A miniaturized continuous dielectrophoretic cell sorter and its applications

Abstract

There is great interest in highly sensitive separation methods capable of quickly isolating a particular cell type within a single manipulation step prior to their analysis. We present a cell sorting device based on the opposition of dielectrophoretic forces that discriminates between cell types according to their dielectric properties, such as the membrane permittivity and the cytoplasm conductivity. The forces are generated by an array of electrodes located in both sidewalls of a main flow channel. Cells with different dielectric responses perceive different force magnitudes and are, therefore, continuously focused to different equilibrium positions in the flow channel, thus avoiding the need of a specific cell labeling as discriminating factor. We relate the cells' dielectric response to their output position in the downstream channel. Using this microfluidic platform that integrates a method of continuous-flow cell separation based on multiple frequency dielectrophoresis, we succeeded in sorting viable from nonviable yeast with nearly 100% purity. The method also allowed to increase the infection rate of a cell culture up to 50% of parasitemia percentage, which facilitates the study of the parasite cycle. Finally, we prove the versatility of our device by synchronizing a yeast cell culture at a particular phase of the cell cycle avoiding the use of metabolic agents interfering with the cells' physiology.

Tracking and synchronization of the yeast cell cycle using dielectrophoretic opacity

“…We have recently developed equilibrium-based approaches to dielectrophoretic separation, where the direct volume dependency cancels out. 19 Here we show that it is possible to characterize and continuously sort different yeast cell division stages using this equilibrium-based dielectrophoresis approach. We characterize the different cell cycle stages in terms of the opacity as defined by the ratio of dielectrophoretic forces at two different frequencies.…”

“…For the calculation of n x , we use our geometrical model of the yeast cells as single or connected ellipsoids for nondividing and dividing yeast cells respectively, given in Supplementary Information 2. ‡ For single, closed ellipsoids, formulas for the form factor are available in literature, 24 for the budding yeast, we provide the calculation in Supplementary Information 4 (namely, eqn (19) in Supplementary Information 4 ‡). The resulting form factors throughout yeast growth and division are represented in Fig.…”

“…1-A). This opposition of dielectrophoretic forces eliminates the first order dependence of the force on the volume, 19 increasing the sensitivity to changes in cell shape throughout the division cycle. The arrangement has two additional important advantages: 18,20 First, the cell sorting takes place perpendicular to the flow, such that the device can be operated continuously; and second, the cells are pushed towards a characteristic equilibrium position for the different division stages, independently of the flow speed ( Fig.…”

Efficient manipulation of microparticles in bubble streaming flows

“…Many applications require control over position and concentration of the objects in order to induce mixing, 3 chemical reactions, 4 biomolecular tagging, 5 or a host of other processes. The necessary manipulations of the objects often rely on actively applying various external force fields, including hydrodynamic (inertial), [6][7][8] electrokinetic, 9-12 dielectrophoretic, [13][14][15][16] magnetic, 17,18 optical 19,20 or acoustic [21][22][23] (ultrasound standing waves, surface acoustic waves) forces. Such forces will usually act differently on particles depending on their size, geometry, and mechanical or electromagnetic properties; as a result, particle separation and sorting become possible.…”

A practical guide for the fabrication of microfluidic devices using glass and silicon

“…Examples are the electrical characterization of biological samples by impedance spectroscopy, 116 particle manipulation by dielectrophoresis, [117][118][119] and microfluidic fuel cells. 120 Any electrodes placed inside microfluidic channels must usually be connected to the outside world.…”