(40h) Self-Assembly of Nanoparticles at Membrane Interface

Self-assembled nanostructures formed by membrane-mediated aggregation of nanoparticles and proteins on biomembranes play a crucial role in synthetic biology, drug delivery, material design, and cellular and biological processes. We perform Monte Carlo simulations of a coarse-grained membrane model to investigate membrane interaction with nanoparticles and proteins. We report novel highly-stable tubular membrane structures induced by adsorbed spherical nanoparticles on vesicles that enclose linear aggregates of particles and protrude into the vesicles [1]. The tubular structures may provide a new route to encapsulate nanoparticles in vesicles for drug delivery applications. Our simulations also explain how cellular uptake of nanoparticles depends on membrane curvature [2,3] and size and shape of the particles [4]. We report an orientational change during internalisation of ellipsoidal nano particles [4] consistent with experimental observations on elongated particles uptake by the macrophage cells [5]. Using discontinuous molecular dynamics simulations we found distinct size-dependent wrapping and penetrating regimes of nano particles translocating across DPPC bilayers [6]. While larger particles undergo wrapping, the smaller ones embed themselves within the inner hydrophobic core of the bilayer. Besides direct particle–particle interactions, nanoparticles adsorbed to biomembranes experience indirect interactions that are mediated by the membrane curvature arising from particle adsorption. We show that the curvature-mediated interactions of adsorbed Janus particles depend on the initial curvature of the membrane prior to adsorption, that is, on whether the membrane initially bulges toward or away from the particles in our simulations [7]. The curvature-mediated interaction can be strongly attractive for Janus particles adsorbed to the outside of a membrane vesicle, which initially bulges away from the particles. For Janus particles adsorbed to the vesicle inside, in contrast, the curvature-mediated interactions are repulsive. We find that the area fraction of the adhesive Janus particle surface is an important control parameter for the curvature-mediated interaction and assembly of the particles [7]. Our simulations confirm vesicle scission by rings of Janus nanoparticles and aggregates of arc shaped proteins [8].

References

(1) Bahrami, A. H., Lipowsky, R., & Weikl, T. R., Phys. Rev. Lett. 2012, 109, 188102.

(2) Bahrami, A. H. et. al, Advances in colloid and interface science 2014, 208, 214-224.

(3) Bahrami, A. H., Lipowsky, R., & Weikl, T. R., Soft Matter 2016, 12(2), 581-587.

(4) Bahrami, A. H., Soft Matter 2013, 9(36), 8642-8646.

(5) Champion J. A, Mitragotri S., PNAS 103 (13), 4930-4934.

(6) EM Curtis, AH Bahrami, TR Weikl, CK Hall, Nanoscale 7 (34), 14505-14514.

(7) Bahrami, A. H., & Weikl, Nano Letters 2018, 18(2), 1259-1263.

(8) A. Bahrami, A. H Bahrami, Submitted to Nanotechnology.