Interactions of DMPC and DMPC/gemini liposomes with the cell membrane investigated by electrorotation

The electrorotation technique was utilized to investigate the interactions between a mouse fibroblast cell lineand zwitterionic liposomes formed by a natural phospholipid or cationic liposomes formulated with the samephospholipid and a cationic gemini surfactant. The application of this technique allowed an accurate characterizationof the passive dielectric behavior of the plasmamembrane by the determination of its specific capacitanceand conductance. Changes of these parameters, upon interaction with the liposomes, are related to variations inthe structure and or in the transport properties of the membrane. Cells were exposed to both types of liposomesfor 1 or 4 h. Electrorotation data showa dramatic reduction of the dielectric parameters of the plasma membraneafter one hour treatment. After 4 h of treatment the effects are still observed only in the case of the cationic liposomes.Surprisingly, these same treatments did not cause a relevant biological damage as assessed by standardviability tests. A detailed discussion to rationalize this phenomenon is presented.