Today’s best practices for cryopreservation of samples are the result of decades of trail and error. Since early false beliefs that all cells could be preserved using the same methods, we’ve learned the key to successful cryo storage.
One critical factor to consider is the rate of cooling required for the particular cell type you are working with. When it comes to preparing your cells for storage, are you matching the composition of your samples to optimal cooling speeds?
Want to learn more? Explore our on-demand webinar: Avoid The Icebergs! Managing Sample Preparation For Cyro Storage, in the Cell Culture Café Webinar
Cold as (intracellular) ice
It’s crucial to understand the varying needs of different cell types when freezing and thawing your samples. While a cooling rate of 1℃ per minute is a good place to start, each type of cell—mammalian or bacterial, blood or stem cell—will benefit from dramatically different cooling rates. Freeze too slow, and cell injury results. Freeze too fast, and the formation of intracellular ice can devastate your cell cultures’ viability.
A good guideline: The larger the cells, the more complex their freezing protocol. You’ll want to consider both cooling rate and the cryoprotective agent (CPA) or agents you use in determining how to proceed.
Stem cells, for example, can benefit from vitrification, which moves the sample rapidly into the gas phase and maintains it at -150℃. Rapid cooling into and thawing from a vitrified state has been shown in certain studies to increase stem cell viability. A recommended CPA for this type of culture consists of 5-10% DMSO and 20-90% serum.
Other cell types can be similarly preserved through vitrification, but with different recommended agents. Always monitor the current literature to determine the best CPA for your application. Ongoing studies of vitrification’s effects are promising, but not every cell type’s reaction has been studied.
Given the distinct needs of many different cell types, consider the value that controlled-rate freezing, through a mechanical, programmable freezer, could offer to help ensure the right conditions for the samples you work with. (Read more in a discussion regarding proper cold storage selection, covered in a previous blog post.)
More on cryopreservation
Learn more best practices associated with protecting and preparing your samples for cryopreservation in our on-demand webinar, Avoid The Icebergs! Managing Sample Preparation For Cyro Storage, in the Cell Culture Café.
For even more help in your planning, please refer to our Guide for Proper Cryogenic Preservation.