Numerical simulation of dielectric spectra of aqueous suspensions of non-spheroidal differently shaped biological cells

Abstract

The effect of shape on the dielectric and conductometric spectra of aqueous suspensions of non-spheroidal biological cells has been investigated by means of numerical simulation methods. This work extends our previous investigation directed to biological cell systems where a superficial electric charge distribution is present on the outer interface of the cell membrane. This generalization results in a more composite dielectric spectra, where a low-frequency and a high-frequency contribution are expected. We consider different geometries, from ellipsoids, discoids, pear-shaped vesicles, cup-shaped vesicles to budded vesicles, which model a biological cell during different processes of biological relevance. The overview of the evolution of the dielectric spectra with the progressive change in the cell shape, maintaining constant the electrical properties of the different media involved and the fractional volume of the dispersed cells, offers a preliminary opportunity to separate contributions derived exclusively from the geometry to those due to the bulk and/or interface polarizations. These aspects are particularly relevant since dielectric spectroscopy of biological cell suspensions has proved its effectiveness in the characterization of the passive electrical properties of the cell membrane and also in controlled manipulations of biological systems.

Quantifying the membrane potential during E. coli growth stages

“…The independent input parameters entering the formula are: the volume fraction p of the cell solution, the outer and inner average radius of the cell's membrane, R 1 and R 2 (d = R 1 − R 2 ; consideration of a strict ellipsoidal shape for the cells makes very little difference [20,21]), the complex dielectric function of the medium ε 0 ⁎ = ε 0 + σ 0 / jω, of the membrane ε 1 ⁎ = ε 1 + σ 1 / jω and of the inner cell region ε 2 ⁎ = ε 2 + σ 2 / jω; the diffusion constant D of surface charges accumulated around the membrane and the resting membrane potential ΔV.…”

Time-varying electric field induced transmembrane potential of a core-shell model of biological cells

“…It turns out that similar approximation of biological cell has been used to describe the dielectric spectra of aqueous suspensions of nonspheroidal biological cells. 21,30 These Cassinian structures appear in the upper panel of Fig. 7.…”

“…8 and 9 offers an opportunity to discriminate contributions derived from geometry to those due to interfacial polarization. The observation by di Biasio et al 30 of the evolution of the effective permittivity spectra with the progressive change in the cell shape, maintaining constant the intrinsic dielectric characteristics of the different phases and their compositions, was an exciting advance but their numerical results were restricted to low frequencies, i.e., below the ␤ relaxation frequency of the cell ͑see Figs. 7 and 8 of Ref.…”

Modeling of Transmembrane Potential in Realistic Multicellular Structures before Electroporation

“…Here, we describe a method to develop a realistic finite element (FE) model for a tightly packed multicellular cluster directly from epifluorescence microscopy images. The benefits and challenges of developing such an FE model are discussed, and it is demonstrated how this framework can be effectively implemented for generalized pulse parameters applied to the geometry of an arbitrary multicellular structure (7,14). The pulse parameters chosen here were selected to emphasize the effects of two different applied electric fields inspired by pulses used in IRE and H-FIRE (15).…”