Soft nanoparticles charge expression within lipid membranes: The case of amino terminated dendrimers in bilayers vesicles.

Interactions of charged nanoparticles with model bio-membranes provide important insights about the soft interaction involved and the physico-chemical parameters that influence lipid bilayers stability, thus providing key features of their cytotoxicity effects onto cellular membranes. With this aim, the self-assembly processes between polyamidoamine dendrimers (generation G = 2.0 and G = 4.0) and dipalmitoylphosphatidylcholine (DPPC) lipids were investigated by means of Zeta potential analysis, x-rays, Raman and quasielastic light scattering experiments. Raman scattering data evidenced that dendrimers penetration produce a perturbation of the DPPC vesicles alkyl chains. A linear increase of liposome zeta-potential with increasing PAMAM concentration evidenced that only a fraction of the dendrimers effective charge contributes to the expression of the charge at the surface of the DPPC liposome. The linear region of the zeta-potential extends toward higher PAMAM concentrations as the dendrimer generation decreases from G = 4.0 to G = 2.0. Further increase in PAMAM concentration, outside of the linear region, causes a perturbation of the bilayer characterized by the loss in multilamellar correlation and the increase of DPPC liposome hydrodynamic radius. The findings of our investigation help to rationalize the effect of nanoparticles electrostatic interaction within lipid vesicles as well as to provide important insights about the perturbation of lipid bilayers membrane induced by nanoparticles inclusion.