Dielectric properties of nucleated erythrocytes as simulated by the double spherical-shell model*

Abstract

The dielectric properties of nucleated erythrocytes from bullfrogs were measured in a frequency range of 10 kHz–110 MHz. The complex permittivity (ε *), complex conductivity (κ *), and complex resistivity (ρ *) were analyzed and compared in the 10.63% to 37.58% haematocrit (Hct) range. The relaxation behavior, the passive electrical properties, and the cellular structure parameters, including the cell membrane, the cytoplasm, the nuclear membrane, and the nucleoplasm of the nucleated erythrocyte suspensions were investigated. The method used is based on the binomial Cole–Cole equation and the double spherical-shell physical models. Upon the elimination of the electrode polarization effect, two definite relaxations related to the interfacial polarization are observed on low- and high-frequency dispersions. The permittivity values and the characteristic frequency values differ by one order of magnitude: the low-frequency relaxation increments [Δ ε 1 = (5.63 ± 1.43)× 103] and the characteristic frequency [f c1 = (297.06 ± 14.48) kHz] derived from the cell membrane, the high-frequency relaxation increments [Δ ε 2 = (5.21 ± 1.20) × 102] and the characteristic frequency [f c2 = (3.73 ± 0.06) MHz] derived from the dielectric response to the external electric field of the nuclear membrane, respectively. Moreover, the other core dielectric parameters, such as the relative permittivity of the cell membrane [ε m = (7.57 ± 0.38)] and the nuclear envelope [ε ne = (23.59 ± 4.39)], the conductivity of the cytoplasm (hemoglobin, κ Hb = (0.50 ± 0.13) S/m] and the nuclear endoplasm [κ np = (2.56 ± 0.75) S/m], and the capacitance of the bilayer membranes [C m: (0.84 ± 0.04) μF/cm2], and C ne: (0.52 ± 0.10) μF/cm2] were also accurately and reliably measured. This work presents a feasible method to evaluate the dielectric parameters and the cellular structure of the erythrocytes of bullfrogs. Moreover, it paves the way for new studies on the haematology of frogs and the detection of nucleated cells via dielectric impedance spectroscopy.