From shallow to full wrapping: geometry and deformability dictate lipid vesicle internalization

TL;DR

This study combines experiments and simulations to show how vesicle deformability and geometry influence their internalization by lipid membranes, providing insights relevant to biological and synthetic systems.

Contribution

It provides the first direct experimental validation of how vesicle deformability affects engulfment, linking theoretical models with measurable parameters.

Findings

Engulfment depends on vesicle size relative to a bendo-capillary length scale.

Deformability influences the transition between shallow and full wrapping.

Geometry dominates engulfment when vesicle size exceeds the length scale.

Abstract

The deformability of vesicles critically influences their engulfment by lipid membranes, a process central to endocytosis, viral entry, drug delivery, and intercellular transport. While theoretical models have long predicted this influence, direct experimental validation has remained elusive. Here, we combine experiments with continuum simulations to quantify how vesicle deformability affects the engulfment of small giant unilamellar vesicles (GUVs) by larger GUVs under depletion-induced adhesion. Using 3D confocal reconstructions, we extract vesicle shape, curvature, wrapping fraction, and the bendo-capillary length, a characteristic length scale that balances membrane bending and adhesion forces. We find that when vesicle size exceeds this length scale, engulfment is primarily governed by geometry. In contrast, when vesicle size is comparable to this scale, deformability strongly affects the transition between shallow, deep, and fully wrapped states, leading to suppression of full engulfment of vesicles. These findings connect theoretical predictions with direct measurements and offer a unified framework for understanding vesicle-mediated uptake across both synthetic and biological systems, including viral entry, synthetic cell design, drug delivery, and nanoparticle internalization.