Why do Labs Use -80 Freezers?
For biology fans only. The rest of you will be bored by this one.
Why do Biology Labs use those huge -80 Freezers? Why not use liquid Nitrogen? Why not just use a normal home freezer?
One big reason is that home freezers just don’t get cold enough to preserve biologicals long term. Also they are not reliable enough. So labs tend to use -60 or -80C freezers, that are more reliable, colder, and typically have alarms to let you know when they fail. Freezers have moving parts, and these will wear out, so eventually the freezer Will fail.
That said, Liquid Nitrogen is a good solution, that few labs appear to use. It will evaporate at a predictable rate, and won’t surprise you by failing suddenly in the middle of the night. So I have always wondered why so few people use them.
If you talk to people who have been in a biolab for many years, they can probably tell you a horror story of what happens when a big Ultracold freezer fails. It will likely happen in the middle of the night, and it’s an ‘all hands on deck’ situation. Imagine that you are a company storing bull semen or stem cells or years of research vaccines in that freezer. It may have many millions of dollars worth of intellectual capital or material thawing out. In a recent college class, someone at a major health organization was asked what their worse day was, and that was the answer - A middle-of-the-night freezer failure.
Some Background
The standard way to freeze mammal cells in culture is to cool them at the rate of -1°C/minute. That is ideal for cryopreservation of most cells and cell lines. The way you do that is to put them into a vial with a cryo chemical (like DMSO), then into a Mr Frosty ($160) or Corning CoolCell container ($500), in combination with a -80°C freezer. This expensive setup is basically just a container that insulates just enough to allow cooling at the ideal freezing rate. It’s absurd that they cost this much. But all labs use these, so they can publish that they did the ‘standard method’ for freezing cells. There are very similar methods for fungi, bacteria, and other biologicals. (mammal cells are just the most fragile case)
You could buy any of this on eBay for a lot less. Or you could build your own, but then you risk being labeled as non-standard, and your results will be questioned. “Maybe the cells froze at the wrong rate, and that caused some unknowns.”
In biology, we pay a big price for following our standards, so that the published research has an apples to apples comparison.
For example, recall that -80 freezer, that cells are cryo cooled in? You do need something that will get below -60 so you can avoid the damaging ice crystals, so a household freezer just will not work. Liquid Nitrogen could work, but then you have −196 °C (−321 °F), so it may cool faster. Or LN2 could leak into the container. Obviously, you could have a thicker amount of insulation, and ensure that the cooling containers do not leak.
Why not LN2?
LN2 is colder, so it preserves better. Less molecular motion. Also, it is solid state. In other words, a middle-of-the-night power failure doesn’t cause your samples to begin thawing out, necessitating a midnight lab visit to save samples.
For expensive or irreplaceable samples, that is very important.
So why don’t more labs use LN2?
I’ve asked lab managers this question, and I really don’t love many of the answers. But here are some reasons that I have been given by various people and AIs.
Safety: Liquid nitrogen is extremely cold and can cause severe burns or asphyxiation if not handled properly. People have been killed by a room filled with Nitrogen gas. It isn’t toxic, but it can displace all of the Oxygen in the room. Many labs require sensors to avoid the asphyxiation issue, if LN2 is in use, which adds to costs as well. In some labs, there are regulations that require extra monitoring if you have LN2.
Cost/convenience: Depending on how you could things, liquid nitrogen is more expensive than -80°C freezers, especially for large-scale storage. Safety sensors and procedures add to the expense. LN2 generators have to be weighed against the cost of regular deliveries.
For a small lab, LN2 in a dewar can be cheap and easy to start and stored outdoors for safety. But these provide much less storage volume than you might imagine, and a wide mouth dewar, loses more LN2 and needs more frequent refilling. This adds to the cost and disruption.
Also -80°C freezers are easier to access and use daily. Liquid nitrogen storage requires specialized handling procedures and safety precautions.
Equipment and maintenance: Specialized equipment and regular maintenance are required to store and handle liquid nitrogen. For example, you may need regular deliveries from a liquid gas vendor, or you may invest in your own LN2 generator.
Outsourcing.
Just as you can outsource some tasks to someone else’s data center or Cell Bank, you can also also outsource long-term biological storage to someone else. In other words, you could keep some short-term storage onsite, and store some valuable samples with someone who has the big expensive and well monitored freezers. This is comparable with computers, where some of your data backups are stored in someone else’s data center (like AWS, Google, Azure). You can mix and match these strategies as a company grows, just like you would with the computing needs.
Startups and Biohackers
Startup labs and biohackers have something in common. They don’t want to pay too much for equipment. You could buy an ultracold freezer (-60°C, -80°C, -90°C) and a Mr Frosty on Ebay for about $2000. You can get a LN2 dewar for $500 and refilling is about $30 every few months.
I found a new Mr Frosty for $160 or a Corning CoolCell container is $500. A -80°C freezer is $2000 for a portable small one with few features. That is the cheapest that I have found this setup, and you would probably want a new one, not a used one on Ebay if this is your single-point-of-failure.
You could build your own Frosty cool-down container out of a block of styrofoam and trim off styrofoam to get to the ideal cooling rate, but now you risk being ‘non standard’ if you go to publish. But it should work. NOTE: you have to fully understand the vitrification process to build your own. For example, vitrification has to continue down to -60°C at least before storing at -90°C or LN2 at −196°C. If you do this in a -40° Freezer, and then LN2, you will kill more cells via ice crystals.
But these scale way up in size and features and cost. A good feature for Ultracold freezers is “calling you to get you out of bed in case of a failure, so you don’t lose all of your samples”. And prices for a freezer with these features go up to many thousands for a thousand pound monster freezer with lots of extra features. They suck power so expect to see the noticeable impact on your power bill.
This expensive setup is basically just a container that insulates just enough to allow the ideal freezing rate. Then store them very cold. It’s absurd that they cost this much. But all labs use these, so they can publish that they did the ‘standard method’ for freezing cells.
In Summary
If none of this makes sense to you, but you need long term bio storage, just buy a -90°C freezer and follow the instructions on a Mr Frosty container. Or let a salesman sell you one. Or outsource it. If you want to think it through, here are the conclusions that I have arrived at.
Liquid nitrogen is the preferred method for long-term cryopreservation of cells, especially for sensitive or valuable cell types, and when indefinite storage is needed.
-80° to -90°C freezers are suitable for short to medium-term storage, less sensitive cell types, and other biological materials, offering a more cost-effective and convenient option. You can just reach in and get the cells, quickly and with little risk.
Ultimately, the choice between liquid nitrogen and -80°C freezers depends on the specific needs of the lab, the type of cells being stored, the intended storage duration, regulations, and the available resources.
Great, informative article. Thank you