The ones I know of are the body-world’s-style wax infiltration technique, resin embedding as is used for electron microscopy, and various kinds of fluid preservation mostly involving alcohols but sometimes involving spicy things like mercury compounds, etc. A really good book on this stuff is Fluid Preservation, a comprehensive reference, though physical copies are hard to come by.
The body worlds version is a non-starter because it doesn’t preserve nanostructure. It prioritizes color and visible structure, but if you looked at that tissue under an electron microscope there would be a lot of damage. (the reason it causes damage is gas bubbles + a bunch of other stuff. Also the last time that I checked on this method was 12 years ago, I’m only 75% certain I remember this part correctly.)
Resin embedding does preserve nanostructure. It doesn’t preserve lipids nearly as well as glutaraldehyde (because lipids are more soluble in the resin than in water), but you can partially stabilize the lipids by crosslinking them with osmium tetroxide or other related compounds. But unfortunately, no one knows how to infiltrate osmium tetroxide or resins into tissue if the tissue is large. I spent a year trying to get osmium tetroxide and resin perfusion to work, and got some impressive results, but never managed to get a whole mouse brain to fully embed; there’s always small mm-sized regions that get washed out. It’s a very annoying problem. Recently the ODeCOprotocol and other similar protocols look like they might be able to get a whole mouse brain. Maybe. But these methods all use immersion and diffusion and sometimes weeks to complete (check out the methods section of the ODeCO preprint, it’s fascinating). If it takes more than a week to process a mouse brain that’s 0.35 ml of total volume, it will take much longer than a year to process a human brain that’s ~1,200 ml.
Alcohol preservation is done with diffusion so it would need initial fixation to preserve nanostructure. And alcohol will disrupt lipids more than cryoprotectant will as I understand it. But I think alcohol preservation is pretty underrated and worth exploring—there’s some very beautiful specimens that have lasted for hundreds of years at the Royal Society, for instance.
Other methods of chemical preservation:
The ones I know of are the body-world’s-style wax infiltration technique, resin embedding as is used for electron microscopy, and various kinds of fluid preservation mostly involving alcohols but sometimes involving spicy things like mercury compounds, etc. A really good book on this stuff is Fluid Preservation, a comprehensive reference, though physical copies are hard to come by.
The body worlds version is a non-starter because it doesn’t preserve nanostructure. It prioritizes color and visible structure, but if you looked at that tissue under an electron microscope there would be a lot of damage. (the reason it causes damage is gas bubbles + a bunch of other stuff. Also the last time that I checked on this method was 12 years ago, I’m only 75% certain I remember this part correctly.)
Resin embedding does preserve nanostructure. It doesn’t preserve lipids nearly as well as glutaraldehyde (because lipids are more soluble in the resin than in water), but you can partially stabilize the lipids by crosslinking them with osmium tetroxide or other related compounds. But unfortunately, no one knows how to infiltrate osmium tetroxide or resins into tissue if the tissue is large. I spent a year trying to get osmium tetroxide and resin perfusion to work, and got some impressive results, but never managed to get a whole mouse brain to fully embed; there’s always small mm-sized regions that get washed out. It’s a very annoying problem. Recently the ODeCO protocol and other similar protocols look like they might be able to get a whole mouse brain. Maybe. But these methods all use immersion and diffusion and sometimes weeks to complete (check out the methods section of the ODeCO preprint, it’s fascinating). If it takes more than a week to process a mouse brain that’s 0.35 ml of total volume, it will take much longer than a year to process a human brain that’s ~1,200 ml.
Alcohol preservation is done with diffusion so it would need initial fixation to preserve nanostructure. And alcohol will disrupt lipids more than cryoprotectant will as I understand it. But I think alcohol preservation is pretty underrated and worth exploring—there’s some very beautiful specimens that have lasted for hundreds of years at the Royal Society, for instance.