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#cell freezing

2 public questions tagged with this topic.

Animal Tissue Culture 2

The temperature of liquid nitrogen used for cryopreservation is:

Liquid nitrogen provides ultralow storage temperature of -196°C at atmospheric pressure, close to its boiling point. At this temperature, kinetic energy of molecules becomes extremely low, effectively halting all biochemical reactions, enzymatic activity, solute diffusion, and ice recrystallization processes. Cells suspended in DMSO-containing freezing medium enter glassy state preventing further ice growth. Long-term viability preserved for decades to theoretically indefinitely. Mechanical ultra-low freezers at -80°C slow metabolism but do not fully arrest chemical reactions; free radical accumulation and gradual ice crystal growth over months reduce viability, making -80°C suitable only for temporary holding. Storage can be in liquid phase immersing vials directly achieving -196°C or vapor phase at -150°C to -180°C reducing risk of cross-contamination between leaky vials and transmission of adventitious agents. Inventory systems with alphanumeric racking, cryovial labeling resistant to nitrogen, and continuous temperature alarms with liquid nitrogen level monitors ensure security of master and working cell banks including valuable induced pluripotent stem cells.

Ref: ATCC Animal Cell Culture Guide Liquid Nitrogen -196°C arrests metabolism; Freshney Ch.22 Vapor vs liquid phase storage principles.

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Animal Tissue Culture 2

Cryopreservation of animal cells commonly uses:

Cryopreservation of mammalian cells routinely employs dimethyl sulfoxide as penetrating cryoprotectant at 5-10% concentration. DMSO is small amphipathic molecule freely crossing lipid bilayer, replacing intracellular water and disrupting hydrogen bonding network required for ice lattice formation. During controlled slow cooling at -1°C per minute achieved using isopropanol containers like Mr. Frosty or programmable freezers, extracellular ice forms first creating osmotic gradient that draws water out of cells dehydrating them. DMSO lowers freezing point, promotes vitrification where residual intracellular water transitions to amorphous glass rather than sharp damaging crystals that would shear membranes, organelles and chromosomes. DMSO also stabilizes proteins through preferential exclusion. At ambient temperature DMSO exhibits cytotoxicity and can trigger differentiation of hematopoietic lines, so after thawing rapid dilution in large volume medium reduces concentration below 1%. Glycerol penetrates slower favoring insect and embryonic stem cells, while ethanol and formaldehyde are lethal and unsuitable. DMSO thus became standard in ATCC and cell bank protocols.

Ref: Freshney Ch.22 Cryopreservation DMSO prevents intracellular ice; Mazur Science 1984 kinetics of water loss and vitrification by DMSO.

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