Chemical signal-impermeable mask

• US 20010020125A1
• Filed: 03/16/2001
• Published: 09/06/2001
• Est. Priority Date: 09/12/1995
• Status: Active Grant

• Current Assignee: Animas Technologies LLC (Johnson & Johnson)
• Original Assignee: Cygnus, Inc. (Johnson & Johnson)
• Inventors: Kurnik, Ronald T., Tamada, Janet, Tierney, Michael
• Granted Patent: US 6,370,410 B2
• Time in Patent Office: Days
• US Class Current: 600/347
• 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. An assembly for use in a monitoring device for monitoring a chemical signal comprising:

a) an ionically conductive material having a first face having a chemical signal target area, the material comprising; and

b) a mask characterized by being substantially impermeable to a chemical signal, the mask being positioned on a second ionically conductive material face opposite the first material 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.

2. The assembly of

claim 1

, wherein the mask has an opening through which chemical signal flows in a direction substantially perpendicular to the target area.

3. The assembly of

claim 2

, wherein the opening in the mask constitutes an area which is in the range of 1% to 90% of area encompassed by the entire mask plus opening.

4. The assembly of

claim 2

, wherein the outer perimeter of the mask extends out beyond the outer perimeter of the catalytic surface and the opening in the mask has a perimeter which is equal to or circumscribed within the outer perimeter of the target area.

5. The assembly of

claim 1

, wherein the mask is solid and the target area is annular.

6. The assembly of

claim 1

, wherein the ionically conductive material comprises:

i) a hydrophilic compound which forms a gel in the presence of water, which compound is present in an amount of about 4% or more by weight based on the weight of the ionically conductive material;

ii) water in an amount of about 95% or less based on the weight of the hydrogel patch; and

iii) a chloride containing salt.

7. The assembly of

claim 1

, wherein the ionically conductive material comprises glucose oxidase and the chemical signal is glucose.

8. The assembly of

claim 1

, wherein the ionically conductive material has two planar surface areas each with an area in the range of from about 0.5 to about 10 cm² and a thickness in the range of from about 5 mils to about 50 mils.

9. The patch assembly of

claim 1

, wherein the mask has a thickness in the range of about 0.5 mil to 10 mils and the ionically conductive material has a thickness in the range of about 10 mils to 50 mils.

10. A sensor assembly for use with a chemical signal monitoring device, comprising;

a sensor housing having a top portion and a bottom portion, the bottom portion defining a bottom portion opening within the bottom portion;

a chemical signal impermeable mask positioned between the top portion and the bottom portion, the mask having a surface area greater than or equal to the surface area of the bottom portion opening, and defining a mask opening, the mask being positioned so that the mask opening and the bottom portion opening are aligned; and

a working electrode positioned in the top portion of the sensor housing;

wherein prior to use a hydrogel is inserted between the sensor housing bottom portion and top portion such that when the sensor assembly is closed, the top portion is positioned directly over the bottom portion such that a first hydrogel face contacts the mask, and the working electrode is in contact with a second hydrogel face opposite the first hydrogel face, the working electrode being positioned directly opposite the bottom portion opening.

11. The sensor assembly of

claim 10

, wherein the hydrogel comprises glucose oxidase, the mask is impermeable to glucose, and the working electrode comprises platinum.

12. The sensor assembly of

claim 10

, wherein the surface area of each of the hydrogel surface-contacting mask face, the mask-contacting hydrogel face, and the electrode-contacting face is in a range of about 0.5 cm² to 10 cm².

13. The sensor assembly of

claim 10

, wherein the mask has a thickness in the range of about 0.5 mils to 10 mils.

14. The sensor assembly of

claim 10

, wherein the hydrogel has a thickness in the range of about 10 mils to 50 mils.

15. The sensor assembly of

claim 10

, wherein the assembly has a total thickness of from about 5 mils to 50 mils.

16. A method of measuring the amount of a chemical signal present in the bloodstream of a mammalian subject, the method comprising:

contacting with a mammalian subject'"'"'s skin a sensor assembly comprising a) a chemical signal impermeable mask, the mask defining an opening in the mask and having a first face in contact with the skin;

b) an ionically conductive material having a first face in contact with a second face of the first mask face; and

c) a working electrode in contact with a second face of the ionically conductive material opposite the first ionically conductive material face, the working electrode positioned on the ionically conductive material directly opposite the mask opening;

transporting in a direction substantially axial to a catalytic face of the working electrode a chemical signal from the subject'"'"'s bloodstream, through the subject'"'"'s skin, into the opening defined by the mask, and through the ionically conductive material; and

monitoring an electrical signal generated at the working electrode by catalytic conversion of the chemical signal into an electric signal at the catalytic face of the working electrode;

wherein the electrical signal generated at the working electrode is correlated with an amount of chemical signal present in the bloodstream of the mammalian subject.

17. The method of

claim 16

, wherein the assembly further comprises an electroosmotic electrode in contact with the ionically conductive material and said transporting is accomplished by applying an electrical current to the electroosmotic electrode for a period sufficient to electrically draw in a direction substantially axial to a catalytic face of the working electrode a chemical signal from the mammalian subject'"'"'s bloodstream, through the subject'"'"'s skin, into the opening defined by the mask, and through the ionically conductive material.

18. The method according to

claim 16

, wherein the chemical signal is glucose, the ionically conductive material is a hydrogel comprising glucose oxidase, and the catalytic face of the working electrode comprises a material selected from the group consisting of platinum oxide and platinum dioxide.

19. An assembly for use in monitoring a chemical signal, comprising:

(a) an ionically conductive material comprised of water, electrolyte and an enzyme;

(b) a working electrode having a catalytic surface comprised of a material selected from the group consisting of platinum, palladium, nickel, and oxides, dioxides and alloys thereof, the catalytic surface contacting a first face of the ionically conductive material; and

(c) a chemical signal impermeable mask positioned on a second face of the ionically conductive material (a) opposite the first ionically conductive material face and opposite the catalytic surface of the electrode (b), the mask having an outer perimeter which is equal to or extends beyond an outer perimeter of the working electrode (b) and having an opening therein which has a perimeter which is equal to or circumscribed within the outer perimeter of the working electrode.

20. The assembly of

claim 19

, wherein the material (a), electrode (b), and mask (c) are such that the mask blocks substantially all chemical signal flowing to the catalytic surface which is not flowing in a direction substantially perpendicular to the catalytic surface and allows substantially all chemical signal to flow to the catalytic surface which is flowing to that surface in a substantially perpendicular path.

21. The assembly of

claim 19

, wherein the ionically conductive material (a) has two planar surfaces each having a geometric surface area in the range of about 0.5 cm² to 10 cm² and a thickness in the range of about 5 to about 50 mils, further wherein the working electrode (b) has a catalytic surface with a geometric surface area in the range of about 0.25 to about 5.0 cm², and still further wherein the mask (c) has a thickness in the range of about 0.5 mil to about 10 mils.

22. An assembly for use in a monitoring device for monitoring a chemical signal, comprising:

a) an ionically conductive material; and

b) a mask characterized by being impermeable to the chemical signal, the mask being positioned between ionically conductive material and a source of chemical signal;

wherein the mask is concentric to a working electrode which measures chemical signal transported from the source of chemical signal to a catalytic surface of the electrode, and further wherein the chemical signal that passes through a plane of the mask is that chemical signal that is transported from the source to the catalytic surface in a manner which is substantially perpendicular to the catalytic surface.

23. The patch assembly of

claim 22

, wherein the ionically conductive material is a hydrogel having an enzyme therein and the catalytic surface is comprised of a material selected from the group consisting of platinum, palladium, nickel, oxides thereof, dioxides thereof and alloys thereof.