Fiber optic evanscent wave sensor for immunoassay

• US 5,494,798 A
• Filed: 12/09/1993
• Issued: 02/27/1996
• Est. Priority Date: 12/09/1993
• Status: Expired due to Fees

• Current Assignee: Imaging Science Technologies Fiber Optic Div., Inc.
• Original Assignee: Imaging Science Technologies Fiber Optic Div., Inc.
• Inventors: Herr, John C., Gerdt, David W.
• Primary Examiner(s): Spiegel, Carol A.
• Application Number:
  US08/163,709
• Time in Patent Office: 810 Days
• Field of Search: 435/6, 435/7.1, 435/7.4, 435/7.8, 435/7.9, 436/501, 436/518, 436/527, 436/546, 436/164, 436/805, 436/807, 422/82.06, 422/82.11, 427/2, 427/2.11, 356/448, 385/13, 385/30
• US Class Current: 435/6.12
• CPC Class Codes: C12Q 1/6825 Nucleic acid detection involving sensors
• CPC Class Codes: G01N 33/54373 involving physiochemical end-point determination, e.g. wave-guides, FETS, gratings

Abstract

A coupled pair of fiber optic fibers are used an immunoassay device. The fibers are first coupled and then drawn down to a single mode diameter. The coupler senses output ratio change due to chemical, biochemical, bioaffinity, immunogenic-type interactions and other molecular activity occuring within the evanescent field. The fusion joint of the coupler is coated with a first immunoassay component, and then surrounded with a second immunoassay component.

Claims

1. A fiber optic sensor for immunoassay comprising:

a fiber optic coupler having a plurality of input optical fibers each having a core;

said cores being coupled for exchange of optical signals in a waist region;

a plurality of output optical fibers emerging from said waist region;

said fiber optic coupler distributing an input optical signal incident to one of said input optical fibers between said plurality of output optical fibers;

a first immunoreactant coated on said waist region, wherein said first immunoreactant is capable of specifically binding to a target analyte and wherein said first immunoreactant is an antibody or an antigen;

means for inserting light into at least one of said input optical fibers, whereby an evanescent region is produced surrounding said waist region;

means for measuring light magnitude emitted from a plurality of said output optical fibers; and

means for comparing the magnitude of light emitted at least two of said output optical fibers.

2. The fiber optic sensor in accordance with claim 1 wherein the first immunoreactant is an antibody and is coated on said waist region and wherein the target analyte is an antigen.

3. The fiber optic sensor in accordance with claim 1 wherein the first immunoreactant is an antigen and is coated on said waist region and wherein the target analyte is an antibody.

4. The fiber optic sensor in accordance with claim 1 wherein the evanescent filed extends approximately 1 wavelength beyond said waist region.

5. The fiber optic sensor in accordance with claim 1 wherein the fiber optic coupler is a single mode coupler.

6. The fiber optic sensor in accordance with claim 1 wherein said light inserted into said at least one input optical fiber is coherent light.

7. The fiber optic sensor in accordance with claim 1 wherein said means for measuring the magnitude of light comprises a light meter.

8. An immunoassay sensor comprising in combination:

a fiber optic coupler having a fusion joint;

means for light input into said fiber optic coupler, whereby an evanescent field is produced surrounding said fusion joint;

a first immunoassay reagent attached to the fusion joint and within said evanescent field, whereby said first immunoassay reagent is capable of specifically binding to a target immunoreactant;

means for detecting a light output ratio change due the specific binding of the target immunoreactant to said first immunoassay reagent.

9. The immunoassay sensor in accordance with claim 8 wherein said fusion joint is of a single mode coupler.

10. The immunoassay sensor according to claim 8 wherein said first immunoassay component is an antigen.

11. The immunoassay sensor according to claim 8 wherein said first immunoassay component is an antibody.

12. A method of immunoassay measurement of a target component comprising the steps of:

forming a coupler fusion joint from a plurality of single mode fiber optic fibers;

coating the fusion joint of the coupler with a first immunoassay component capable of specifically binding to the target component;

surrounding the coated fusion joint of the single mode fiber optic coupler with the target component;

inserting light into one of said optic fibers after coating the fusion joint;

measuring light output from two or more the optic fibers before and after surrounding the fusion joint with the target component; and

determining the presence or concentration of the target component by measuring changes in the output of light from said two or more optic fibers due to the specific binding of the target component to the first immunoassay component.

13. A biosensor for detecting a target nucleic acid sequence comprising:

a single mode optical fiber coupler having coated thereon a first oligonucleotide capable of hybridizing to said target nucleic acid sequence;

a means for inputting light into the single mode optical fiber coupler, whereby an evanescent region is produced around the single mode optical fiber coupler; and

a means for detecting a light output ratio change due to hybridizing of the target nucleic acid sequence to said first oligonucleotide.

14. A biosensor in accordance with claim 13, wherein said first oligonucleotide is selected from the group consisting of sense cDNA, anti-sense cDNA and genomic DNA and RNA.

15. A method of immunoassay or nucleic acid hybridization measurement of a target component in a fluid comprising the steps of:

making a single mode fiber optic coupler comprising a fusion joint of at least two single mode optical fibers;

making a biosensor by coating the fusion joint of the coupler with a first measurement material capable of specifically binding to or hybridizing to the target component wherein the first measurement material is selected from the group consisting of an antigen, an antibody and a nucleic acid sequence;

surrounding the fusion joint of the coupler with the target component wherein the target component is selected from the group consisting of an antigen, an antibody and a nucleic acid sequence capable of being specfically bound or hybridized to the biosensor;

inserting light into one of said optical fibers;

measuring and summing the output of light from two of more of the optical fibers before and after surrounding the coupler with the target component; and

determining the presence or concentration of the target component in the fluid by comparing changes in the light output levels of said two or more optical fibers due to the specific binding or hybridization of the target component to the first measurement material.

16. The method of measurement in accordance with claim 15 wherein said first measurement material is selected from the group consisting of an oligonucleotide, cDNA, RNA, and genomic DNA.

17. The method of measurement in accordance with claim 15 wherein said step of measuring and summing comprises a plurality of measurements made over a predetermine time interval and further determining rate of change of the light output and said step of comparing comprises comparing the rate of change of the light output as an indication of the concentration of the target material in the fluid.

18. An immunoassay method for determining a target analyte in a fluid sample, which method does not use labeled reagents and is based upon measuring changes in refractive index in an evanescent field surrounding a fiber optic coupler, comprising:

providing a fiber optic coupler comprised of a plurality of optical fibers which are first coupled and then drawn to a single mode diameter;

immobilizing an antibody or antigen capable of specifically binding to the target analyte on the fiber optic coupler;

illuminating at least one of the plurality of optical fibers to provide the surrounding evanescent field;

obtaining a first refractive index of the surrounding evanescent field by measuring a first ratio of light output by the fiber optic coupler;

contacting the fluid sample to the fiber optic coupler such that any target analyte in the fluid sample specifically binds to the immobilized antibody or antigen;

obtaining a second refractive index of the surrounding field by measuring a second ratio of light output by the fiber optic coupler; and

determining the presence or concentration of the target analyte in the fluid sample by measuring the change in refractive index produced by specific binding of the target analyte to the immobilized antibody or antigen on the fiber optic coupler.