The Microscopic Forces That Break Hearts

https://thewaitlist.substack.com/p/the-microscopic-forces-that-break

by surprisetalk • 11 months ago

26 8 11 months ago

thewaitlist.substack.com

If you've ever used liquid nitrogen to snap-freeze tissue in gluteraldeyde for electron microscopy, the problem is readily apparent: you can't get the heat out of large chunks of meat fast enough. And by large, I mean 1 cm cubed. 0.5 cm cubed, maybe.

chasil2• 11 months ago

I've read pages at the Alcor site on cryonics that address these issues.

They had posted many years ago that a rabbit kidney had been vitrified, stored for a month in liquid nitrogen, then thawed and restored in a live rabbit.

While I am finishing the article, it appears that the field of cryonics has advanced.

https://www.alcor.org/library/alcor-presentation-at-cambridg...

From the above article: "What works perfectly for preserving a rat heart might be disastrous for a human heart - not because bigger organs are inherently harder to preserve, but because the physics of heat flow and mechanical stress changes with size in surprising ways...

"To solve this problem, scientists developed an ingenious approach: they add magnetic nanoparticles to the preservation solution. By exposing these particles to an alternating magnetic field, they can generate heat throughout the tissue rather than just at its surface. But Rabin's computational studies revealed a catch: the nanoparticles don't distribute evenly through the tissue. The heart chambers end up with higher concentrations than the heart muscle—with chambers containing nearly seven times more nanoparticles than the surrounding tissue—creating a variable distribution based on the heart's anatomy. This uneven heating creates complex thermal gradients that can actually amplify mechanical stress rather than reduce it. Rabin's models showed that optimizing nanoparticle concentration isn't just about getting enough particles, it's about achieving the right distribution pattern to counterbalance the natural stress profiles that develop during warming. Too few particles in the myocardium means insufficient warming, too many in the chambers means excessive thermal expansion—both scenarios leading to potential structural failure."

polishdude20• 11 months ago

I feel like adding magnetic nano particles to a heart to be able to freeze it is kind of in-elegant? Like, maybe the solution is something much simpler but we haven't found it yet.

chasil2• 11 months ago

It is not freezing, it is vitrifying.

If ice crystals form, then cell walls are destroyed. The water must not expand as it cools. It must become an amorphous solid, a glass.

Making this happen, reversibly, will need heat to manage stress.

I can't imagine how much more complex brain vitrification will be. Hearts are far less challenging.

thunderbong• 11 months ago

Fantastic article. Started from low temperature biology, to thermodynamics, all the way to nano particles while being completely understandable to a layman like me.

Didn't know so much went into freezing organs, and even more importantly, to thawing them back.

Thanks

agumonkey• 11 months ago

Yeah can't wait for the second part

____tom____• 11 months ago

The gamma knife/stereotactic radiosurgery is a tool for precise applying radiation to a specific part of the body.

I wonder if something similar could be done with microwaves, to specifically adjust the heat in targeted areas.

gryfft• 11 months ago

You might be interested in this paper: https://pmc.ncbi.nlm.nih.gov/articles/PMC1363505/

The Microscopic Forces That Break Hearts

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