Morphological analysis of the interaction of charged surfactant vesicles (SVs) with human cultured cells

We analyzed the binding and fusogenic properties of surfactant vesicles (SV s), composed of ionic and nonionic surfactants and cholesterol, with the su rface of different human lymphoid cells. The influence of charge on SVs-cel l interaction was evaluated by monitoring the presence of fluorescent sodiu m calcein artificially entrapped in the vesicles using optical fluorescence microscopy and laser scanning confocal microscopy, Our results clearly ind icate that only negatively charged vesicles bind and fuse with the plasma m embrane of human lymphoid cells, and the number of SVs bound to the cell su rface was variable among the positive cells. Thin section electron microsco py illustrated that the fusogenic events of SVs with the cell plasma membra ne mostly occurred at smooth and nonvillous regions of the cell surface, Ta ken together, our results suggest that binding and fusion of SVs with the c ell plasma membrane might be dependent on interactions with specific membra ne components that preferentially recognize negatively charged SVs.