Biosensor, iontophoretic sampling system, and methods of use thereof

• US 6,587,705 B1
• Filed: 03/10/1999
• Issued: 07/01/2003
• Est. Priority Date: 03/13/1998
• Status: Expired due to Term

• 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
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/267,750
• Time in Patent Office: 1,574 Days
• Field of Search: 600/347, 600/365, 600/345, 600/346, 600/398, 600/350, 435/14, 435/808, 435/281--28, 435/286.6, 435/25, 436/8, 436/17, 436/149, 436/150-151, 702/19, 702/22, 702/23, 73/10.1, 73/10.2, 482/6.1, 482/68.1, 482/63, 482/67, 482/82.01, 482/82.03, 204/400, 204/403
• US Class Current: 600/347
• 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 or amount of an analyte present in a biological system, said sampling system comprising:

(a) a collection reservoir comprising 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 collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the collection reservoir, wherein said sampling means is in operative contact with the collection reservoir; and

(c) a sensor element in operative contact with the collection reservoir, said sensor element comprising an electrode, wherein said electrode reacts electrochemically with the hydrogen peroxide produced in the collection reservoir to provide a detectable signal, said electrode comprising a geometric surface area that ranges from about 0.1 to 3 cm², a background current that ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity that 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 comprises first and second collection reservoirs, wherein each collection reservoir comprises an ionically conductive medium and at least one collection reservoir further comprises an enzyme capable of reacting with the analyte to produce hydrogen peroxide and said sampling means uses reverse iontophoresis to extract the analyte from the biological system.

6. The sampling system of claim 5, wherein the sampling means comprises an iontophoretic electrode comprising 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 1, wherein the sensor element comprises a sensing electrode, a counter electrode, and a reference electrode.

9. The sampling system of claim 1, wherein the sampling means to extract the analyte from the biological system is selected from the group consisting of sonophoresis, suction, electroporation, thermal poration, passive diffusion, microfine lances, microfine cannulas, subcutaneous implants, subcutaneous insertions, microdialysis, and laser.

10. The sampling system of claim 9, wherein the sampling means to extract the analyte from the biological system is selected from the group consisting of sonophoresis, suction, electroporation, thermal poration, passive diffusion, subcutaneous implants, subcutaneous insertions, microdialysis, and laser.

11. The sampling system of claim 10, wherein (i) said biological system comprises a skin surface, and (ii) said sampling system further comprises a skin permeability enhancer, said skin permeability enhancer comprising micro-needles.

12. The sampling system of claim 1, wherein the analyte comprises glucose, and the enzyme comprises glucose oxidase.

13. The sampling system of claim 1, wherein said collection reservoir further comprises an ionically conductive medium.

14. The sampling system of claim 13, wherein the ionically conductive medium comprises a hydrogel comprising said enzyme capable of reacting with the analyte to produce hydrogen peroxide.

15. The sampling system of claim 1, wherein the electrode comprises 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.

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

17. The sampling system of claim 1, wherein the electrode exhibits passive hydrogen peroxide depletion in the range of about 25%.

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

7. 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 comprises a sensing electrode and a reference electrode.

18. The sampling system of 1, wherein (i) said biological system comprises a skin surface, and (ii) said sampling system further comprises a skin permeability enhancer, said skin permeability enhancer comprising micro-needles.

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

(a) first and second collection reservoirs, wherein each collection reservoir comprises an ionically conductive medium and at least one collection reservoir further comprises 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 collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the collection reservoir, wherein said sampling means is in operative contact with the collection reservoir and comprises first and second iontophoretic electrodes in contact with said first and second collection reservoirs, wherein each iontophoretic electrode comprises 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 collection reservoirs, wherein each sensor element comprises an electrode that reacts electrochemically with the hydrogen peroxide produced in the collection reservoir to provide a detectable signal, each electrode comprising a geometric surface area that ranges from about 0.1 to 3 cm² , a background current that ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity that ranges from about 6 to 180 nA/μ

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

21. The sampling system of claim 20, wherein the iontophoretic electrodes provide for at least 48 anodic/cathodic cycles in a 24 hour period.

22. The sampling system of claim 20, wherein the iontophoretic electrodes comprise silver/silver chloride (Ag/AgCl) dispersed in a polymer binder.

23. The sampling system of claim 22, 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.

24. The sampling system of claim 20, wherein the ionically conductive medium comprises a hydrogel.

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

26. The sampling system of claim 20, wherein each sensor element comprises a sensing electrode, a counter electrode, and a reference electrode.

27. The sampling system of claim 20, herein each iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and each sensor element comprises a sensing electrode and a reference electrode.

28. The sampling system of claim 20, wherein the analyte comprises glucose, and the enzyme comprises glucose oxidase.

29. The sampling system of 20, wherein (i) said biological system comprises a skin surface, and (ii) said sampling system further comprises a skin permeability enhancer, said skin permeability enhancer comprising micro-needles.

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

(a) extracting said analyte from the biological system into a collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in said collection 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 comprising an electrode that reacts electrochemically with the hydrogen peroxide to produce a detectable signal, said electrode comprising a geometric surface area that ranges from about 0.1 to 3 cm², a background current that ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity that 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 or amount of the analyte in the biological system; and

(f) performing repeated cycles of steps (a)-(e) over a time period to monitor the concentration or amount of the analyte in the biological system.

31. The method of claim 30, wherein said time period is at least about 12 hours.

32. The method of claim 30, wherein the biological system is a mammalian subject.

33. The method of claim 32, wherein said extracting of the analyte comprises extracting the analyte by transdermal extraction.

34. The method of claim 33, wherein said extracting of the analyte comprises use of a sampling means comprising first and second collection reservoirs, wherein each collection reservoir comprises an ionically conductive medium and at least said first collection reservoir further comprises an enzyme capable of reacting with the analyte to produce hydrogen peroxide and said sampling means uses reverse iontophoresis to extract the analyte from the biological system.

35. The method of claim 34, wherein said extracting of the analyte comprises using a reverse iontophoresis sampling system comprising first and second iontophoretic electrodes each comprising a geometric area ranging from about 0.3 to 1.0 cm², and that are capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm² of electrode area.

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

37. The method of claim 35, wherein at least said first iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein the sensor element comprises a sensing electrode and a reference electrode.

38. The method of claim 33, wherein said extracting of the analyte comprises using a sampling means selected from the group consisting of sonophoresis, suction, electroporation, thermal poration, passive diffusion, microfine lances, microfine cannulas, subcutaneous implants, subcutaneous insertions, microdialysis, and laser.

39. The method of claim 33, wherein said extracting of the analyte comprises sonophoresis.

40. The method of claim 33, wherein said extracting of the analyte comprises using a sampling means selected m the group consisting of sonophoresis, suction, electroporation, thermal poration, passive diffusion, subcutaneous implants, subcutaneous insertions, microdialysis, and laser.

41. The method of claim 40, wherein said biological system comprises a skin surface and said extracting of analyte from the biological system into a collection reservoir further comprises enhancement of skin permeability.

42. The method of claim 30, wherein said time period is at least about 24 hours.

43. The method of claim 30, wherein the analyte is present in the biological system at a concentration or amount ranging from about 0.1 to 200 millimolar (mM).

44. The method of claim 30, wherein the analyte comprises glucose, and the enzyme comprises glucose oxidase.

45. The method of claim 30, wherein the sensor element electrode exhibits reduced passive hydrogen peroxide depletion in the range of about 25% or less.

46. The method of claim 30, wherein said biological system comprises skin, and said extracting of analyte from the biological system into a collection reservoir further comprises enhancement of skin permeability by pricking the skin with micro-needles.

47. A method for monitoring the concentration or amount 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 collection reservoirs, wherein each collection reservoir comprises an ionically conductive medium and at least the first collection reservoir further comprises 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 collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the collection reservoir, wherein said sampling means comprises first and second iontophoretic electrodes in operative contact with said first and second collection reservoirs, wherein each iontophoretic electrode comprises 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 collection reservoirs, wherein each sensor element comprises an electrode capable of reacting electrochemically with the hydrogen peroxide produced in the collection reservoir to provide a detectable signal, each electrode comprising a geometric surface area that ranges from about 0.1 to 3 cm², a background current that ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity that ranges from about 6 to 180 nA/μ

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

(b) extracting said analyte from the biological system into the first collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the first collection 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 that 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 or amount of the analyte in the biological system; and

(g) performing repeated cycles of steps (b)-(f) over a time period to monitor the concentration or amount of the analyte in the biological system.

48. The method of claim 47, wherein said time period is at least about 12 hours.

49. The method of claim 47, wherein said time period is at least about 24 hours.

50. The method of claim 49, wherein the iontophoretic electrodes provide for at least 48 anodic/cathodic cycles in a 24 hour period.

51. The method of claim 47, wherein the biological system is a mammalian subject.

52. The method of claim 47, wherein the analyte is present in the biological system at a concentration or amount ranging from about 0.1 to 200 millimolar (mM).

53. The method of claim 47, wherein the analyte comprises glucose, and the enzyme comprises glucose oxidase.

54. The method of claim 47, wherein at least said first sensor element comprises a sensing electrode, a counter electrode, and a reference electrode.

55. The method of claim 47, wherein each iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein each sensor element comprises a sensing electrode and a reference electrode.

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

57. A method for monitoring the concentration or amount 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 collection reservoirs, wherein each collection reservoir comprises 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 collection reservoirs to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the collection reservoirs, wherein said sampling means comprises first and second iontophoretic electrodes in operative contact with said first and second collection reservoirs, wherein each iontophoretic electrode comprises 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 collection reservoirs, wherein each sensor element comprises an electrode capable of reacting electrochemically with the hydrogen peroxide produced in the collection reservoir to provide a detectable signal, each electrode comprising a geometric surface area that ranges from about 0.1 to 3 cm², a background current that ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity that ranges from about 6 to 180 nA/μ

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

(b) extracting said analyte from the biological system into the first collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the first collection 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 that 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 or amount of the analyte in the biological system;

(g) extracting said analyte from the biological system into the second collection reservoir to obtain a sub-millimolar (sub-mM) concentration or amount of the analyte in the second collection 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 that 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 or amount of the analyte in the biological system; and

(l) performing repeated cycles of (i) steps (b)-(e) alternating with (ii) steps (g)-(j) over a time period, and periodically performing steps (f) and (k) over the time period to monitor the concentration or amount of the analyte in the biological system.

58. The method of claim 57, wherein the biological system is a mammalian subject.

59. The method of claim 57, wherein the analyte is present in the biological system at a concentration or amount ranging from about 0.1 to 200 millimolar (mM).

60. The method of claim 57, wherein the analyte comprises glucose, and the enzyme comprises glucose oxidase.

61. The method of claim 57, wherein each sensor element comprises a sensing electrode, a counter electrode, and a reference electrode.

62. The method of claim 57, wherein each iontophoretic electrode is a bimodal electrode that is also able to act as a counter electrode, and wherein each sensor element comprises a sensing electrode and a reference electrode.

63. The method of claim 57, wherein said biological system comprises skin, and said extracting of analyte from the biological system into a collection reservoir further comprises enhancement of skin permeability by pricking the skin with micro-needles.