Dielectric properties of dipicrylamine-doped erythrocytes, cultured cells and lipid vesicles

• Dipicrylamine-doped cells and liposomes were studied by dielectric spectroscopy.
• Low-frequency (LF) dielectric dispersion was found around a few kHz.
• The LF dispersion is due to translocation of dipicrylamine ions in the membranes.
• Theoretical analysis provided the kinetic parameters of the translocation.

Horse erythrocytes, murine lymphoblasts (L5178Y) and lipid vesicles that were treated with dipicrylamine (DPA) as a lipophilic ion were studied by dielectric spectroscopy over a frequency range of 10 Hz to 10 MHz. The DPA-treated cells and lipid vesicles showed low-frequency (LF) dielectric dispersion around 1–10 kHz in addition to β-dispersion due to the Maxwell–Wagner effect. The LF dispersion corresponds to that found in previous electrorotation (ROT) studies on DPA-treated cells, being due to the translocation of mobile ions in the plasma membranes. Analysis of the LF dispersion based on the mobile charge model provided the area-specific concentration Nt of DPA ions adsorbed at the membrane interfaces and their translocation rate constant ki between the interfaces. The values of Nt and ki were respectively 13–21 nmol/m2 and 0.7–1.6 × 104 s− 1 for both horse erythrocytes and L5178Y cells at 10 μM DPA, being consistent with those determined by ROT for human erythrocytes and cultured cells.