I was rereading Artemis Fowl: The Eternity Code the other day- a great read, by the way. For those unfamiliar with this book series, it combines scientific/technological advancements with magic. There was one part of this book that really stretched my understanding of what is scientific and what is magical. Artemis’s bodyguard was just shot trying to protect his charge, and what happens next, well, see for yourself:
The seconds were ticking by. Artemis was growing angry with himself. Time was against them. Time was the enemy. Time needed to be stopped… (The Eternity Code, 45)
A peculiar thought! But Artemis Fowl only has minutes to come up with a solution, so opening a wormhole and travelling along a CTC (closed timelike curve) is probably not feasible. So what can he do?
Cryogenics. It was their only chance. The science of freezing a body until medicine had evolved sufficiently to revive it. Generally dismissed by the medical community, it nevertheless made millions each year from the estates of rich eccentrics.. (45)
Could this actually be possible? Let’s analyze:
We first make a semantic distinction- cryogenics is the study of material production and behavior at low temperatures. Cryonics is the study of cryopreservation, which is the low temperature preservation of living organisms’ organs and tissues. Empirical research has shown that storing cells and organs in very cold (~ -200ºC) temperatures slow down biological activity. Liquid nitrogen is usually used as the ultracold medium carrier to essentially halt biological activity at these low temperatures- from kinetics we know that decreasing temperatures decrease the rate of reactions, so basic processes such as ATP production and DNA function slow down rapidly. From theory, the only reactions that are thermodynamically favorable at these temperatures are photoradicalization- but astonishingly in practice, cell fatality hasn’t been observed!
That’s great that we can slow or even halt cellular activity by lowering the temperature, but surely there are some risks involved? Certainly! One main concern is the freezing of water- water comprises a large portion of a typical living cell, and as a liquid it transports materials to various areas inside and outside the cell. When freezing the cell, ice crystal formation can damage the internal organelles by creating high concentration solute regions in addition to cell dehydration. This process can be countered by cooling the water to the glassy state (~ -130ºC) via vitrification. Ice formation is skipped and the cell is preserved in a ‘cold water’ state. One way to think of this is that the water becomes liquid glass, as the glassy transition temperature is achieved.
The main problem with vitrification is for the cell/organ to stay intact during the freezing and heating period right below zero Celsius- both for water freezing/unfreezing and DNA’s processivity at lower temperatures. This problem is usually abetted with some antifreeze cryoprotectant– i.e. propylene glycol or DMSO. And in fact, recent studies have shown that a rabbit’s kidney was successfully recovered (functional at room temperature when transplanted into a rabbit) after cryopreservation!
It’s great that one organ has the capability of being cryopreserved, but what about whole organisms? Nature, as always, continues to amaze us with her brilliance. Tardigrades, or water bears, are one of the few discovered organisms on the planet that can survive crazy, extreme environmental conditions- anywhere from the top of the Himalayas to the heat vents close to the bottom of the ocean (to outer space!). This is absolutely crazy, but there are some more impressive things about these tiny bears (outside of being somewhat adorable):
Tardigrades have the remarkable ability of reversibly suspending their metabolism– i.e. in very cold climates, they rapidly dehydrate their bodies to ~0.01% of their original water content and survive on large concentrations of a sugar. As previously discussed, it is important for the solid crystallization to not occur- so the tardigrade turns into glass. The sugar acts as the cryoprotectant and allows the tardigrade to reverse the reaction and resume normal function. They can exist in these states for upto 30 years! So this is literally a case of ‘add water and grow’:
So young Artemis’s quick thinking is not totally out of line. But wait- even assuming you have a way of preserving the original organs, won’t the brain die after lack of blood circulation and oxygen transport? After all, if the brain dies, the patient is as good as dead. When blood circulation stops and oxygen diffusion essentially vanishes, the patient still has roughly 30 minutes before showing signs of severe brain damage upon recovery. And there are certainly some rare cases- in fact, a skier in 2000 fell into ice and had a body temperature of ~14ºC when pronounced clinically dead. She was trapped for over an hour and a half before being rescued and saved. Eight months later, she only felt residual tingling in her hands. It’s amazing what lowering the temperature does to slow the reaction kinetics of the body!
Still, that particular case was an hour and a half. Could preserving the brain for a longer time be plausible? A very recent study actually indicates yes- the group was successfully able to vitrify rabbit (and pig) brains using a (mainly) ethylene glycol cryoprotectant and an aldehyde-stabilized cryopreservation (ASC) technique to stabilize the brains during vitrification. One of the keys to their method was the slow injection of the cryoprotectant agent (CPA) during freezing and slow removal during warming. This led to no cracks in the rabbit brains in either of the thermal cycles, which is crucial to full recovery of the brain. And most importantly, the group was able to achieve reversible results- i.e. the brain was functional upon warming.
Looks like Artemis Fowl wasn’t totally incorrect. In fact, multiple cryonics institutes exist in the world right now, and some even deal with neuropreservation! The hope is that in the future, we can revive these bodies after halting their passage through time. Perhaps what we really should be doing is trying to find those elusive fairies below ground.