# Haptotactic Motion of Multivalent Vesicles Along Ligand-Density Gradients

## TL;DR

This paper explores how multivalent vesicles move along ligand-density gradients, offering insights into passive haptotaxis and potential applications in biomimetic systems.

## Contribution

The study introduces a passive mechanism for haptotaxis using multivalent lipid vesicles and DNA linkers to control adhesion.

## Key findings

- Vesicle motion directionality correlates with binding strength and vesicle size.
- The model system demonstrates passive haptotactic movement toward higher ligand densities.
- Findings suggest design rules for biomimetic systems with directed motion.

## Abstract

Multivalent adhesion
between cell-membrane receptors and surface-
or particle-anchored ligands underpins a range of active cellular
processes, such as cell crawling and pathogen invasion. In these circumstances,
motion is often caused by gradients in ligand density, which constitutes
a simple example of haptotaxis. To unravel the biophysics of a potential
passive mechanism for haptotaxis, we have designed an experimental
model system in which multivalent lipid vesicles adhere to a substrate
and migrate toward higher ligand densities. Adhesion occurs via vesicle-anchored
receptors and substrate-anchored ligands, both consisting of synthetic
DNA linkers that allow precise control over binding strength. Experimental
data, rationalized through numerical and theoretical models, reveal
that motion directionality is correlated to both binding strength
and vesicle size. Besides providing insights into a potential mechanism
for adhesive haptotaxis, our results highlight design rules applicable
to the future development of biomimetic systems capable of directed
motion.