Cell-by-cell dielectric and mechanical phenotyping of oocytes

The biomechanics and dielectric properties of mammalian oocytes are key determinants of developmental competence. However, conventional approaches such as optical deformation cytometry are limited by their reliance on high-resolution imaging, requiring complex image analysis techniques and making them unsuitable for large, optically dense cells like oocytes. Here, we present a differential microfluidic impedance cytometry platform that integrates frequency-resolved dielectric profiling with constriction-based deformation analysis. The hybrid glass-SU-8 chip with integrated coplanar electrodes enables high-fidelity measurements up to 30 MHz. Using hydrogel microspheres for calibration, we confirmed that their impedance response was largely frequency-independent. In contrast, porcine oocytes displayed classical β-dispersion, reflecting membrane capacitance and cytoplasmic conductivity, as well as pressure-dependent impedance dynamics indicating viscoelastic resistance. Two-dimensional impedance mapping enabled robust discrimination between hydrogels and oocytes. In addition, fresh oocytes and oocytes recovered from a severe freeze–thaw injury model showed separable electrical and transit-dynamic signatures. Impedance-derived peak-to-valley transit ( PVT ) analysis notably provided a fully electrical surrogate for deformation dynamics, eliminating the need for video-based tracking. To our knowledge, this is the first application of impedance cytometry to mammalian oocytes and the first demonstration of frequency-resolved differential impedance analysis of mammalian oocytes during pressure-driven constriction transit. Compared with subjective morphological assessment and imaging-dependent deformation analysis, this approach provides objective electrical readouts of dielectric and transit-dynamic phenotypes without labelling. Uniting dielectric profiling with mechanically coupled transit metrics in a single, label-free assay enables discrimination of individual treatment-associated electromechanical phenotypes within oocyte populations. These findings establish the technical feasibility of label-free single-oocyte electromechanical phenotyping.