Liposomes-Induced Nanostar Self-Assemblies of Spherical Nanoparticles

Using molecular dynamics of a coarse-grained implicit-solvent model, we show that liposomes can self-assemble spherical nanoparticles, adhering to the liposomes' inner surface, into novel quasi-two-dimensional star-like nanoclusters. The geometric details of these nanostar assemblies depend on the number of adhering nanoparticles. The simulations indicate that for weak adhesion strength, the spatial correlations of the adhering nanoparticles are weak. However, over a wide range of intermediate values of the adhesion strength, the increased nanoparticles' degree of wrapping leads them to deform the spherical vesicle from a three-dimensional geometry to a flattened two-dimensional star-like geometry, in which the nanoparticles' positions are highly correlated. At high adhesion strength, the nanoparticles are exocytosed. Interestingly, several long-lived transient states, depending on the number of nanoparticles, including tetrahedra, triangular prisms, octahedra, etc., form during the transformation of the nanoclusters' geometries from three to two dimensions. The stability of the nanoclusters is inferred from free energy calculations based on the Helfrich Hamiltonian. These novel two-dimensional nanoassemblies should have various applications. For example, they can be used as bio-friendly gears in molecular machines.