title: Dielectric properties of biological cells in the dipolar approximation for the single-shell ellipsoidal model: the effect of localized surface charge distributions at the membrane interface.
abstract: In this paper, we describe the dielectric properties of a biological cell suspension of shelled ellipsoidal cells with a layer of localized charges at the membrane interfaces. In so doing, we are dealing with two different problems encountered in finding an analytical solution of the dielectric problem. The first one concerns the calculation of the electrical polarizability of a shelled ellipsoidal cell in the presence of a localized layer of charges. We will show that what we call the dipolar approximation is good enough to ensure a meaningful behavior of the dielectric spectra, whatever the cell parameters are, contrarily to what happens if one estimates the polarizability without taking into account the appropriate correction term deriving from the localized charge distribution. The second problem we face concerns the fact that the interfaces of the different adjacent media should be surfaces of constant coordinates, within a certain set of coordinate types. This implies, for ellipsoidal geometries, the requirement of a confocal condition which leads to a cell membrane of nonconstant thickness. Even if the membrane thickness is at least two orders of magnitude lower than the typical cell size, its nonconstancy leads to serious discrepancies in the shape of the dielectric spectra, which are heavier the larger the membrane conductivity is or larger as the value of the conductivity of the surface charge layers is. As far as this latter problem is concerned, we propose a compromise that saves the confocality condition and, at the same time, reduces significantly the effects of the nonuniform membrane thickness. We present here some dielectric spectra of shelled ellipsoidal cells (both prolate and oblate in shape) over an extended frequency range, showing their main characteristics, arising from the combined presence of localized charge distributions and polarization charge distributions. Finally, we compare some of these results with the ones obtained using different approximations.
authors.affiliation: Department of Physics, Università di Camerino, Camerino, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Di Biasio
authors.forename: L
authors.initials: L
authors.lastname: Ambrosone
authors.forename: C
authors.initials: C
authors.lastname: Cametti
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D017097:Electric Impedance; D008954:Models, Biological