J. Gomez-Pastora, M. Weigand, J. Kim, J.J. Chalmers
The Ohio State University,
Keywords: RBC separation, magnetic fractionation, aged blood cells, sickle cell anemia
Summary:Approximately 36,000 units of red blood cells (RBCs) are needed every day in the U.S. Although 6.8 million donors give 13.6 million units of blood per year, there is still a great challenge for hospitals to maintain a reliable supply given the 42-day expiration from the date of drawing and match the donor and recipient antigen types (A,B,O). Intense research has been conducted to develop storage mediums (i.e. saline containing adenine, glucose, citrate and phosphate), such as AS-3, which have the requirements of limiting cell lysis below the threshold of 0.8% and maintain a survival rate of the transfused cells of more than 75% at 24 hours after transfusion. However, little attention is directed towards potential fractionation methods to remove unwanted cell debris or aged blood cells from storage blood units prior to transfusion, which could not only expand the shelf life of blood units but also avoid adverse events in the transfused patients. Such fractionation methods could also revolutionize the number of transfusions required for treating certain pathologies, like sickle cell disease (SCD). SCD affects 90,000 to 100,000 people in the U.S., who require regular blood exchange transfusions throughout their lives. The procedure involves slowly removing the person's blood and replacing it with fresh donor blood. However, part of the patient’s blood that is discarded contains fully functional cells that could be returned to the patient in order to reduce both the amount of blood that needs to be transfused and the number of transfusions per year. We have previously shown that healthy RBCs lose, on average, 17% of their hemoglobin (Hb) after 42 days of storage, the maximum FDA-approved length of time for the cold storage of RBCs in additive solution. This difference in Hb concentration was attributed to cell aging. It was hypothesized that the changes in Hb content in RBCs are related to the Hb in RBC-derived microvesicles (which are created to remove damaged cell constituents such as oxidized Hb). Given the magnetic character of deoxygenated- or met-Hb, in this work, we propose the use of a quadrupole magnetic sorter (QMS) to fractionate blood cells based on their Hb content from both healthy storage blood units and SCD blood. In our QMS, a cylindrical microchannel placed inside the center of the quadrupolar magnets is subjected to high magnetic fields and constant field gradients (286 T/m), which causes the deflection of the paramagnetic, Hb-enriched, and functional RBCs from their original path and their collection into a different outlet. Based on their deflection, proportional to the Hb content, we expect to be able to separate the iron-rich (and presumably healthy) fractions from the iron-poor, aged or sickle RBCs.