Electrochemical urea sensors and methods of making the same

• US 20040256227A1
• Filed: 06/09/2004
• Published: 12/23/2004
• Est. Priority Date: 02/11/2003
• Status: Abandoned Application

• Current Assignee: Instrumentation Lab Co (Instrumentation Lab)
• Original Assignee: Instrumentation Lab Co (Instrumentation Lab)
• Inventors: Shin, Jungwon, Cosofret, Vasile V.
• Application Number:
  US10/864,908
• Publication Number:
  US 20040256227A1
• Time in Patent Office: Days
• US Class Current: 204/403.03
• CPC Class Codes: C12Q 1/005 involving specific analytes or enzymes including groups of enzymes, e.g. oxydases; C12Q1/004 takes precedence
• CPC Class Codes: G01N 33/492 Determining multiple analytes
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: G01N 33/54393 Improving reaction conditions or stability, e.g. by coating or irradiation of surface, by reduction of non-specific binding, by promotion of specific binding
• CPC Class Codes: G01N 33/62 involving urea

Abstract

An electrochemical sensor for detecting urea in a sample includes a composite membrane that includes an enzymatic layer and an outer diffusional layer. The outer diffusional layer is disposed between the enzymatic layer and the analytical sample, preventing direct contact between the enzymatic layer and the analytical sample.

Claims

1. A sensor for detecting urea in a sample, comprising:

an electrode;

an enzymatic layer; and

an outer diffusional layer disposed between the sample and the enzymatic layer, wherein the outer diffusional layer is permeable to urea.

2. The sensor of claim 1, wherein the electrode comprises a metal electrode.

3. The sensor of claim 2, wherein the electrode comprises a silver/silver chloride electrode.

4. The sensor of claim 1, wherein the enzymatic layer catalyzes the hydrolysis of urea to ammonium ions.

5. The sensor of claim 4, wherein the enzymatic layer comprises urease.

6. The sensor of claim 1, wherein the enzymatic layer further comprises one or more enzyme stabilizers.

7. The sensor of claim 6, wherein the enzyme stabilizer is selected from the group consisting of polypeptides and inert proteins.

8. The sensor of claim 7, wherein the polypeptide comprises glutathione.

9. The sensor of claim 7, wherein the inert protein comprises bovine serum albumin.

10. The sensor of claim 1, wherein the enzymatic layer comprises urease cross-linked to glutathione.

11. The sensor of claim 10, further comprising one or more inert proteins cross-linked to at least one of the urease and the glutathione.

12. The sensor of claim 11, wherein the inert protein comprises bovine serum albumin.

13. The sensor of claim 1, wherein the outer diffusional layer comprises a polymer.

14. The sensor of claim 13, wherein the polymer is selected from the group consisting of polyurethane, a poly(tetrafluoroethylene) ionomer, poly-(2-hydroxymethyl methacrylate), polyvinyl chloride, carboxylated polyvinyl chloride, hydroxylated polyvinyl chloride, polycarbonate, cellulose acetate, and mixtures thereof.

15. The sensor of claim 14, wherein the polymer comprises polyurethane.

16. The sensor of claim 1, further comprising an ion-selective membrane disposed between the electrode and the enzymatic layer.

17. The sensor of claim 16, wherein the ion-selective membrane comprises an ammonium ion-selective membrane.

18. The sensor of claim 17, wherein the ion-selective membrane comprises:

a polymer matrix; and

an ammonium-selective ionophore disposed therein.

19. The sensor of claim 18, wherein the polymer matrix is selected from the group consisting of polyvinyl chloride, carboxylated polyvinyl chloride, hydroxylated polyvinyl chloride, polyurethane, poly(tetrafluoroethylene), poly(methyl methacrylate), silicone rubber, and mixtures thereof.

20. The sensor of claim 19, wherein the polymer matrix comprises polyvinyl chloride.

21. The sensor of claim 18, wherein the ionophore is selected from the group consisting of nonactin, monactin, dinactin, trinactin, tetranactin, narasin, hexaoxaheptacyclotritrtracontane, benzocrown ethers, cyclic depsipeptides, and mixtures thereof.

22. The sensor of claim 21, wherein the ionophore comprises nonactin.

23. The sensor of claim 1, wherein the sample is selected from the group consisting of blood, serum, plasma, cerebro-spinal fluid, saliva, and urine.

24. The sensor of claim 23, wherein the sample is blood.

25. A sensor card comprising:

a substrate; and

one or more sensors of claim 1 disposed on or in the substrate.

26. A method of forming the sensor of claim 1, the method comprising the steps of:

providing an electrode;

applying to at least one surface of the electrode an enzymatic layer; and

applying an outer diffusional layer over the enzyme layer,

wherein the sensor detects or measures urea in a sample.

27. A method of forming the sensor of claim 15, the method comprising the steps of:

providing an electrode;

applying to at least one surface of the electrode an ion-selective membrane;

applying to the ion-selective membrane an enzymatic layer; and

applying an outer diffusional layer over the enzyme layer,

wherein the sensor detects or measures urea in a sample.