Mechanisms for the interaction between nonstationary electric fields and biological systems I. Linear dielectric theory and its limitations

Kell, Douglas B.; Astumian, R. Dean; Westerhoff, Hans V.

doi:10.1080/00150198808227004

Cited by 33 publications

(4 citation statements)

References 57 publications

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“…(C) Complex admittance diagram using the value of the "high-frequency" permittivity (70) obtained in (B). which is becoming increasingly widespread as studies of the dielectric behaviour of biological [4,5,15,60,61] and other [17,62,63] As regards the exploitation of the dielectric method in the estimation of the biomass of growing animal cell cultures, where one would preferably make measurements at frequencies towards the lower end of the P-dispersion [21], we had hoped to obtain a value for the internal conductivity (u') of these cells using the equations derived by Schwan [1,7,14,16,21,37]. This would permit us to obtain the value of the characteristic frequency to be expected in growth media [64] which have a conductivity some ten-fold greater than that used (for reasons of minimizing the contribution of electrode polarization to the dielectric data) in the present work, and thus a value for the appropriate measuring frequency to use.…”

Section: When Dielectric Measurementsmentioning

confidence: 99%

On the audio- and radio-frequency dielectric behaviour of anchorage-independent, mouse L929-derived LS fibroblasts

Davey

Kell

Кемп

et al. 1988

Journal of Electroanalytical Chemistry and Interfacial Electroc

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The utility of dielectric methods as a means for estimating the biomass of animal cells in suspension culture was assessed, using mouse L929-derived LS fibroblasts. The dielectric increment of the /3-dispersion was found to be a linear function of both cell number (30-70 permittivity units per lo6 cells/ml, depending on the batch of cells) and volume fraction in the range measured (up to 1.28 x 10s cells/ml. volume fraction = 0.14). The notional distribution of relaxation times as encompassed in the Cole/Cole a (0.13 kO.03 SD) was rather modest. If the cells were treated as spherical shell capacitors of their observable diameter and number, the apparent capacitance of the plasma membrane was some 1.9-4.0 pFF/cm2. This value significantly exceeded those (0.5-l pF/cm2) usually encountered or claimed, due predominantly to the possession by these cells of numerous plasma membrane protrusions. As the osmolarity of the suspending medium was increased using the non-permeant solute sorbitol, the apparent specific capacitance of the plasma membrane and the Cole/Cole a were increased, whilst the dielectric increment per 10" cells/ml was unchanged. In addition, a secondary /3-dispersion, with a characteristic frequency greater than that of the main P-dispersion, became increasingly prominent as the medium osmolatity was increased. It is proposed that this a,-dispersion is dominated by a Maxwell-Wagner mechanism taking place in the region of the plasma membrane protrusions of these cells.

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Section: When Dielectric Measurementsmentioning

confidence: 99%

On the audio- and radio-frequency dielectric behaviour of anchorage-independent, mouse L929-derived LS fibroblasts

Davey

Kell

Кемп

et al. 1988

Journal of Electroanalytical Chemistry and Interfacial Electroc

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“…Biological cells are dielectric spheres that can steer external electric fields [13,14]. When millions of T-cells are randomly positioned between two macro-or micro-scale electrodes, the presence of the cells alters the spatial distribution of the external electric field.…”

Section: Introductionmentioning

confidence: 99%

Label-free purification of viable human T-lymphocyte cells from a mixture of viable and non-viable cells after transfection by electroporation

Jayasooriya

Nawarathna

2019

J. Phys. D: Appl. Phys.

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Recent developments in chimeric antigen receptor (CAR) T-cell therapy for cancer have shown promising results. CAR T-cells are engineered mainly by AC or DC electroporation to express CAR molecules on their surfaces. Electroporation has detrimental effects on the majority of T-cells and causes cell death via apoptosis or necrosis. These non-viable cells have potentially harmful effects on other healthy T-cells. Because there are no unique biomarkers that pinpoint the apoptosis and necrosis of T-cells, currently available cell separation methods are incapable of purifying healthy T-cells after electroporation. To address this critical issue, we have used dielectrophoretic cell isolation in a simple microfluidics chip. Our results indicate that it is possible to purify cell samples after electroporation and achieve ~100% purity and >90% target cell recovery. Therefore, this work presents a viable solution to a critical need in CAR T-cell manufacturing.

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“…However, it is a knowledge of the underlying linear and nonlinear dielectric properties of such materials and systems which must underpin any mechanistic understanding of such effects (see e.g. Grant et al 1978;Schanne and Ceretti 1978;Pethig 1979;Pethig and Kell 1987;Schwan 1986, 1989;Kell et al 1988;Westerhoffet al 1988; Kell 1989, 1990).…”

Section: Introductionmentioning

confidence: 99%

Substitution and spreadsheet methods for analysing dielectric spectra of biological systems

Davey¹,

Markx²,

Kell³

1990

Eur Biophys J

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1. Two major problems are encountered when one wishes to fit audio-and radio-frequency dielectric spectra of biological cell suspensions (or other materials): (a) changes in the apparent frequency-dependent permittivity of the system due to the phenomena of electrode polarisation can dominate those due to the biological system, and (b) because of the overlap of different dispersions it may be very difficult to deconvolute the individual contributions of the underlying biophysical mechanisms. 2. The extent of electrode polarisation depends substantially upon the conductivity of the medium surrounding the cells, but only marginally on the nature of the ions of a given valency contribution to it. 3. This, and the fact that the apparent time constants of the phenomena contributing to electrode polarisation are much greater than those of biological dielectric dispersions, permits one to use a simple substitution method to extract the latter in the presence of the former. This is shown both by simulation and by experiments using suspensions of human erythrocytes. 4. A spreadsheet method is described for the display of dielectric data and their conformance to the double Cole-Cole equation. The method provides a rapid and convenient approach, based on interactive graphical outputs, for the fitting of dielectric data to this equation. 5. Estimates derived from the spreadsheet program may be used in a BASIC program to arrive at the optimal fit. 6. The method is applied to the strongly-overlapping ~-and fl-dispersions of erythrocytes, permitting their deconvolution and providing a high level of accuracy.

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Mechanisms for the interaction between nonstationary electric fields and biological systems I. Linear dielectric theory and its limitations

Cited by 33 publications

References 57 publications

On the audio- and radio-frequency dielectric behaviour of anchorage-independent, mouse L929-derived LS fibroblasts

On the audio- and radio-frequency dielectric behaviour of anchorage-independent, mouse L929-derived LS fibroblasts

Label-free purification of viable human T-lymphocyte cells from a mixture of viable and non-viable cells after transfection by electroporation

Substitution and spreadsheet methods for analysing dielectric spectra of biological systems

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