cryoprotectantssubstances

Cryoprotectant substances are chemical agents used to protect biological samples from damage during freezing and thawing. They work by reducing ice formation, limiting crystal growth, and stabilizing cellular components to improve survival after cryopreservation. Cryoprotectants are generally classified as permeating (penetrating) or non-permeating.

Permeating cryoprotectants enter cells and help mitigate intracellular ice formation. Common examples include glycerol, dimethyl sulfoxide (DMSO), ethylene glycol, and propylene glycol. These compounds lower the freezing point inside cells, shield membranes, and can promote vitrification in rapid-freezing protocols. Non-permeating cryoprotectants stay outside cells and protect by creating an osmotic gradient that dehydrates cells and stabilizes extracellular ice. Examples include sugars such as sucrose and trehalose, as well as certain polymers like hydroxyethyl starch and polyvinylpyrrolidone.

Cryoprotectants are used in a range of applications, including the cryopreservation of blood and immune cells, stem cells, sperm, oocytes, embryos, and various tissues. In clinical settings, protocols often combine permeating and non-permeating agents to balance protection with toxicity, while vitrification or slow-freezing approaches determine the cooling strategy.

Key considerations include toxicity and concentration limits, exposure time, and the need to remove residual cryoprotectants after thawing. The choice of agents and protocol depends on the sample type, desired survival outcomes, and regulatory guidelines. Ongoing research seeks safer, more effective formulations and approaches to preserve complex tissues and organs with higher viability.