Classification of tumor subtypes leveraging constriction-channel based impedance flow cytometry and optical imaging

As label-free biomarkers, electrical properties of single cells have been widely used for cell-type classification and cell-status evaluation. However, as intrinsic bioelectrical markers, previously reported membrane capacitance and cytoplasmic resistance (e.g., specific membrane capacitance C_{specific membrane} and cytoplasmic conductivity σ_cytoplasm ) of tumor subtypes were derived from tens of single cells, lacking statistical significance due to low cell numbers. In this study, tumor subtypes were constructed based on phenotype (treatment with 4-methylumbelliferone) or genotype (knockdown of ROCK1) modifications and then aspirated through a constriction-channel based impedance flow cytometry to characterize single-cell C_{specific membrane} and σ_cytoplasm . Thousands of single tumor cells with phenotype modifications were measured, resulting in significant differences in 1.64 ± 0.43 μF/cm² vs. 1.55 ± 0.47 μF/cm² of C_{specific membrane} and 0.96 ± 0.37 S/m vs. 1.24 ± 0.47 S/m of σ_cytoplasm for 95C cells (792 cells of 95C-control vs. 1529 cells of 95C-pheno-mod); 2.56 ± 0.88 μF/cm² vs. 2.33 ± 0.56 μF/cm² of C_{specific membrane} and 0.83 ± 0.18 S/m vs. 0.93 ± 0.25 S/m of σ_cytoplasm for H1299 cells (962 cells of H1299-control vs. 637 cells of H1299-pheno-mod). Furthermore, thousands of single tumor cells with genotype modifications were measured, resulting in significant differences in 3.82 ± 0.92 vs. 3.18 ± 0.47 μF/cm² of C_{specific membrane} and 0.47 ± 0.05 vs. 0.52 ± 0.05 S/m of σ_cytoplasm (1100 cells of A549-control vs. 1100 cells of A549-geno-mod). These results indicate that as intrinsic bioelectrical markers, specific membrane capacitance and cytoplasmic conductivity can be used to classify tumor subtypes.