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What Agents Are Used for (Human) Cryopreservation?

Find out what cryoprotective agents are currently in use for cryopreservation at Tomorrow Bio and other providers.

The field of Biostasis aka cryonics is much more complex than just “freezing” and warming up. Whether it’s standby team, vitrification, cryogenic storage dewars, or cryoprotective agent, there are a lot of aspects that go into a high quality cryopreservation. Unfortunately, most of them aren’t self-explanatory, so we’ve made it our mission to explain them.

In this article we go over some of the basics of cryopreservation and dive deep into one of the most important considerations we have to make: which cryoprotective agents should we use to have the highest possible quality cryopreservation?

What Is Cryopreservation?

Cryopreservation is a type of preservation for cells, tissues and other biological materials (as complex as whole-bodies). It’s done by slowly lowering the core temperature to sub-freezing levels below the so-called “glass transition temperature” at around -130°C, achieving vitrification in the process. At Tomorrow Bio we currently use temperatures of -196°C for long-term storage of cryopreserved patients (with ITS coming soon), which is the temperature of liquid nitrogen. Cryoprotective agents are used to protect the cell structure from hazards like ice-crystal formation. We generally use a mixture of multiple cryoprotection substances, in order to balance out their toxicity and protection capabilities and to cause the least damage to the cells as possible. Via cooling and through the cryopreservation process, metabolic rates are reduced significantly, stopping biological activity completely. Once vitrified, the body is on complete “biological pause”, meaning that patients can be stored in this state practically indefinitely without degradation.

How Is Cryopreservation Currently Used?

Using this method, many cell and tissue types have been successfully cryopreserved and rewarmed in the past. Cryopreservation is actively used on sperm, red blood cells, embryos and more, to preserve them for future use.

The most well-known use of cryopreservation nowadays comes in the form of sperm-banking. The first baby born from a cryopreserved sperm, back then cooled on dry ice, was born in 1953, a whole decade before Robert Ettinger, the “father of cryonics”, first proposed the cryopreservation of humans. With the introduction of liquid nitrogen, and with it better preservation conditions, many more men decided to preserve or donate their semen. The procedure has become a staple in healthcare ever since and has allowed people who were previously unable to get a baby, to fulfill their wish for parenthood. 

To learn more about today’s use cases of cryopreservation, including some you might not have known of, feel free to take a look at one of our other articles.

Human sperm can be cryopreserved for future fertilization

Preserving Humans

Our vision at Tomorrow Bio is to give everyone the option to decide how long they want to live. We love life, and understand that many of you feel this way too. Not all of us are granted a long and healthy life and many die of diseases today that will most likely be treatable in the future. Which is why we’ve made effective, safe and indefinite human cryopreservation our goal. We want to build a bridge towards that future and give people the chance to get the future treatment that will save their lives. But while preservation of other, smaller organisms is a common practice today, the vitrification of humans is not (yet) and, in fact, revival from cryopreservation is not feasible. This is mainly because it is a lot harder to preserve fully grown humans than tiny embryos. Let’s take a look at some of the difficulties we are facing and how our medical research team is trying to overcome them.

Why Is It Harder to Preserve Humans?

Bigger isn’t always better, especially not in the field of biostasis. Here, “bigger” usually correlates with a lot more complications. In the case of sperm or other small entities, the entire organism can be cooled down and rewarmed all at once. The biology of a human body is far too large in size and different organs warm at different rates, which would be causing a lot of damage to human tissue.

Another issue is the protection of the cells during the cryopreservation process from damages. If we simply froze humans (which we don’t), the water inside the body would freeze and ice-crystals would form. These crystals have sharp edges that we definitely don’t want inside our patients, as they would cause damage to cell-structures and tissue.

We prevent this from happening by perfusing, i.e. swapping out the water inside the body with specialized cryoprotective agents. This approach removes one problem, but sadly, adds another (less problematic) one. If you want to learn more about the general usage, benefits and problems of these agents, please refer to the link above. All caught up on the basics? Perfect. Let’s take a deeper look at which cryoprotective agents we use at Tomorrow Bio.

The human body consists of many organs that all warm up at different rates

What Cryoprotective Agents Are There?

Each cryoprotective agent consists of a mixture of penetrating and non-penetrating chemicals. (1) Cryobiology has made a multitude of discoveries regarding the effectiveness and safety of cryoprotectants such as:

  • Penetrating chemicals are effective at shielding the cells from freezing, but are inherently toxic.
  • Non-penetrating chemicals are less effective at shielding cells from freezing, but reduce the exposure of cells to toxic cryoprotectants.
  • The right mixture of both can provide a high amount of protection with a low amount of toxicity, without reducing the quality of vitrification.
  • A measure called qv* can predict the general toxicity of an agent - helpful in formulating the best possible solution
  • Toxicity can further be reduced by adding so-called synthetic “ice blockers” to the mixture.

… and more.


The most common agents produced with this knowledge today are M22 and VM1.

Which Agent Do We Use?

Alcor Life Extension uses M22 for their cryopreservations. M22 is the most documented cryoprotectant currently in use, and promises the best overall results according to Alcor, but this comes at a price, a very high price. Each usage of M22 has costs somewhere in the mid-5-figure-range, increasing the cost of cryopreservation by a lot.

The competitor, VM1, while is slightly less well documented (we’re changing that as we speak), has a comparatively puny price point of just a few hundreds of Euros per use. Having less data doesn’t necessarily mean that VM1 agents are any worse at protecting cryopreserved patients than M22 agents in real-life human cryopreservation cases.

Cryonics Institute, the largest American Biostasis provider, uses the agent CI-VM-1, a modified version of VM1 to keep their costs low, and is still providing high-quality cryopreservation.

Tomorrow Bio believes that this stark difference in cost warrants using (a modified version of) VM1 as well. Despite similarities, Tomorrow’s VM1 agent is different from the one CI uses. Our protectant is specially created by Tomorrow Bio’s R&D department, which is constantly improving our cryoprotective agents to guarantee a first-rate cryopreservation for our members. 

Here is some more insight on why we chose VM1 over M22.

Tomorrow Bio’s cryoprotective agent

Even the Best Agent Can’t Save What’s Gone

A high-quality cryopreservation consists of three key values:

  1. Time (the faster the better)
  2. Protection (the stronger the better)
  3. Stability (the safer the better)

Everybody pretty much agrees that time is (by far) the most important factor. Afterall, cryoprotectants can only shield what’s still there. The more time passes between legal death (or more precisely, after circulatory arrest) and the start of your preservation, the further along degradation of your brain will already have come. Intervening that process is our first priority.

Therefore, we have decided to use a modified VM1. This way the additional funds can be allocated towards better logistics, geographical infrastructure and better trained Standby-Teams, resulting in much faster response times. Which overall, has a bigger impact on quality in almost all cases. To further ensure quality, our researchers have made additional slight adjustments to the regular version of VM1, making it more effective than the original version.

Nevertheless, Tomorrow Bio is fundamentally agnostic about which cryopreservation agent to use. If there is ever data, that other agents perform better or a completely different preservation method is superior, we will switch over (of course, all of our members would be informed well in advance). 


Tomorrow Bio is dedicated to steadily improving cryoprotectant agents for cryopreservation of humans. We believe that the chemical mixture of VM1 provides a good basis for that endeavor, resulting in both an effective and affordable solution for our patients. We will continue to invest money and resources into progressing this field of science and cryoprotectant agents are an important part of this. If you want to help us fulfill our mission, check out our Tomorrow Fellow Program and start supporting Biostasis research today!

Do you have questions that you want to ask us personally? Then schedule a call with us! We are looking forward to hearing from you!

Tomorrow Bio is the worlds fastest growing human cryopreservation provider. Our all inclusive cryopreservation plans start at just 31€ per month. Learn more here.