Even though “slow” freezing permits storage for an indefinite length of time, the drop and subsequent rise in temperature often results in damage, especially between the temperatures of ∼0°C to −15°C. Consequently, during freezing, cells are exposed to varying pressures (thermal, chemical and mechanical) which can affect their proper function.
Vitrification is an alternative to “slow” freezing for live tissue and cells, offering the benefit of avoiding extra- and intracellular ice crystal formation. It is a revolutionary technique that achieves the conversion of a material into vitreous form free from crystalline structures, through the use of increased concentrations of special cryoprotectant solutions and the ultra-rapid temperature drop. Eggs and embryos to be vitrified are exposed to special cryoprotectant solutions and then placed in special vessels that are hermetically sealed. Next, they are immersed directly into liquid nitrogen at -196°C, where they are stored.