What problems currently exist for chemopreservation?

By Admin2

Posted June 24, 2015

Cracking As the plastic resin hardens, it can crack and cause microscopic fissures in the preserved brain.
Incomplete diffusion of fixative and other chemicals Initial fixatives are delivered via vascular perfusion. If the vasculature of the brain is damaged in some way, and these chemicals do not reach a certain part of the brain, then that brain region will be severely damaged during the water extraction and curing process. Later fixative, dehydration steps, and resin infiltration steps are today delivered via simple diffusion (the whole brain being immersed in a chemical bath). Diffusion of chemicals into large blocks of tissue can be problematic and has only been demonstrated on volumes the size of a mouse brain so far.
Toxicity and and cost of preservation chemicals Most of the brain preservation chemicals, such as glutaraldehyde, which fixes (crosslinks) proteins are relatively inexpensive and only mildly toxic. But the chemical currently most favored for fixing fats, osmium tetroxide, is both strongly toxic and expensive. Unless a substitute to osmium can be found, its cost alone may end up being the majority cost of the procedure. Several osmium substitutes currently exist, but their fat-fixing abilities are less effective, and it is not yet known what level of fat fixation will be sufficient to preserve the information of memory and identity. One new brain preservation method, CLARITY, removes fats altogether from whole small animal brains and replaces them with a hydrogel. It is not yet known whether this process can be scaled to a human brain, or whether such a brain would still contain the critical ultrastructure of memory and identity.
Water removal and plastination Presently, the final step in chemopreservation involves water removal via organic solvent extraction, and infiltration of the brain with plastic resin. It is not yet known whether this step involves the loss of any critical molecular features of memory and identity. If so, chemopreservation followed by vacuum dehydration or by cryopreservation (a hybrid technique) may become a leading brain preservation technique.

Admin2