Method for detecting target compound

Abstract

According to an aspect of the invention, there is provided a method for detecting a target compound including: injecting a test liquid containing a target compound into a colloid solution of magnetic nano-particles having an average particle diameter of 50 nm or less to allow the target compound to bind to the magnetic nano-particles, thereby forming bound magnetic nano-particles having a diameter of 100 nm or more; and bringing a dispersion liquid containing the bound magnetic nano-particles in proximity to a magnetic sensor including at least a magnetoresistive (MR) element and a permanent magnet while measuring the change in magnetic resistance to selectively detect the bound magnetic nano-particles, thereby indirectly detecting the target compound.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a magnetic sensor used for a detection method of the invention;

FIG. 2 is a side view of a magnetic sensor used for a detection method of the invention viewed from the terminal side;

FIG. 3 shows a circuit structure of a magnetic sensor used for a detection method of the invention;

FIGS. 4A and 4B show the size of detection elements of a magnetic sensor used for a detection method of the invention;

FIG. 5 is a block diagram of a measuring circuit used for a detection method of the invention; and

FIG. 6 is a graph obtained by measuring the output voltage of the sample in Example 1.

Claims

1. A method for detecting a target compound comprising: injecting a test liquid containing a target compound into a colloid solution of magnetic nano-particles having an average particle diameter of 50 nm or less to allow the target compound to bind to the magnetic nano-particles, thereby forming bound magnetic nano-particles having a diameter of 100 nm or more; andbringing a dispersion liquid containing the bound magnetic nano-particles in proximity to a magnetic sensor comprising at least a magnetoresistive (MR) element and a permanent magnet while measuring the change in magnetic resistance to selectively detect the bound magnetic nano-particles, thereby indirectly detecting the target compound.

2. The method of claim 1, wherein the magnetic nano-particles have, on the surface thereof, a ligand for specifically binding to the target compound.

3. The method of claim 1, wherein the distance between the magnetic sensor and the dispersion liquid is 1 mm or less when the dispersion liquid is brought in proximity to the magnetic sensor.

4. The method of claim 1, wherein the surface magnetic flux density of the permanent magnet is from 0.01 to 10T.

5. The method of claim 1, wherein the magnetoresistive element contains an n-type InSb semiconductor.

6. The method of claim 1, wherein the magnetic nano-particles comprise iron oxide or ferrite.

7. A method for detecting a target compound comprising: injecting a test liquid containing a target compound into a colloid solution of magnetic nano-particles having an average particle diameter of 50 nm or less to allow the target compound to bind to the magnetic nano-particles, thereby forming bound magnetic nano-particles having a diameter of 100 nm or more;concentrating the formed bound magnetic nano-particles by magnetic separation, thereby obtaining a concentrated dispersion liquid of the bound magnetic nano-particles; andbringing the concentrated dispersion liquid in proximity to a magnetic sensor comprising at least a magnetoresistive (MR) element and a permanent magnet while measuring the change in magnetic resistance to selectively detect the bound magnetic nano-particles, thereby indirectly detecting the target compound.

8. The method of claim 7, wherein the magnetic nano-particles have, on the surface thereof, a ligand for specifically binding to the target compound.

9. The method of claim 7, wherein the distance between the magnetic sensor and the dispersion liquid is 1 mm or less when the dispersion liquid is brought in proximity to the magnetic sensor.

10. The method of claim 7, wherein the surface magnetic flux density of the permanent magnet is from 0.01 to 10T.

11. The method of claim 7, wherein the magnetoresistive element contains an n-type InSb semiconductor.

12. The method of claim 7, wherein the magnetic nano-particles comprise iron oxide or ferrite.

13. A method for detecting a target compound comprising: injecting from 0.1 to 1000 μL of a test liquid containing a target compound into a colloid solution of magnetic nano-particles having an average particle diameter of 50 nm or less, the colloid solution flowing at a flow rate from 0.001 to 100 mL/minute in a flow channel having a cross section from 10 to 107 μm2, to allow the target compound to bind to the magnetic nano-particles, thereby forming bound magnetic nano-particles having a diameter of 100 nm or more; andbringing the resulting liquid mixture containing the bound magnetic nano-particles in proximity to a magnetic sensor comprising at least a magnetoresistive (MR) element and a permanent magnet while measuring the change in magnetic resistance to selectively detect the bound magnetic nano-particles, thereby indirectly detecting the target compound.

14. The method of claim 13, wherein the magnetic nano-particles have, on the surface thereof, a ligand for specifically binding to the target compound.

15. The method of claim 13, wherein the distance between the magnetic sensor and the dispersion liquid is 1 mm or less when the dispersion liquid is brought in proximity to the magnetic sensor.

16. The method of claim 13, wherein the surface magnetic flux density of the permanent magnet is from 0.01 to 10T.

17. The method of claim 13, wherein the magnetoresistive element contains an n-type InSb semiconductor.

18. The method of claim 13, wherein the magnetic nano-particles comprise iron oxide or ferrite.