Salt Gradient-Induced Phoresis of Vesicles and Enhanced\nMembrane Fusion in a Crowded Milieu

Phoresis\nof biocolloidal objects in response to chemical gradients\nis a matter of interest among diverse scientific disciplines owing\nto their importance in the spatiotemporal orchestration of biochemical\nprocesses. Although there are reports of soft matter transport/phoresis\nin the gradient of ions or salts in the aqueous system, their phoretic\nbehavior in the presence of macromolecular crowder is largely unexplored.\nNotably, cellular cytoplasm is illustrated as a crowded milieu and\nthereby understanding biomolecular phoresis in the presence of polymeric\nmacromolecules would endorse phoretic behavior in a biomimetic environment.\nHere, we report the phoresis-induced enhanced aggregation and fusion\nof vesicles in gradients of monovalent (NaCl) and divalent salt (MgCl<sub>2</sub>), in the presence of polymeric crowder, polyethylene glycol\nof molecular weight 400 (PEG 400). Apart from diffusiophoresis, depletion\nforce plays a crucial factor in crowded environments to control localized\nvesicle aggregation in a salt gradient. This demonstration will potentially\nshow the pathway to future research related to spatiotemporally correlated\nliposomal transport and membrane-dependent function (such as content\nmixing and signaling) in a physiologically relevant crowded environment.