A hemocompatible cryoprotectant inspired by freezing-tolerant plants

Cryopreservation can extend the storage time of red blood cells (RBCs) for even decades, offering a promising solution to blood waste and shortage caused by routinely used hypothermic preservation method (˜42 days). Currently, organic solvents such as glycerol or dimethyl sulfoxide are the state-of-the-art cryoprotectants (CPAs). However, severe RBC hemolysis induced by solvent CPA removal has raised serious concerns, which has been the bottleneck problem for RBC cryopreservation. Here, inspired by freezing-tolerant plants, we reported a natural zwitterionic betaine-based approach for effective RBC cryopreservation without the need of any organic solvent. Using a time-saving ultrarapid freezing protocol, about 80% of post-thaw RBC integrity rate could be achieved. Most importantly, RBC integrity was not affected during betaine removal, indicating its hemocompatibility. Mechanistically, we presented that betaine could inhibit ice formation and recrystallization during freeze-thaw cycle to protect cells from ice injury; moreover, betaine probably could be promptly taken up and released by cells to prevent them from osmotic injury. This approach provides an attractive solution for long-distance/long-term RBC transport/storage, and may benefit current cryopreservation technologies to support the lifesaving RBC transfusion.