Deep Freezing Cells

(put information describing Deep Freezing Cells, what it is, how it works, why we do it, how long cells last, etc.)

Summary

Maintaining your cell culture is crucial in order to make sure you have cells to perform experiments with. Aside from passaging active cell cultures each week, many labs have samples of their cell lines frozen at -80C or in liquid nitrogen. Having these frozen samples serves multiple purposes. First, these samples can be thawed out and re-plated if a cell culture is ever need to be restarted (such as if a cell culture gets infected or dies for other reasons). Additionally, cell lines can be frozen to perserve their passage number. When cell lines reach high numbers of passages, they may behave differently and having a frozen sample to use to restart a new line would be beneficial in this scenario.

In Our Lab

We currently do not have access to liquid nitrogen, so our cell samples are freezing in the -80C freezer in the shared equipment room on the second floor. Ideally, frozen cells will be moved over to liquid nitrogen for long term storage when we get access to it.

We use CryoStor CS2 Freezing Media as the medium to freeze our cells, which contains DMSO to faciliate the cell's survival at such low temperatures. We use this freezing medium over other cell culture freezing medias because CryoStor's freezing media is bes suited between -70C and -196C, while other media are more appropriate for 0C to ~ -20C, which is not a cold enough temperature to store frozen cell lines at. In addition to this, a Mr. Frosty is used to slowly freeze the cells when initially put into the -80C freezer. The Mr. Frosty functions to prevent the cells from freezing too fast when initially placed in the freezer, as rapidly going from ~ room temperature to -80C will kill the cells or cause them to burst.

We often have multiple tubes of cells freezing at -80C at any given time, and it is important to keep track of the number of tubes of each cell line freezing. The Cell Culture materials list contains information regarding the number of tubes of each cell line frozen at a given time. The table should be updated if any tubes are frozen/thawed, and it is highly recommended to have at least one, but usually multiple tubes freezing at any given time so that an entire cell line will not be wiped out without the potential to be restarted.

Link to Cell Culture Protocols

More information about freezing cells can be found here https://www.thermofisher.com/us/en/home/references/gibco-cell-culture-basics/cell-culture-protocols/freezing-cells.html