Hello Felix,

Freezing intact tissue without prior dissociation can lead to ice crystal formation, which can damage cells and the surrounding tissue structure. This damage makes it significantly harder to achieve a successful, viable single-cell suspension when you attempt to dissociate the tissue after it has been frozen.

So, you should dissociate the postmortem human brain tissue first and then freeze the resulting single-cell suspension, if your goal is to obtain a suspension of viable, single cells. To freeze the cells, you can pellet the cells by centrifugation and then resuspend them in a cryoprotective solution to store them at a low temperature (for instance, -80°C or in liquid nitrogen). This preserves cell viability for later use.

Best,

Thanks for the answer Malcolm Nobre

I tried to understand why that would be and I found a possible mechanism: Ice crystals form in buffer first because lower salt concentration, increases osmotic pressure of buffer and pulls water out of cells, and ice crystal formation in the cells is hindered even further than it already was through the high salt concentration and cryoprotectants, with the water instead becoming glassy. It sounds reasonable, but any number of explanation can sound reasonable. Do you know more about the specific mechanism for why that would be the case?