Cryoprotectants for red blood cells: Evaluate safety and effectiveness by in vitro measures

The transfusion of red blood cells (RBCs) is crucial in current medicinal research. The shelf-life of donated RBCs preserved by the normal method is very short, limiting their clinical application. Cryopreservation is a reliable and effective technology for the long-term storage of RBCs. During the process, ice formation will cause irreversible injuries to RBCs. Glycerol is used as a cryoprotectant (CPA) for RBCs to mitigate cryoinjuries. But it severely induces RBC hemolysis and deformation. This review introduces some biocompatible and effective CPAs used for RBC cryopreservation, outlining recent advances. Currently, there is no uniform standard to determine whether a CPA is suitable for RBCs. According to previous studies, we summarize for the first time comprehensive methods to evaluate the performance of CPAs by ensuring their safety and effectiveness. The safety of CPAs is defined as the degree of damage to RBCs, while the effectiveness is demonstrated by the properties of thawed RBCs, including membrane properties, protein activities, rheological properties, and metabolites levels. A novel CPA that is confirmed suitable for RBCs by these methods may be applied to other cells. We believe comprehensive methods can thoroughly evaluate the performance of CPAs and promote the development of transfusion therapy in clinic.