Dielectrophoretic detection of membrane morphology changes in Jurkat T-cells undergoing etoposide-induced apoptosis

Abstract

A dielectrophoresis (DEP) cell profiler, with concurrent FACS measurements, was used to monitor the morphological changes of Jurkat T-cells as they progressed through chemically induced apoptosis using etoposide. The cell 'physiometry' profiling technique measures the radius and the so-called DEP crossover frequency f(xo) of individual cells in a suspension, and this information was used to determine the effective plasma membrane capacitance of each cell. Control cells (n=526) exhibited a dynamic spread of f(xo) values, ranging from 50 to 250 kHz, and as apoptosis progressed over 6 h, the upper value for f(xo) progressively increased and extended beyond 500 kHz. This corresponded to a reduction in plasma membrane capacitance from 13.34 (+/-2.88) to 10.49 (+/-4.00) mF/m(2), and reflected a general smoothing of the membrane through loss of microvilli, for example. This is in broad agreement with previously reported studies of HL-60 cells undergoing apoptosis, but the authors' observation of a dynamic spread of f(xo) values does not agree with the earlier report that the f(xo) values for viable and apoptotic cells fall into two separable, relatively narrow, frequency bands. This has implications when devising protocols for the efficient DEP separation of viable, apoptotic and necrotic cells.

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

“…209 For a fixed cell radius, the effective membrane capacitance of a smooth cell will be less than that for a cell having a complex cell surface topography associated with the presence of microvilli, blebs, membrane folds, or ruffles, for example. This will influence the value observed for f xo1 , which has important implications for applying DEP to characterize and selectively isolate target cells from other cells.…”

Refinement of the theory for extracting cell dielectric properties from dielectrophoresis and electrorotation experiments

“…(3) and (24) give the same result, they were derived under different assumptions. Equation (24) given here is derived using Eqs. (1a), (16b), (4), and (23a), which differ significantly from Eqs.…”

“…This approximation has been used in the DEP and ER studies of cell apoptosis, [22][23][24] as well as for studies of induced cell differentiation and activation, 19,25,26 for example. In summary, the state-of-art theory and method in the current literature for deriving cell dielectric properties from the peak frequency measurement of ER and the crossover frequency measurement of DEP are based on two physical reasons: (1) the definitions of peak and crossover frequencies, which are associated with the Maxwell-Wagner phenomenon and (2) the low frequency (DC) limits for representing the effective cell permittivity and conductivity.…”

Dielectrophoretic separation of mouse melanoma clones

“…The buffer consists of 8.6% ͑w/w͒ sucrose, 0.3% ͑w/w͒ dextrose, and 1.0 mg/ml Bovine Serum Albumin ͑Sigma-Aldrich, St. Louise, MO͒ and sufficient amount of modified eagle's minimum essential media ͑ATCC͒ to reach 0.16 S/m. 7 The conductivity of the cell suspension media was measured by a conductivity meter ͑OMEGA, PHH-80PMS, Stamford, CT͒. The cell motion was observed under an inverted microscope ͑Olympus IX71, Cenmter Valley, PA͒ and at least three snapshots were taken at the steady state by a charge coupled device camera ͑Q Imaging, Surrey, BC, Canada͒.…”

“…In one study, morphology changes in stimulated Jurkat T-cells were investigated by calculating the cell membrane capacitance from the DEP crossover frequency. 7 In this study, we present a method that can differentiate between two malignant cells of the same origin, which differ from each other by small changes in their melanin content. This study is a precursor for future efforts on DEP separation of metastatic human melanoma cells using microfluidic platforms.…”