Lipid-Vesicles Mediate Self-Limited Self-Assembly of Polymer-Grafted Janus Nanoparticles

Recent studies have extensively explored the interactions between nanoparticles (NPs) and lipid membranes. The fluidity and elasticity of lipid membranes allow them to deform and conform to the surface of adhering nanoparticles, with the extent of deformation determined by the competition between adhesive interactions and the membrane's curvature elasticity. An interesting consequence of these deformations is the emergence of long-range, membrane-curvature-mediated interactions between adhering NPs. Previous research have shown that surface modification of NPs into Janus nanoparticles, composed of one moiety that preferentially adheres to lipid membranes and the other that is hydrophilic and interacts repulsively with the membrane, can form highly ordered nanoclusters, some of which are Platonic solids. The organization of these clusters depends on the number of NPs adhering to the vesicle, and within these clusters, the NPs remain spatially separated. However, as more NPs adhere to the vesicle, these ordered nanostructures become disrupted, leading to disordered clusters in which some NPs undergo oligomerization. Using extensive and large-scale molecular dynamics simulations, we demonstrate here that partial surface modification of NPs by grafting polymers, such as polyethylene glycol, to one moiety of the NPs, not only reliably prevents their oligomerization but also acts as a steric barrier that inhibits further NP adhesion to the vesicle. Consequently, polymer grafting provides an effective means to engineer tunable, highly ordered self-limited assemblies of NPs on vesicle scaffolds, where the number of NPs in the assembly is controlled by the polymer's molecular weight, their grafting density, and the diameters of both the NPs and the vesicle.