Sensor element and method for making the same

• US 5,330,718 A
• Filed: 10/14/1992
• Issued: 07/19/1994
• Est. Priority Date: 08/16/1989
• Status: Expired due to Fees

• Current Assignee: Puritan Bennett Corp. (Medtronic Plc)
• Original Assignee: Puritan Bennett Corp. (Medtronic Plc)
• Inventors: Bankert, Charles S., Hui, Henry K.
• Primary Examiner(s): Johnston, Jill A.
• Application Number:
  US07/960,903
• Time in Patent Office: 643 Days
• Field of Search: 422/58, 422/57, 422/82.06-82.08, 385/13, 427/2, 436/68, 436/166, 128/634
• US Class Current: 422/82.07
• CPC Class Codes: G01N 2021/174 either absorption-reflection or emission-fluorescence
• CPC Class Codes: G01N 2021/6434 Optrodes
• CPC Class Codes: G01N 2021/772 Tip coated light guide
• CPC Class Codes: G01N 2021/773 Porous polymer jacket; Polymer matrix with indicator
• CPC Class Codes: G01N 2021/775 Indicator and selective membrane
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 2021/7796 Special mountings, packaging of indicators
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B
• CPC Class Codes: G01N 31/223 for investigating presence of specific gases or aerosols G01N31/221, G01N31/222 take precedence; actuation of fire alarm by presence of smoke or gases G08B17/10

Abstract

A sensor element includes an analyte-permeable matrix which supports and maintains an emulsion of a sensing solution containing an analyte-sensitive indicator substance in a plurality of tiny vesicles. The sensing solution is immiscible with the matrix material, and contains a dye indicator which dissociates into two different species. The sensing solution is initially mixed with an agent which modifies the equilibrium of dissociation of the dye indicator for optimal sensitivity. The liquid matrix preferably includes a curing inhibitor to allow the matrix to remain liquid until applied to a sensing surface, such as the tip of an optical fiber. The sensing solution remains suspended in these homogeneously dispersed vesicles after the matrix solidifies.

Claims

1. A sensor element for sensing carbon dioxide in a sample comprising:

an optical fiber having a surface portion covered with a matrix made from a hydrophobic material that is permeable to carbon dioxide; and

a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including a dye indicator which dissociates into two different species in response to the presence of carbon dioxide, an agent for modifying the equilibrium of dissociation of said dye indicator to be within a range for optimal sensitivity to said carbon dioxide, and an aqueous base for raising the pH of said aqueous sensing solution to be outside a physiological range of carbon dioxide concentration when said dye indicator is not exposed to carbon dioxide, and to be within said physiological range of carbon dioxide concentration when said dye indicator is exposed to carbon dioxide, said dye indicator being exposable to an external excitation through said matrix, and at least one species of said dye indicator producing an emission of light in response to said excitation, with said emission of light being related to the content of carbon dioxide in said sample, whereby exposure of the dye indicator to carbon dioxide will cause the equilibrium of dissociation of the indicator to be within said range for optimal sensitivity.

2. The sensor element as defined in claim 1, wherein said agent for modifying the equilibrium of dissociation of said dye indicator is polyvinylpyrrolidone.

3. The sensor element as defined in claim 1, wherein said matrix is only sightly thicker than the size of one of said vesicles in said matrix.

4. The sensor element as defined in claim 1 wherein said sensing solution and said matrix material are mutually immiscible.

5. The sensor element as defined in claim 1 wherein said vesicle are homogenous dispersed throughout said matrix.

6. The sensor element as defined in claim 1 wherein said matrix material is silicone.

7. The sensor element as defined in claim 1, wherein said dye indicator is a fluorescent dye indicator.

8. The sensor element as defined in claim 1, further comprising a plurality of vesicles containing a second sensing solution containing a second dye indicator responsive to said excitation to produce a second emission of light related to the content of a second analyte in said sample, with said emissions of light from said indicator dyes being of different wavelength ranges, and said first aqueous sensing solution and said second sensing solution being mutually immiscible.

9. A sensor element for sensing carbon dioxide content of a sample comprising:

an optical fiber having a surface portion covered with a matrix made from a hydrophobic material that is permeable to carbon dioxide; and

a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including polyvinylpyrrolidone, an aqueous base, and a dye indicator which undergoes dissociation into two different species, said dissociation being sensitive to carbon dioxide, said aqueous sensing solution having a pH set to approximately 9 before exposure to carbon dioxide gas, said dye indicator being exposable to an external excitation through said matrix, and said dye indicator producing an emission of light in response to said excitation, with said emission of light being related to the content of carbon dioxide in said sample.

10. The sensor element as defined in claim 9, wherein said matrix is only sightly thicker than the size of one of said vesicles in said matrix.

11. The sensor element as defined in claim 9, wherein said sensing solution and said matrix material are mutually immiscible.

12. The sensor element as defined in claim 9, wherein said vesicle are homogenous dispersed throughout said matrix.

13. The sensor element as defined in claim 9, wherein said matrix material comprises diphenyldimethylpolysiloxane.

14. The sensor element as defined in claim 9, wherein said dye indicator is a fluorescent dye indicator.

15. The sensor element as defined in claim 9, wherein said dye indicator is hydroxypyrenetrisulfonic acid.

16. The sensor element as defined in claim 9, further comprising a plurality of vesicles containing a second sensing solution containing a second dye indicator responsive to said excitation to produce a second emission of light related to the content of a second analyte in said sample, with said emissions of light from said indicator dyes being of different wavelength ranges, and said first aqueous sensing solution and said second sensing solution being mutually immiscible.

17. A method for making a sensor element for sensing an analyte in a sample, said sensor including an optical fiber having a surface portion covered with a matrix made from a material that is permeable to the analyte, and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including a fluorescent dye indicator which has an equilibrium of dissociation into two different species which is sensitive to said analyte, comprising the steps of:

adding said fluorescent dye indicator substance that is sensitive to said analyte to an aqueous solution and an agent for modifying the equilibrium of dissociation of said dye indicator substance to be within an optimal range of sensitivity to said analyte;

adding an aqueous base to said aqueous solution to change the pH of said aqueous solution to be outside an optimal range of sensitivity of said dye indicator substance in said aqueous solution to form said aqueous sensing solution;

adding said aqueous sensing solution to a liquid silicone matrix containing a curing inhibitor for prolonging the liquid state of said matrix;

homogeneously dispersing the aqueous solution throughout said liquid matrix solution to form an emulsion of said sensing solution in a plurality of vesicles in said liquid matrix;

coating said surface of said optical fiber with said emulsion; and

heating said emulsion to cure said matrix of said emulsion into a solid semi-permeable membrane that is permeable to said analyte.

18. The method of claim 17, wherein said surface of said optical fiber is coated with a thickness of said dye indicator matrix only slightly more than the size of one of said vesicles.

19. The method of claim 17, further comprising the step of adding a curing catalyst to said liquid matrix.

20. The method of claim 17, further comprising the steps of adding a second sensing solution containing a second dye indicator responsive to a second analyte to said liquid matrix and said first aqueous sensing solution, said first sensing solution and said second sensing solution being mutually immiscible, and homogeneously dispersing said first and second sensing solutions in said liquid matrix to form a plurality of vesicles in said liquid matrix containing said first sensing solution and a plurality of vesicles containing said second sensing solution.

21. A method for making a sensor element for sensing the carbon dioxide content of a sample, said sensor including an optical fiber having a surface portion covered with a matrix made from a material that is permeable to carbon dioxide, and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including polyvinylpyrrolidone and a fluorescent dye indicator responsive to carbon dioxide, comprising the steps of:

adding polyvinylpyrrolidone and said fluorescent dye indicator substance that is sensitive to carbon dioxide to an aqueous solution;

titrating said aqueous solution containing polyvinylpyrrolidone and said dye indicator with an aqueous base to a pH of 9 to form said aqueous sensing solution;

adding said aqueous sensing solution to a liquid silicone matrix containing a curing inhibitor for prolonging the liquid state of said matrix;

homogeneously dispersing the aqueous solution throughout said liquid matrix to form an emulsion of said sensing solution in a plurality of vesicles in said liquid matrix;

coating said surface of said optical fiber with said emulsion in a thickness slightly more than the size of one of said vesicles; and

heating said emulsion to a temperature between about 180 and 220 degrees Centigrade to cure said matrix into a solid semi-permeable membrane that is permeable to carbon dioxide.

22. The method of claim 21 further comprising the step of adding a curing catalyst to said liquid matrix.

23. The method of claim 21 further comprising the steps of adding a second sensing solution containing a second dye indicator sensitive to a second analyte to said liquid matrix and said first aqueous sensing solution, said first sensing solution and said second sensing solution being mutually immiscible, and homogeneously dispersing said first and second sensing solutions in said liquid matrix to form a plurality of vesicles containing said first sensing solution and a plurality of vesicles in said liquid matrix containing said second sensing solution.

24. A sensor element for sensing an analyte in a sample comprising:

an optical fiber having a surface portion covered with a matrix made from a material that is permeable to the analyte;

a first plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including a first dye indicator which dissociates into two different species in response to the presence of said analyte, and an agent for modifying the equilibrium of dissociation of said first dye indicator to be within a range for optimal sensitivity to said analyte, said first dye indicator being exposable to an external excitation through said matrix, and at least one species of said first dye indicator producing an emission of light in response to said excitation, with said emission of light being related to the content of said analyte in said sample; and

a second plurality of vesicles containing a second sensing solution including a second dye indicator responsive to said excitation to produce a second emission of light related to the content of a second analyte in said sample, with said emissions of light from said indicator dyes being of different wavelength ranges, said first aqueous sensing solution and said second sensing solution being mutually immiscible.

25. A sensor element for sensing carbon dioxide content of a sample comprising:

an optical fiber having a surface portion covered with a matrix made from a material that is permeable to carbon dioxide;

a first plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including polyvinylpyrrolidone and a first dye indicator which undergoes dissociation into two different species, said dissociation being sensitive to carbon dioxide, said aqueous sensing solution having a pH set to approximately 9 before exposure to carbon dioxide gas, said dye indicator being exposable to an external excitation through said matrix, and said dye indicator producing an emission of light in response to said excitation, with said emission of light being related to the content of carbon dioxide in said sample, and

a second plurality of vesicles containing a second sensing solution including a second dye indicator responsive to said excitation to produce a second emission of light related to the content of a second analyte in said sample, with said emissions of light from said indicator dyes being of different wavelength ranges, said first aqueous sensing solution and said second sensing solution being mutually immiscible.