Just as an update to the -20 to -80 thing. While the original presentation showed the benefits of freezing at -20 vs -80.
SWMBO'd offers this advice:
They use liquid nitrogen only when they want to arrest the cells at a given stage or when they want to rupture the cells to harvest protein or RNA from the cells and don't care about the shearing of the cell walls. Viability is essentially lost doing a flash-freeze like this, so it is of no use to us homebrewers.
As for -80 vs -20. They go from room temp to -80. No messing around at -20 or step-freezing. She does admit that slowly freezing the samples would improve viability, but they don't INSTANTLY freeze when you put them into the -80 from room temp, so this is good enough. Again, the goal is long term storage and viability vs high viability at like 16 months. You're going to have to step them up from a small starter regardless of how you decide to store them, so what's the difference between 25% and 33% viability at 12 weeks or whatever that presentation stated. That timeframe is basically irrelevant if your goal is a LONG term storage bank and only representative of the loss of viability due to the freezing process itself, not the effect of the storage temp per se, IMO.
but even if I assume the numbers in the presentation are correct and the percentage of viable cells is in the 25% range (going to
I agree with what you've stated. All of the cell work in the labs I've been store cells at -80C or in a liquid nitrogen dewar, the later being preferred for the long-term storage of certain mammalian cell lines.
