SUBCUTANEOUS GLUCOSE SENSOR

• US 20130060107A1
• Filed: 02/15/2011
• Published: 03/07/2013
• Est. Priority Date: 02/19/2010
• Status: Abandoned Application

• Current Assignee: Lightship Medical Limited
• Original Assignee: Lightship Medical Limited
• Inventors: Crane, Barry Colin, Mackenzie, Alasdair Allan, Cairns, Neil, Gilchrist, John
• Application Number:
  US13/579,240
• Publication Number:
  US 20130060107A1
• Time in Patent Office: Days
• US Class Current: 600/316
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: G01N 33/542 with steric inhibition or signal modification, e.g. fluorescent quenching
• CPC Class Codes: G01N 33/66 involving blood sugars, e.g. galactose

Abstract

A glucose sensor for measurement of glucose in subcutaneous tissue, the sensor comprising: a probe for subcutaneous insertion, the probe containing an indicator system comprising a receptor for selectively binding to glucose and a fluorophore associated with said receptor, wherein the fluorophore has a fluorescence lifetime of less than 100 ns; a detector head which is optically connected to the probe and which is for location outside the body; a light source; and a detector arranged to receive fluorescent light emitted from the indicator system, wherein the light source and detector are optionally located within the detector head; wherein the sensor is arranged to measure glucose concentration in subcutaneous tissue by monitoring the fluorescence lifetime of the fluorophore.

Claims

1. A glucose sensor for measurement of glucose in subcutaneous tissue, the sensor comprising:

a probe for subcutaneous insertion, the probe containing an indicator system comprising a receptor for selectively binding to glucose and a fluorophore associated with said receptor, wherein the fluorophore has a fluorescence lifetime of less than 100 ns;

a detector head which is optically connected to the probe and which is for location outside the body;

a light source; and

a detector arranged to receive fluorescent light emitted from the indicator system,

wherein the light source and detector are optionally located within the detector head;

wherein the sensor is arranged to measure glucose concentration in subcutaneous tissue by monitoring the fluorescence lifetime of the fluorophore.

2. A sensor according to claim 1, wherein the detector is a single photon avalanche diode.

3. A sensor according to claim 2, further comprising:

a driver arranged to modulate the light source intensity at a first frequency;

a bias voltage source arranged to apply a bias voltage to the single photon avalanche diode, wherein the bias voltage is modulated at a second frequency, different from the first frequency, and wherein the bias voltage is above the breakdown voltage of the single photon avalanche diode; and

a signal processor arranged to determine information related to a fluorescence lifetime of the fluorophore based on at least the output signal of the single photon avalanche diode.

4. A sensor according to claim 1 wherein the receptor is an enzyme or a compound containing one or more boronic acid groups.

5. A sensor according to claim 1, wherein the fluorophore has a fluorescence lifetime of 30 ns or less.

6. A sensor according to claim 1, wherein the fluorophore has a fluorescence lifetime of 20 ns or more.

7. A sensor according to claim 1, wherein the fluorophore is a non-metallic fluorophore.

8. A sensor according to claim 1, wherein the indicator system comprises a fluorophore-receptor construct which is bound to a hydrogel.

9. A sensor according to claim 8, wherein the hydrogel is a fluid hydrogel having a water content of at least 30% w/w.

10. A sensor according to claim 1, wherein the indicator system is provided as an aqueous solution.

11. A sensor according to claim 1, comprising (a) a non-disposable detector head and (b) a disposable probe unit comprising the probe and a connector arranged to connect the probe to the detector head.

12. A sensor according to claim 1, further comprising a reader unit arranged to connect to, or receive data from, the detector head, wherein the light source and detector are optionally located within the reader unit.

13. A sensor according to claim 12, wherein the detector head comprises the light source and detector and additionally comprises a power supply and a transmitter arranged to wirelessly transmit data relating to the output of the detector to a receiver, and wherein the reader unit comprises a receiver arranged to receive data transmitted by the transmitter.

14. A sensor according to claim 1, further comprising a microprocessor arranged for controlling the sensor to provide two or more measurements of glucose concentration at defined intervals and a memory arranged for storing information on the fluorescence lifetime data, or glucose concentration.

15. A disposable probe unit for use in a glucose sensor as defined in claim 1, comprising (a) a probe for subcutaneous insertion, the probe containing an indicator system as defined in any one of claims 1 or 4 to 10, and (b) a connector arranged to optically connect the probe to a detector head comprising, or being itself further optically connected to, a light source and a detector.

18. A method of measuring glucose concentration in subcutaneous tissue, which comprises

(a) inserting the probe of a sensor as defined in claim 1 into subcutaneous tissue;

(b) providing incident light to the indicator system from the light source;

(c) receiving fluorescent light, emitted from the indicator system in response to the light incident on the indicator system from the light source, using the detector and generating an output signal; and

(d) determining information related to the fluorescence lifetime of the fluorophore based on at least the output signal of the detector.

19. A method according to claim 18, which further comprises (e) wirelessly transmitting data relating to the output signal of the detector or to the fluorescence lifetime of the fluorophore, to a receiver located in a reader unit, wherein step (e) may be carried out either before or after step (d).

20. A method according to claim 18 wherein the detector is a single photon avalanche diode and the method further comprises the steps of:

(f) modulating the light source intensity at a first frequency; and

(g) applying a bias voltage to the single photon avalanche diode, wherein the bias voltage is modulated at a second frequency, different from the first frequency, and wherein the bias voltage is above the breakdown voltage of the single photon avalanche diode.

21. A method according to claim 18, wherein glucose concentration is monitored continuously by carrying out at least steps (b), (c) and (d) two or more times at defined intervals and storing the obtained information in a memory.

16. A detector head adapted for connection to a separate probe unit, wherein the detector head comprises a detector which is a single photon avalanche diode, the detector being arranged to receive light from the probe unit, the detector head being adapted to monitor fluorescence lifetimes of less than 100 ns.

17. A detector head according to claim 16, wherein the detector is adapted to monitor fluorescence lifetimes of 20 ns or more.