I knew that tissue damage from ice crystal formation is one of the main problems with cryopreservation, but I didn't realize that current vitrification techniqu

I knew that tissue damage from ice crystal formation is one of the main problems with cryopreservation, but I didn't realize that current vitrification techniques had largely solved that problem during the freezing process (implied by the article), and that the we "just" don't have a way of successfully unfreezing samples without causing ice crystal damage. The research papers states the problem thus: > "Unfortunately, advances in tissue and organ cooling for cryopreservation have not been matched by similar advances in rewarming. Two technological barriers have proven difficult to overcome. > > First, the critical warming rates to avoid devitrification, the process of crystallization during warming, are typically an order of magnitude higher than the corresponding critical cooling rates [interesting!]." >... > "Second, these rates need to be sufficiently uniform throughout the material to avoid large thermal gradients, which produce thermal stress that often drives fractures or cracks within the tissue if they exceed the strength of the material (the tensile strength of vitrified VS55 [the cryoprotective solution used in the study] is 3.2 MPa)." >... > >"...although we can vitrify and occasionally rewarm roughly 15 g of rabbit kidneys (10), and we can physically vitrify and rewarm in 80-ml systems, we do not have the technology to reproducibly rewarm these systems at sufficiently quick and uniform rates to avoid failure by devitrification and/or cracking using convection alone." So, true, we still can't thaw out any of those frozen heads at Alcor, but potentially they aren't totally wrecked and could be safely warmed someday in the future...