Concentration measuring method, concentration measuring kit, and sensor chip for use in the method

1. A method for measuring the concentration of an analyte, which comprises:

(i) obtaining a sensor chip comprising:

an optical waveguide layer configured to propagate a light within the layer by total reflection of the light,

an antibody-immobilized layer, having an immobilized antibody, formed on at least a part of a surface of the optical waveguide layer,

a frame member adhered on a surface of the optical waveguide layer, surrounding the antibody-immobilized layer, for constituting a cell, and

a liquid-repelling film formed on a part of the optical waveguide layer except where a frame member is located, said film having a surface level higher than the antibody-immobilized layer and lower than the frame member to form a reaction hole that exposes at least one part of the antibody-immobilized layer;

(ii) immobilizing the analyte and an enzyme-labeled antibody, which is labeled with a labeling enzyme, on the antibody-immobilized layer in the reaction hole of the sensor chip;

(iii) precipitating a color-developed enzyme reaction product by allowing a coloring reagent and the labeling enzyme on the antibody-immobilized layer to react;

(iv) reflecting totally a light impinged on the sensor chip from the outside at an interface between the optical waveguide layer and the antibody-immobilized layer;

(v) detecting a change in reflection light intensity caused absorption of an evanescent wave by the color-developed enzyme reaction product at the antibody-immobilized layer; and

(vi) measuring a concentration of the analyte based on the change of the reflection light intensity.

2. The method according to claim 1 , wherein the antibody-immobilized layer has a thickness of 30 nm to 500 nm.

3. The method according to claim 1 , wherein the labeling enzyme is horseradish peroxidase.

4. The method according to claim 1 , wherein the coloring reagent is a benzidine-base coloring reagent selected from the group consisting of 4-chloro-1-naphtol, 3,3′-diaminobenzidine and 3,3′,5,5′-tetramethyl benzidine.

5. The method according to claim 4 , wherein the coloring reagent is 3,3′,5,5′-tetramethyl benzidine.

6. The method according to claim 1 , wherein the analyte is selected from the group consisting of insulin, casein, β-lactoglobulin, ovoalbumin, calcitonin, C-peptide, leptin, β-2-microgloburin, lethinol-binding protein, α-1-microglobulin, α-fetoprotein, carcinoembryonic antigen, troponin-I, glucagons-like peptide, insulin-like peptide, tumor growth factor, fibroblast growth factor, platelet growth factor, epithelial cell growth factor, cortisol, triiode thyronine, thyroxin, digoxin, theophylline, bacteria, viruses, hepatitis antibody, and IgE, major protein complex of buckwheat, and soluble proteins including Arah2 of peanuts.

7. The method according to claim 6 , wherein the analyte is insulin.

8. A kit for measuring the concentration of an analyte, which comprises:

an antibody labeled with a labeling enzyme;

a coloring reagent comprising at least a coloring substrate and a substrate for the labeling enzyme, the coloring reagent developing a color by an enzyme reaction and forming a precipitating enzyme reaction product; and

a sensor chip, comprising:

an optical waveguide layer configured to propagate a light within the layer by total reflection of the light;

an antibody-immobilized layer, having an immobilized antibody, formed on at least a part of a surface of the optical waveguide laver;

a frame member adhered on a surface of the optical waveguide layer, surrounding the antibody-immobilized layer, for constituting a cell; and

a liquid-repelling film formed on a part of the optical waveguide layer except where a frame member is located, said film having a surface at a level higher than the antibody-immobilized layer and lower than the frame member to form a reaction hole that exposes at least one part of the antibody immobilized layer,

wherein the sensor chip, the antibody and the coloring reagent are independently packed and assembled together.

9. The kit according to claim 8 , wherein the coloring substrate is a benzidine-base coloring reagent and the labeling enzyme is peroxidase.

10. The kit according to claim 8 , wherein the antibody is any one of an anti-insulin antibody, an anti-casein antibody, an anti-β-lactoglobulin antibody, an anti-ovoalbumin antibody, an anti-buckwheat major protein complex antibody and an anti-peanuts Arah2 soluble protein.

11. The kit according to claim 10 , wherein the antibody is the anti-insulin antibody.

12. The kit according to claim 8 , wherein the coloring reagent is a benzidine-base coloring reagent selected from the group consisting of 4-chloro-1-naphtol, 3,3′-diaminobenzidine and 3,3′, 5,5′-tetramethyl benzidine.

13. The kit according to claim 12 , wherein the coloring reagent is 3,3′,5,5′-tetramethyl benzidine.

14. A sensor chip comprising:

an optical waveguide layer configured to propagate a light within the layer by total reflection of the light;

an antibody-immobilized layer that forms at least a part of the surface of the optical waveguide layer for total reflection of the light;

a frame member adhered on the surface of the optical waveguide layer, surrounding the antibody-immobilized layer, for constituting a cell; and

a liquid-repelling film formed on a part of the optical waveguide layer, except where a frame member is located, said film having a surface at a level higher than the antibody-immobilized layer and lower than the frame member, and having a reaction hole exposing at least one part of the antibody-immobilized layer.

15. The sensor chip according to claim 14 , wherein the antibody immobilized layer has a thickness of 30 nm to 500 nm.

16. The sensor chip according to claim 14 , wherein the antibody-immobilized layer is hydrophilic.