Membrane-mediated dimerization of spherocylindrical nanoparticles.

Abstract

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, <i>ξ</i>, the SCNPs are monomeric and adhere to the membrane in the parallel mode. As <i>ξ</i> is slightly increased, the SCNPs dimerize into wedged dimers, with an obtuse angle between their major axes that decreases with increasing <i>ξ</i>. However, as <i>ξ</i> is further increased, we found that the final adhesion state of the two SCNPs is strongly affected by the initial distance, <i>d</i>₀, between their centers of mass, upon their adhesion. Namely, the SCNPs dimerize into wedged dimers, with an acute angle between their major axes, if <i>d</i>₀ is relatively small. However, for relatively high <i>d</i>₀, they adhere individually to the membrane in the monomeric normal mode. For even higher values of <i>ξ</i> and small values of <i>d</i>₀, the SCNPs cluster into tubular dimers. However, they remain monomeric if <i>d</i>₀ is high. Finally, the SCNPs endocytose either as a tubular dimer, if <i>d</i>₀ is low or as monomers for large <i>d</i>₀, with the onset value of <i>ξ</i> of dimeric endocytosis being lower than that of monomeric endocytosis. Dimeric endocytosis requires that the SCNPs adhere simultaneously at nearby locations.