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Postdoctoral Research

Biomimetism of cellular movement

Soft interfaces

Postdoctoral Research

My postdoctoral work focuses mainly on the study of the mechanical properties of cells and tissues using micromanipulation techniques. The motivation for our work is to understand what are the differences between healthy cells and cancerious ones, from physical point of view. On single cell level, we characterize the adhesion strength between the membrane of a cell and its underlying cytoskeleton. We use biomimetic cells to better understand the mechanisms by which the cortex is influencing the mechanical properties of the membrane.

On tissue level, we study tissue mechanics when it is subjected to external stress. We probe the role of intercellular cohesion on the viscosity, elasticity and the surface tension of spherical cellular aggregates.

Aspiration of tissues

As model tissues, we use cellular aggergates that form spheres when suspended in the culture medium. aggregate aspiration We investigate the response of these aggregates to applied aspiratation pressures ranging in between 0.5-5 kPa. The aspiration dynamics of these aggregates show a viscoelastic behavior. At short times they deform as a rubber whereas at long times they flow like a liquid. When the aspiration pressure is stopped, the tongue starts to retract and the aggregate finds its original spehrical form as shown in this movie.

Membrane tubes from artificial "cells"

Artificial "cells" are biomimetic systems where actin filaments are polymerized at the membrane inside a giant unilammelar vesicle. In these systems, the actin network is connected to the membrane through specific binders, the density of which can be controlled as needed.

In our group we are interested in measuring the binding energy between the lipid membrane and the actin network by pulling membrane nanotubes on these biomimetic systems and probe the tube dynamics as the density of the binders are varied. The results will be compared to those obtained for red blood cells and other eukaryotic cells. We use hydrodynamic tether extrusion technique to pull tubes. Briefly, the vesicle is attached to a microneedle by the mediation of adhering proteins. The needle is then placed into a microchannel where it is exposed to a controlled flow. The flow exerts a force (drag force) in the range of picoNewton on the vesicle and a membrane tether forms between the microneedle and the cell body located downstream. Following the dynamics of the tube, we can estimate the surface tension, the adhesion energy as well as the viscosity of the membrane.

hysdrodynamic extrusion