How does liquid nitrogen preserve blood, tissue, and other biological materials?

Liquid nitrogen is used in cryopreservation to store biological materials like blood, tissue, and bone marrow by maintaining them at extremely low temperatures, which effectively halts biological activity.12

The process relies on the following principles:

• Controlled Freezing: To prevent cell death, biological materials are typically cooled using a controlled-rate freezer. This prevents rapid cellular dehydration and the formation of intracellular ice crystals, which can destroy cell organelles.1
• Cryoprotective Agents: Before freezing, substances such as dimethyl sulfoxide (DMSO) or glycerol are often added to cells. These molecules enter the cells to further protect them from damage caused by ice formation.1
• Storage: Once frozen, samples are transferred to a liquid-nitrogen freezer. These systems maintain the materials at temperatures low enough to ensure long-term viability, allowing cells to remain alive for more than a decade.1

By keeping materials in this state of suspended animation, medical professionals can preserve vital resources like hematopoietic stem cells for future therapeutic use.1