Fractionation of Aged RBCs Based on Hemoglobin Content

Red blood cell (RBC) transfusion is clinically used to treat hemodynamic instability and O2 carrying deficits in patients with acute blood loss, and patients with chronic anemia caused by bone marrow failure/suppression. Currently, cold storage of human RBCs (hRBCs) can preserve hRBCs for a maximum of six weeks (i.e. 42 days). This relatively short ex vivo storage length has been set by the United States Food and Drug Administration (US FDA) based on the post transfusion viability (PTV) of stored hRBCs at 24 hours, which must be greater than or equal to 75 ± 9% and the percent hemolysis of stored hRBCs which must be less than 1% (8). Despite widespread clinical use, stored RBCs face two major problems, namely: the steadily decreasing supply of RBC units, and the questionable clinical safety of RBCs stored for extended periods of time. It is well known that upon transfusion of stored RBCs, there is a population of RBCs (i.e. healthy RBCs) that circulate for more than 24 hours, and another smaller population (i.e. damaged RBCs) that are cleared within 24 hours post transfusion. Therefore, it could be clinically beneficial if the damaged RBCs in any unit of RBCs could be separated leaving a population of only healthy RBCs behind for transfusion. Utilizing technology that exploits the intrinsic magnetization of the deoxygenated form of Hb inside RBC's in an applied magnetic field, the Yazer, Chalmers and Zborowski laboratories demonstrated that RBCs lose magnetization during storage, which indicates that the aged RBCs lose Hb during storage. In this application, we hypothesize and experimentally test that RBCs with higher Hb content (i.e. healthy RBCs) correlate with higher deformability and PTV versus RBCs with lower Hb content (i.e. damaged RBCs).