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.

Mammals can recognize a vast number of odorants by using olfactory receptors (ORs) known as G protein-coupled receptors. The OR gene family is one of the most diverse gene families in mammalian genomes. Because of the vast combinations of ORs and odorants, few ORs have thus far been linked to specific odorants. Here, we established a functional screening method for OR genes by using a microchamber array containing >5,400 single olfactory epithelium-derived cells from mice applied to time-lapse single-cell array cytometry. This method facilitated the prompt isolation of single olfactory sensory neurons (OSNs) responding to the odorant of interest. Subsequent single-cell RT-PCR allowed us to isolate the genes encoding respective ORs. By using volatile molecules recognized as biomarkers for lung cancers, this method could deorphanize ORs and thereby reconstitute the OR-mediated signaling cascade in HEK293T cells. Thus, our system could be applied to identify any receptor by using specific ligands in the fields of physiopathology and pharmacology.