Sommaire:

Interaction between micro- and nano- particles and lipid membranes controls processes such as endocytosis, drug delivery and microbial infections. Dramatic changes in particle motion and membrane properties can be observed when a particle approaches a membrane. A shape transition of the membrane may occur to accommodate the particle, and partial or complete particle wrapping by the membrane takes place as a function of the energy of adhesion, membrane tension and bending. Furthermore, the interaction between a hard particle and a soft membrane may lead to complex dynamics when the system is driven out of equilibrium. Here, I will present experiments showing complex dynamics such as the physics of particle wrapping by a membrane, the transport of vesicles by active particles, and the orbital motion of active colloids around vesicles. Recent optical tweezers experiments on particle penetration inside giant vesicles will be presented and discussed in the limit of a vanishing adhesion energy [1]. In a wide range of experimental conditions, we have observed that a self-propelled Janus colloid is able to perform orbital motion around a giant vesicle remaining in a non-wrapped state [2]. Still, the active particle is able to impart a force of the order of 0.01 pN on the vesicle, which is however too small to trigger membrane wrapping. By applying external forces in the 1-100 pN range, we were able to observe membrane wrapping of bare and Janus colloids by a giant vesicle, which leads to the transport of vesicle by an active colloid [3]. References: - [1] F. Fessler, V Sharma, P Muller, A Stocco. (2023) Entry of Microparticles into Giant Lipid Vesicles by Optical Tweezers, https://arxiv.org/abs/2301.02504 (accepted in PRE).
- [2] V Sharma, E Azar, AP Schroder, CM Marques, A Stocco. (2021) Active colloids orbiting giant vesicles, Soft Matter.
- [3] V Sharma, CM Marques, A Stocco. (2022) Driven Engulfment of Janus Particles by Giant Vesicles in and out of thermal equilibrium, Nanomaterials.

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