Glucose measuring assembly with a hydrogel
This invention relates to methods for reducing the presence of a compound in an ionically conductive material, e.g., for use in iontophoretic devices, wherein the presence of the compound interferes with detecting a selected analyte. Removal of the compound can typically take place either during or after the manufacture of the ionically conductive material or an assembly comprising this material. Also disclosed are methods for generating selectively permeable barriers on the reactive faces of electrodes. Further, this invention relates to hydrogels comprising one or more biocides, as well as assemblies containing such hydrogels.
1. A collection assembly for use in a glucose sampling system and for electrochemical detection of an amount or concentration of glucose, said collection assembly comprising:
a collection insert layer comprising a first hydrogel having a first surface and a second surface, said first hydrogel comprising:
polyethylene oxide present in an amount of about 5% to about 20% by weight based on the total weight of the hydrogel;
water in an amount of about 50% or more and about 95% or less based on the total weight of the hydrogel;
a chloride salt, wherein background electrical signal in the gel is less than approximately 200 nA;
a phosphate buffer in an amount sufficient to maintain a pH in the hydrogel in the range of 6 to 8;
an enzyme composition comprising glucose oxidase, said glucose oxidase present in an amount of from about 10 units to about 5,000 units per gram of the total weight of the hydrogel; and
a biocide comprising an undecylenate;
a mask layer comprising a material that is substantially impermeable to glucose and derivatives thereof, wherein the mask layer (i) has an inner face and an outer face and the inner face is positioned in facing relationship with the first surface of the first hydrogel and (ii) defines a first opening that exposes at least a portion of the first surface of the first hydrogel; and
a gel retaining layer comprising an inner face and an outer face wherein (i) the inner face is positioned in facing relationship with the second surface of the first hydrogel, and (ii) the gel retaining layer defines a first opening that exposes at least a portion of the second surface of the first hydrogel.
2. The collection assembly of claim 1 , wherein said collection assembly is a laminate.
3. The collection assembly of claim 1 , further comprising a liner in contact with the mask layer.
4. The collection assembly of claim 3 , further comprising a plow-fold liner in contact with the gel retaining layer.
5. The collection assembly of claim 1 , wherein structural integrity of the hydrogel includes crosslinking the polyethylene oxide.
6. The collection assembly of claim 5 , wherein said crosslinking is achieved by thermal reaction, chemical reaction, or providing ionizing radiation.
7. The collection assembly of claim 6 , wherein said ionizing radiation is provided by electron beam radiation, UV radiation, or gamma radiation.
8. The collection assembly of claim 1 , wherein said biocide comprises undecylenic acid, a salt of undecylenic acid, or mixtures thereof.
9. The collection assembly of claim 1 , wherein said background electrical signal is less than approximately 50 nA.
10. The collection assembly of claim 1 , wherein said enzyme composition further comprises a mutarotase enzyme.
11. The collection assembly of claim 1 , wherein (i) said glucose oxidase can catalyze a reaction between glucose and oxygen resulting in the generation of hydrogen peroxide, and (ii) hydrogen peroxide degradative components of the enzyme composition are reduced such that quantitation of hydrogen peroxide produced by the glucose oxidase reaction is not compromised.
12. The collection assembly of claim 1 , wherein said hydrogel further comprises a structural support material embedded in the hydrogel.
13. The collection assembly of claim 1 , wherein one or more components of said hydrogel have been treated to remove compounds that cause background electrical signal.
14. The collection assembly of claim 13 , wherein one or more of said hydrogel components have been treated using a diafiltration procedure to remove electroactive compounds therefrom.
15. The collection assembly of claim 1 , wherein said hydrogel further comprises bisacrylamide.
16. The collection assembly of claim 1 , wherein said biocide is present in the hydrogel at a concentration of between about 0.01% to about 5% based on the total weight of the hydrogel.
17. The collection assembly of claim 16 , wherein said biocide is present in the hydrogel at a concentration of between about 0.1% to about 1% based on the total weight of the hydrogel.
18. The collection assembly of claim 17 , wherein said biocide is present in the hydrogel at a concentration of between about 0.2% to about 0.5% based on the total weight of the hydrogel.
19. The colleetion assembly of claim 1 , wherein the collection insert layer further comprises a second hydrogel having a first surface and a second surface, said second hydrogel comprising:
polyethylene oxide present in an amount of about 5% to about 20% by weight based on the total weight of the hydrogel;
water in an amount of about 50% or more and about 95% or less based on the total weight of the hydrogel;
a chloride salt, wherein background electrical signal in the gel is less than approximately 200 nA;
a phosphate buffer in an amount sufficient to maintain a pH in the hydrogel in the range of 6 to 8;
an enzyme composition comprising glucose oxidase, said glucose oxidase present in an amount of from about 10 units to about 5,000 units per gram of the total weight of the hydrogel; and
a biocide comprising an undecylenate;
said inner face of the mask layer (i) is positioned in facing relationship with the first surface of the second hydrogel, and (ii) defines a second opening that exposes at least a portion of the first surface of the second hydrogel;
said inner face of the gel retaining layer (i) is positioned in facing relationship with the second surface of the second hydrogel, and (ii) defines a second opening that exposes at least a portion of the second surface of the second hydrogel.