Biosensor and methods of use thereof

1. A sensor element comprising

a sensing electrode that reacts electrochemically with hydrogen peroxide to provide a detectable signal, the sensing electrode comprising

platinum, graphite, a polymer matrix, and a geometric surface area that ranges from about 0.1 in about 3 cm 2 , wherein the electrode is affixed to a non-conductive surface, has a background current that ranges from about 2 to about 60 nA or less when measured in a buffer solution at an applied potential of 0.6V, and has a sensitivity of at least about 6 to about 180 nA/μM of hydrogen peroxide when measured in a buffer solution at an applied potential of 0.6V.

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

3. The sensor element of claim 1 , wherein the non-conductive surface is a rigid or flexible substrate.

4. The sensor element of claim 1 , wherein, for the sensing electrode, the platinum and graphite are dispersed within a polymer matrix.

5. The sensor element of claim 1 , wherein the sensing electrode has a surface area of about 0.5 to about 2 cm 2 .

6. The sensor element of claim 1 , wherein the sensing electrode has a surface area of about 1 cm 2 .

7. The sensor element of claim 6 , wherein the sensing electrode has a background current of about 20 nA or less, and a sensitivity of at least about 60 nA/μM of hydrogen peroxide.

8. The sensor element of claim 1 , wherein the sensing electrode has a surface area of about 0.1 cm 2 .

9. The sensor element of claim 8 , wherein the sensing electrode has a background current of about 2 nA or less and sensitivity of at least about 6 nA/μM of hydrogen peroxide.

10. The sensor element of claim 1 , wherein the sensing electrode has a surface area about 3 cm 2 , a background current of about 60 nA or less, and sensitivity of at least about 180 nA/μM of hydrogen peroxide.

11. The sensor element of claim 1 , wherein the polymer matrix is an electrochemically inert binder.

12. The sensor element of claim 11 , wherein the binder comprises a polymer or resin binder.

13. The sensor element of claim 12 , wherein the binder is a polymer comprising a polymer selected from the group consisting of vinyl, acrylic, epoxy, phenoxy, and polyester polymers.

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

contacting the analyte with an enzyme that reacts with the analyte to produce hydrogen peroxide;

detecting the hydrogen peroxide with a sensor element comprising a sensing electrode that reacts electrochemically with hydrogen peroxide to produce a detectable signal, the sensing electrode comprising platinum, graphite, a polymer matrix, and a geometric surface area that ranges from about 0.1 to about 3 cm 2 , wherein the electrode is affixed to a non-conductive surface, has a background current that ranges from about 2 to about 60 nA or less when measured in a buffer solution at an applied potential of 0.6V, and has a sensitivity of at least about 6 to about 180 nA/μM of hydrogen peroxide when measured in a buffer solution at an applied potential of 0.6V; and

measuring the detectable signal, wherein the detectable signal is related to analyte amount or concentration in the biological system.

15. The method of claim 14 , wherein the biological system is a mammalian subject.

16. The method of claim 15 , wherein the analyte is extracted across a skin or mucosal surface.

17. The method of claim 14 , wherein the analyte is glucose and the enzyme comprises glucose oxidase.

18. The method of claim 14 , wherein the sensor element further comprises a counter electrode and a reference electrode.

19. The method of claim 14 , further comprising correlating the measured detectable signal with an amount or concentration of analyte in the biological system.

20. The method of claim 14 , wherein the analyte is provided using a sampling technique comprising a sampling technique selected from the group consisting of iontophoresis, sonophoresis, suction, electroporation, thermal poration, passive diffusion, microfine lances, microfine cannulas, and laser.

21. The method of claim 14 , wherein the sensing electrode is in operative contact with a collection reservoir.

22. The method of claim 21 , wherein the collection reservoir comprises the enzyme.

23. The method of claim 22 , wherein the collection reservoir comprises a hydrogel.

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

a sensing device comprising (i) a collection reservoir comprising an enzyme capable of reacting with the analyte to produce hydrogen peroxide, and (ii) 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 cm 2 , 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/μM of hydrogen peroxide when measured in a buffer solution at 0.6V;

one or more microprocessors in operative communication with the sensing device comprising programming to control operation of the sensing device; and

a sampling device comprising microneedles, microfine lances, or microfine cannulas.

25. The sampling system of claim 24 , wherein the sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

26. The sampling system of claim 24 , wherein the sampling system also employs a sampling technique selected from the group consisting of sonophoresis, iontophoresis, suction, electroporation, thermal poration, passive diffusion, and laser poration.

27. The sampling system of claim 24 , wherein the analyte is glucose, and the enzyme comprises glucose oxidase.

28. The sampling system of claim 24 , wherein the electrode is printed onto a rigid or flexible substrate.

29. The sampling system of claim 24 , wherein the collection reservoir further comprises a reservoir selected from the group consisting of a hydrogel, tube, vial, capillary collection device, cannula, and miniaturized flow paths.

30. The sampling system of claim 29 , wherein said reservoir comprises a miniaturized etched, ablated or molded flow path.

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

a sensing device comprising

(i) a collection reservoir comprising an enzyme capable of reacting with the analyte to produce hydrogen peroxide, and

(ii) 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, the sensing electrode comprising a platinum-group metal, graphite, a polymer matrix, and a geometric surface area that ranges from about 0.1 to about 3 cm 2 , wherein the electrode has a background current that ranges from about 2 to about 60 nA or less when measured in a buffer solution at an applied potential of 0.6V, and has a sensitivity of at least about 6 to about 180 nA/μM of hydrogen peroxide when measured in a buffer solution at an applied potential of 0.6V;

one or more microprocessors in operative communication with the sensing device comprising programming to control operation of the sensing device; and

a sampling device comprising microneedles, microfine lances, or microfine cannulas.

32. The sampling system of claim 31 , wherein the sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

33. The sampling system of claim 31 , wherein the sampling system also employs a sampling technique selected from the group consisting of sonophoresis, iontophoresis, suction, electroporation, thermal poration, passive diffusion, and laser poration.

34. The sampling system of claim 31 , wherein the analyte is glucose, and the enzyme comprises glucose oxidase.

35. The sampling system of claim 31 , wherein the electrode is printed onto a rigid or flexible substrate.

36. The sampling system of claim 31 , wherein the collection reservoir further comnrises a reservoir selected from the group consisting of a hydrogel, tube, vial, capillary collection device, cannula, and miniaturized flow paths.

37. The sampling system of 36 , wherein said reservoir comprises a mnuaturized etched, ablated or molded flow path.

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

a sensing device comprising

(i) a collection reservoir comprising an enzyme capable of reacting with the analyte to produce hydrogen peroxide, and

(ii) 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, the sensing electrode comprising platinum, graphite, a polymer matrix, and a geometric surface area that ranges from about 0.1 to about 3 cm 2 , wherein the electrode has a background current that ranges from about 2 to about 60 nA or less when measured in a buffer solution at an applied potential of 0.6V, and has a sensitivity of at least about 6 to about 180 nA/μM of hydrogen peroxide when measured in a buffer solution at an applied potential of 0.6V;

one or more microprocessors in operative communication with the sensing device comprising programming to control operation of the sensing device; and

a sampling device comprising microneedles, microfine lances, or microfine cannulas.

39. The sampling system of claim 38 , wherein the sensor element includes a sensing electrode, a counter electrode, and a reference electrode.

40. The sampling system of claim 38 , wherein the sampling system also employs a sampling technique selected from the group consisting of sonophoresis, iontophoresis, suction, electroporation, thermal poration, passive diffusion, and laser poration.

41. The sampling system of claim 38 , wherein the analyte is glucose, and the enzyme comprises glucose oxidase.

42. The sampling system of claim 38 , wherein the electrode is printed onto a rigid or flexible substrate.

43. The sampling system of claim 38 , wherein the collection reservoir further comprises a reservoir selected from the group consisting of a hydrogel, tube, vial, capillary collection device, cannula, and miniaturized flow paths.

44. The sampling system of claim 43 , wherein said reservoir comprises a miniaturized etched, ablated or molded flow path.