Lipid-phase-modulated interactions of gold nanoparticles with supported vesicular and planar membranes

The thorough understanding of the interactions between nanoparticles and lipid membranes has attracted major interest over the past few decades. This spans fundamental biophysics and biomechanics, as well as medical applications, where nanoparticles could serve as potential drug carriers. The influence of the lipid phase in these interactions has been studied to markedly less extent with respect to the nanoparticle size, shape and coating, as well as the presence of electric charge in either the nanoparticles or the membranes. Seeking to gain new insights into the lipid phase, we have systematically investigated the role of the liquid-disordered, the gel-ordered, as well as the seldom-studied ripple phases in modulating the interaction strength between nanoparticles and biomimetic membranes. Supported lipid vesicles and supported lipid bilayers of different composition and amount of electric charge, as well as spherical functionalized Au nanoparticles with and without charge have formed our experimental platform. The results, obtained by quartz crystal microbalance with dissipation monitoring and complemented by atomic force microscopy, reveal a strikingly different mechanistic picture of the interactions between the various lipid phases and types of nanoparticles. We demonstrate enhanced vesicle rupture in the case of stiffer membranes, consistent with recent theoretical studies, yet supported by limited existing experimental evidence. This work advances fundamental understanding of lipid-state-driven nanoparticle-membrane interactions. Such insight is essential, as dynamic changes in bilayer rigidity, composition, and surface charge determine how membranes and nanoparticles interact.