Optical detector for enzyme activation

• US 20040215134A1
• Filed: 04/25/2003
• Published: 10/28/2004
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc), Metronic Incorporated
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Soykan, Orhan, Donovan, Maura G.
• Granted Patent: US 7,473,548 B2
• Time in Patent Office: Days
• US Class Current: 604/66
• CPC Class Codes: A61B 5/0071 by measuring fluorescence emission
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: C12Q 1/37 involving peptidase or proteinase
• CPC Class Codes: C12Q 1/56 involving blood clotting factors, e.g. involving thrombin, thromboplastin, fibrinogen
• CPC Class Codes: G01N 2021/6415 with two excitations, e.g. strong pump/probe flash
• CPC Class Codes: G01N 2021/6441 with two or more labels
• CPC Class Codes: G01N 2021/6484 Optical fibres
• CPC Class Codes: G01N 2021/8528 Immerged light conductor
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/8507 Probe photometers, i.e. with optical measuring part dipped into fluid sample
• CPC Class Codes: G01N 33/86 involving blood coagulating time or factors, or their receptors

Abstract

Activation of an enzyme in a bodily fluid is detected based on the amount of cleavage of a substrate for the enzyme. The substrate is tagged with two fluorescent dyes—a donor and an acceptor. The tagged substrate is presented to the bodily fluid. A device emits energy at a first wavelength into the bodily fluid, and detects energy at second and third wavelengths emitted by the dyes in response to the energy at the first wavelength. Prior to enzymatic cleavage of the substrate, the acceptor emits energy at the third wavelength in response to energy at the second wavelength received through fluorescent resonant energy transfer (FRET) from the donor. After enzymatic cleavage of the substrate, the donor emits energy at the second wavelength. The device can determine the concentration of activated enzyme within the bodily fluid based on the relative intensities of energy at the second and third wavelengths.

Claims

1. A method of detecting enzyme activation in an implantable medical device, comprising:

emitting energy at a first wavelength into a bodily fluid that contains an enzyme and a substrate tagged with at least two fluorescent dyes;

detecting energy emitted by a first one of the dyes at a second wavelength based on fluorescent resonant energy transfer from a second one of the dyes in response to the emitted energy at the first wavelength; and

detecting activation of the enzyme based on the detected energy.

2. The method of claim 1, wherein the bodily fluid is blood, and emitting and detecting energy comprises emitting and detecting energy via an optical fiber that includes a distal end located in a blood vessel of a patient.

3. The method of claim 1, further comprising detecting energy emitted by the second one of the dyes at a third wavelength in response to the emitted energy at the first wavelength, wherein detecting activation of the enzyme comprises:

determining a ratio between a first detected intensity of energy at the second wavelength and a second detected intensity of energy at the third wavelength; and

detecting a concentration of activated enzyme within the bodily fluid based on the ratio.

4. The method of claim 3, wherein the substrate includes a first product and a second product, the first product tagged with the first one of the dyes, and the second product tagged with the second one of the dyes, and

wherein the enzyme cleaves the substrate, and the first one of the dyes absorbs energy received from the second one of the dyes at the third wavelength via fluorescent resonant energy transfer and emits energy at the second wavelength in response to receiving the energy at the third wavelength prior to cleavage of the substrate by the enzyme.

5. The method of claim 1, further comprising presenting the substrate to the bodily fluid.

6. The method of claim 5, wherein the bodily fluid is blood, and presenting the substrate to the bodily fluid comprises controlling a pump to present the substrate to the blood via a catheter with a distal end located in a blood vessel of a patient.

7. The method of claim 1, wherein the energy is visible light.

8. The method of claim 1, wherein the enzyme is a protease enzyme.

9. The method of claim 8, wherein the enzyme is one of thrombin and kallikrein.

10. The method of claim 1, further comprising:

storing information relating to the detection of enzyme activation; and

delivering the information to a user.

11. The method of claim 1, further comprising activating an alarm in response to the detection of enzyme activation.

12. The method of claim 1, further comprising delivering therapy to the patient based on the detection of enzyme activation.

13. The method of claim 12, wherein delivering therapy comprises delivering at least one of an anticoagulant, a pain relieving drug, and neurostimulation therapy.

14. An implantable medical device comprising:

an emitting element to emit energy at a first wavelength into a bodily fluid that contains an enzyme and a substrate tagged with at least two fluorescent dyes;

a detector to detect energy emitted by a first one of the dyes at a second wavelength based on fluorescent resonant energy transfer from a second one of the dyes in response to the emitted energy at the first wavelength; and

a processor to control the emitting element to emit energy at the first wavelength, receive an indication of an intensity of energy detected by the detector, and detect enzyme activation based on the indicated energy intensity.

15. The device of claim 14, wherein the detector detects energy emitted by the second one of the dyes at a third wavelength in response to the emitted energy at the first wavelength, and

wherein the processor receives an indication of an intensity of energy detected by the detector at the second and third wavelengths, determines a ratio between a first detected intensity at the second wavelength and a second detected intensity at the third wavelength, and determines a concentration of activated enzyme within the bodily fluid based on the ratio.

16. The device of claim 15, wherein the substrate includes a first product and a second product, the first product tagged with the first one of the dyes, and the second product tagged with the second one of the dyes, and

wherein the enzyme cleaves the substrate, and the first one of the dyes absorbs energy received from the second one of the dyes at the third wavelength via fluorescent resonant energy transfer and emits energy at the second wavelength in response to receiving the energy at the third wavelength prior to cleavage of the substrate by the enzyme.

17. The device of claim 15, wherein the detector comprises a first detector to detect energy emitted at the second wavelength and a second detector to detect energy at the third wavelength, the device further comprising:

a first filter to pass energy at the second wavelength to the first detector; and

a second filter to pass energy at the third wavelength to the second detector.

18. The device of claim 14, further comprising an optical fiber optically coupled to the emitting element and the detector, wherein a distal end of the optical fiber is located in the bodily fluid, the emitting element emits energy into the bodily fluid via the optical fiber, and the detector detects energy emitted by the first one of the dyes via the optical fiber.

19. The device of claim 18, wherein the fluid is blood and the distal end of the optical fiber is located within a blood vessel of a patient.

20. The device of claim 18, wherein the optical fiber includes a cladding, and wherein the optical fiber includes a region at which the cladding is removed from the optical fiber, and wherein the substrate is linked to the region of the optical fiber where the cladding is removed.

21. The device of claim 20, wherein the region is a distal region of the fiber.

22. The device of claim 18, further comprising:

a first reel;

a second reel; and

a reel rotation mechanism to move a tape between the first reel and the second reel along a path that is substantially parallel and proximate to the optical fiber,

wherein the substrate is linked to the tape, the optical fiber includes a cladding, the cladding is removed from a portion of the optical fiber, and the processor controls the reel rotation mechanism to move the tape such that uncleaved substrate is proximate to the unclad portion of the optical fiber.

23. The device of claim 22, wherein at least one of the first and second reels is coupled to the optical fiber.

24. The device of claim 14, further comprising:

a reservoir that contains the substrate;

a pump in fluid communication with the reservoir; and

a catheter that includes a proximal end in fluid communication with the pump and a distal end located in the bodily fluid,

wherein the processor controls the pump to present the substrate to the bodily fluid via the catheter.

25. The device of claim 24, wherein the bodily fluid is blood and the distal end of the catheter is located in a blood vessel of a patient.

26. The device of claim 14, wherein the energy is visible light.

27. The device of claim 14, wherein the enzyme is a protease enzyme.

28. The device of claim 27, wherein the enzyme is one of thrombin and kallikrein.

29. The device of claim 14, further comprising:

a memory to store information relating to the detection of enzyme activation; and

a telemetry circuit,

wherein the processor delivers the information to a user via the telemetry circuit.

30. The device of claim 14, further comprising an alarm, wherein the processor activates the alarm based on the detection of enzyme activation.

31. The device of claim 14, further comprising:

a reservoir containing a drug;

a pump in fluid communication with the reservoir; and

a catheter with a proximal end in fluid communication with the pump and a distal end located within a patient,

wherein the processor controls the pump to deliver the drug to the patient via the catheter based on the detection of enzyme activation.

32. The device of claim 31, wherein the drug comprises one of an anticoagulant and a pain relieving drug.

33. The device of claim 14, wherein the device is implanted in a patient.

34. An implantable medical device system comprising:

a first medical device to optically detect activation of an enzyme within a bodily fluid of a patient; and

a second medical device to deliver a therapy to the patient based on the detection of enzyme activation.

35. The system of claim 34, wherein the first medical device comprises:

an emitting element to emit energy at a first wavelength into a bodily fluid;

a detector to detect energy emitted at a second wavelength and a third wavelength by products of a tagged substrate in the bodily fluid in response to the energy at the first wavelength; and

a processor to control the emitting element to emit energy at the first wavelength, receive indications of intensities of energy detected by the detector, and determine a concentration of activated enzyme that cleaves the substrate within the bodily fluid based on the indicated energy intensities, wherein the second medical device delivers the therapy to the patient based on the determined concentration.

36. The system of claim 34, wherein the second medical device comprises a drug pump to deliver a drug based on the detection of enzyme activation.

37. The system of claim 34, wherein the second medical device comprises a neurostimulation device to deliver neurostimulation therapy based on the detection of enzyme activation.

38. The system of claim 34, wherein the first and second medical devices are integrated within a single housing.

39. The system of claim 34, wherein at least one of the first and second medical devices are implanted in a patient.

40. An optical fiber comprising:

a core; and

a cladding surrounding the core,

wherein the cladding is partially removed from a section of the fiber to expose a section of the core, and a substrate for an enzyme within a bodily fluid is linked to the section of the core.

41. The optical fiber of claim 40, wherein the section of the fiber is proximate to a distal end of the fiber.

42. The optical fiber of claim 40, wherein the enzyme is one of kallikrein and thrombin.

43. The optical fiber of claim 40, wherein the substrate is linked to the core by cross-linkers.

44. The optical fiber of claim 43, wherein the substrate is tagged with at least two fluorescent dyes.

45. The optical fiber of claim 44, wherein the absorption spectrum of a first one of the dyes overlaps an emission spectrum of a second one of the dyes.