This post was made by cryomorph at the end of a different thread, but I think it deserves its own thread.
Here is a copy of a post that I put up on NCN earlier today. Save me having to write it all out again. Thought I'd copy it over to this thread as I know you don't 'tune in' to NCN so much these days. Maybe it's something you have already looked into, but either way, I would be interested to hear your views on this one.
Although the recent ASC research for cryonics purposes was based upon the use of formaldehyde/glutaraldehyde fixation, which is generally accepted as one of the most efficient permanent fixers available. There is at least one alternative to the more commonly used fixers that could provide some of the benefits without the permanence of the 2nd phase cross linking of molecules that formaldehyde and glutaraldehyde routinely produce.
Conventional fixing is a 2 phase process, the first phase of cross linking which is reversible takes about 24 - 48 hours to complete however, the 2nd phase (irreversible), can take up to 30 days dependent upon certain conditions mainly due to the process being temperature sensitive and given that cool down commences immediately after perfusion, it is likely to take substantially longer in most cryonics cases.
By comparison oxaldehyde based fixers such as Glyoxal penetrate tissue faster and assuming the preparation conditions are met, provide 1st phase fixation (reversible), only. It does not continue to go on to produce the 2nd phase of permanent cross linking of molecules. Oxaldehyde fixing is far less aggressive than conventional fixers and produces substantially less undesirable product than both formaldehyde and glutaraldehyde. It is also much less toxic to clinicians and lab workers than glutaraldehyde and formaldehyde, needing no special venting equipment. (Once diluted into water it is held in solution and doesn't vapourise).
So far I've been unable to find any papers regarding the efficacy of Glyoxal for whole organ preservation, everything I've found so far relates to histological research which isn't ideal it has to be said. Having said that it would appear that it has potential for use within cryonics, but some experimentation would be necessary in order to completely understand its mechanisms and effects prior to using it as part of any suspension procedure.
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Thank you for bringing this up. I have looked into glyoxal, and there are some claims that it penetrates faster and preserves cell morphology better. I'm not at all interested in any reversibility qualities. My ideal brain preservation would look like a solid block of epoxy, so I consider reversibility to be a downside, not a benefit. The thing about any fixative is that they each require years of practice in order to get good results. It takes a lot of work to develop the expertise. So, while a different fixative might seem like a good idea, that has to be weighed against the cost of another few years of developing proficiency. For example, glyoxal seems to require a lower pH and the addition of ethanol. We would need to figure out where to obtain it and how to store it. And, as you pointed out, we lack papers describing perfusion. It's complicated. So maybe, someday, if the pros outweigh the cons.
The reversibility of Glyoxal does not impair the quality of preservation. It could still be worth using it if only for the other benefits as detailed in the above posts. To make it permanent you only need to raise the PH values and it becomes a permanent fix. I take your point about the lack of perfusion data but I am still looking out for it, if I find anything I will copy you in. Anything we can do to improve the overall preservation quality of the suspension as a whole deserves consideration I would have thought.
The only way to improve quality is going to be to nurture a set of dedicated full-time professionals who routinely perform a case every few weeks. That's just the baseline for obtaining decent quality in any business. Changing fixative, technique, or equipment is irrelevant without that foundation in place. Since we currently have zero professionals in cryonics, and since it takes a least two years of full-time work to develop proficiency, it will be at least 3-4 years until we have good quality.