Biosensor, iontophoretic sampling system, and methods of use thereof

• US 6,736,777 B2
• Filed: 01/29/2003
• Issued: 05/18/2004
• Est. Priority Date: 03/13/1998
• Status: Expired due to Term

• Current Assignee: LifeScan IP Holdings, LLC
• Original Assignee: Cygnus, Inc. (Johnson & Johnson)
• Inventors: Potts, Russell O., Tierney, Michael J., Parris, Norman A., Kim, Lynn
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US10/353,734
• Publication Number:
  US 20030135100A1
• Time in Patent Office: 475 Days
• Field of Search: 600/345-350, 600/573
• US Class Current: 600/365
• CPC Class Codes: A61B 5/14514 using means for aiding extraction of interstitial fluid, e.g. microneedles or suction
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• 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

Abstract

The present invention relates generally to a sensor for use in monitoring the amount or concentration of target chemical analytes present in a biological system. For example, the invention relates to a sensor for measuring the amount or concentration of one or more analytes in a transdermally extracted sample. In one embodiment, the invention includes a sensor element comprising, a sensing electrode that reacts electrochemically with hydrogen peroxide to provide a detectable signal, wherein the sensing electrode comprises a platinum-group metal.

Claims

1. A sensor element comprising,

a sensing electrode that reacts electrochemically with hydrogen peroxide to provide a detectable signal, said sensing electrode comprising a platinum-group metal, a geometric surface area that ranges from about 0.1 to about 3 cm², a background current that ranges from about 2 to about 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity of at least about 6 to about 180 nA/μ

M of hydrogen peroxide when measured in a buffer solution at 0.6V.

2. The sensor element of claim 1, wherein said platinum-group metal is selected from the group consisting of platinum, palladium, rhodium, ruthenium, osmium, and iridium.

3. The sensor element of claim 2, wherein the sensing electrode comprises platinum.

4. The sensor element of claim 3, wherein the sensing electrode comprises platinum and graphite dispersed within a polymer matrix.

5. The sensor element of claim 4, wherein the sensing electrode is configured to provide a geometric surface area of about 0.5 to about 2 cm².

6. The sensor element of claim 5, wherein the sensing electrode is configured to provide a geometric surface area of about 1 cm².

7. The sensor element of claim 4, wherein the sensing electrode comprises about 3% to about 7% by weight of platinum.

8. The sensor element of claim 6, wherein the sensing electrode comprises a background current of about 20 nA when measured in a buffer solution at 0.6V, and a sensitivity of at least about 60 nA/μ

M of hydrogen peroxide when measured in a buffer solution at 0.6V.

9. The sensor element of claim 1, wherein the sensing electrode is printed onto a non-conductive rigid or flexible substrate.

10. The sensor element of claim 1, wherein the sensing electrode exhibits about 10% to about 25% passive hydrogen peroxide degradation.

11. The sensor element of claim 1, wherein the sensing electrode exhibits less than about 20% passive hydrogen peroxide degradation.

12. The sensor element of claim 1, wherein the sensor element further comprises a counter electrode and a reference electrode.

13. The sensor element of claim 12, wherein the counter electrode comprises Ag/AgCl.

14. The sensor element of claim 13, wherein the counter electrode is a bimodal electrode that functions non-simultaneously as the counter electrode and as an iontophoretic electrode.

15. The sensor element of claim 1, further comprising a collection reservoir wherein the sensing electrode is capable of quantifying an amount or concentration of analyte in the collection reservoir.

16. The sensor element of claim 15, wherein the collection reservoir comprises an ionically conductive material.

17. The sensor element of claim 15, wherein the collection reservoir comprises a hydrogel and the hydrogel comprises the ionically conductive material.

18. The sensor element of claim 17, wherein the ionically conductive material comprises one or more enzymes.

19. The sensor element claim 18, wherein at least one of the enzymes comprises glucose oxidase.

20. A method of making the sensor element of claim 1, comprising

formulating a sensing electrode composition, said composition comprising a platinum-group metal and a binder;

and

affixing the sensing electrode composition to a non-conductive surface to provide the sensor element comprising the sensing electrode of claim 1.

21. The method of claim 20, wherein said sensing electrode composition comprises platinum and further comprises graphite.

22. The method of claim 21, further comprising before formulating said sensing electrode composition, (i) said platinum is sputtered onto a graphite powder, or (ii) said platinum is precipitated onto a graphite powder, or (iii) said platinum is adsorbed onto a graphite powder.

23. The method of claim 20, wherein the binder is an electrochemically inert polymer or resin.

24. The method of claim 20, wherein said affixing is accomplished using a thin-film technique.

25. The method of claim 20, wherein said affixing is accomplished using a thick-film technique.

26. The method of claim 20, wherein said affixing is accomplished using a method selected from the group consisting of screen printing, pad printing, inkjet printing, and transfer roll printing.