Transcutaneous analyte sensor
The present invention relates generally to systems and methods for measuring an analyte in a host. More particularly, the present invention relates to systems and methods for transcutaneous measurement of glucose in a host.
1. A device for measurement of an analyte concentration in a host, the device comprising:
a sensor comprising a first electrode and a second electrode coaxially located with the first electrode, wherein the sensor comprises an in vivo portion configured for insertion into a host and an ex vivo portion configured for electrical connection to sensor electronics located outside of the host, wherein the ex vivo portion comprises a first electrical connection area associated with the first electrode and a second electrical connection area associated with the second electrode;
a membrane system disposed on an electroactive portion of the first electrode; and
a contact subassembly configured to electrically connect the sensor with sensor electronics, wherein a first electrically conductive portion of the contact subassembly circumscribes at least a portion of a periphery of the first electrical connection area, and wherein a second electrically conductive portion of the contact subassembly circumscribes at least a portion of a periphery of the second electrical connection area.
2. The device of claim 1 , wherein the electroactive portion of the first electrode has a surface area of from about 0.000084 cm 2 to about 0.016 cm 2 .
3. The device of claim 1 , wherein the first and second electrodes each comprise working electrodes.
4. The device of claim 1 , wherein the second electrode is juxtapositioned to the first electrode.
5. The device of claim 1 , wherein the first electrode is configured to generate a first signal associated with analyte and non-analyte related measurements, and wherein the second electrode is configured to generate a second signal associated with non-analyte related measurements, wherein non-analyte related measurements comprise a baseline measurement or an interfering species measurement.
6. The device of claim 5 , wherein the sensor electronics are configured to subtract the second signal from the first signal.
7. The device of claim 5 , wherein the membrane system comprises an interference domain configured to restrict flow of one or more interfering species.
8. The device of claim 1 , wherein the first electrode is formed from a wire of less than about 0.01 inches in diameter.
9. The device of claim 1 , wherein the electroactive portion of the second electrode is distributed along a length of the first electrode.
10. The device of claim 1 , wherein a sizing of the first electrode, a resistivity of the membrane system to glucose, and a configuration of the sensor electronics are configured and arranged such that the system generates less than about 100 picoAmps of current per 1 mg/dL of glucose concentration.
11. The device of claim 1 , wherein the first electrode comprises a core of a first metal and an outer layer of a second metal, wherein the outer layer is electroplated on the core.
12. The device of claim 1 , wherein the first electrode is formed from a plated wire.
13. The device of claim 1 , wherein the first electrode comprises a core of a first metal and an outer layer of a second metal, wherein the first metal comprises stainless steel and the second metal comprises platinum.
14. The device of claim 1 , wherein at least a portion of the sensor is configured for insertion through a dermis of a host, and wherein the sensor comprises a level of flexibility sufficient to provide for flexing of the sensor with movements of host tissue during use.
15. The device of claim 14 , wherein the sensor is configured for insertion within a needle through the dermis.
16. The device of claim 1 , wherein the first electrode comprises a core of a first metal and an outer layer of a second metal, wherein the outer layer is thin relative to the core.
17. The device of claim 1 , wherein the first electrode comprises a core of a first metal and an outer layer of a second metal, wherein the outer layer comprises a monolithic coating circumscribing a length of the core.
18. The device of claim 1 , wherein at least a portion of the contact subassembly is configured to comply upon application of pressure.
19. The device of claim 1 , wherein the contact subassembly comprises one or more of a domed metallic contact, a metallic spring, a conductive elastomer, a cantilevered finger, a pogo pin, or a stiff plastic.
20. The device of claim 1 , wherein at least a portion of the contact subassembly is configured to provide a wiping action between the contact subassembly and mating contacts of the sensor electronics during electrical connection between the contact subassembly and the sensor electronics.
21. The device of claim 1 , wherein at least a portion of the contact subassembly is configured to apply a force against mating contacts of the sensor electronics during electrical connection between the contact subassembly and the sensor electronics.
22. The device of claim 1 , wherein at least a portion of the membrane system comprises an enzyme, and wherein the device further comprises a material comprising a fluorochemical or a silicone, wherein the material is configured to enhance oxygen transport to the enzyme.
23. The device of claim 22 , wherein the material is configured to extend from the ex vivo portion to the in vivo portion.
24. The device of claim 22 , wherein the membrane system comprises the material.
25. The device of claim 22 or 24 , wherein the material comprises a fluorocarbon.
26. The device of claim 1 , wherein the first electrode comprises the working electrode, and wherein the second electrode comprises a reference electrode or counter electrode.
27. The device of claim 1 , wherein the first electrode comprises a core of a first metal and an outer layer of a second metal, wherein the first electrode comprises a core formed of a first metal and an outer layer formed of a second metal.
28. The device of claim 1 , wherein the first electrical connection area is longitudinally spaced relative to the second electrical connection area along a longitudinal axis of the sensor.
29. The device of claim 1 , further comprising an insulator disposed between the first electrode and the second electrode.
30. A sensor for measurement of a glucose concentration in a host, the sensor comprising:
a first wire comprising a metallic rod coated with an insulating material;
first and second electrodes located on an outer surface of the insulating material; and
a membrane system disposed on an electroactive portion of the first electrode, wherein the membrane system comprises a permeability ratio of oxygen-to-glucose of at least about 50:1, wherein the electroactive portion of the first electrode has a surface area of from about 0.000084 cm 2 to about 0.016 cm 2 , and wherein the sensor is configured to generate less than about 100 picoAmps of current per 1 mg/dL of glucose concentration.
31. The sensor of claim 30 , wherein the membrane system comprises a permeability ratio of oxygen-to-glucose of at least about 200:1.
32. The sensor of claim 30 , wherein the insulated rod has a diameter of less than about 0.001 inches.
33. The sensor of claim 30 , wherein the first electrode is deposited on the first wire.