Increased binding of liposomes to cells by electric treatment.

The influence of electric field treatments on the interaction of large unilamellar vesicles (liposomes) with animal cells was monitored by the fluorescence assay based on the use of the liposomes loaded by a dye 1-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). It was shown that application of a short electric pulse (100 microseconds of 3-4 kV/cm) to the suspension of cells in presence of vesicles resulted in significant (more than 2 times) increase of the fluorescence associated with cells. The pH-sensitivity of the excitation spectrum of the dye and its interaction with the quencher were used to determine the nature of the phenomenon as the increase of the liposome binding onto the cell surface but not the consequence of a promotion of liposome uptake into the cells by endocytosis. The higher affinity for the liposome caused by the electric field has a lifetime of several minutes. The possible relation of the effect described to the electroporation of cell membranes and to macroscopic changes in membrane structure is discussed.