Lipid Membranes-Mediated Interactions and self-assembly of spherocylindrical Nanoparticles

This dissertation highlights the pivotal role of nanoparticles (NPs) anisotropy on their adhesion and potential self-assembly on lipid membranes. The research, which is performed in the context of spherocylindrical NPs (SCNPs), offers valuable insights into the complex interaction between NPs and lipid membranes and the utilization of lipid membranes as a medium for SCNPs self-assembly, potentially opening the door to various advanced applications. Modeling SNCPs as triangulated hollow shells, the adhesion modes and endocytosis of SCNPs on tensionless planar membranes are investigated using molecular dynamics simulations of a coarse-grained implicit-solvent model. The SCNPs are shown to adhere to the membrane through two main modes, namely a parallel mode and a normal mode. We found that increasing the aspect ratio of the SCNPs facilitates the transition from the parallel to the normal mode. This exploration was extended to investigate the adhesion modes, dimerization, and endocytosis of two SCNPs on planar lipid membranes. The SCNPs exhibit five different modes of adhesion, depending on their diameter, aspect ratio, and adhesion strength values. Furthermore, when two SCNPs adhere in close proximity to a membrane, they tend to dimerize, forming either wedged or tubular dimers. In contrast, they adhere in the monomeric normal mode when their initial separation is substantial. Moreover, highly ordered nanoclusters with diverse geometries are obtained when surface-modified Janus SCNPs, such that one moiety interacts more attractively with the lipid head groups, and the other moiety that is hydrophilic and interacts more favorably with the solvent are placed on lipid vesicles. Similarly, the arrangement of uniform SCNPs on the inner side of lipid vesicles is explored, revealing their self-assembly into highly ordered polygonal and quasi-two-dimensional star-like structures, a phenomenon not observed when NPs adhere to the vesicle’s outer side. The geometries of the SCNPs’ nanoclusters are influenced by their aspect ratio, number, and adhesion strength. These structures are characterized by analyzing various quantities, including their symmetry point groups, coplanarity, and nematic order parameter