Rotation of cells in nonuniform alternating fields

Abstract

Rotation of "lone" cells of the baker's yeast Saccharomyces cerevisiae under the influence of nonuniform alternating fields is studied.The spinning rate of the ceils shows a quadratic dependence on the applied voltage and no threshold effect when the influence of gravitation is cancelled out by adjusting the density of the buffer to that of the cells. These observations are in agreement with theories established by different authors.Among the various effects that nonuniform alternating electric fields exhibit on biological material, rotation is one of the most interesting. It was described by several authors for different organisms such as amoebae (Teixeira-Pinto, et al., 1960), erythrocytes (Fiiredi and Ohad, 1964) and yeasts (Pohl and Crane, 1971). Rotation seemed to be a quite general phenomenon of living and dead cells or inanimate materials that could be observed in a broad range of frequencies. As this effect is closely related to dielectrophoresis (DEP;Pohl, 1978) and to the effective dielectric constant of the particle in the surrounding medium, it may offer an elegant method to determine this parameter and to investigate the physical state of biological material.Although rotating fields were mentioned briefly (Pohl and Crane, 1971), they were only recently employed to investigate the spinning of single cells (Arnold and Zimmermann, 1982a, 1982b;Mischel, et al., 1982;Mischel and Pohl, 1983). Also recently, theories were developed to explain the occurrence of rotation in cells in the neighborhood of other ones (Holzapfel et al., 1982) and in single cells .Pohl and Crane (1971) used the description term "cellular spin resonance" (CSR) for this phenomenon, because the spinning of cells appears at a sharply resonant frequency of the external field. If highly homogeneous cell cultures are used nearly all cells spin in the same small frequency interval (Zimmermann et al., 1981). Nevertheless, it is possible to find spinning cells at all applied frequencies, mainly in direct contact with the electrodes.Although rotation of cells was described long ago, to our knowledge Mischel and Lamprecht (1980) were the first to give qumltitative data about spinning rates and their connections with some physical and biologic parameters. These first experiments were performed in a DEP chamber which consisted of a microslide with a central well of 1.0 mm, into which two electrodes dipped at an angle of about 10 ~ . The electrodes were produced from a platinum plate 0.5 mm thick with carefully rounded and polished tops. The minimum distance between the electrodes amounted to 2 mm. The height of the electrode tips above the floor of the well measured 0.3 mm or 35 cell diameters.A new type of DEP chamber used in recent experiments consisted of a microslide to which two similar platinum electrodes (0.2 mm thick) were glued with epoxy resin with a minimum separation of 0.2 mm or 0.5 mm, resp. Much care was taken in smoothing and polishing the electrode surface and the edges. The surface quality was so high that the refl...

Behavior and Viability of Tobacco Protoplasts in Response to Electrofusion Parameters

“…of protoplasts from each sample was determined by fluorescein 3ince protoplast alignment occurred throughout a broad range diacetate staining. Although (9,22,25,27). Pohl and Branden (13,14) have described the dielectrophoretic behavior and cellular spin resonance of yeast and murine cells in AC fields, and Zimmermann (22) (Figs.…”

The effects of nanoparticles uptaken by cells on electrorotation

“…The effective dipole moment for a homogeneous dielectric particle in a stationary AC electric field, however, is always either parallel or anti-parallel to the electric field, which means that there is no possibility for the existence of electric torque in a stationary AC electric field. Nevertheless, a spontaneous rotation of spheres in a uniform AC electric field may occur with a threshold electric field if the dipole moment is inverted and any small perturbation leads to the breaking of the bifurcation, as in Turcu's prediction [10]. In our system, metal and dielectric nanoparticles uptaken by cells can show results quite different from TEM micrographs.…”

“…Another rotation of cells in an AC electric field was observed by Holzapfel et al [9] in 1982; they hypothesized that this field-induced rotation is evident only when cells are proximate to one another in the form of chains. The dipole-dipole interaction mechanism is, however, unable to describe the rotation of lone cells in a uniform or nonuniform AC electric field without the influence of adjacent cells reported by Pohl and Crane (1971) and Mischel and Lamprecht [10] (1983), respectively. In order to interpret the contradiction between Holzapfel et al, [9] , Pohl and Crane [8] and Turcu [11] in 1987 published a theoretical analysis of a sphere rotation about some axis perpendicular to an AC electric field, showing that this was indeed possible under certain conditions.…”

Cellular spin resonance: A new method for determining the dielectric properties of living cells

“…In the first, lone cells which appear to be little affected by local field perturbations due to delayed polarizations can be seen to spin resonantly and to spin at a frequency of rotation which is much, much less than the frequency of the applied field. In the second type, particles spin because [7]), and Pohl and Braden [5]. The observation of the spinning of lone cells out in the medium is usually only very brief, for the cells often move quickly to an electrode or form pearl chains with other cells nearby.…”

“…This is the usual result of dielectrophoretic forces or other rather more mechanical forces such as streaming, thermal upsets, etc. Lone cells can, however, also be more easily observed to spin when they are against a mirror-smooth noble metal electrode while they are in the presence of no other visible source of perturbation by polarizable particles [7]. The theory for this first type of CSR, of lone, living, nucleate cells in a two-pole ac field was discussed by Pohl [8,9].…”