Core–Shell Microfiber Encapsulation Enables Glycerol-Free Cryopreservation of RBCs with High Hematocrit

Cryopreservation of red blood cells (RBCs) provides great potential benefits for providing transfusion timely in emergencies. High concentrations of glycerol (20% or 40%) are used for RBC cryopreservation in current clinical practice, which results in cytotoxicity and osmotic injuries that must be carefully controlled. However, existing studies on the low-glycerol cryopreservation of RBCs still suffer from the bottleneck of low hematocrit levels, which require relatively large storage space and an extra concentration process before transfusion, making it inconvenient (time-consuming, and also may cause injury and sample lose) for clinical applications. To this end, we develop a novel method for the glycerol-free cryopreservation of human RBCs with a high final hematocrit by using trehalose as the sole cryoprotectant to dehydrate RBCs and using core–shell alginate hydrogel microfibers to enhance heat transfer during cryopreservation. Different from previous studies, we achieve the cryopreservation of human RBCs at high hematocrit (> 40%) with high recovery (up to 95%). Additionally, the washed RBCs post-cryopreserved are proved to maintain their morphology, mechanics, and functional properties. This may provide a nontoxic, high-efficiency, and glycerol-free approach for RBC cryopreservation, along with potential clinical transfusion benefits.