Woohoo, it's the Bank holiday weekend!

I've topped up our liquid nitrogen storage tank to keep our cells at a cool -196C while I'm out in the sunshine this weekend.  At this temperature, metabolic activity ceases and in theory the cells can be stored indefinitely.  It's really important that cells are stored in the vapour phase of a nitrogen store and not in the liquid, for 3 reasons: First, safety: small droplets of liquid can enter the threads of the vial cap, and cause the vial to explode upon thawing, especially in older designs of cryovials.  Second, to avoid contamination: it may be hard to imagine, but cases have been documented of mycoplasma contamination spreading between vials stored in the liquid phase.  And third: cost.  Liquid nitrogen is a major expense for cell culture labs.Why fill the storage vessel to the brim with liquid nitrogen, when using only a small percentage of the volume would actually do a better job?....
OK, on that note I will sign off for the week.  You all have a fab bank holiday weekend, and we'll catch up next week with more cell culture info and tips!  Cheers, Cellwyn.

Why cells need specialised freezing techniques

If cells were placed into a standard -20C or -80C freezer without any prior treatment, their delicate membranes and organelles would be destroyed by the formation of ice crystals, which would literally break the cell apart upon thawing.  This is why specialised freezing (cryopreservation) techniques are critical and have been developed to minimise the formation of intracellular ice crystals.  Cryopreservation technology involves the use of a cryoprotectant, typically dimethyl sulfoxide (DMSO), which stabilises the intracellular components, disrupts the lattice structure of ice crystals, and slowly draws water out of the cell during the freezing process.  The use of a cryoprotectant is combined with a slow cooling rate (typically 1 degree Celsius per minute), to minimise ice crystal formation and encourage the extracellular migration of water.  This technique helps to optimise cell viability upon thawing.

Freezing cells

Today I've frozen down some cells for a new project - the first time I've frozen down my own supply, so fingers crossed!  Cryopreservation is an essential technique in order to maintain a long term, consistent supply of cells.  Continuous culture of cell lines, without cryoprservation, leads to a number of problems including genetic drift, loss of key characteristics and an increased probability of microbial contamination.  So learning to cryopreserve cells effectively is a critical skill in cell culture.  Over the next few days I'll be sharing hints and tips with you as I learn more about it here at XCellR8......