Dielectrophoresis crossover frequencies of yeast mitochondria determined by microscopic observation for evaluating their dielectric properties

Dielectrophoresis (DEP) is an electrokinetic phenomenon caused by the polarization of dielectric particles in a non-uniform electric field. Since DEP behavior is closely linked to the dielectric properties of the target, it can be used to infer these properties. This study investigated the DEP characteristics of yeast mitochondria by observing their DEP crossover frequencies, where DEP-induced motion ceases. Fluorescently stained mitochondria were suspended in media with varying conductivities, and the frequency of an applied voltage was swept to identify the crossover points. Two distinct crossover frequencies were observed, indicating a core-shell structure consistent with mitochondrial morphology. By analyzing these crossover frequencies across different conductivity conditions, we estimated the dielectric properties of individual mitochondrial components. These results demonstrate that DEP-based analysis can be used not only for whole cells but also for organelles, providing new insights into subcellular biophysics and laying the foundation for future studies on organelle-level dynamics. • DEP crossover frequencies of yeast mitochondria were directly observed. • Two crossover frequencies indicate a core–shell structure of mitochondria. • A double-shell dielectric model estimated the mitochondrial component properties. • Estimated dielectric parameters showed species-specific differences vs. mammals. • Enables organelle-level dielectric characterization and real-time DEP monitoring.