# Active elastohydrodynamics of vesicles in narrow, blind constrictions

## TL;DR

This paper investigates the active transport of vesicles through narrow, blind constrictions using simulations and theory, revealing how geometry, forces, and hydrodynamics influence transit times and dynamics.

## Contribution

It introduces a combined simulation and semi-analytical approach to understand vesicle transport in constricted geometries, emphasizing the role of hydrodynamics and motor forces.

## Key findings

- Transport into blind ends forms lubrication layers that impede motion.
- Motor and fluid forces create multistable vesicle dynamics.
- Hydrodynamic effects significantly influence vesicle transit kinetics.

## Abstract

Fluid-resistance limited transport of vesicles through narrow constrictions is a recurring theme in many biological and engineering applications. Inspired by the motor-driven movement of soft membrane-bound vesicles into closed neuronal dendritic spines, here we study this problem using a combination of passive three-dimensional simulations and a simplified semi-analytical theory for active transport of vesicles that are forced through such constrictions by molecular motors. We show that the motion of these objects is characterized by two dimensionless quantities related to the geometry and the strength of forcing relative to the vesicle elasticity. We use numerical simulations to characterize the transit time for a vesicle forced by fluid pressure through a constriction in a channel, and find that relative to an open channel, transport into a blind end leads to the formation of an effective lubrication layer that strongly impedes motion. When the fluid pressure forcing is complemented by forces due to molecular motors that are responsible for vesicle trafficking into dendritic spines, we find that the competition between motor forcing and fluid drag results in multistable dynamics reminiscent of the real system. Our study highlights the role of non-local hydrodynamic effects in determining the kinetics of vesicular transport in constricted geometries.