TITLE: Duragel Application for Acute Electrophysiology Recordings
AUTHORS: anna.lakunina

[DESCRIPTION]
This protocol describes the process of coating an implant with duragel in preparation for in vivo electrophysiology experiments. Duragel seals and protects the surface of the brain while also being soft enough for silicon probes to penetrate through, allowing recordings to take place without disturbing or damaging the brain. It is possible to perform acute recordings for up to two weeks after the duragel layer has been added.

[BEFORE_START]
Wear appropriate PPE including gloves, lab coat and optional face mask. Have biohazard waste and sharps disposal accessible.

[STEPS]
SECTION: Setup
1. Draw up the white and blue duragel components into separate 1 mL Luer lock syringes. Attach 20G needles.
 

SECTION: Setup
2. Turn on microscope lights and heating pad.
SECTION: Setup
3. Wrap heating pad in press ‘n’ seal.
SECTION: Setup
4. Anesthetize the mouse (see section Prepare the anesthesia system and anesthetize the mouse (all procedures) in protocol General Setup and Takedown Procedures for Rodent Neurosurgery).
SECTION: Setup
5. Transfer mouse to stereotax.
SECTION: Setup
6. If the mouse does not currently have a well and well cap, attach a well to the headframe at this time.
SECTION: Procedure
7. Clean the surface of the implant and the ground wire with an alcohol wipe.
SECTION: Procedure
8. Using forceps, peel away the elastomer covering the implant.



SECTION: Procedure
9. Using forceps, insert the ground wire into the designated grounding hole in the implant.
 

 

SECTION: Procedure
10. Prepare the duragel mixture.
SECTION: Procedure
10.1. Add the white and blue components to a clean weigh boat, using a ratio of 35:50 white to blue.
 

SECTION: Procedure
10.2. Use the broken end of a cotton swab to mix the two components until the mixture is uniform in color.
SECTION: Procedure
11. Apply the duragel to the surface of the implant.
 

SECTION: Procedure
11.1. Apply a few drops at a time with the broken end of a cotton swab (you can use the same swab you used to mix the components). Do not apply directly to the holes in the implant as this can cause bubbles. Try to apply near the holes and let the mixture flow into the holes.


SECTION: Procedure
11.3. Continue applying until all parts of the implant are covered with a layer of duragel at least 1 mm thick.
 

SECTION: Procedure
11.2. If bubbles do form in the holes, try to push them out with the cotton swab.
SECTION: Procedure
12. Wait to allow the duragel to cure. You can test this by checking the unused mixture in the weigh boat: tilt the boat to see if the mixture is still flowing. If it's not, the duragel is cured enough. This usually takes around ten minutes.
SECTION: Procedure
13. Replace well cap and return mouse to its cage. 

 

SECTION: Take Down
14. Dispose of the syringes containing the duragel components in the sharps container.
SECTION: Take Down
15. Dispose of the elastomer implant cover and any other consumable that came in contact with the mouse in the biohazard waste container.
SECTION: Take Down
16. Turn off oxygen and isoflurane flow.
SECTION: Take Down
17. Turn off heating pad and microscope lights.
SECTION: Take Down
18. Clean and disinfect stereotax, surfaces, and induction chamber with 70% ethanol.
SECTION: Procedure
8.1. If the holes in the implant fill with CSF, gently dab it away with a Sugi or Kimwipe.