# From Shallow to Full Wrapping: Geometry and Deformability Dictate Lipid Vesicle Internalization

## TL;DR

This study explores how the shape and flexibility of lipid vesicles affect their engulfment by other membranes, important for processes like drug delivery and cell transport.

## Contribution

The research introduces a mechanical model and experimental system to predict and control vesicle engulfment based on geometry and deformability.

## Key findings

- Vesicle engulfment is governed by geometry when size exceeds the bendocapillary length.
- Deformability controls transitions between different wrapping states near the bendocapillary length.
- Light-responsive lipids enable on-demand switching between wrapping states.

## Abstract

The deformability
and adhesion of vesicles critically
influence
their engulfment by lipid membranes, a process that is central to
endocytosis, viral entry, drug delivery, and intercellular transport.
We developed a versatile experimental system of giant unilamellar
vesicles (GUVs) that interact via depletion-induced adhesion. Combining
experiments with continuum simulations, we construct a state diagram
identifying conditions for the endo- and exocytic engulfment of small
GUVs by larger ones. Leveraging full 3D confocal reconstructions of
vesicle curvature, we experimentally quantify the bendocapillary length,
a scale governing the competition between membrane bending and adhesion.
When the vesicle size exceeds this length, wrapping is governed by
geometry. In contrast, near this scale, deformability controls transitions
between shallow, deep, and fully wrapped states, suppressing full
engulfment. Finally, we demonstrate on-demand, light-induced switching
between wrapping states using photoresponsive lipids. These results
establish a mechanical criterion for vesicle engulfment and provide
a tunable platform for studying soft cargo uptake.