Characterizing the Dielectric Properties of Human Mesenchymal Stem Cells and the Effects of Charged Elastin-like Polypeptide Copolymer Treatment

Human mesenchymal stem cells (hMSCs) have three key properties that make them desirable for stem cell therapeutics: differentiation capacity, trophic activity, and ability to self-renew. However, current separation techniques are inefficient, time consuming, expensive and in some cases alter hMSCs cellular function. Dielectrophoresis (DEP) is a technique that uses alternating current (AC) electric fields to separate biological cells based on the dielectric properties of their membrane and cytoplasm. This work characterizes hMSCs dielectric signature and homogenizes its morphology. A quadrapole Ti-Au electrode microdevice was used to quantify the dielectric properties based on the cross-over frequency and DEP spectra of hMSCs from 0.01-35MHz in dextrose buffer solutions (0.03S/m and 0.10S/m). The membrane capacitance and permittivity were found to be 2.17pF and 4.53 in 0.03S/m and 1.70pF and 1.41 in 0.10S/m. Elastin-like polypeptide (ELP-) polyethyleneimine (PEI) copolymer was used to modify hMSCs morphology to spheroidal clusters. Results demonstrated that ELP-PEI treatment increased hMSCs membrane permittivity and shifted the cross-over frequency above 35MHz.