(16f) Sculpting Vesicles with Active Particles: Less Is More

Biological cells actively respond to external stimuli, extend protrusions to explore their environment, and experience non-equilibrium fluctuations. Artificial soft matter systems, which mimic various features of biological systems, can help us to understand an abundance of complex cellular phenomena. One of the prominent questions in synthetic biology is whether such soft artificial systems with high local forces, mimicking some aspects of biological cells, can be engineered. One key aspect is to understand how to generate and control shape changes from within. In this talk, we present a simplified biomimetic experimental model system in order to address the question how cells reconfigure their shape and how the membrane respond to a localized point forces from inside, such as those exerted by cytoskeleton. In our experimental model system, the cell membrane is mimicked by a giant unilamellar vesicles of lipid bilayers, and the local internal forces are generated by enclosing self-propelled particles [1]. We demonstrate that the propulsion forces of individual self-propelled particles, as small as ~ 0.1 pN, are sufficient to induce dramatic vesicle shapes and lead to active membrane fluctuations. Microscopic visualization is revealing, strikingly, the formation of tethered, dendric-like structures at low volume fractions and tensions, whereas more global deformations of the vesicle shape are observed for increasing particle loadings. Moreover, the analysis of the mechanical properties of the membrane via shape fluctuation spectra demonstrates a strong deviation from the Helfrich model elucidating the specific role of active non-equilibrium processes. Strikingly - less is more - the most dramatic shape changes are observed at low particle concentrations, as is evidenced by a state diagram. Our results pave a way to better understanding the interplay between active local forces and cell shapes.

References.

[1]. H.R. Vutukuri, G. Gompper, and J. Vermant, submitted.

Acknowledgments: H.R.V. is supported by a Marie Skłodowska-Curie Intra European Fellowship (G.A. No. 708349- SPCOLPS) within Horizon 2020.