Dielektrophoretische Untersuchungen an biologischen Systemen

Lamprecht, I.; Mischel, Maja

doi:10.1007/bf00365373

Cited by 10 publications

(1 citation statement)

References 16 publications

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“…Recently, Lamprecht and Mischel (1981)and Mischel (1982) reported that at low frequencies of the applied electric fields and high cell concentration yeast cells (Saccharomyces cerevisiae) settled out on the floor of dielectrophoresis chambers in a manner to form branching networks. In the regions near the electrodes the ceils were seen to be moving in a spiral-like manner.…”

Section: Introductionmentioning

confidence: 99%

Dynamic and static cord-structure: A new dielectrophoretic phenomenon

et al. 1983

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During the dielectrophoresis of ceils or other particles it is observed that unusual distributions of the cells appear on the floor of the test chamber. In certain narrow frequency ranges, the distributions are cord-like, with the "cords" running more or less parallel to the electrode faces, but also developing highly branched structures. It is observed that the cells within the cords form "pearl-chains" along the field lines and across the cords. Within the cords, the cells move actively in spiralized paths. This the dynamic cord-structure is considered to be due to the combined action of negative dieleetrophoresis, Brownian motion, and gravity. Outside the conditions requisite for dynamic cord formation, the cells are seen to assume conformations reflective of simple negative dielectrophoresis which merely causes them to amass into regions of low field strength. The theory for the effects is presented, together with experimental evidence for the kinetic behavior of the dynamic cord effect.

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Section: Introductionmentioning

confidence: 99%

Dynamic and static cord-structure: A new dielectrophoretic phenomenon

et al. 1983

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Natural cellular electrical resonances

Pohl

2009

Int. J. Quantum Chem.

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That living cells are the source of natural electrical radio frequency oscillations is shown by several experimental means. The causes and consequences of these natural resonances need clarification. These experiments, including dielectrophoresis and cellular spin resonance, are reviewed and compared. The natural cellular resonance are detectable in a very wide range of cell types, including bacteria, yeasts, algae, and avian and mammalian cells, and hence are probably "universal." The electrical oscillations appear to be associated with reproduction, for in at least one species (yeasts), they are maximal at or near mitosis. Questions arise as to how, why, and in what role these oscillations appear. When we pose the question, "Are these observed natural radio frequency oscillations necessity or frill in cellular operations?" one is led to assume that they are necessary, for they have persisted through the various evolutionary paths. But if such natural electrical oscillations are necessary in a cell's reproductive sequence, this implies that there must be an electrical aspect to cellular growth and its control. The implications of this to the well-known phenomenon of "contact" or "density" inhibition of cell growth are discussed. Mechanisms whereby such natural electrical cellular resonances occur are also suggested and discussed.

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Cellular spin resonance inversion by ion‐induced dipoles

Pollock

Pohl

1987

Int J of Quantum Chemistry

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Cellular spin resonance (CSR) or electrorotation is the spinning of cells or other particulate matter in rotating electric fields. The spin rate of the (bio)particle varies markedly with the applied frequency and often is seen to have rather sharp maxima as the frequency is varied. In certain frequency ranges, living cells often are observed to undergo a striking inversion of their spin rate and then spin counter-clockwise ( c c w ) while the direction of rotation of the applied electric field is clockwise (cw).The CSR spectra are presumably due to dipolar interactions with the applied field, as are the spectra obtained by straightforward dielectrophoresis (DEP) techniques. The two spectra, however, differ radically in the low frequency ranges (below about I MHz). It is our objective to explain this apparently anomalous behavior.We believe that the anomaly appears primarily because one is comparing rotational with translational force responses. In the DEP techniques, the simpler translational force arising from the comparative polarizability of cell versus medium (water) gives a straightforward measure of the differential polarizability owing to volume and surface effects pro forma. In the CSR techniques the spin rate reflects the torque on the cells and hence emphasizes polarization at the outer periphery of the cells rather than that of the average overall polarizability.The problem is considered in terms of a living or dead cell rotating with an angular velocity R in a fluid medium of viscosity r) when it is subject to an electric Weld rotating at angular frequency w . It is observed in many experiments that R < w , and also that the sign of R for the same cell can change from cw to ccw and back to cw as the applied frequency w of the cw electric field is increased. Moreover, the sign and magnitude of the CSR spectra differ for living and dead cells. All of these experimental results can be explained quantitatively by using Maxwell's equations and the dielectric properties of a lossy dielectric sphere in an ionically conductive dielectric fluid.

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Dielektrophoretische Untersuchungen an biologischen Systemen

Cited by 10 publications

References 16 publications

Dynamic and static cord-structure: A new dielectrophoretic phenomenon

Dynamic and static cord-structure: A new dielectrophoretic phenomenon

Natural cellular electrical resonances

Cellular spin resonance inversion by ion‐induced dipoles

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