already activated for many applications. Magnetic particles can be moved by using a magnetic field.
The separation methods of magnetic particles presently used include settling a reaction vessel in a magnetic field so that particles are accumulated into a so-called pellet at the bottom of the vessel. Thereafter, the liquid which is free from particles is decanted or removed by aspiration. However, the removal of the liquid from the vessel must be carried out very carefully so as not to remove the particles at the same time.
Publication EP-140787 (corresponding publication U.S. Pat. No. 4,649,116) proposes a method by which magnetic particles are separated from a liquid by using a magnetic rod which is pushed into the liquid. The particles are pulled off the rod by using a stronger magnet.
Publication WO-87/05536 suggests a device for separating magnetic particles which contains a rod movable in a vertical bore and provided with a magnet at the lower end thereof. The device is introduced into a liquid containing particles with the magnet in a lower position, whereby particles are collected at the end of the rod. When the magnet is allowed in an upper position, particles can be detached from the rod. In this way, particles can be collected and transferred from one liquid to another. The tip of the device is shaped like a cylinder tinner than the arm.
Publication WO-94/18565 proposes an assay method in which magnetic particles are separated from a liquid by using a rod comprising a conical tip and containing a movable magnet. In the application according to FIGS. 2, the rod comprises a concave and tapering tip part but particles are collected above this tip part, as shown in FIG. 2b.
However, the proposed separation devices and methods of magnetic particles are not very well-adapted to applications in which particles have to be transferred into very small vessels. The known devices are not very well-adapted for those applications either in which particles are collected from a large volume with respect to the means of separation.


SUMMARY OF THE INVENTION

Now, a transfer device according to claim 1 has been invented. Some preferred applications of the invention are presented in the other claims.
The device according to the invention comprises an elongated body comprising a means which can be used to align a magnetic field in the direction of the body to the tip of the body when particles are to be collected on the tip and eliminate the effect of this magnetic field when particles are to be released from the tip. Such a magnetic field is especially advantageous in such cases where particles are first collected in some other way, e.g., from a concentration of particles provided on the wall of a test tube. The tip part of the body is tapered and comprises a concave surface. The height of the tip part is slightly higher than the height of the vessel in which the particles are released. The width of the tip part at the upper part thereof is slightly smaller than the diameter of the vessel. When the tip is pushed into the vessel, the surface of the liquid in it rises along the surface of the tip under the influence of surface tension. The edge of the moving liquid surface wipes the particles off the tip and into the liquid. The detachment can be improved by moving the rod. Correspondingly, when the tip is raised from the well, the surface of the liquid moves as an integral film towards the end of the tip. In this w

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