- When temperatures drop below freezing, cells and tissues encounter several challenges, leading to a series of damaging events.
- As water freezes, it forms ice crystals that can puncture cell membranes and damage cell membrane and internal organelles. Additionally, ice crystal growth causes mechanical stress due to volume expansion, as water expands by approximately 9% when frozen.
- During the crystallization process, the forming ice lattice excludes solutes, resulting in their concentration in the remaining unfrozen liquid phase. As more ice forms, the liquid phase shrinks, raising solute concentrations to potentially lethal levels. This high solute concentration disrupts the cell’s natural osmotic balance and can denature proteins.
- Cryoprotectants help prevent this damage through their unique chemical properties. These agents form strong hydrogen bonds with water molecules. This interaction serves two crucial functions: it lowers water’s freezing point and reduces the number of free water molecules available to form ice crystals. By limiting the water molecules that can interact with each other, these cryoprotectants reduce the formation of critical nucleation sites needed for ice crystal formation, thereby protecting cellular structures from both mechanical and chemical damage.
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