Label-free isolation of circulating tumor cells using negative lateral dielectrophoresis-assisted inertial microfluidics

A dielectrophoresis (DEP)-assisted inertial microfluidics method is introduced in this study for the isolation of circulating tumor cells (CTCs) from diluted blood samples. The method is based on the negative DEP, provided with the laterally allocated microelectrodes as well as the proper selection of the applied electric field frequency and voltage to suppress the limited purity arising from the overlapped sizes of CTCs and white blood cells. The dynamics of polystyrene microparticles (with the sizes of 5 and 15 & mu;m) were first investigated numerically and experimentally within the DEP-assisted inertial microfluidic device. While the dynamics of the larger microparticles were governed by the inertial and DEP forces, those of the smaller microparticles were subject to the Dean drag force. In the absence of the DEP force, the larger microparticles migrate to two stable equilibrium positions corresponding to the upper and lower walls for the microchannel cross section. In the presence of the DEP force, however, the equilibrium position corresponding to the lower wall is considerably displaced, while the top wall-associated equilibrium position remains almost intact. Finally, it was found that the proposed method outperformed the corresponding solely inertial method in terms of purity in the isolation of CTCs from diluted blood samples. For instance, at a hematocrit of 1%, the purity of isolated MDA-MB-231 cells spiked in diluted blood samples was 85.3% by the use of the solely inertial microfluidic device, while viable CTCs were captured by the DEP-assisted inertial microfluidic device with a purity of 94.1% at the total flow rate and applied voltage of, respectively, 650 & mu;L min(-1) and 50 V.