Refinement of the theory for extracting cell dielectric properties from dielectrophoresis and electrorotation experiments

Abstract

A modified theory is proposed for extracting cell dielectric properties from the peak frequency measurement of electrorotation (ER) and the crossover frequency measurement of dielectrophoresis (DEP). Current theory in the literature is based on the low frequency (DC) approximations for the equivalent cell permittivity and conductivity, which are valid when the measurements are performed in a medium with conductivity less than 1 mS=m. The present theory extracts the cell properties through optimizing an expression for the medium conductivity in terms of the peak ER, or DEP crossover, frequency according to its definition using full expressions of equivalent cell permittivity and conductivity. Various levels of approximation of the theory are proposed and discussed through a scaling analysis. The present theory can extract both membrane and interior properties from the low and the high peak ER, or DEP crossover, frequencies for any medium conductivity provided the peak ER, or DEP crossover, frequency exists. It can be reduced to the linear theory for the low peak ER and DEP crossover frequencies in the literature when the medium conductivity is less than 10 mS=m. However, we can determine the membrane capacitance and conductance via the slope and intercept, respectively, of the straight line fitting of the ER peak and DEP frequency against medium conductivity data according to the linear theory only when the intercept dominates the experimental uncertainty, which occurs when the medium conductivity is less than 1 mS=m in practice.

Estimation of the physical properties of neurons and glial cells using dielectrophoresis crossover frequency

“…6 Linear fitting of (f ⋅ r) against σ m , based on data from Fig. 4c and the formula in [26], predicts cell membrane effective capacitance well within our suggested range, verifying the accuracy of our fitting procedure most severe situation (only 10% sucrose). Sufficiently high viability (87%) was achieved for hippocampal cells after short-term (30 min) exposures to sucrose, compared with the control sample (88%) in pure cell culture media.…”

“…From Table 3, most of the conductivity of the suspension mixture is magnitudes higher than that of DEP buffers previously used [11,14,21,24,26,27] because of the addition of cell culture media, which compromises the validity of the lowfrequency approximation, as mentioned earlier. In order to ensure the survival of cells in these suspension mixtures, we investigated the viability of hippocampal cells in the Fig.…”

“…In Fig. 6, the fitted linear equation has a slope of 21.241, which, based on [26], satisfies the following expression:…”

“…For instance, the work reported by Pethig et al [12,17] and Gascoyne et al [20,24] determined the effective cell membrane capacitance from the slope of the plots of CF versus the medium conductivity based on a low-frequency (DC) approximation of Schwan [25], to represent the effective permittivity and conductivity of a cell. However, this DC approximation can only be applied when the CF measurement is performed in a medium with lower conductivity (e.g., <10 −3 Sm −1 ), where the measured CF is sufficiently lower than the dispersion frequency (∼1 MHz) [26,27], which is usually associated with the internal polarization between the cell membrane and cytoplasm. Furthermore, extended exposure to a low-conductivity medium often causes an ionic flux out of the cell membrane, which could compromise the cytoplasmic integrity [27].…”

Biomarker-free dielectrophoretic sorting of differentiating myoblast multipotent progenitor cells and their membrane analysis by Raman spectroscopy

“…(2) leads to an accurate measurement of the membrane capacitance. 16 Labeed et al 17 have recently reported that the neurogenic potential of human neural stem/progenitor cell populations can be discriminated by their f xo and derived C m values. On the basis of the efficient DEP-based cell separations reported here, the same conclusion may be reached regarding discrimination between stages of C2C12 myoblast cell differentiation.…”