Magnetic beads for reducing leukocyte interference in immunoassays

• US 8,394,325 B2
• Filed: 06/14/2010
• Issued: 03/12/2013
• Est. Priority Date: 06/14/2010
• Status: Active Grant

• Current Assignee: Abbott Point Of Care Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Point Of Care Incorporated (Abbott Laboratories Incorporated)
• Inventors: Campbell, John Lewis Emerson, Davis, Graham
• Primary Examiner(s): Gabel, Gail R
• Application Number:
  US12/815,132
• Publication Number:
  US 20110306070A1
• Time in Patent Office: 1,002 Days
• Field of Search: 435/7.1, 435/7.2, 435/7.24, 435/7.32, 435/7.9, 435/7.92, 435/7.93, 435/7.94, 435/287.2, 435/287.9, 436/506, 436/512, 436/513, 436/518, 436/523, 436/524, 436/528, 436/529, 436/540, 436/166, 436/175, 436/177, 422/73, 422/417, 422/425, 422/426, 422/430, 422/82.01, 422/82.03, 422/82.11, 422/527, 422/554
• US Class Current: 422/73
• CPC Class Codes: G01N 33/54326 Magnetic particles
• CPC Class Codes: Y10T 436/25125 Digestion or removing interfering materials

Abstract

Methods and devices for reducing interference from leukocytes in an analyte immunoassay are provided. In one embodiment, a method is provided comprising the steps of amending a biological sample with magnetic sacrificial beads opsonized to leukocytes, binding leukocytes in the sample to the magnetic sacrificial beads, and magnetically retaining the beads out of contact from an immunosensor.

Claims

1. A cartridge for performing a competitive immunoassay for a sample analyte suspected of being present in a blood sample containing leukocytes, the cartridge comprising:

a sample inlet for receiving the blood sample;

a metering chamber for metering the blood sample to form a metered sample;

one or more dry reagent coating layers within the cartridge comprising magnetic beads opsonized to leukocytes and a labeled analyte, wherein the opsonized magnetic beads are present in an amount in excess of the leukocytes in the blood sample sufficient to substantially sequester any leukocytes present in the sample;

an electrode comprising an immobilized antibody to the sample analyte and to the labeled analyte; and

one or more pumping elements for moving the metered sample and the labeled analyte to the electrode.

2. The cartridge of claim 1, further comprising a magnet in the cartridge for positioning the magnetic beads.

3. A cartridge for performing a non-competitive immunoassay for a sample analyte suspected of being present in a blood sample containing leukocytes, the cartridge comprising:

a sample inlet for receiving the blood sample;

a metering chamber for metering the blood sample to form a metered sample;

one or more dry reagent coating layers within the cartridge comprising magnetic beads opsonized to leukocytes and a signal antibody to the analyte, wherein the opsonized magnetic beads are present in an amount in excess of the leukocytes in the blood sample sufficient to substantially sequester any leukocytes present in the sample;

an electrode comprising an immobilized antibody to the sample analyte; and

one or more pumping elements for moving the metered sample to the electrode.

4. The cartridge of claim 3, further comprising a magnet in the cartridge for positioning the magnetic beads.

5. A kit for performing an analyte immunoassay in a whole blood sample, comprising:

magnetic beads opsonized to leukocytes, wherein the magnetic beads are movable by a magnetic field, and wherein magnetic beads are present in an amount in excess of the leukocytes in the blood sample sufficient to substantially sequester any leukocytes present in the sample;

a magnet in the cartridge for retaining the magnetic beads; and

an immunosensor, wherein leukocytes in the whole blood sample bind to said magnetic beads, and wherein the magnetic field is capable of retaining at least a portion of said magnetic beads out of contact from said immunosensor.

6. The kit of claim 5, wherein the immunoassay is a sandwich assay.

7. The kit of claim 5, wherein the immunoassay is a competitive assay.

8. The kit of claim 5, wherein the kit further comprises an anticoagulant.

9. The kit of claim 5, wherein the magnetic beads comprise a magnetite (Fe₃O₄) core coated with a styrene-acrylic acid copolymer.

10. The kit of claim 5, wherein the magnetic beads comprise magnetic beads coated with non-human IgG or fragments thereof.

11. The kit of claim 5, wherein the magnetic beads have an average particle size of from 0.01 μ

m to 20 μ

m.

12. The kit of claim 5, wherein the magnetic beads have an average particle size of from 0.1 μ

m to 5 μ

m.

13. The kit of claim 5, wherein the magnetic beads have an average particle size of from 3 μ

m to 5 μ

m.

14. The kit of claim 5, wherein the magnetic beads are in one or more dissolvable dry reagent coatings in the cartridge.

15. The kit of claim 5, wherein the magnet is a permanent magnet.

16. The kit of claim 5, wherein the magnet is an electromagnet.

17. The kit of claim 5, wherein at least 50 wt. % of the magnetic beads are retained out of contact from the immunosensor.

18. The kit of claim 5, wherein at least 75 wt. % of the magnetic beads are retained out of contact from the immunosensor.

19. A cartridge for performing a competitive immunoassay for a sample analyte suspected of being present in a blood sample containing leukocytes, the cartridge comprising:

a sample inlet for receiving the blood sample;

a metering chamber for metering the blood sample to form a metered sample;

one or more dry reagent coating layers on the cartridge comprising magnetic beads opsonized to leukocytes and a labeled analyte, wherein the magnetic beads are present in an amount sufficient to provide a dissolved bead concentration of at least 5 micrograms per microliter of sample which is an amount in excess of the leukocytes in the blood sample sufficient to substantially sequester any leukocytes present in the sample;

an electrode comprising an immobilized antibody to the sample analyte and to the labeled analyte; and

one or more pumping elements for moving the metered sample and the labeled analyte to the electrode.

20. The cartridge of claim 19, wherein the magnetic beads are present in an amount sufficient to provide a dissolved bead concentration of at least 10 micrograms per microliter of sample.

21. The cartridge of claim 19, wherein the magnetic beads are present in an amount sufficient to provide a dissolved bead concentration of at least 15 micrograms per microliter of sample.