Contactless dielectrophoresis (cDEP) is a recently developed method of cell manipulation in which the electrodes are physically isolated from the sample. Here we present two microfluidic devices capable of selectively isolating live human leukemia cells from dead cells utilizing their electrical signatures. The effect of different voltages and frequencies on the gradient of the electric field and device performance was investigated numerically and validated experimentally. With these prototype devices we were able to achieve greater than 95% removal efficiency at 0.2–0.5 mm s⁻¹ with 100% selectivity between live and dead cells. In conjunction with enrichment, cDEP could be integrated with other technologies to yield fully automated lab-on-a-chip systems capable of sensing, sorting, and identifying rare cells.

Significance: Cell separation is a fundamental process in biomedicine, but is presently complicated, cumbersome, and expensive. We present a technique that can sort cells at a rate equivalent to or faster than gold-standard techniques such as fluorescence- and magnetic-activated cell sorting, but can do it label-free and with very low cell loss. The system uses dielectrophoresis to sort cells electrostatically, using an electrode chip that eschews microfabrication in favor of a laminate drilled with 397 electrode-bearing wells. This high level of parallelization makes the system immune to the bubbles that limit labs-on-chip, while also increasing capacity and throughput to levels comparable with high-throughput FACS and MACS, whereas the chip is cheap enough to be disposable, preventing interseparation contamination.

A rapid, low-cost and label-free method of cell analysis compares favorably to Annexin-V, MTT and trypan blue for assessment of apoptosis and IC ₅₀ .

Circadian rhythms organize many aspects of cell biology and physiology to a daily temporal program that depends on clock gene expression cycles in most mammalian cell types. However, circadian rhythms are also observed in isolated mammalian red blood cells (RBCs), which lack nuclei, suggesting the existence of post-translational cellular clock mechanisms in these cells. Here we show using electrophysiological and pharmacological approaches that human RBCs display circadian regulation of membrane conductance and cytoplasmic conductivity that depends on the cycling of cytoplasmic K⁺ levels. Using pharmacological intervention and ion replacement, we show that inhibition of K⁺ transport abolishes RBC electrophysiological rhythms. Our results suggest that in the absence of conventional transcription cycles, RBCs maintain a circadian rhythm in membrane electrophysiology through dynamic regulation of K⁺ transport.