The Electrorotation as a Tool to Monitor the Dielectric Properties of Spheroid During the Permeabilization.

This paper proposes to monitor the spheroid's permeabilization within a dedicated microfluidic device using electrorotation analyses. The combination of two electric solicitations, the negative dielectrophoresis force (nDEP) for the spheroid trapping and the electrorotation torque for its dielectric characterization, is used. An estimation of the spheroid dielectric parameters is obtained through the analysis of the rotational velocity curve versus the electric field frequency before and after the PEF application. An observation set-up includes a fast camera that allows time controlled image sequence acquisition. Frames are then digitalized and from the analysis of the rotational velocity of the spheroid, its complex permittivity is determined. Different models, involving the variation of the dielectric properties of the concentric shells that constitute the spheroid, as well as the heterogeneity of cells within each shell, are proposed and used to determine its dielectric properties.