Inherent bioelectrical parameters of hundreds of thousands of single leukocytes based on impedance flow cytometry

As label-free biomarkers, bioelectrical properties of single cells have been widely used in hematology analyzers for 3-part differential of leukocytes, in which, however, instrument dependent bioelectrical parameters (e.g., DC/AC impedance values) rather than inherent bioelectrical parameters (e.g., diameter D_c, specific membrane capacitance C_sm and cytoplasmic conductivity σ_cy) were used, leading to poor comparisons among different instruments. In order to address this issue, this study collected inherent bioelectrical parameters from hundreds of thousands of white blood cells based on a home-developed impedance flow cytometry with corresponding 3-part differential of leukocytes realized. More specifically, leukocytes were separated into three major subtypes of granulocytes, monocytes and lymphocytes based on density gradient centrifugation. Then these separated cells were aspirated through a constriction-microchannel based impedance flow cytometry where inherent bioelectrical parameters of D_c, C_sm and σ_cy were quantified as 9.8 ± 0.7 μm, 2.06 ± 0.26 μF/cm², and 0.34 ± 0.05 S/m for granulocytes (n_cell = 134,829); 10.4 ± 1.0 μm, 2.45 ± 0.48 μF/cm², and 0.42 ± 0.08 S/m for monocytes (n_cell = 40,226); 8.0 ± 0.5 μm, 2.23 ± 0.34 μF/cm², and 0.35 ± 0.08 S/m for lymphocytes (n_cell = 129,193). Based on these inherent bioelectrical parameters, neural pattern recognition was conducted, producing a high “classification accuracy” of 93.5% in classifying these three subtypes of leukocytes. These results indicate that as inherent bioelectrical parameters, D_c, C_sm, and σ_cy can be used to electrically phenotype white blood cells in a label-free manner.