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We have shown the potential of a new method for optimizing the separation of human stem cell subsets from
peripheral blood based on a novel cell labeling technique that leverages the capabilities of a new commercially available
high speed magnetic cell sorting system (IKOTECH LLC, New Albany, IN). This new system sorts cells in a
continuously flowing manner using a Quadrupole Magnetic cell Sorter (QMS). The sorting mechanism is based upon
the magnetophoretic mobility of the cells, a property related to the relative binding distributions of magnetic particles per
cell, as determined by the utilization of a Magnetic Cell Tracking Velocimeter (MCTV). KG-1 cells were competitively
labeled with anti-CD34 magnetic beads and anti-CD34 FITC to obtain an optimal level of magnetophoretic mobility as
visualized by the MCTV for high throughput sort recovery in the QMS.
In QMS sorting, the concept of split-flow thin channel (SPLITT) separation technology is applied by having a sample
stream enter a vertical annular flow channel near the channel's interior wall followed by another sheath flow entering
near the exterior wall. The two flows are initially separated by a flow splitter. They pass through the bore of a Halbach
permanent quadrupole magnet assembly, which draws magnetized cells outward and deflects them into a positive
outflow, while negative cells continue straight out via the inner flow lamina. QMS sorts cells based upon their
magnetophoretic mobility, or the velocity of a cell per unit ponderomotive force, the counterpart of fluorescence
intensity in flow cytometry. The magnetophoretic mobility distribution of a cell population, measured by automated
MCTV, is used as input data for the algorithmic control of sample, sheath, and outlet flow velocities of the QMS. In this
study, the relative binding distributions of magnetic particles per cell were determined by MCTV using novel sorting and
sizing algorithms. The resulting mobility histograms were used to set the QMS flow parameters so that desired cell
populations could be selected on the basis of a mobility "window". The MCTV and the QMS are able to work together
to provide good sort boundaries for cell populations that are mathematically defined as opposed to the traditional
magnetic sort systems that solely rely on whether a cell is simply "magnetized" or not.
One long-term application of this new high speed cell sorting system is to sterilely isolate large numbers of human
stem cells directly from a donor's blood for subsequent manipulation in tissue culture for regenerative medicine within
that same patient. This will eliminate the need for immune suppressive drugs in an autologous transplantation procedure.
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