Differential electronic detector to monitor apoptosis using dielectrophoresis-induced translation of flowing cells (dielectrophoresis cytometry)

Abstract

The instrument described here is an all-electronic dielectrophoresis (DEP) cytometer sensitive to changes in polarizability of single cells. The important novel feature of this work is the differential electrode array that allows independent detection and actuation of single cells within a short section ([Formula: see text]) of the microfluidic channel. DEP actuation modifies the altitude of the cells flowing between two altitude detection sites in proportion to cell polarizability; changes in altitude smaller than 0.25 μm can be detected electronically. Analysis of individual experimental signatures allows us to make a simple connection between the Clausius-Mossotti factor (CMF) and the amount of vertical cell deflection during actuation. This results in an all-electronic, label-free differential detector that monitors changes in physiological properties of the living cells and can be fully automated and miniaturized in order to be used in various online and offline probes and point-of-care medical applications. High sensitivity of the DEP cytometer facilitates observations of delicate changes in cell polarization that occur at the onset of apoptosis. We illustrate the application of this concept on a population of Chinese hamster ovary (CHO) cells that were followed in their rapid transition from a healthy viable to an early apoptotic state. DEP cytometer viability estimates closely match an Annexin V assay (an early apoptosis marker) on the same population of cells.

Monitoring the dielectric response of single cells following mitochondrial adenosine triphosphate synthase inhibition by oligomycin using a dielectrophoretic cytometer

“…Larger cells and cells passing closer to the electrodes produce larger signals. 27 The two peaks form the detection signature for each cell. When a DEP voltage is applied, the cells will be attracted or repelled from the higher density electric field region; meaning depending on the magnitude and sign of the Claussius Mossotti factor the second peak will be larger or smaller than the first peak.…”

“…The DEP cytometer is based on differential detection of single cells before and after DEP actuation in a microfluidic channel and has been described in detail by Nikolic-Jaric et al 27 Briefly, the cell first passes over a first pair of detection electrodes, Fig. 3(c), and produces a signal with a peak value of P 1 .…”

Dielectric model for Chinese hamster ovary cells obtained by dielectrophoresis cytometry

“…Fig. 10 shows the simulated spectrum of RefK CM g for a CHO cell with parameters given in Table II and medium conductivity of 0.01 and 0.17 S/m (close to medium conductivities used in several pervious works 10,39,43,59,[62][63][64] ). It demonstrates that changing the radius of the nucleus by 25% (while keeping all other parameters the same) causes a noticeable change in the spectrum for medium conductivity 0.17 S/m.…”

On-chip microelectrode impedance analysis of mammalian cell viability during biomanufacturing

“…Discrepancies between dye exclusion and electrical properties based viability assays have been reported and analyzed by other groups as well, where the electrical technique based viability decreases at a faster rate than the dye exclusion test based viability. 38,39 The rapid decrease in cell viability measured by our technique, relative to the dye exclusion test, suggests that the detected changes in the cell polarization response capture the transition to a suboptimal physiological state occurring during the initial stages of cell death. NS0 cells, analyzed by us in this study, have been previously reported to be susceptible to their environment and their apoptosis can be triggered relatively easily compared to other industrial cell lines.…”