Lipid membrane-assisted condensation and assembly of amphiphilic Janus particles

Vesicle constriction by rings of Janus nanoparticles and aggregates of curved proteins

Membrane constriction and associated scission by proteins and nano structures are crucial to many processes in cellular and synthetic biology. We report mechanical constriction of vesicles by rings of adsorbed Janus nanoparticles that represent synthetic nano structures and mimic contractile proteins, and by aggregates of curved crescents that mimic scaffold proteins. Membrane energetics from Monte Carlo simulations and simulated annealing of the elastic membrane model confirms spontaneous vesicle constriction by aggregates of sufficiently-curved crescents of various lengths and by rings of Janus nanoparticles with a variety of ring lengths, particle sizes, and particle area fractions. We show that shorter rings of smaller particles with higher area fractions reinforce the constriction by increasing the energetic drive towards the constricted vesicle with smaller constriction radius. We demonstrate that vesicle constriction by crescent aggregates strongly depends on the crescent curvature. In contrast to aggregates of sufficiently-curved crescents that are capable of inducing full vesicle constriction, those of near flat crescents with negligible curvature leave the vesicle unconstricted. Our results offer promising perspectives for designing membrane-constricting nano structures such as nanoparticle aggregates and clusters of synthetic curved proteins such as DNA origami scaffolds with applications in synthetic biology. Our findings reveal the significant contribution of highly-curved F-BAR domains to cell division and explain how contractile protein rings such as dynamin GTPase, actomyosin rings, and endosomal sorting complexes required for transport constrict the membrane.

Cooperative assembly of Janus particles and amphiphilic oligomers: the role of Janus balance

Cooperative assembly of nanoparticles and amphiphiles has emerged as a significant strategy for constructing hybrid nanocomposites with desired architectures and properties. It is of great significance to develop novel hybrid nanostructures with controlled spatial localization of nanoparticles within hybrid assemblies. Here, by adopting dissipative particle dynamics simulations, the cooperative assembly of Janus particles and amphiphilic oligomers is studied. We demonstrate that a variety of defined hybrid nanostructures such as balls, sticks, disks, lines, vesicles, and networks can be achieved by the cooperative assembly of Janus particles and amphiphilic oligomers. Furthermore, the investigation of the kinetic pathway illustrates that the formation of hybrid assemblies is an entropy-driven process. Our simulation results suggest that the Janus balance of nanoparticles can significantly affect the structure and size of hybrid aggregates and the spatial localization of Janus particles within hybrid assemblies. These findings not only enrich our understanding of the cooperative assembly of Janus nanoparticles and amphiphiles, but also offer a feasible strategy to prepare hybrid materials with controlled localization of nanoparticles.

Curvature-Mediated Assembly of Janus Nanoparticles on Membrane Vesicles

Besides direct particle-particle interactions, nanoparticles adsorbed to biomembranes experience indirect interactions that are mediated by the membrane curvature arising from particle adsorption. In this Letter, 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. 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, besides the initial membrane curvature.

Interrogating Cellular Functions with Designer Janus Particles

Janus particles have two distinct surfaces or compartments. This enables novel applications that are impossible with homogeneous particles, ranging from the engineering of active colloidal metastructures to creating multimodal therapeutic materials. Recent years have witnessed a rapid development of novel Janus structures and exploration of their applications, particularly in the biomedical arena. It, therefore, becomes crucial to understand how Janus particles with surface or structural anisotropy might interact with biological systems and how such interactions may be exploited to manipulate biological responses. This perspective highlights recent studies that have employed Janus particles as novel toolsets to manipulate, measure, and understand cellular functions. Janus particles have been shown to have biological interactions different from uniform particles. Their surface anisotropy has been used to control the cell entry of synthetic particles, to spatially organize stimuli for the activation of immune cells, and to enable direct visualization and measurement of rotational dynamics of particles in living systems. The work included in this perspective showcases the significance of understanding the biological interactions of Janus particles and the tremendous potential of harnessing such interactions to advance the development of Janus structure-based biomaterials.