Haptotactic Motion of Multivalent Vesicles Along Ligand-Density Gradients

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.