Method for mixing and separation employing magnetic particles

• US 6,228,268 B1
• Filed: 01/03/2000
• Issued: 05/08/2001
• Est. Priority Date: 02/21/1995
• Status: Expired due to Term

• Current Assignee: Sigris Research Incorporated
• Original Assignee: Iqbal W. Siddiqi Phd
• Inventors: Siddiqi, Iqbal W.
• Primary Examiner(s): Savage, Matthew O.
• Application Number:
  US09/476,258
• Time in Patent Office: 491 Days
• Field of Search: 210/222, 210/695, 436/526, 366/273, 366/274
• US Class Current: 210/695
• CPC Class Codes: B01F 33/451 wherein the mixture is directly exposed to an electromagnetic field without use of a stirrer, e.g. for material comprising ferromagnetic particles or for molten metal
• CPC Class Codes: B03C 1/01 by addition of magnetic adjuvants
• CPC Class Codes: B03C 1/24 with material carried by travelling fields
• CPC Class Codes: B03C 1/288 disposed at the outer circumference of a recipient
• CPC Class Codes: B03C 2201/26 for use in medical or biological applications

Abstract

A method for carrying out the affinity separation of a target substance from a liquid test medium by mixing magnetic particles having surface immobilized ligand or receptor within the test medium to promote an affinity binding reaction between the ligand and the target substance. The test medium with the magnetic particles in a suitable container is removably mounted in an apparatus that creates a magnetic field gradient in the test medium. This magnetic gradient is used to induce the magnetic particles to move, thereby effecting mixing. The mixing is achieved either by movement of a magnet relative to a stationary container or movement of the container relative to a stationary magnet. In either case, the magnetic particles experience a continuous angular position change with the magnet. Concurrently with the relative angular movement between the magnet and the magnetic particles, the magnet is also moved along the length of the container causing the magnetic field gradient to sweep the entire length of the container. After the desired time, sufficient for the affinity reaction to occur, movement of the magnetic gradient is ended, whereby the magnetic particles are immobilized on the inside wall of the container nearest to the magnetic source. The remaining test medium is removed while the magnetic particles are retained on the wall of the container. The test medium or the particles may then be subjected to further processing.

Claims

1. A method of mixing magnetic particles in a liquid medium for producing an affinity binding reaction between a target substance in said liquid medium and said particles, the method comprising the steps of:

placing said liquid medium and said magnetic particles into a magnetically permeable container;

generating a magnetic field gradient of a desired field strength inside the container in a portion of the liquid medium to define a magnetic field cavity in the liquid medium by a magnet on the outside of the container;

changing the relative angular position between the magnetic particles in the container and the magnet to have movement of the magnetic particles throughout the magnetic cavity in the liquid medium; and

concurrently with said changing the relative angular position, moving the magnetic field cavity from one end of the liquid medium in the container, to another end of the liquid medium in the container while the magnetic particles are mixing throughout the magnetic field cavity.

2. The method of claim 1 further comprising the step of:

keeping constant the relative angular position of the magnet and the magnetic particles in the container to concentrate the particles on an inside surface of the container.

3. The method of claim 2 further comprising the step of:

moving the magnet closer to the wall of the container after the keeping constant step.

4. The method of claim 1 wherein said step of changing the relative angular position between the magnetic particles and the magnet comprises rotating the container on a concentric axis relative to stationary magnet at a speed of at least 40 rpm.

5. The method of claim 4 wherein said rotating the container comprises rotating the container in step increments of a preselected angular distance at predetermined time delays between step increments.