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.