Quantifying Heterogeneity According to Deformation of the U937 Monocytes and U937-Differentiated Macrophages Using 3D Carbon Dielectrophoresis in Microfluidics

Abstract

A variety of force fields have thus far been demonstrated to investigate electromechanical properties of cells in a microfluidic platform which, however, are mostly based on fluid shear stress and may potentially cause irreversible cell damage. This work presents dielectric movement and deformation measurements of U937 monocytes and U937-differentiated macrophages in a low conductive medium inside a 3D carbon electrode array. Here, monocytes exhibited a crossover frequency around 150 kHz and presented maximum deformation index at 400 kHz and minimum deformation index at 1 MHz frequencies at 20 Vpeak-peak. Although macrophages were differentiated from monocytes, their crossover frequency was lower than 50 kHz at 10 Vpeak-peak. The change of the deformation index for macrophages was more constant and lower than the monocyte cells. Both dielectric mobility and deformation spectra revealed significant differences between the dielectric responses of U937 monocytes and U937-differentiated macrophages, which share the same origin. This method can be used for label-free, specific, and sensitive single-cell characterization. Besides, damage of the cells by aggressive shear forces can, hence, be eliminated and cells can be used for downstream analysis. Our results showed that dielectric mobility and deformation have a great potential as an electromechanical biomarker to reliably characterize and distinguish differentiated cell populations from their progenitors.

Dielectrophoretic characterization of macrophage phenotypes

“…Even this type of analysis with better resolution than our binary method showed substantial variability for the DEP response at each frequency at 10 V pp . At 50 kHz, only 30% of the cells experience strong pDEP, whereas the rest were in varying degrees of nDEP [57]. Similar heterogeneity of DEP response of macrophages was observed when the frequencies were further increased to 1 MHz.…”

Single-Cell Mechanophenotyping in Microfluidics to Evaluate Behavior of U87 Glioma Cells

“…The images of the cells were obtained every 12 h between 48 to 120 h. ImageJ was used to manually measure the diameter and perimeter of the cells. The single-cell deformation indexes (D) of each cell were calculated using Equation (1) [ 39 , 40 ], where is 3.14. Figure 5 illustrates the deformation index of single cells in the microfluidic cell culture platform.…”

Evaluating carbon-electrode dielectrophoresis under the ASSURED criteria

“…Further, isolation of U937 monocytes was achieved from a cell mixture of monocytes and macrophages using carbonDEP with a separation efficiency of 70%. Elitas and Sengul further characterized the biophysical deformation of U937 monocytes and macrophages differentiated from the same monocytes under the dielectrophoretic forces ( 55 ). The monocytes exhibited a higher deformation index under DEP forces compared to macrophages from the same origin.…”