- Trehalose is a non‑reducing disaccharide composed of two glucose molecules linked by an α,α‑1,1‑glycosidic bond. It is one of the most remarkable natural cryoprotectants, widely used by organisms capable of surviving extreme dehydration, freezing, and environmental stress. In cryobiology, trehalose functions as a non‑permeating cryoprotective agent, protecting cells and tissues by stabilizing membranes, preserving proteins, and modifying water behaviour during freezing. Its unique biochemical properties make trehalose an important component of slow freezing protocols, vitrification mixtures, and advanced biobanking strategies.
- Trehalose is best known for its ability to replace water molecules around biological structures. During cooling or dehydration, trehalose forms hydrogen bonds with phospholipids and proteins, maintaining structural integrity even when water is removed or immobilized. This “water replacement” mechanism prevents membrane fusion, phase transitions, and protein denaturation. Trehalose also forms a glassy matrix at low temperatures, immobilizing cellular components and reducing molecular motion. This glass‑forming ability is central to its cryoprotective function and is similar to the vitrification behaviour of permeating CPAs, though trehalose itself remains extracellular unless artificially introduced into cells.
- As a non‑permeating CPA, trehalose increases extracellular osmotic pressure during cooling, promoting controlled cellular dehydration. This reduces the likelihood of intracellular ice formation, one of the most damaging events in cryopreservation. Trehalose also slows ice nucleation and crystal growth by increasing solution viscosity. These combined effects make trehalose particularly valuable when used alongside permeating CPAs such as DMSO, ethylene glycol, or propylene glycol. Trehalose‑CPA mixtures reduce the concentration of toxic permeating agents while improving overall cryoprotection. More details on CPA combinations are available in Cryoprotective Agents.
- Trehalose is widely used in reproductive cryobiology. In oocyte and embryo freezing, trehalose enhances membrane stability and reduces osmotic shock during CPA loading and removal. Many vitrification kits include trehalose or sucrose as non‑permeating additives to support rapid dehydration and prevent ice formation. Trehalose also improves post‑thaw developmental potential by protecting proteins and organelles from cold‑induced damage. In sperm cryopreservation, trehalose enhances motility recovery and reduces membrane disruption.
- Beyond reproductive applications, trehalose is used in the preservation of stem cells, immune cells, and various tissues. It is particularly valuable in biobanking and regenerative medicine, where long‑term stability and low toxicity are essential. Trehalose is also used in lyophilization (freeze‑drying) of biological materials, where its ability to stabilize proteins and membranes during dehydration is critical.
- Trehalose exhibits very low toxicity, especially compared with permeating CPAs. Because it does not enter cells naturally, it avoids intracellular chemical interactions that cause damage. However, high extracellular concentrations can cause osmotic stress if added too rapidly. Stepwise addition and removal are therefore recommended. Some advanced methods introduce trehalose directly into cells using membrane transporters, nanoparticles, or electroporation, enabling intracellular protection similar to natural anhydrobiotic organisms.
- Overall, trehalose is one of the most versatile and biologically compatible cryoprotectants in modern cryobiology. Its ability to stabilize membranes, protect proteins, reduce ice formation, and lower CPA toxicity makes it a valuable component of many freezing and vitrification protocols. As research advances toward organ cryopreservation, biobanking, and synthetic anhydrobiosis, trehalose continues to play a central role in improving the safety and effectiveness of low‑temperature biological storage.
