Abstract
Membrane capacitances and cytoplasm conductivities of hematopoietic cells were investigated by simultaneous electrorotation (ROT) systems of multiple cells. Simultaneous ROT was achieved by the rotation of electric fields in grid arrays formed with three-dimensional interdigitated array (3D-IDA) electrodes that can be easily fabricated using two substrates with IDA electrodes. When AC signals were applied to four microband electrodes with a 90° phase difference to each electrode, cells dispersed randomly in the 3D-IDA device started to rotate and moved to the center of each grid. Multiple cells were simultaneously rotated at the center of grids without friction from contact with other cells and substrates. The averages and variance of ROT rates of cells at each frequency can be measured during a single operation of the device within 5 min, resulting in the acquisition of ROT spectra. Membrane capacitances and cytoplasm conductivities of hematopoietic cells (K562 cells, Jurkat cells, and THP-1 cells) were determined by fitting ROT spectra obtained experimentally to the curves calculated theoretically. The values determined by using the simultaneous ROT systems well coincided with the values reported previously. The membrane capacitances and cytoplasm conductivities of WEHI-231 cells were firstly determined to be 8.89 ± 0.25 mF m-2 and 0.28 ± 0.03 S m-1, respectively. Furthermore, the difference of the ROT rates based on the difference of the electric properties of cells was applied to discriminate the types of cells. The acquisition of rotation rates of multiple cells within a single operation makes the statistical analysis extremely profitable for determining the electrical properties of cells.
Highlights
Electrorotation (ROT) has been utilized to characterize the electrical properties of single cells.[16,17] A torque is induced to cells by the electrostatic interaction between the constant rotating electric field generated by the configuration of multielectrodes and the dipole moment formed by the difference in electrical polarizabilities of cells and media in the electric field
Electric fields rotated to a clockwise direction in grids which were surrounded by microband electrodes (a), (i), (b) and (ii) in a counterclockwise direction
Over 1500 grids surrounded by four microband electrodes for the ROT of cells can be fabricated by using two interdigitated microband array (IDA) electrodes as upper and lower substrates
Summary
Electrorotation (ROT) has been utilized to characterize the electrical properties of single cells.[16,17] A torque is induced to cells by the electrostatic interaction between the constant rotating electric field generated by the configuration of multielectrodes and the dipole moment formed by the difference in electrical polarizabilities of cells and media in the electric field. In the ROT techniques, quadrupole electrodes with the gaps patterned in a crisscross on the substrate were conventionally used to induce a rotating electric field at the center of the quadrupole electrodes by applying sine waves with a 90° phase difference to each other. The ROT techniques have been applied to study eukaryotic parasite transmission stages.[18] a relatively long experimental period was required because several single cells must be repeatedly arranged at a center of quadrupole electrodes
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