Optimized sensor geometry for an implantable glucose sensor

• US 20040199059A1
• Filed: 08/22/2003
• Published: 10/07/2004
• Est. Priority Date: 04/04/2003
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Brauker, James H., Carr-Brendel, Victoria, Martinson, Laura A., Neale, Paul V.
• Granted Patent: US 7,134,999 B2
• Time in Patent Office: Days
• US Class Current: 600/309
• CPC Class Codes: A61B 2562/187 Strain relief means
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/415 the glands, e.g. tonsils, adenoids or thymus
• CPC Class Codes: A61B 5/418 lymph vessels, ducts or nodes
• CPC Class Codes: A61B 5/6882 Anchoring means

Abstract

An implantable sensor for use in measuring a concentration of an analyte such as glucose in a bodily fluid, including a body with a sensing region adapted for transport of analytes between the sensor and the bodily fluid, wherein the sensing region is located on a curved portion of the body such that when a foreign body capsule forms around the sensor, a contractile force is exerted by the foreign body capsule toward the sensing region. The body is partially or entirely curved, partially or entirely covered with an anchoring material for supporting tissue ingrowth, and designed for subcutaneous tissue implantation. The geometric design, including curvature, shape, and other factors minimize chronic inflammatory response at the sensing region and contribute to improved performance of the sensor in vivo.

Claims

1. An implantable sensor for use in measuring a concentration of an analyte in a bodily fluid, the sensor comprising:

a body comprising a sensing region adapted for transport of analytes between the sensor and the bodily fluid, wherein the sensing region is located on a curved portion of the body such that when a foreign body capsule forms around the sensor, a contractile force is exerted by the foreign body capsule toward the sensing region.

2. The sensor of claim 1, wherein the sensor is a subcutaneous sensor.

3. The sensor of claim 1, wherein the sensor is an intramuscular sensor.

4. The sensor of claim 1, wherein the sensor is an intraperitoneal sensor.

5. The sensor of claim 1, wherein the sensor is an intrafascial sensor.

6. The sensor of claim 1, wherein the sensor is suitable for implantation in an axillary region.

7. The sensor of claim 1, wherein the sensor is suitable for implantation in a soft tissue of a body.

8. The sensor of claim 1, wherein the sensor is suitable for implantation at the interface between two tissue types.

9. The sensor of claim 1, wherein the sensor comprises a plurality of sensor regions.

10. The sensor of claim 9, wherein the plurality of sensor regions are located on curved portions of the body.

11. The sensor of claim 1, wherein the body comprises a first major surface and a second major surface, and wherein the sensing region is located on said first surface, and wherein said second surface is flat.

12. The sensor of claim 1, wherein the body comprises a first major surface and a second major surface, and wherein the sensing region is located on said first major surface, and wherein said second major surface comprises a curvature.

13. The sensor of claim 1, wherein the body comprises a first major surface and a second major surface, and wherein the sensor region is situated at a position on said first major surface offset from a center point of said first major surface.

14. The sensor of claim 1, wherein the body comprises a first major surface and a second major surface, and wherein the sensor region is situated on said first major surface approximately at a center point of said first major surface.

15. The sensor of claim 1, wherein the body comprises a first surface and a second surface, and wherein the sensor region is situated approximately at an apex of said first surface.

16. The sensor of claim 1, wherein the body comprises a first surface and a second surface, and wherein said first surface, when viewed from a direction perpendicular to a center of said first surface, has a substantially rectangular profile.

17. The sensor of claim 1, wherein the body comprises a first surface and a second surface, and wherein said first surface, when viewed from a direction perpendicular to a center of said first surface, has a substantially rectangular profile with rounded corners.

18. The sensor of claim 1, wherein the body comprises a first surface and a second surface, and wherein said first surface, when viewed from a direction perpendicular to a center of said first surface, has a substantially oval profile.

19. The sensor of claim 1, wherein the body comprises a first surface and a second surface, and wherein said first surface, when viewed from a direction perpendicular to a center of said first surface, has a substantially circular profile.

20. The sensor of claim 1, wherein the body is substantially cuboidal defined by six faces, eight vertices, and twelve edges, wherein at least one of said faces comprises the sensing region.

21. The sensor of claim 20, wherein at least two of said faces are substantially curved.

22. The sensor of claim 20, wherein at least four of said faces are substantially curved.

23. The sensor of claim 20, wherein all six of said faces are substantially curved.

24. The sensor of claim 20, wherein said edges are substantially rounded.

25. The sensor of claim 24, wherein said vertices are substantially rounded.

26. The sensor of claim 20, wherein the entire body is curved.

27. The sensor of claim 1, wherein the body is substantially cylindrical defined by a curved lateral surface and two ends, and wherein the sensor region is located on said lateral surface.

28. The sensor of claim 1, wherein the body is substantially cylindrical defined by a curved lateral surface and two ends, and wherein at least one of said ends comprises the substantially curved portion on which the sensor region is located.

29. The sensor of claim 1, wherein the body is substantially spherical.

30. The sensor of claim 1, wherein the body is substantially ellipsoidal.

31. The sensor of claim 1, wherein the body comprises a first surface on which the sensing region is located and a second surface, and wherein said first surface comprises anchoring material thereon for supporting tissue ingrowth.

32. The sensor of claim 31, wherein said second surface is located opposite said first surface, and wherein said second surface comprises anchoring material thereon for supporting tissue ingrowth.

33. The sensor of claim 1, wherein said second surface is located opposite said first surface, and wherein said second surface is substantially smooth and comprises a biocompatible material that is non-adhesive to tissues.

34. The sensor of claim 33, said second surface is curved.

35. The sensor of claim 1, further comprising a mechanical anchoring mechanism formed on the body.

36. The sensor of claim 1, wherein said curved portion comprises a plurality of radii of curvature.

37. The sensor of claim 1, wherein said curved portion comprises a radius of curvature between about 0.5 mm and about 10 cm.

38. The sensor of claim 1, wherein said curved portion comprises a radius of curvature between about 1 cm and about 5 cm.

39. The sensor of claim 1, wherein said curved portion comprises a radius of curvature between about 2 cm and about 3 cm.

40. The sensor of claim 1, wherein said curved portion comprises a radius of curvature between about 2.5 cm and about 2.8 cm.

41. The sensor of claim 1, wherein the sensor comprises a major surface and wherein said curved portion is located on at least a portion of the major surface.

42. The sensor of claim 41, wherein the body further includes a flat portion adjacent said curved portion.

43. The sensor of claim 42, wherein an interface between the flat portion and the curved portion comprises a gradual transition.

44. The sensor of claim 1, wherein the body comprises a first major surface on which said sensing region is located and a second major surface, and wherein the first and second major surfaces together account for at least about 40% of the surface area of the device.

45. The sensor of claim 44, wherein the first and second major surfaces together account for at least about 50% of the surface area of the device.

46. The sensor of claim 1, wherein the body comprises a first major surface on which said sensing region is located and a second major surface, wherein the first major surface has edges between which a width of the first major surface can be measured, and wherein the sensing region is spaced away from the edges by a distance that is at least about 10% of the width of the first major surface.

48. The sensor of claim 46, wherein the sensing region is spaced away from the edges by a distance that is at least about 20% of the width of the first major surface.

49. The sensor of claim 46, wherein the sensing region is spaced away from the edges by a distance that is at least about 25% of the width of the first major surface.

50. The sensor of claim 46, wherein the sensing region is spaced away from the edges by a distance that is at least about 30% of the width of the first major surface.

51. The sensor of claim 46, wherein the spacing of the sensing region from the edges is true for at least two width measurements, which measurements are taken generally transverse to each other.

52. The sensor of claim 41, wherein the body comprises a first major surface on which said sensing region is located and a second major surface, wherein the first major surface is at least slightly convex.

53. The sensor of claim 52, wherein a reference plane may be defined that touches the first major surface at a point spaced in from edges of the first major surface, and is generally parallel to the first major surface, and is spaced away from opposite edges of the first major surface due to convexity of the first major surface, and wherein a location of an edge is the point at which a congruent line or a normal line is angled 45 degrees with respect to the reference plane.

54. The sensor of claim 53, wherein the reference plane is spaced from the edges a distance that is at least about 3% from the edges, and not more than 50% of the width.

55. The sensor of claim 53, wherein the reference plane is spaced from the edges a distance that is at least about 3% from the edges, and not more than 25% of the width.

56. The sensor of claim 53, wherein the reference plane is spaced from the edges a distance that is at least about 3% from the edges, and not more than 15% of the width.

57. The sensor of claim 1, wherein the body comprises a first major surface on which said sensing region is located, and wherein edges of the first major surface are rounded and transition smoothly away from the first major surface.

58. The sensor of claim 1, wherein the body defines a surface area, and wherein between 10% and 100% of the surface area is convexly curved.

59. The sensor of claim 1, wherein the body defines a surface area, and wherein a substantial portion of the surface area is convexly curved.

60. The sensor of claim 1, wherein the body defines a surface area, and where at least about 90% of the surface area is convexly curved.

61. The sensor of claim 1, wherein the body comprises plastic.

62. The sensor of claim 61, wherein the plastic is selected from the group consisting of thermoplastic and thermoset.

63. The sensor of claim 61, wherein the thermoset is epoxy.

64. The sensor of claim 61, wherein the thermoset is silicone.

65. The sensor of claim 61, wherein the thermoset is polyurethane.

66. The sensor of claim 61, wherein the plastic is selected from the group consisting of metal, ceramic, and glass.

67. The sensor of claim 1, further comprising a porous biointerface material that covers at least a portion of the sensing region.

68. The sensor of claim 67, wherein the biointerface material comprises interconnected cavities dimensioned and arranged to create contractile forces that counteract with the generally uniform downward fibrous tissue contracture caused by the foreign body capsule in vivo and thereby interfere with formation of occlusive cells.

69. The sensor of claim 67, wherein the sensor is a glucose sensor.

47. The sensor of 46, wherein the sensing region is spaced away from the edges by a distance that is at least about 15% of the width of the first major surface.

70. An implantable sensor for use in measuring a concentration of an analyte in a bodily fluid, the sensor comprising:

a body comprising a sensing region on a major surface of said body, wherein said major surface comprises a continuous curvature substantially across the entire surface such that when a foreign body capsule forms around the sensor, a contractile force is exerted by the foreign body capsule toward the sensing region.

71. A wholly implantable sensor adapted to measure a concentration of an analyte in a bodily fluid, comprising:

a wholly implantable body comprising a sensing region adapted for transport of analytes between the sensor and the bodily fluid, wherein the sensing region is located on a curved portion of a first surface of said body and wherein said first surface comprises anchoring material thereon for supporting tissue ingrowth.

72. An implantable sensor adapted to measure a concentration of an analyte in a bodily fluid, comprising:

a body having a first major surface and, opposite thereto, a second major surface, wherein the first major surface is generally planar, slightly convex, and has rounded edges, with a sensor region located on the first major surface that is spaced away from the rounded edges, wherein the first major surface is sufficiently convex that when a foreign body capsule forms around the sensor, contractile forces are exerted thereby generally uniformly towards the sensing region.

73. An implantable sensor for use in measuring a concentration of an analyte in a bodily fluid, the sensor comprising:

a body, the body comprising a sensing region adapted for transport of analytes between the sensor and the bodily fluid, wherein the sensing region is located on a curved portion of the body, and wherein a thermoset material substantially encapsulates the body outside the sensing region.

74. An implantable sensor for use in measuring a concentration of an analyte in a bodily fluid, the sensor comprising:

sensing means for measuring a concentration of analyte in a bodily fluid; and

housing means for supporting said sensing means,

wherein said sensing means is located on a curved portion of housing means such that when a foreign body capsule forms around the housing means, a contractile force is exerted by the foreign body capsule toward the sensing means.

75. An implantable drug delivery device that allows transport of analytes between the device and a bodily fluid, the device comprising:

a body comprising an analyte transport region adapted for transport of analytes between the device and the bodily fluid, wherein the transport region is located on a curved portion of the body such that when a foreign body capsule forms around the device, a contractile force is exerted by the foreign body capsule toward the analyte transport region.

76. An implantable cell transplantation device that allows transport of analytes between the device and a bodily fluid, the device comprising:

a body comprising an analyte transport region adapted for transport of analytes between the device and the bodily fluid, wherein the transport region is located on a curved portion of the body such that when a foreign body capsule forms around the device, a contractile force is exerted by the foreign body capsule toward the analyte transport region.