Colloquium: Hybrid active matter: when particles and living cells play together

Datum

14.05.2018

Zeit

16:30 - 17:30

Sprecher

Francoise Brochard

Zugehörigkeit

Curie Institute, Paris, France

Serie

MPI-PKS Kolloquium

Sprache

en

Hauptthema

Physik

Andere Themen

Physik

Beschreibung

We introduce the broad field of active matter, a novel class of non-equilibrium materials composed of many interacting units that individually consume energy and collectively generate motion or mechanical stresses. Unlike swarms of fish and flocks of birds, cells or ants can support static loads because cells are bound by transient links. This leads to the concept of “entangled active matter” , which emerged recently to provide a unified understanding of the behavior of swarms of adhesive particles ranging from vibrating staples, to ants, and to cellular aggregates [1]. Recently we have focused on cellular aggregate – nanoparticles hybrid systems. This system is of great interest as it has been previously shown that particles can modify the mechanical properties of cells in terms of adhesion area, proliferation and motility. We study both small particles (up to few microns), which are digested by cells by endocytosis and phagocytosis, and larger particles, which do not enter in the cells, leading to a completely different physics. Nanostickers (size 20 nm ) [2] We show that nanoparticles, within a limited size range, can be used as a glue “nanostickers”to enable the formation of self-assembled aggregates by promoting cell–cell interactions. We model the cell-cell adhesion induced by the nanostickers using a three states dynamical model where the NPs are free, adsorbed on the membrane or internalized by endocytosis. We find that carboxylated polystyrene NPs are more efficient than the silica NPs of the same size, which were reported to induce fast wound healing and to glue soft tissue by Leibler et al. Nanostickers by increasing the cohesion of tissues and tumors may have important applications for cellular therapy and cancer treatment. Microparticles ( size 1micron): gluttonous cells[3]. We study the spreading of cell aggregates deposited on adhesive substrates decorated with microparticles. A cell monolayer expands around the aggregate. The cells at the periphery uptake the microparticles by phagocytosis, clearing the substrate and forming an aureole of cells full of particles. We study the dynamics of spreading, the width of the aureole, and the level of cell internalization as a function of the size, nature and density of the beads. The radius and width of the aureole allow quantification of the MP volume fraction incorporated by the cell, leading to an easy, fast, and inexpensive cell – particle internalization measurement. Macroparticles ( size 2-20 microns) ”Activated Brownian motion” Performing the same experiment with particles which are too big to be eaten, we observed that they are put into motion by the cells.We also describe also the mechanical properties of hybrid particles-cells aggregates (surface tension, elastic modulus, viscosity) using pipette aspiration technique [4], the phase separation between dead and living matter and how they spread . [1] F Brochard-Wyart et al, Entangled Active Matter: from ants to living cells EPJE 2015 [2] B.Brunel et al Nanostickers for cells: a model study using cell–nanoparticle hybrid aggregates Soft Matter 12 (38), 7902-7907. 2015 [3] Grégory Beaune^1 et al *5,6How gluttonous cell aggregates clear substrates coated with microparticles, Scientific Reports 7, Article number: 15729 (Nov 2017).[4] David Gonzalez-Rodriguez et al. Soft Matter Models of developing Tissues and Tumors. Science 338, 910; 1226418 (2012)

Letztmalig verändert: 14.05.2018, 10:02:25