Magnetic immunoassay system

Patent metadata

Field	Value
Publication number	US-8945469-B2
Application number	US-71591607-A
Country	US
Kind code	B2
Filing date	Mar 9, 2007
Priority date	Mar 9, 2006
Publication date	Feb 3, 2015
Grant date	Feb 3, 2015

Abstract

A magnetic immunoassay system with a mechanism for compensating the direct current residual magnetic field in the vicinity of the specimen measurement position, in a direction perpendicular to the magnetic marker direction of magnetization for the measurement target. This invention reduces the effects of the magnetic field emitted from the unbound magnetic marker due to the residual magnetic field in the specimen solution and detects with high sensitivity the signal of the bound target magnetic marker. The magnetic field at the measurement position is regulated so as to intersect the direction of magnetization of the magnetic marker for the measurement target, in order to make the magnetization direction of the magnetic marker that is unbound due to residual magnetism or remanence in the sample solution, intersect the magnetization direction of the magnetic marker for the measurement target. The signal of the bound target magnetic marker can be therefore measured with high sensitivity since it is isolated from the unbound magnetic marker signal.

First claim

What is claimed is:

1. A magnetic immunoassay system which measures a remnant magnetic signal generated from a sample for detecting an antigen contained in the sample, comprising:
a nonmagnetic reaction chamber where a plurality of capturing antibodies, for binding antigens to-be-detected in the sample, are affixed to a surface of the chamber;
a mechanism which moves the reaction chamber;
a magnetic sensor which measures the magnetic signal from the chamber containing a mixture of the sample in a liquid state antibodies which are to bind to the antigens to be detected and further which are labeled with magnetic nanoparticles;
a magnetic shield which blocks a magnetic noise in the periphery of the magnetic sensor;
a magnetic field compensator comprising an electromagnet and an adjustment controller for adjusting a magnetic field applied by the electromagnet, the electromagnet configured to apply a DC magnetic field relative to a sensing direction of the magnetic sensor, the DC magnetic field being in a range between 1 nano tesla and 100 micro tesla,
the adjustment controller operatively associated with the electromagnet so as to vary current through the electromagnet to thereby direct the DC magnetic field such that the first summed magnetization direction of the first group of magnetic nanoparticles binding to the first group of the antigens that are bound to the capturing antibodies is affixed indirectly to the nonmagnetic reaction chamber square with a second summed magnetization direction of (1) a second group of magnetic nanoparticles respectively bound to a second group of the antigens that are not bound to the capturing antibodies and (2) a third group of magnetic nanoparticles that are bound to neither the first group of the antigens nor the second group of the antigens;
a current source which supplies an optimal DC current of a predetermined value to the electromagnet; and
a processor which processes signals from the magnetic sensor to extract signals from the first group of magnetic nanoparticles binding to the first group of the antigens that are bound to the capturing antibodies and thereby affixed indirectly to the nonmagnetic reaction chamber.

2. The magnetic immunoassay system according to claim 1 , wherein the magnetic sensor is a superconducting quantum interference device.

3. The magnetic immunoassay system according to claim 1 , wherein the electromagnet, which makes the first summed magnetization direction intersect the second summed magnetization direction, applies the magnetic field acting in a direction perpendicular to a pickup coil surface of the magnetic sensor for detecting magnetism.

4. The magnetic immunoassay system of claim 1 , wherein the magnetic field compensator comprises a compensation coil and the adjustment controller varies current applied to the compensation coil.

5. A magnetic immunoassay system which measures a remnant magnetic signal generated from a sample, comprising:
a nonmagnetic reaction chamber;
nonmagnetic beads which surfaces are bound with capturing antibodies for binding to antigens to be detected;
a mechanism which moves the reaction chamber;
a magnetic sensor which measures the magnetic signal from the sample in a liquid state containing a first group of the antibodies labeled with a first group of magnetic nanoparticles which bind to a first group of the antigens;
a magnetic field compensator comprising an electromagnet and an adjustment controller for adjusting a magnetic field applied by the electromagnet, the electromagnet configured to apply a DC magnetic field relative to a sensing direction of the magnetic sensor, the magnetic field being in a range between 1 nano tesla and 100 micro tesla, the adjustment controller operatively associated with the electromagnet so as to vary current through the electromagnet to thereby direct the DC magnetic field such that the first summed magnetization direction of the first group of magnetic nanoparticles binding to the first group of the antibodies which are affixed to the surfaces of the nonmagnetic beads and further bind to the first group of the antigens, the first summed magnetization direction intersecting a second summed magnetization direction of (1) a second group of magnetic nanoparticles each bound to a second group of the antigens that is not bound to the antibodies affixed to the surfaces of the nonmagnetic beads and (2) a third group of magnetic nanoparticles unbound to either the antibodies or the antigens;
a current source which supplies an optimal DC current of a predetermined value to the electromagnet; and
a processor which processes signals from the magnetic sensor to extract signals from the first group of magnetic nanoparticles labeling the first group of the antibodies which are affixed to the surfaces of the nonmagnetic beads and bound to the first group of the antigen.

6. The magnetic immunoassay system according to claim 5 , wherein the magnetic sensor is a superconducting quantum interference device.

7. The magnetic immunoassay system according to claim 5 , wherein the electromagnet, which makes the first summed magnetization direction intersect the second summed magnetization direction, applies the magnetic field acting in a direction perpendicular to a pickup coil surface of the magnetic sensor for detecting magnetism.

8. The magnetic immunoassay system of claim 5 , wherein the magnetic field compensator comprises a compensation coil and the adjustment controller varies current applied to the compensation coil.

Assignees

• Tsukamoto Akira
• Saitoh Kazuo
• Hitachi Ltd

Inventors

• Tsukamoto Akira
• Saitoh Kazuo

Classifications

• G01N33/54326 Primary

  Magnetic particles · CPC title