Highly Ordered Nanoassemblies of Janus Spherocylindrical Nanoparticles Adhering to Lipid Vesicles.

In recent years, there has been a heightened interest in the self-assembly of nanoparticles (NPs) that is mediated by their adsorption onto lipid membranes. The interplay between the adhesive energy of NPs on a lipid membrane and the membrane's curvature energy causes it to wrap around the NPs. This results in an interesting membrane curvature-mediated interaction, which can lead to the self-assembly of NPs on lipid membranes.

Nanoparticles insertion and dimerization in polymer brushes.

Molecular dynamics simulations are conducted to systematically investigate the insertion of spherical nanoparticles (NPs) in polymer brushes as a function of their size, strength of their interaction with the polymers, polymer grafting density, and polymer chain length. For attractive interactions between the NPs and the polymers, the depth of NPs' penetration in the brush results from a competition between the enthalpic gain due to the favorable polymer-NP interaction and the effect of osmotic pressure resulting from displaced polymers by the NP's volume. A large number of simulations show that the average depth of the NPs increases by increasing the strength of the interaction strength.

Non-close-packed hexagonal self-assembly of Janus nanoparticles on planar membranes.

The adhesion modes of an ensemble of spherical Janus nanoparticles on planar membranes are investigated through large-scale molecular dynamics simulations of a coarse-grained implicit-solvent model. We found that the Janus nanoparticles adhering to planar membranes exhibit a rich phase behavior that depends on their adhesion energy density and areal number density. In particular, effective repulsive membrane-curvature-mediated interactions between the Janus nanoparticles lead to their self-assembly into an ordered hexagonal superlattice at intermediate densities and intermediate to high adhesion energy density, with a lattice constant determined by their areal density.

Lipid vesicles induced ordered nanoassemblies of Janus nanoparticles.

Since many advanced applications require specific assemblies of nanoparticles (NPs), considerable efforts have been made to fabricate nanoassemblies with specific geometries. Although nanoassemblies can be fabricated through top-down approaches, recent advances show that intricate nanoassemblies can also be obtained through self-assembly, mediated for example by DNA strands. Here, we show, through extensive molecular dynamics simulations, that highly ordered self-assemblies of NPs can be mediated by their adhesion to lipid vesicles (LVs).

Membrane-mediated dimerization of spherocylindrical nanoparticles.

We present a numerical investigation of the modes of adhesion and endocytosis of two spherocylindrical nanoparticles (SCNPs) on planar and tensionless lipid membranes, using systematic molecular dynamics simulations of an implicit-solvent model, with varying values of the SCNPs' adhesion strength and dimensions. We found that at weak values of the adhesion energy per unit of area, , the SCNPs are monomeric and adhere to the membrane in the parallel mode. As is slightly increased, the SCNPs dimerize into wedged dimers, with an obtuse angle between their major axes that decreases with increasing .

Modes of adhesion of spherocylindrical nanoparticles to tensionless lipid bilayers.

The adhesion modes and endocytosis pathway of spherocylindrical nanoparticles (NPs) are investigated numerically using molecular dynamics simulations of a coarse-grained implicit-solvent model. The investigation is performed systematically with respect to the adhesion energy density ξ, NP's diameter D, and NP's aspect ratio α. At weak ξ, the NP adheres to the membrane through a parallel mode, i.

Modes of adhesion of two Janus nanoparticles on the outer or inner side of lipid vesicles.

Using molecular dynamics simulations of a coarse-grained model, in conjunction with the weighted histogram analysis method, the adhesion modes of two spherical Janus nanoparticles (NPs) on the outer or inner side of lipid vesicles are explored. In particular, the effects of the area fraction, , of the NPs that interact attractively with lipid head groups, the adhesion strength and the size of the NPs on their adhesion modes are investigated. The NPs are found to exhibit two main modes of adhesion when adhered to the outer side of the vesicle.

Spatial arrangements of spherical nanoparticles on lipid vesicles.

We report results of a numerical investigation of the modes of adhesion of two spherical nanoparticles (NPs) on lipid vesicles based on molecular dynamics simulations, in conjunction with the weighted histogram analysis method, of an implicit-solvent model of self-assembled membranes. Our investigation shows that the NPs exhibit a sequence of three modes of adhesion. For low adhesive interactions, the adhering NPs are apart from each other.

Binding, unbinding and aggregation of crescent-shaped nanoparticles on nanoscale tubular membranes.

Using molecular dynamics simulations of a coarse-grained implicit solvent model, we investigate the binding of crescent-shaped nanoparticles (NPs) on tubular lipid membranes. The NPs adhere to the membrane through their concave side. We found that the binding/unbinding transition is first-order, with the threshold binding energy being higher than the unbinding threshold, and the energy barrier between the bound and unbound states at the transition that increases with increasing the NP's arclength L or curvature mismatch μ = R/R, where R and R are the radii of curvature of the tubular membrane and the NP, respectively.

Adhesion and Aggregation of Spherical Nanoparticles on Lipid Membranes.

We present a review of recent results on the adhesion, wrapping and aggregation of spherical nanoparticles (NPs) on lipid membranes via molecular dynamics simulations of an implicit solvent model. We show that the degree of wrapping of small NPs, by tensionless planar membranes, can increase continuously with the adhesion strength. However, the degree of wrapping exhibits a discontinuity for large NPs or short interaction range.

Discontinuous wrapping transition of spherical nanoparticles by tensionless lipid membranes.

We present a numerical study of the wrapping of spherical nanoparticles by tensionless lipid membranes using molecular dynamics simulations of a coarse-grained implicit solvent model. We found that the degree of wrapping of small nanoparticles increases continuously with the adhesion strength for nanoparticles with diameter less than or about 15 nm. In contrast, the increase in the degree of wrapping becomes discontinuous for larger nanoparticles and exhibits a clear hysteresis when upward and downward annealing scans with respect to adhesion strength are performed.

Stability of membrane-induced self-assemblies of spherical nanoparticles.

The self-assembly of spherical nanoparticles, resulting from their adhesion on tensionless lipid membranes, is investigated through molecular dynamics simulations of a coarse-grained implicit-solvent model. Our simulations indicate that, with increasing adhesion strength, while reshaping the membrane, the nanoparticles aggregate into a sequence of self-assemblies corresponding to in-plane chains, two-row tubular (bitube) chains, annular (ring) chains, and single-row tubular (tube) chains. Annealing scans, with respect to adhesion strength, show that the transitions between the various phases are highly first-order with significant hystereses.

Partial wrapping and spontaneous endocytosis of spherical nanoparticles by tensionless lipid membranes.

Computer simulations of an implicit-solvent particle-based model are performed to investigate the interactions between small spherical nanoparticles and tensionless lipid bilayers. We found that nanoparticles are either unbound, wrapped by the bilayer, or endocytosed. The degree of wrapping increases with increasing the adhesion strength.

Membrane-mediated aggregation of anisotropically curved nanoparticles.

Using systematic numerical simulations, we study the self-assembly of elongated curved nanoparticles on lipid vesicles. Our simulations are based on molecular dynamics of a coarse-grained implicit-solvent model of self-assembled lipid membranes with a Langevin thermostat. Here we consider only the case wherein the nanoparticle-nanoparticle interaction is repulsive, only the concave surface of the nanoparticle interacts attractively with the lipid head groups and only the outer surface of the vesicle is exposed to the nanoparticles.

Computer simulation of cytoskeleton-induced blebbing in lipid membranes.

Blebs are balloon-shaped membrane protrusions that form during many physiological processes. Using computer simulation of a particle-based model for self-assembled lipid bilayers coupled to an elastic meshwork, we investigated the phase behavior and kinetics of blebbing. We found that blebs form for large values of the ratio between the areas of the bilayer and the cytoskeleton.