Fast fourteen-frequency impedance spectroscopy of single erythrocytes and yeast cells in flow

The dielectric properties of biological cells provide critical insights into cellular physiology and have long been exploited for label-free diagnostics. While traditional approaches relied on bulk tissue or suspension measurements, advances in microfabrication have enabled single-cell electrical characterization, revealing subtle heterogeneities essential for precision medicine. Building on recent progress in single-cell impedance spectroscopy, we present a novel microfluidic impedance-based platform capable of rapid dielectric characterization of flowing cells at fourteen simultaneous, logarithmically spaced frequencies between 250 kHz and 50 MHz, achieving an unprecedented resolution of 6.1 data points per decade. The system integrates two synchronized lock-in amplifiers and a tailored signal-processing algorithm to reconstruct high-resolution impedance spectra at a throughput of up to 40 spectra per second. We demonstrate the approach on red blood cells (RBCs) and yeast cells, both under native conditions and under stress. For RBCs, chemical stress induced by antimicrobial peptides (AMPs) DNS-PMAP23 and trichogin GA IV revealed distinct dielectric alterations, while yeast cells exhibited measurable changes under thermal stress. Thousands of spectra were acquired and fitted to physically grounded models, enabling extraction of intrinsic parameters such as membrane capacitance and intracellular conductivity, as well as cell size. This work demonstrates the feasibility of high-throughput, high-resolution impedance spectroscopy of single cells, opening avenues for advanced diagnostics and biotechnological applications.