Biosensor, iontophoretic sampling system, and methods of use thereof

• US 20030135100A1
• Filed: 01/29/2003
• Published: 07/17/2003
• Est. Priority Date: 03/13/1998
• Status: Active Grant

• Current Assignee: LifeScan IP Holdings, LLC
• Original Assignee: Cygnus, Inc. (Johnson & Johnson)
• Inventors: Berner, Bret, Potts, Russell O., Tierney, Michael J., Tamada, Janet, Parris, Norman A., Kim, Lynn
• Granted Patent: US 6,736,777 B2
• Time in Patent Office: Days
• 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

An automated system for continual transdermal extraction of analytes present in a biological system is provided. The system can be used for detecting and/or measuring the concentration of the analyte using an electrochemical biosensor detection means. The system optionally uses reverse iontophoresis to carry out the continual transdermal extraction of the analytes.

Claims

1. A sampling system for monitoring the concentration of an analyte present in a biological system, said sampling system comprising:

(a) a reservoir containing an ionically conductive medium and an enzyme capable of reacting with the analyte to produce hydrogen peroxide;

(b) sampling means for extracting the analyte from the biological system into the reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoir which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means is in operative contact with the reservoir; and

(c) a sensor element in operative contact with the reservoir, wherein said sensor element reacts electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal, and said sensor element comprises an electrode having a geometric surface area which ranges from about 0.1 to 3 cm², a background current which ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity which ranges from about 6 to 180 nA/μ

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

2. The sampling system of claim 1, wherein the sensor element comprises a platinum-group metal-containing electrode.

3. The sampling system of claim 2, wherein the platinum-group metal is platinum.

4. The sampling system of claim 3, wherein the electrode comprises about 3-7% by weight of platinum dispersed in a polymer matrix.

5. The sampling system of claim 1, wherein the sampling means uses reverse iontophoresis to extract the analyte from the biological system.

6. The sampling system of claim 1, wherein the sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

7. The sampling system of claim 1, wherein the sampling means comprises an iontophoretic electrode having a geometric area ranging from about 0.3 to 1.0 cm², and capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm² of electrode area.

8. The sampling system of claim 7, wherein the iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein the sensor element includes a sensing electrode and a reference electrode.

9. The sampling system of claim 1, wherein the sampling means uses sonophoresis to extract the analyte from the biological system.

10. The sampling system of claim 1, wherein the analyte is glucose, and the enzyme is glucose oxidase.

11. The sampling system of claim 1, wherein the ionically conductive medium comprises a hydrogel.

12. The sampling system of claim 1, wherein the electrode has a geometric area of about 1 cm², a background current of about 20 nA, and a sensitivity of about 60 nA/μ

M of hydrogen peroxide.

13. The sampling system of claim 1, wherein the electrode is printed onto a rigid or flexible substrate.

14. The sampling system of claim 1, wherein the electrode exhibits passive hydrogen peroxide depletion in the range of about 25% or less as measured by the methods of Example 2.

15. A sampling system for monitoring the concentration of an analyte present in a biological system, said sampling system comprising:

(a) first and second reservoirs where each reservoir contains an ionically conductive medium and at least one reservoir further contains an enzyme capable of reacting with the analyte to produce hydrogen peroxide;

(b) reverse iontophoretic sampling means for extracting the analyte from the biological system into the reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoir which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means is in operative contact with the reservoir and comprises first and second iontophoretic electrodes in contact with said first and second reservoirs, wherein each iontophoretic electrode has a geometric area ranging from about 0.3 to 1.0 cm², and is capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm² of electrode area; and

(c) first and second sensor elements in operative contact with the first and second reservoirs, wherein said sensor element reacts electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal.

16. The sampling system of claim 15, wherein the iontophoretic electrodes provide for at least 48 anodic/cathodic cycles in a 24 hour period.

17. The sampling system of claim 15, wherein the iontophoretic electrodes comprise silver/silver chloride (Ag/AgCl) dispersed in a polymer binder.

18. The sampling system of claim 17, wherein the iontophoretic electrodes each have a geometric area of about 0.85 cm², and provide a reproducible total charge passage in both anodic and cathodic directions of about 270 mC at a current density of about 0.35 mA/cm².

19. The sampling system of claim 15, wherein the ionically conductive medium comprises a hydrogel.

20. The sampling system of claim 15, wherein the iontophoretic electrodes are printed onto a rigid or flexible substrate using a low temperature screen print.

21. The sampling system of claim 15, wherein each sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

22. The sampling system of claim 15, wherein each iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and each sensor element includes a sensing electrode and a reference electrode.

23. The sampling system of claim 15, wherein the analyte is glucose, and the enzyme is glucose oxidase.

24. A method for monitoring the concentration of an analyte present in a biological system, said method comprising:

(a) extracting said analyte from the biological system into a reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in said reservoir;

(b) contacting the analyte extracted in step (a) with an enzyme that reacts with the analyte to produce hydrogen peroxide;

(c) detecting the hydrogen peroxide produced in step (b) with a sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal, wherein said sensor element comprises an electrode having a geometric surface area which ranges from about 0.1 to 3 cm², a background current which ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity which ranges from about 6 to 180 nA/μ

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

(d) measuring the signal produced in step (c);

(e) correlating the measurement obtained in step (d) with the concentration of the analyte in the biological system; and

(f) performing steps (a)-(d) continually, and step (e) periodically to monitor the concentration of the analyte in the biological system.

25. The method of claim 24, wherein steps (a)-(d) are performed continually, and step (e) is performed periodically, over a period of at least about 12 hours.

26. The method of claim 24, wherein the biological system is a mammalian subject.

27. The method of claim 26, wherein the analyte is transdermally extracted.

28. The method of claim 27, wherein the analyte is extracted using reverse iontophoresis.

29. The method of claim 28, wherein the analyte is extracted using a reverse iontophoresis sampling system comprising first and second iontophoretic electrodes each having a geometric area ranging from about 0.3 to 1.0 cm², and which are capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm² of electrode area.

30. The method of claim 24, wherein steps (a)-(d) are performed continually, and step (e) is performed periodically, over a period of at least about 24 hours.

31. The method of claim 27, wherein the analyte is extracted using sonophoresis.

32. The method of claim 24, wherein the analyte is present in the biological system at a concentration ranging from about 0.1 to 200 millimolar (mM).

33. The method of claim 24, wherein the analyte is glucose, and the enzyme is glucose oxidase.

34. The method of claim 24, wherein the sensor element electrode exhibits reduced passive hydrogen peroxide depletion in the range of about 25% or less as measured by the methods of Example 2.

35. The method of claim 29, wherein the sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

36. The method of claim 29, wherein the iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein the sensor element includes a sensing electrode and a reference electrode.

46. The method of claim 24, wherein said biological system includes skin, and said extracting of analyte from the biological system into a reservoir further comprises enhancement of skin permeability by pricking the skin with micro-needles.

37. A method for monitoring the concentration of an analyte present in a biological system, said method comprising:

(a) contacting a sampling system with the biological system, said sampling system comprising

(i) first and second reservoirs where each reservoir contains an ionically conductive medium and at least the first reservoir further contains an enzyme capable of reacting with the analyte to produce hydrogen peroxide;

(ii) reverse iontophoretic sampling means for extracting the analyte from the biological system into the first reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoir which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means comprises first and second iontophoretic electrodes in operative contact with said first and second reservoirs, wherein each iontophoretic electrode has a geometric area ranging from about 0.3 to 1.0 cm², and is capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm² of electrode area; and

(iii) first and second sensor elements in operative contact with the first and second reservoirs, wherein each sensor element is capable of reacting electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal;

(b) extracting said analyte from the biological system into the first reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the first reservoir, wherein said extracting is carried out using the reverse iontophoretic system;

(c) contacting the analyte extracted in step (b) with an enzyme that reacts with the analyte to produce hydrogen peroxide;

(d) detecting the hydrogen peroxide produced in step (c) with the first sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal;

(e) measuring the signal produced in step (d);

(f) correlating the measurement obtained in step (e) with the concentration of the analyte in the biological system; and

(g) performing steps (b)-(e) continually, and step (f) periodically to monitor the concentration of the analyte in the biological system.

38. The method of claim 37, wherein steps (b)-(e) are performed continually, and step (f) is performed periodically, over a period of at least about 12 hours.

39. The method of claim 37, wherein steps (b)-(e) are performed continually, and step (f) is performed periodically, over a period of at least about 24 hours.

40. The method of claim 39, wherein the iontophoretic electrodes provide for at least 48 anodic/cathodic cycles in a 24 hour period.

41. The method of claim 37, wherein the biological system is a mammalian subject.

42. The method of claim 37, wherein the analyte is present in the biological system at a concentration ranging from about 0.1 to 200 millimolar (mM).

43. The method of claim 37, wherein the analyte is glucose, and the enzyme is glucose oxidase.

44. The method of claim 37, wherein the sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

45. The method of claim 37, wherein each iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein the sensor element includes a sensing electrode and a reference electrode.

47. The method of claim 37, wherein said biological system includes skin, and said extracting of analyte from the biological system into a reservoir further comprises enhancement of skin permeability by pricking with micro-needles.

48. A method for monitoring the concentration of an analyte present in a biological system, said method comprising:

(a) contacting a sampling system with the biological system, said sampling system comprising

(i) first and second reservoirs where each reservoir contains an ionically conductive medium and an enzyme capable of reacting with the analyte to produce hydrogen peroxide;

(ii) reverse iontophoretic sampling means for extracting the analyte from the biological system into the reservoirs to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoirs which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means comprises first and second iontophoretic electrodes in operative contact with said first and second reservoirs, wherein each iontophoretic electrode has a geometric area ranging from about 0.3 to 1.0 cm², and is capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm² of electrode area; and

(iii) first and second sensor elements in operative contact with the first and second reservoirs, wherein each sensor element is capable of reacting electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal;

(b) extracting said analyte from the biological system into the first reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the first reservoir, wherein said extracting is carried out using the reverse iontophoretic system;

(c) contacting the analyte extracted in step (b) with an enzyme that reacts with the analyte to produce hydrogen peroxide;

(d) detecting the hydrogen peroxide produced in step (c) with the first sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal;

(e) measuring the signal produced in step (d);

(f) correlating the measurement obtained in step (e) with the concentration of the analyte in the biological system;

(g) extracting said analyte from the biological system into the second reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the second reservoir, wherein said extracting is carried out using the reverse iontophoretic system;

(h) contacting the analyte extracted in step (g) with an enzyme that reacts with the analyte to produce hydrogen peroxide;

(i) detecting the hydrogen peroxide produced in step (h) with the second sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal;

(j) measuring the signal produced in step (i);

(k) correlating the measurement obtained in step (j) with the concentration of the analyte in the biological system; and

(l) continually performing (i) steps (b)-(e) alternating with (ii) steps (g)-(j), and periodically performing steps (f) and (k) to monitor the concentration of the analyte in the biological system.

49. The method of claim 48, wherein the biological system is a mammalian subject.

50. The method of claim 48, wherein the analyte is present in the biological system at a concentration ranging from about 0.1 to 200 millimolar (mM).

51. The method of claim 48, wherein the analyte is glucose, and the enzyme is glucose oxidase.

52. The method of claim 48, wherein each sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

53. The method of claim 48, wherein each iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein each sensor element includes a sensing electrode and a reference electrode.

54. The method of claim 48, wherein said biological system includes skin, and said extracting of analyte from the biological system into a reservoir further comprises enhancement of skin permeability by pricking the skin with micro-needles.

55. The sampling system of 1, wherein said biological system has a skin surface, and said extracting of analyte from the biological system into a reservoir further comprises enhancement of skin permeability by pricking with micro-needles.

56. The sampling system of 15, wherein said biological system has a skin surface, and said extracting of analyte from the biological system into a reservoir further comprises enhancement of skin permeability by pricking with micro-needles.