Analyte sensor apparatuses comprising multiple implantable sensor elements and methods for making and using them

1. An apparatus for monitoring an analyte in a patient, the apparatus comprising:

a base adapted to secure the apparatus to the patient;

a first piercing member coupled to and extending from the base;

a first electrochemical sensor operatively coupled to the first piercing member, wherein the first electrochemical sensor comprises a plurality of working, counter and reference electrodes that are grouped together as a unit and positionally distributed in a repeating pattern of units;

a second piercing member coupled to and extending from the base;

a second electrochemical sensor operatively coupled to the second piercing member, wherein the second electrochemical sensor comprises a plurality of working, counter and reference electrodes that are grouped together as a unit and positionally distributed in a repeating pattern of units; and wherein:

the plurality of working electrodes, the plurality of counter electrodes and the plurality of references electrodes in the first electrochemical sensor and the second electrochemical sensor are clustered together in repeating units consisting essentially of one working electrode, one counter electrode and one reference electrode;

at least one physiological characteristic monitored by the first or the second electrochemical sensor comprises a concentration of a naturally occurring analyte in the patient;

the first and second piercing members are disposed on the base in a configuration selected so that the first piercing member disposes the first electrochemical sensor in a first tissue compartment of the patient and the second piercing member disposes the second electrochemical sensor in a second tissue compartment of the patient; and

the first and second piercing members are disposed on the base in a configuration selected to avoid a physiological response that can result from implantation of the first electrochemical sensor from altering a sensor signal generated by the second electrochemical sensor.

2. The apparatus of claim 1 , further comprising:

a contact pad;

an electrical conduit which connects an electrochemical sensor electrode to an electrical connection element that is operatively coupled to the contact pad; and wherein:

the base comprises a flexible sensor substrate; and

the contact pad, the electrical conduit and the electrochemical sensor electrode are operatively coupled to the flexible sensor substrate in a configuration that allows the apparatus to function as it twists and bends in response to movement of implanted electrochemical sensors in the patient.

3. The apparatus of claim 2 , wherein the apparatus comprises two contact pads connected to two electrical conduits and two sets of electrochemical sensor electrodes comprising a working, a counter and a reference electrode arranged such that:

the two contact pads are disposed together in a central region of the flexible sensor substrate so as to facilitate electrical connection to a power source and each of the two sets of electrochemical sensor electrodes is disposed on an opposite side of the flexible sensor substrate so as to maximize sensor separation;

the two contact pads are disposed together one side of the flexible sensor substrate so as to facilitate electrical connection to a power source and the two sets of electrochemical sensor electrodes are disposed together in a row on an opposite side of the flexible sensor substrate so as to provide a compact design for patient use; or

the two contact pads are disposed together one side of the flexible sensor substrate so as to facilitate electrical connection to a power source and the two sets of electrochemical sensor electrodes are disposed together in a staggered arrangement on an opposite side of the flexible sensor substrate so as to provide a compact design for patient use while providing a greater distance between each set of electrochemical sensor electrodes as compared to sensor electrodes not disposed together in a staggered arrangement.

4. The apparatus of claim 1 , wherein at least one electrochemical sensor electrode comprises oxidoreductase that generates hydrogen peroxide upon exposure to a ligand for the oxidoreductase.

5. The apparatus of claim 4 , wherein:

a working electrode in the first electrochemical sensor is coated with glucose oxidase; and

no working electrode in the second electrochemical sensor is coated with glucose oxidase.

6. The apparatus of claim 1 , wherein the first and second electrochemical sensors are operatively coupled to a processor coupled to the sensor input, wherein the processor characterizes one or more signals received from the first and second electrochemical sensors.

7. The apparatus of claim 6 , wherein the processor is capable of comparing a first signal received from a working electrode in response to a first working potential with a second signal received from a working electrode in response to a second working potential.

8. The apparatus of claim 7 , wherein a pulsed voltage is used to obtain a signal from an electrode.

9. An apparatus for monitoring glucose in a patient, the apparatus comprising:

a base adapted to secure the apparatus to the patient;

a first piercing member coupled to and extending from the base element;

a first electrochemical sensor operatively coupled to the first piercing member, wherein the first electrochemical sensor comprises a plurality of working, counter and reference electrodes that are grouped together as a unit and positionally distributed in a repeating pattern of units;

a second piercing member coupled to and extending from the base;

a second electrochemical sensor operatively coupled to the second piercing member, wherein the second electrochemical sensor comprises a plurality of working, counter and reference electrodes that are grouped together as a unit and positionally distributed in a repeating pattern of units; and wherein:

the plurality of working electrodes, the plurality of counter electrodes and the plurality of references electrodes in the first electrochemical sensor and the second electrochemical sensor are clustered together in repeating units consisting essentially of one working electrode, one counter electrode and one reference electrode;

at least one of the first or the second electrochemical sensor monitors a concentration of glucose in the patient; and

the first and second piercing members are disposed on the base in a configuration selected so that when the first and second piercing members are inserted into the patient, the first and second sensors are separated by at least 5 millimeters of tissue.

10. The apparatus of claim 9 , wherein at least one of the first and the second electrochemical sensor comprise:

an analyte sensing layer disposed on a working electrode; and

an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer comprises a composition that modulates the diffusion of glucose diffusing through the analyte modulating layer.

11. The apparatus of claim 9 , wherein at least two working electrodes in the first and second electrochemical sensors are coated with glucose oxidase.

12. The apparatus of claim 9 , further comprising a processor capable of characterizing a plurality of signals received from the first and second electrochemical sensors.

13. The apparatus of claim 12 , wherein the first electrochemical sensor comprises a working electrode coated with glucose oxidase and the second electrochemical sensor comprises no working electrode coated with glucose oxidase and the processor is capable of obtaining information on glucose concentrations in the patient by comparing the signals received from said working electrodes so as to identify a background signal that is not based on a glucose concentrations in the patient.

14. The apparatus of claim 12 , wherein the working electrode in the first and second electrochemical sensors are coated with glucose oxidase and the processor is capable of obtaining information on glucose concentrations in the patient by comparing the signals received from said working electrodes coated with glucose oxidase.

15. The apparatus of claim 14 , wherein a pulsed voltage is used to obtain a signal from an electrode.

16. The apparatus of claim 9 , wherein the processor is capable of comparing a first signal received from a working electrode in response to a first working potential with a second signal received from a working electrode in response to a second working potential.

17. The analyte apparatus of claim 9 , wherein:

at least one working electrode in the first and second electrochemical sensors is coated with glucose oxidase; and

at least one working electrode in the first and second electrochemical sensors is not coated with glucose oxidase.

18. The apparatus of claim 9 , wherein the plurality of working electrodes, the plurality of counter electrodes and the plurality of reference electrodes are parallel to the planar surface of the base when the analyte sensor apparatus is implanted within the mammal.