(419a) Characterizing the Dielectric Properties of Human Mesenchymal Stem Cells Using a Quadrupole Microfluidic Device

Characterizing the dielectrophoretic response of stem cells at various stages of growth and in the presence of promoters is an important first step in designing an electrokinetic microdevice to separate stem cell types [1]. Dielectrophoresis is a technique utilizing nonuniform electric field to polarize cells based on the polarizability and dielectric properties of their membrane, cytosol, and other structurally dominant organelles. The DEP force is also tunable via adjustments to the electric field magnitude and shape and the surrounding medium [2, 3]. Hemapoetic stem cell identification has been accomplished via antibody tagging of unique cell-surface antigens followed by flow cytometry and fluorescence-activated cell sorting, but adaptation to other types of stem cells has been limited [1]. Therefore, there is a need for an identification techique that does not require tagging and is versatile enough to identify and separate all types of stem cells. Dielectrophoretic separations are advantegous because identification of stem cells can be coupled with separation in a microfluidic device.   In this work, a microfluidic device with gold quadrupole electrodes, microchannel and a pumping system will be used to characterize the DEP response of human mesenchymal stem cells. Mesenchymal stem cells are multipotent adult stem cells and can differentiate into osteoblasts, adipocytes, chondrocytes, astrocytes, and myoblasts based on environmental promoters [4]. The mesenchymal stem cells will be characterized at frequencies ranging from 100kHz to 80MHz in a medium with conductivity ranging between 0.01 and 0.5 S/m[t1] . These experiments will map out the cross-over frequency of the human mesenchymal stem cells in different stages of growth and in the presence of promoters.  COMSOL simulations and MATLAB will be used to fit the data to a single or multishelled spherical DEP polarization model in order to back out structural polarizability and conductivities of components of the human mesenchymal stem cells. The broader implications of electrokinetically identifying differences in stem cells lie in purification and control for tissue engineering and cell therapy applications [4].

References:

1. Flanagan, L.A., Lu, J., Wang, L., Marchenko, S.A., Jeon, N.L., Lee, A.P., and Monuki, E., Stem Cells, 26, 656-665, 2008.
2. Hawkins, B.G., Huang, C., Arasanipalai, S., and Kirby, B.J., Analytical Chemistry, 83, 3507-3515, 2011.
3. Kirby, B.J., Micro- and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices, New York: Cambridge University Press, 2010.
4. Wu, H.W., Lin, C.C., and Lee, G.B., Biomicrofluidics, 5, 013401-013426 2011.