This article details a method for measuring the mechanical properties of mouse brain tissue using a calibrated rheometer. The procedure involves applying oscillatory motion to assess the tissue's elastic and viscous behavior.
Start with a calibrated rheometer with the sandpaper on the top and bottom plates.
Place the mouse brain tissue on the bottom plate.
Lower the measurement plate until it is fully in contact with the tissue.
Add media over the tissue to maintain hydration.
Lower the thermal hood to maintain the temperature.
Set the motor parameters and start the measurements.
The motor's oscillatory motion introduces shear strain and generates stress.
Gradually increase the strain at a fixed frequency to identify the range of the tissue response.
Then, test at different frequencies at a constant strain to observe the tissue behavior over time.
As a functional imaging tool, the rheometer measures storage modulus, which reflects the tissue's elastic behavior, and loss modulus, which reflects its viscous behavior.
A higher storage modulus in brain tissue, at low frequencies, reflects its predominantly elastic behavior.
Attach sandpaper to the 25-millimeter diameter measurement probe. Next, attach the thermal system and mount the probe. Finally, attach another piece of sandpaper to the bottom plate, aligned with the top plate. Calibrate the rheometer as per the manufacturer's instructions.
First, zero the force on the probe. Second, establish contact between the probe and the bottom plate. Then, measure the inertia of the probe. Finally, perform a motor adjustment. Then, slowly lower the measurement plate. When the plate is within a millimeter of the tissue, lower it in 0.1 increments until the plate is fully in contact, with the top surface of the tissue, and the measured normal force is at the desired value.
Pipette a small volume of medium on the edges of the sample to maintain hydration during the procedure. Lower the thermal hood. Next, click File New, and under the Gel tab, select Frequency Sweep. Then click on Window Measurement 1, frequency sweep, and double click on the oscillation box. Enter the frequency range, the strain, and the number of points. Finally, select OK, and click Start to initiate the frequency sweep.
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