Studying the Regeneration of Functional Connections between Spinal Cord Slices Using a Multi-Electrode Array

Place a multi-electrode array, or MEA, in a petri dish under a stereomicroscope. The MEA comprises electrodes arranged in a grid with two separate zones.

Add a drop of blood plasma to the MEA. Place two spinal cord slices obtained from rat embryos, with their ventral sides facing each other.

Introduce a thrombin solution, mix it with the plasma, and incubate. Thrombin causes plasma coagulation, creating a biological scaffold that facilitates the adhesion of the slices on the MEA.

Add a nutrient medium and incubate under agitation, promoting the formation of cellular connections between the slices and causing their fusion.

Under the stereomicroscope, introduce a lesion by cutting the tissue connections between the slices. Add a nutrient medium and incubate.

During incubation, neurons grow across the lesion to connect the slices.

Using a recording chamber, record electrical activity from both spinal cord slices to assess their regenerated functional connections.

Put a Petri dish with a coated microelectrode array inside, under a stereomicroscope. Bring the array into focus and center a 6-microliter droplet of chicken plasma on the electrode array. Using a small spatula, carefully slide two spinal cord sections with their ventral sides facing each other into the plasma droplet.

Next, add 8 microliters of thrombin around the chicken plasma droplet. Then, use the pipette tip to carefully mix and spread the chicken plasma and thrombin mixture. Just before the chicken plasma and thrombin mixture becomes too stringy and starts to coagulate, aspirate the excess liquid. Then, cap the Petri dish and place it in a humidified chamber. Place the chamber inside an incubator at 37 degrees Celsius for about an hour.

After incubation, carefully add 10 microliters of nutrient medium to the sample. Cap the Petri dish and place it back into the incubator for an additional 45 minutes. Next, place each of the multi-electrode array culture assemblies into a roller tube, and add 3 milliliters of nutrient medium. Close the lid tightly, and place the roller tube into the roller drum. Rotate the drum at 1 to 2 RPM in the incubator at 37 degrees Celsius.

Using sterile rubber-tipped forceps, remove the multi-electrode array culture assemblies from the roller tube and place them into a Petri dish under a stereomicroscope. Bring the tissue into focus and verify that the two slices are fused.

Next, hold the assembly steady and place a scalpel blade in the groove of the multielectrode array close to the tissue slices. Hold the scalpel rather horizontally, and then, lift the scalpel handle up, but let the scalpel blade stay in the groove of the array in such a way that the blade rolls from base to tip, cutting through the tissue covering the groove. Sever any residual tissue connections with a 25-gauge needle tip if necessary. Work only in the area within the groove, and do not touch the tender edges.

Put the multi-electrode array culture assemblies back into the roller tube and add 3 milliliters of fresh nutrient medium to the cultures. Then, place the roller tube back onto the roller drum in the incubator at 37 degrees Celsius.

Mount a multi-electrode array culture assembly into a recording chamber and apply about 500 microliters of extracellular solution to the array. Then, mount the assembly on the microscope. Wait 10 minutes for the system to stabilize and then record basic spontaneous activity from each of the activity-detecting electrodes for 10 minutes.