(438g) Separation of Intrinsically Magnetic Red Blood Cells Using Combination of Numerical Modelling and Microfluidic Magnetic Deposition System

Kim, J., Ohio State University
Chalmers, J. J., The Ohio State University
Annually, an average of 21 million units of human blood components are transfused in the US for various medical purposes. Moreover, as more and more researchers study the human blood components for various medical research purposes, demand for efficient red blood cell (RBCs) separation technique increases as well. The traditional method for the separation of RBCs is centrifugation, which requires a lot of resources (equipment/energy) and time. To overcome this issue, various approach to develop novel RBC separation system has been developed over the years, but opportunities still exist for improvement, and recent development in analysis technology led to focus on the study of red blood cell themselves.

Based on the observation made by Pauling and Coryell back in 1936, the blood community has concluded that RBCs in different chemical state (oxygenated, deoxygenated and oxidized) express different magnetic moment due to different number of unpaired electrons in the iron (stored in hemoglobin). This difference in magnetic moment has led many researchers to develop novel separation devices that could exploit this magnetic susceptibility difference. The magnetic deposition microscopy (MDM) is a system that uses permanent magnets and pole pieces in special configuration to generate magnetic gradient field. This magnetic gradient drives the magnetic entities from a mixture towards the deposition slides and eventually separate them from the non-magnetic population.

For this study, the magnetic separation of the RBCs was conducted using combination of experiment and numerical modelling approach. To model the behavior of RBCs in the MDM system, the magnetic mobility (a parameter that describes the responsiveness of individual entity to a magnetic energy gradient) of the oxidized hemoglobin (metHb) and oxygenated hemoglobin (oxyHb) was measured using the cell tracking velocimetry system (CTV). The CTV system uses charge coupled device camera connected to microscope to record/calculate the magnetic mobility of entities in buffer under the influence of constant magnetic energy gradient in steady state flow. After their magnetic mobility values were recorded, the data was fed into the MDM model developed through combination of the two software, FEMM and ANSYS Fluent. Both software uses finite element and volume analysis method to solve electromagnetic and flow problems. The discrete phase modelling approach connected to custom user defined function, which incorporates the magnetic force balance and the magnetic mobility distribution from CTV, was used to model the behavior of the oxyHbs and metHbs in the system, as well as calculating the theoretical deposition/separation rate of the magnetic RBCs.

Based upon the simulation results, the optimum flow condition was determined to be 0.2 ml/min for the MDM system. Also, the experimental result showed a close match in the deposition location compared to the simulation results. However, this low volumetric flow rate is not yet realistic enough for clinical applications. To overcome this issue, we mean to utilize this study method more vigorously, where current magnetic separation system can be modified and simulated through FEMM, determine the optimal flow setting for RBC lysis using ANSYS Fluent, and finally carry out magnetic separation experiment in the newly designed system. Furthermore, we are now exploring the possibility of using polymer mixed with iron oxide particles to 3-D print a novel disposable magnetic separation system. Using this combinatorial approach, we aim to increase the throughput of the device to separate 5 ml of RBCs unit in 10 minutes.