Chemical signal-impermeable mask

• US 6,771,995 B2
• Filed: 12/20/2002
• Issued: 08/03/2004
• Est. Priority Date: 09/12/1995
• Status: Expired due to Fees

• Current Assignee: Animas Technologies LLC (Johnson & Johnson)
• Original Assignee: Cygnus, Inc. (Johnson & Johnson)
• Inventors: Kurnik, Ronald T., Tierney, Michael, Tamada, Janet
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US10/324,818
• Publication Number:
  US 20030120138A1
• Time in Patent Office: 592 Days
• Field of Search: 600/345-350, 600/365, 600/372
• US Class Current: 600/345
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61N 1/30 Apparatus for iontophoresis, i.e. transfer of media in ionic state by an electromotoric force into the body, or cataphoresis
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/002 Electrode membranes
• CPC Class Codes: C12Q 1/006 for glucose

Abstract

A chemical signal-impermeable mask is positioned in the electrolyte flow such that the mask is between a source of chemical signal and a working electrode which senses the chemical signal transported from the source (e.g., by diffusion). The configuration of the mask is such that the mask prevents substantially all chemical signal transport from the chemical signal source having a radial vector component relative to a plane of the mask and the catalytic face of the working electrode, thus allowing primarily only chemical signal transport that is substantially perpendicular to the place of the mask and the catalytic surface of the working electrode. By reducing or eliminating chemical signal radial transport toward the working electrode, the mask thus significantly reduces or eliminates edge effects. By substantially reducing edge effects created by radial transport of chemical signal, it is possible to obtain a more accurate measurement of the amount (e.g., concentration) of chemical signal that is transported from a given area of source material.

Claims

1. A method of measuring an amount or concentration of a chemical signal present in a mammalian subject, said method comprising:

transporting the chemical signal through a surface of the mammalian subject using an assembly in contact with said surface, wherein said assembly comprises

an ionically conductive material comprising first and second faces, said first face comprising a chemical signal target area, wherein said second face is in contact with said surface;

a working electrode, comprising a catalytic face, said catalytic face aligned with the first face of the ionically conductive material corresponding to said chemical signal target area; and

a mask characterized as being substantially impermeable to said chemical signal, said mask positioned relative to the second face of the ionically conductive material opposite the first face such that chemical signal transported through a plane of the mask, through the ionically conductive material, and toward the chemical signal target area is substantially only that chemical signal transported in a direction substantially perpendicular to the chemical signal target area;

wherein said transporting of the chemical signal is through the surface of the mammalian subject, through the plane of the mask, and through the ionically conductive material toward the chemical signal target area; and

monitoring an electrical signal which is generated at the catalytic surface of the working electrode by catalytic conversion of the chemical signal into the electric signal, wherein the electrical signal generated at the working electrode over a given period of time is correlated with the amount or concentration of chemical signal present in the mammalian subject.

2. The method of claim 1, wherein said subject is human.

3. The method claim 1, wherein said chemical signal is glucose.

4. The method of claim 1, wherein said assembly further comprises an electroosmotic electrode positioned to contact the first face of the ionically conductive material.

5. The method of claim 4, wherein said transporting is accomplished by applying an electrical current to the electroosmotic electrode.

6. The method of claim 1, wherein the ionically conductive material comprises water and an electrolyte.

7. The method of claim 6, wherein the ionically conductive material comprises, (i) a hydrophilic compound that forms a gel in water;

and ii) a chloride containing salt.

8. The method of claim 7, wherein the ionically conductive material comprises a hydrogel.

9. The method of claim 8, wherein the hydrogel comprises a chemical signal-specific enzyme.

10. The method of claim 9, wherein the enzyme is glucose oxidase and the chemical signal is glucose.

11. The method of claim 1, wherein the ionically conductive material comprises a chemical signal-specific enzyme.

12. The method of claim 11, wherein the enzyme is glucose oxidase and the chemical signal is glucose.

13. The method of claim 1, wherein the first and second faces of the ionically conductive material are coplanar and each has a surface area in a range of from about 0.5 cm² to about 10 cm² and the ionically conductive material has a thickness in a range of from about 5 mils to about 50 mils.

14. The method of claim 1, wherein the mask is chemically attached to the ionically conductive material.

15. The method of claim 14, wherein the mask is attached to the ionically conductive material by a chemical adhesive.

16. The method of claim 1, wherein the mask has a thickness in a range of from about 0.5 mils to about 10 mils.

17. The method of claim 1, wherein the mask has an adhesive coated on at least one of said first and second faces.

18. The method of claim 17, wherein the adhesive is a pressure-sensitive adhesive.

19. The method of claim 1, wherein the mask is coated with a material that absorbs one or more compounds or ions that diffuse through the surface of said subject.

20. The method of claim 1, wherein the mask is comprised of a polymeric material.

21. The method of claim 1, wherein the mask is comprised of two or more layers of the same or different materials to provide a chemical signal-impermeable composition.

22. The method of claim 1, wherein the mask defines an opening such that chemical signal transported through said opening, through the ionically conductive material, and toward the chemical signal target area is substantially only that chemical signal transported in a direction substantially perpendicular to the chemical signal target area.

23. The method of claim 22, wherein said opening in the mask constitutes an area which is in a range of 1% to 90% of an area encompassed by the entire mask plus opening.

24. The method of claim 22, wherein the chemical signal target area is substantially circular and the opening in the mask has a perimeter equal to or circumscribed within an outer perimeter of the circular chemical signal target area.

25. The method of claim 1, wherein the chemical signal target area is annular and the mask comprises a solid, circular piece, having an outer perimeter, said mask concentrically positioned with respect to the annular chemical signal target area such that the outer perimeter of the solid circular piece is circumscribed substantially within the annular chemical signal target area.

26. The method of claim 1, wherein the ionically conductive material has a thickness in the range of about 10 mils to 50 mils.

27. The method of claim 1, wherein said working electrode comprises a catalytic surface comprised of a material selected from the group consisting of platinum, palladium, nickel, oxides thereof, dioxides thereof, and alloys thereof.

28. The method of claim 1, wherein the working electrode comprises a catalytic surface with a geometric surface area in a range of about 0.25 to about 5.0 cm.

29. The method of claim 1, wherein the first and second faces of the ionically conductive material each have a geometric surface area in a range of about 0.5 cm² to 10 cm² and the material has a thickness in range of about 5 to about 50 mils, further wherein the working electrode has a catalytic surface with a geometric surface area in a range of about 0.25 to about 5.0 cm², and still further wherein the mask has a thickness in a range of about 0.5 mil to about 10 mils.

30. The method of claim 1, wherein said ionically conductive material comprises a hydrogel.

31. A method of measuring an amount or concentration of glucose present in a mammalian subject, said method comprising:

transporting the glucose through a surface of the mammalian subject using an assembly in contact with said surface, wherein said assembly comprises

an ionically conductive material comprising first and second faces, said first face comprising a glucose target area, wherein said second face is in contact with said surface;

a working electrode, comprising a catalytic face, said catalytic face aligned with the first face of the ionically conductive material corresponding to said glucose target area;

an electroosmotic electrode positioned to contact the first face of the ionically conductive material; and

a mask characterized as being substantially impermeable to said glucose, said mask positioned relative to the second face of the ionically conductive material opposite the first face such that glucose transported through a plane of the mask, through the ionically conductive material, and toward the glucose target area is substantially only that glucose transported in a direction substantially perpendicular to the glucose target area;

wherein said transporting of glucose through the surface of the mammalian subject, through the plane of the mask, and through the ionically conductive material to the glucose target area is accomplished by applying an electrical current to the electroosmotic electrode; and

monitoring an electrical signal which is generated at the catalytic surface of the working electrode by catalytic conversion of the glucose into the electric signal, wherein the electrical signal generated at the working electrode over a given period of time is correlated with the amount or concentration of glucose present in the mammalian subject.

32. The method of claim 31, wherein said subject is human.

33. The method of claim 31, wherein the ionically conductive material comprises an electrolyte.

34. The method of claim 33, wherein the ionically conductive material comprises, (i) a hydrophilic compound that forms a gel in water;

and ii) a chloride containing salt.

35. The method of claim 34, wherein the ionically conductive material comprises a hydrogel.

36. The method of claim 35, wherein the hydrogel comprises glucose oxidase.

37. The method of claim 31, wherein said working electrode comprises a catalytic surface comprised of a material selected from the group consisting of platinum, palladium, nickel, oxides thereof, dioxides thereof, and alloys thereof.