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

This research article investigates the dielectric properties of horse erythrocytes (red blood cells), murine lymphoblasts (mouse lymph cell precursors), and lipid vesicles (small cell-like structures) treated with dipicrylamine (DPA). Using dielectric spectroscopy, researchers found that the DPA-treated cells and lipid vesicles had low-frequency dielectric dispersion in addition to β-dispersion caused by the Maxwell-Wagner effect, consistent with previously observed behaviour in electrorotation studies.

Dielectric Spectroscopy and DPA Treatment

• The study uses dielectric spectroscopy, a technique that studies how a polar material interacts with an electric field, along a frequency range of 10 Hz to 10 MHz. The material in this case comprises horse erythrocytes (red blood cells), murine lymphoblasts (mouse lymph cell precursors), and lipid vesicles.
• These cells and lipid vesicles were treated with dipicrylamine (DPA), a lipophilic ion. Lipophilic substances are those that can dissolve or mix well with lipids, the major component of cell membranes. Thus, DPA ions were easily able to incorporate themselves in the cell membranes for this analysis.

Observations and Analysis

• The DPA-treated cells and lipid vesicles demonstrated low-frequency (LF) dielectric dispersion around 1-10 kHz, in addition to β-dispersion due to the Maxwell-Wagner effect. Low-frequency dispersion is a phenomenon where the response of a material to an applied alternating current changes over certain frequencies. β-dispersion is related to the movement of charges across barriers or interfaces in a system.
• This LF dispersion is the result of the translocation of mobile ions (in this case, DPA ions) across the plasma membranes. This finding is consistent with previously reported results from electrorotation (ROT) studies on DPA-treated cells.
• Analysis of the LF dispersion, utilizing the mobile charge model, provided the researchers with two key measures: the area-specific concentration (Nt) of DPA ions at the membrane interfaces, and their translocation rate constant (ki) between these interfaces.
• The values obtained for both Nt and ki were in line with those measured in previous electrorotation studies performed on human erythrocytes and cultured cells.

Implications and Significance

• This research helps in understanding how treatment with lipophilic ions such as DPA influences the dielectric properties of cells and lipid vesicles. This will contribute to the understanding of biological systems at the ionic and cellular levels, which can be relevant, for instance, in developing better drug delivery methods or in analysing the effects of different treatments at a cellular level.