Cryoprotectants are chemical compounds added to the solution surrounding an embryo before freezing to prevent or minimise ice crystal formation. They work by replacing some of the water in and around the cells with substances that behave differently when cooled.
In IVF vitrification, two categories of cryoprotectants are used: membrane-permeating agents and non-permeating agents. The most commonly used membrane-permeating agents are ethylene glycol and dimethyl sulphoxide, known as DMSO. Non-permeating agents such as sucrose remain outside the cell and help manage the osmotic environment.
Vitrification protocols typically involve a two-step loading process. The embryo is first placed in an equilibration solution containing lower concentrations of cryoprotectant for several minutes. It is then transferred to a vitrification solution containing higher concentrations for a short time, typically 30 to 60 seconds, before being loaded onto the carrier and plunged into liquid nitrogen.
The concentration and combination of cryoprotectants, the temperature at which loading occurs, and the timing of each step are critical variables. Deviation from the validated protocol can result in incomplete cryoprotection and reduced survival, or in cryoprotectant toxicity that damages the embryo before freezing.
Commercial vitrification kits from validated suppliers provide calibrated solutions and standardised protocols, which is why most UK IVF laboratories use commercial kits rather than preparing solutions in-house.
For vitrification workstations, carrier systems, and associated consumables, Cryolab works with UK IVF laboratories on the full workflow. Visit cryolab.co.uk“>Cryolab
