Dielectric Spectroscopy Measurements of Low Volume Cell Fraction Suspensions to Assess Temperature Dependence

<p>Dielectric spectroscopy enables noninvasive measurement of the electrical properties of biological cells; however, these measurements require nonphysiological volume fractions (1-10%) and a fixed temperature. In this study, we demonstrate the feasibility of performing these measurements at volume fractions of Jurkat cells down to 0.002%, or 4 × 10^6 cells/mL for temperatures from 15 ºC to 45 ºC from 9 kHz to 6.5 GHz. We used subtraction and zeroing methods to correct for electrode polarization at low frequencies to extract the electrical properties of Jurkat cells. Electrode polarization hindered accurately extracting cellular properties, particularly nuclear envelope parameters from the double-shell model, above 40 ºC, despite successful characterization of the buffer up to 45 ºC. Cell properties extracted from the single-shell model agreed with prior measurements at room temperature for volume fractions down to 0.002-0.003%. The lower volume loading made the dispersion for nuclear parameters too weak for extraction using the double-shell model. Except for the cell membrane permittivity, which showed negative correlation with temperature at and below physiological temperature, the dielectric properties were insensitive to temperature, while the buffer exhibited noticeable changes. These results elucidate temperature-dependent electrical properties using volume loadings more representative of physiological conditions.</p>