Douglas TA, Cemazar J, Balani N, Sweeney DC, Schmelz EM, Davalos RV. A feasibility study for enrichment of highly aggressive cancer subpopulations by their biophysical properties via dielectrophoresis enhanced with synergistic fluid flow. Electrophoresis. 2017;38: 1507–1514. doi:10.1002/elps.201600530
A common problem with cancer treatment is the development of treatment resistance and tumor recurrence that result from treatments that kill most tumor cells yet leave behind aggressive cells to repopulate. Presented here is a microfluidic device that can be used to isolate tumor subpopulations to optimize treatment selection. Dielectrophoresis (DEP) is a phenomenon where particles are polarized by an electric field and move along the electric field gradient. Different cell subpopulations have different DEP responses depending on their bioelectrical phenotype, which, we hypothesize, correlate with aggressiveness. We have designed a microfluidic device in which a region containing posts locally distorts the electric field created by an AC voltage and forces cells toward the posts through DEP. This force is balanced with a simultaneous drag force from fluid motion that pulls cells away from the posts. We have shown that by adjusting the drag force, cells with aggressive phenotypes are influenced more by the DEP force and trap on posts while others flow through the chip unaffected. Utilizing single-cell trapping via cell-sized posts coupled with a drag-DEP force balance, we show that separation of similar cell subpopulations may be achieved, a result that was previously impossible with DEP alone. Separated subpopulations maintain high viability downstream, and remain in a native state, without fluorescent labeling. These cells can then be cultured to help select a therapy that kills aggressive subpopulations equally or better than the bulk of the tumor, mitigating resistance and recurrence.
(A) Percentage of highly malignant MOSE-LTICv cells in the output populations compared to the initial and untrapped populations at 350 Vrms, 30 kHz applied voltage and different flow rates. N shows the number of trials at each flow rate.(B) Separation data normalized by the initial population, to show percentage enhancement for each population.
Schematic of microfluidic device and cells flowing through device. A mixed population of fluorescently labeled cells flow through the chip. While the voltage is on, some cells trap and others flow through. When the voltage is turned off and cells are released, trapped cells flow through resulting in two subpopulation outputs. (A) Full schematic of chip and function. (B) Post structure inside chip—cells flow through and some cells trap. When DEP buffer is sent through
the chip, untrapped cells flow through, leaving only the trapped population.