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  • Author: Ronald Pethig x
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Marking 100 years since Rudolf Höber’s discovery of the insulating envelope surrounding cells and of the β-dispersion exhibited by tissue

Abstract

Between 1910 and 1913 Rudolf Höber presented proof that the interiors of red blood cells and muscle cells contain conducting electrolytes, and that each conducting core is contained within an insulating membrane. He did this by demonstrating, in a series of remarkable electrical experiments, that the conductivity of compacted cell samples at low frequencies (~150 Hz) was about ten-times less than the value obtained at ~5 MHz. On perforation of the membrane, the low-frequency conductivity increased to a value approaching that exhibited at MHz frequencies. Apart from representing a major milestone in the development of cell biology and electrophysiology, Höber’s work was the first description of what we now call the dielectric β-dispersion exhibited by cell suspensions and fresh tissue.

Open access
Dielectrophoretic Characterisation of Mammalian Cells above 100 MHz

Abstract

Dielectrophoresis (DEP) is a label-free technique for the characterization and manipulation of biological particles - such as cells, bacteria and viruses. Many studies have focused on the DEP cross-over frequency f xo1, where cells in a non-uniform electric field undergo a transition from negative to positive DEP. Determination of f xo1 provides a value for the membrane capacitance from the cell diameter, the means to monitor changes in cell morphology and viability, and the information required when devising DEP cell separation protocols. In this paper we describe the first systematic measurements of the second DEP cross-over frequency f xo2 that occurs at much higher frequencies. Theory indicates that f xo2 is sensitive to the internal dielectric properties of a cell, and our experiments on murine myeloma cells reveal that these properties exhibit temporal changes that are sensitive to both the osmolality and temperature of the cell suspending medium.

Open access