Inducing Traumatic Injury in a Brain Slice Using a Shock Tube Device

Begin with a shock tube setup comprising a proximal driver section, a diaphragm breech assembly, and a distal driven section with pressure sensors and a sample holder.

The device is connected to a pressurized gas cylinder via the control unit.

Insert a blanking rod through the sample holder to align it with the shock tube outlet.

Attach the pressure sensors to a recording device.

Keep the shock tube control closed, and open the gas cylinder outlet to build pressure in the control unit.

Secure a polyester sheet diaphragm in the breech assembly.

Place a bag containing a membrane with brain slices in an experimental medium into the sample holder.

Open the gas control knob of the shock tube, allowing gas to enter the driver section and increase air pressure.

This ruptures the diaphragm, releasing high pressure that generates a shockwave.

This shockwave travels and impacts the brain slices, inducing traumatic tissue injury.

Use a blanking rod to bolt the sterile bag holder frame to the shock tube distal flange, ensuring that the central hole is aligned with the shock tube outlet. Sensor 1, a pressure transducer is located in the middle part of the driven section, and sensor 2 is in the distal flange of the shock tube.

Connect these pressure transducers to an oscilloscope through a current source power unit, and turn on the oscilloscope. Ensure the shock tube solenoid valve and flow control are closed, then, open the external compressed air line, and charge the solenoid valve to 2.5 bar. Open the compressed air cylinder safety valve and slowly open the pressure regulator to increase the pressure to approximately 5 bar.

Next, prepare diaphragms by cutting 23-micron thick polyester sheets into 10-by-10 centimeter squares. Prepare handles from autoclave tape and stick them to the top and bottom of each diaphragm. Position one diaphragm in the breach and ensure they are centered.

Next, clamp the diaphragm using four M24 bolts and nuts. Fasten them sequentially in a diagonally symmetric way while ensuring the diaphragms are wrinkle-free. Clamp a sterile bag in a vertical position on the holder frame, ensuring that the surface of the tissue culture insert with the organotypic hippocampal slices is facing the shock tube outlet, and the tissue culture insert is centered inside the sterile bag.

For the double diaphragm configuration, the bursting pressure is dependent on the gas pressure differential between the driver and the double breech chamber. Therefore, for the diaphragms to burst in a controlled way, the double breech safety valve is opened manually once the target pressures are reached.

Put on ear defenders and safety spectacles, if not already worn. Close the solenoid valve. Switch on the current source power unit to acquire the shock wave data.

Manipulate the flow control knob on the shock tube control panel to slowly pressurize the driver volume section of the shock tube for single diaphragm configuration for both the driver volume section and the double breech section of the shock tube for double diaphragm configuration. As soon as the diaphragm ruptures, quickly close the compressed air flow using the flow knob and open the solenoid valve.

The ideal combination of shock wave parameters should be enough to cause tissue injury, but not so high that it causes tissue culture insert or sterile bag distortion or rupture.