Subcutaneous glucose electrode
A small diameter flexible electrode designed for subcutaneous in vivo amperometric monitoring of glucose is described. The electrode is designed to allow “one-point” in vivo calibration, i.e., to have zero output current at zero glucose concentration, even in the presence of other electroreactive species of serum or blood. The electrode is preferably three or four-layered, with the layers serially deposited within a recess upon the tip of a polyamide insulated gold wire. A first glucose concentration-to-current transducing layer is overcoated with an electrically insulating and glucose flux limiting layer (second layer) on which, optionally, an immobilized interference-eliminating horseradish peroxidase based film is deposited (third layer). An outer (fourth) layer is biocompatible.
1. An electrochemical biosensor having a layered structure, comprising:
a supporting layer having at least one surface;
an electrode in contact with the at least one surface of the supporting layer, the electrode including carbon;
a sensing layer comprising an analyte-responsive enzyme;
a biocompatible layer disposed over the sensing layer of the electrode; and
an interferant eliminating layer comprising a redox enzyme;
wherein at least a portion of the sensing layer and the biocompatible layer allow diffusion of an analyte therethrough;
wherein the electrode is connectable with a device; and further
wherein the electrode is a working electrode, the working electrode comprises the analyte-responsive enzyme and a mediator, at least one of the analyte-responsive enzyme and the mediator is chemically bonded to a polymer disposed on the working electrode, and at least one of the analyte-responsive enzyme and the mediator is crosslinked with the polymer.
2. The biosensor of claim 1 , wherein the biosensor includes the electrode and a second electrode connected to the device.
3. The biosensor of claim 2 , wherein the device is an electrical circuit.
4. The biosensor of claim 3 , wherein the electrical circuit includes a potentiostat.
5. The biosensor of claim 2 , further including a third electrode connected to the device.
6. The biosensor of claim 5 , wherein the device is an electrical circuit.
7. The biosensor of claim 5 , wherein the electrical circuit includes a potentiostat.
8. The biosensor of claim 1 , wherein the supporting layer includes a channel.
9. The biosensor of claim 8 , wherein at least a portion of the electrode is present in the channel.
10. The biosensor of claim 1 , wherein the analyte-responsive enzyme includes glucose oxidase or a dehydrogenase.
11. The biosensor of claim 1 , including a redox compound.
12. The biosensor of claim 11 , wherein the redox compound includes a redox polymer.
13. The biosensor of claim 1 , wherein the biosensor is configured to be operational over a period of up to 72 hours.
14. The biosensor of claim 1 , wherein the biosensor communicates glucose-related information to the device when the device is connected to the biosensor.
15. The biosensor of claim 1 , further including:
an analyte flux limiting layer in contact with the biocompatible layer;
wherein the supporting layer includes an electrically insulating material provided on at least a portion of the electrode.
16. The biosensor of claim 1 , wherein glucose response provided by the electrode of the biosensor over a physiologically relevant concentration range is substantially linear, and wherein the biosensor has substantially no signal output when the concentration of glucose to be measured is zero.
17. The biosensor of claim 1 , wherein the biosensor has a glucose sensitivity selected from a range of an order of magnitude less than 61 pA/mg/dL to approximately 300 pA/mg/dL.
18. The biosensor of claim 1 , wherein the biosensor has a glucose sensitivity selected from a range of an order of magnitude less than 61 pA/mg/dL to an order of magnitude less than 300 pA/mg/dL.
19. The biosensor of claim 1 , wherein the biosensor has a glucose sensitivity selected from a range of an order of magnitude less than 97 pA/mg/dL to approximately 167 pA/mg/dL.
20. The biosensor of claim 1 , wherein the biosensor has a glucose sensitivity selected from a range of an order of magnitude less than 78 pA/mg/dL to approximately 158 pA/mg/dL.
21. The biosensor of claim 1 , wherein the biosensor has a glucose sensitivity of an order of magnitude less than 78 pA/mg/dL.
22. The biosensor of claim 1 , wherein the biosensor has a glucose sensitivity that does not change by more than approximately ±5% for 3 days of operation.
23. The biosensor of claim 1 , wherein the biocompatible layer includes a hydrogel.
24. The biosensor of claim 23 , wherein the hydrogel includes a crosslinked poly(ethylene oxide).
25. The biosensor of claim 1 , wherein the analyte-responsive enzyme includes a glucose-responsive enzyme or a lactate-responsive enzyme.
26. The biosensor of claim 1 , wherein the interferant eliminating layer is optional.