Carbon fiber optrodes for magnetic resonance imaging compatible optogenetics

1. An implantable device comprising an optrode comprising:

a carbon fiber electrode having a first end and a second end, wherein the carbon fiber electrode has a diameter of from 10 μm to 180 μm;

a metal wire or metal connector attached to the carbon fiber electrode at the first end;

a ceramic stick ferrule having a third end and a fourth end, wherein the ceramic stick ferrule has a face at the third end, wherein the face has a first diameter less than a second diameter of the fourth end; and

an optical fiber having a fifth end and a sixth end, wherein a portion of the optical fiber proximate the fifth end is located within the ceramic stick ferrule, wherein the optical fiber is inserted into a concave face of the ceramic stick ferrule such that the fifth end is level with the face of the third end of the ceramic stick ferrule, wherein the third end of the ceramic stick ferrule is configured to be coupled to a light source and a remaining portion of the optical fiber including the sixth end extends from the fourth end of the ceramic stick ferrule, wherein the optical fiber is secured within the ceramic stick ferrule by a first epoxy,

wherein a first portion of the carbon fiber electrode proximate the second end is coupled to a portion of optical fiber proximate the sixth end by a second epoxy such that the portion of the carbon fiber electrode and the portion of the optical fiber are aligned parallel to one another and the second end of the carbon fiber electrode and the sixth end of the optical fiber are aligned such that neither the second end nor the sixth end extends further than the other and the second end and the sixth end are configured to be implanted in a subject,

wherein a second portion of the carbon fiber electrode between the first portion and the first end is coupled to a portion of the ceramic stick ferrule proximate the fourth end by a third epoxy.

2. The device of claim 1 , wherein the carbon fiber electrode has a diameter of from 100 μm to 150 μm.

3. The device of claim 1 , wherein the carbon fiber electrode comprises a bundle of carbon fibers.

4. The device of claim 3 , wherein the bundle of carbon fibers comprises 1000 or less carbon fibers.

5. The device of claim 1 , wherein the carbon fiber electrode comprises an insulation coating.

6. The device of claim 5 , wherein the insulation coating comprises a thermoplastic polyvinylidene fluoride (PVDF), wherein the PVDF is diluted with methyl isobutyl ketone.

7. The device of claim 1 , wherein the carbon fiber electrode is attached to the metal wire or the metal connector with a conductive adhesive, wherein the conductive adhesive is a conductive epoxy adhesive.

8. The device of claim 1 , wherein the carbon fiber electrode has an impedance magnitude of 200 kΩ or less at 100 Hz in 0.9% (w/v) sodium chloride in water.

9. The device of claim 1 , wherein the optrode is adapted for use in magnetic resonance imaging.

10. The device of claim 1 , further comprising the light source coupled to the optical fiber.

11. The device of claim 10 , wherein the light source comprises a laser.

12. A method for monitoring activity in an excitable organ or tissue, the method comprising:

a) surgically implanting the device of claim 1 into an excitable organ or tissue of a subject; and

b) monitoring the activity of the organ or tissue by:

i) conducting functional magnetic resonance imaging on the organ or tissue, wherein the organ or tissue comprises cells that express one or more light-responsive polypeptides; and/or

ii) recording a detectable parameter of the organ or tissue using the device.

13. The method of claim 12 , wherein the detectable parameter comprises one or more of local field potentials, single-unit activity, and multi-unit activity in the organ or tissue.

14. The method of claim 12 , wherein the monitoring comprises chronically monitoring the activity of the organ or tissue.

15. The method of claim 14 , wherein the recording is performed 10 days or more after implanting the device.

16. The method of claim 12 , wherein the one or more light-responsive polypeptides comprises a hyperpolarizing light-responsive polypeptide.

17. The method of claim 12 , wherein the one or more light-responsive polypeptides comprises a depolarizing light-responsive polypeptide.

18. The method of claim 12 , wherein the device comprises the light source coupled to the optical fiber, and the method comprises delivering light to the organ or tissue using the light source.

19. The device of claim 1 , wherein the metal wire or metal connector is attached to the carbon fiber electrode with a conductive adhesive.

20. The device of claim 19 , wherein the conductive adhesive comprises graphite.