Freeze-Drying Human Red Blood Cells: Effect of Hematocrit and Composition of the Freeze-Drying Medium on Red Cell Survival.

A wide variety of medical procedures require transfusion of red blood cells (RBCs). RBCs are currently preserved either at 4°C, at a higher hematocrit (70%) for up to 7–12 weeks or in a frozen state in the presence of glycerol at −80°C for several years. However, each procedure has its demerits. Storage in the dry state offers a possibility for storing the cells for long periods of time under conditions that are far easier to maintain (i.e. room temperature), making the transport to sites of immediate need feasible. We developed a method for freeze-drying RBCs using 15% hematocrit, resulting in a survival of 40% after rehydration, as assessed by the percent hemolysis. In this work, we report the effect of cell hematocrit, concentration of trehalose, salts and overall osmolality of the freeze-drying medium on the survival after freeze-drying and rehydration. Decreasing the percent hematocrit and trehalose in the freeze-drying buffer resulted in about 20% improvement in the post-rehydration survival. Freeze-dried and rehydrated RBCs showed high levels of ATP, 2,3-DPG and low percent methemoglobin. These data are discussed in terms of the glass transition properties of the freeze-drying buffer. This work provides an important step in formulating a freeze drying medium that will provide optimum RBC survival after freeze drying and rehydration.