cryopreservation

Cryopreservation is the process of preserving cells, tissues, or other biological material by cooling them to sub-zero temperatures to halt biological activity. At sufficiently low temperatures, metabolic and chemical processes largely cease, enabling long-term storage with minimal degradation. The technique is widely used in medicine, biology, and conservation to preserve genetic material, samples, and therapeutic materials for future use.

Two main approaches are used: slow freezing and vitrification. Slow freezing gradually lowers temperature while maintaining low, non-toxic concentrations of cryoprotectants to reduce ice crystal formation. Vitrification employs high concentrations of cryoprotectants and rapid cooling to create a glass-like solid that minimizes ice. Common cryoprotectants include glycerol, DMSO, ethylene glycol, and propylene glycol, selected for tissue type. Samples are kept in liquid nitrogen at about −196°C.

Applications span reproductive medicine (sperm, eggs, embryos), regenerative medicine (stem cells, umbilical cord blood), and tissue banking (corneas, cartilage). Cryopreservation also supports research, biodiversity preservation, and biobanking, enabling long-term storage of valuable specimens and the distribution of samples across facilities.

Risks and challenges include ice crystal damage, cryoprotectant toxicity and osmotic stress, contamination, and equipment failure. Warming rate is critical to preserve viability, and successful thawing requires standardized protocols and quality control. The field has evolved with improvements in equipment and ethical and regulatory oversight, particularly in human reproductive applications.