cryoprotectants

Cryoprotectants are substances used to protect biological material from damage during freezing and storage at low temperatures by reducing ice formation, stabilizing cell membranes and proteins, and modulating osmotic stress. They are used in cryopreservation of cells, tissues, and organisms, enabling long-term storage.

They work by two main mechanisms: penetrating cryoprotectants enter cells and reduce intracellular ice formation; non-penetrating cryoprotectants act extracellularly to balance tonicity and lessen ice crystal growth. They also promote vitrification, a glass-like solidification that minimizes ice crystals, especially with rapid cooling and high concentrations.

Common classes include penetrating agents such as dimethyl sulfoxide (DMSO), glycerol, ethylene glycol, and propylene glycol; non-penetrating agents such as sugars (sucrose, glucose, trehalose) and polymers (Ficoll, PEG). Some formulations combine multiple agents to optimize protection.

Applications include cryopreservation of blood cells, stem cells, gametes and embryos for assisted reproduction, tissue banks, and plant germplasm; research on organ preservation and biobanking; and vitrification-based approaches that enable rapid cooling.

Important considerations include toxicity that varies among cell types, requiring optimization of concentration and exposure time; risk of osmotic shock during loading and removal; cooling and warming rates; and the need for careful post-thaw handling to remove or dilute cryoprotectants and restore normal physiology.