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29/11/2018 - Jonathan COTTET

by Laurent Krähenbühl - published on , updated on


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M. Jonathan Cottet defends his PhD on Nov. 29, 2018.
Ecole Centrale de Lyon, bâtiment W1, amphithéâtre 3

Tittle :
Development of microsystems for the controlled formation of cell aggregates by dielectrophoresis

Jury :

  • Albert Van den Berg (Twente, NL); Olivier Français (ESIEE, Paris-Est); Carlotta Guiducci (EPFL, CH); Anne-Marie Gué (LAAS-CNRS, Toulouse); Antonio Ramos Reyes (Seville, E).
  • Thesis supervision : Philippe Renaud (EPFL, CH); Marie Frénéa-Robin and François Buret (Ampère Lab, Lyon)

Abstract :
Cell aggregates are an intermediary model between single cells and tissues used in many applications such as tissue engineering and in vitro drug screening. The creation of cells aggregates of controlled size and properties requires the development of new bottom-up strategies. The work developed in this manuscript aims at presenting the development of microsystems for the electric force-driven controlled formation of cell aggregates under flow conditions. This approach is based on dielectrophoresis, a phenomenon that causes induced motion on dielectric particles placed in a non-uniform electric field. A computational tool, MyDEP, was first developed in order to predict the behavior of cells in a specific medium. It allows to study the dielectric response of particles and cells as a function of frequency. The software also includes a database gathering cell dielectric models available in the literature to help experienced users as well as neophytes to understand the dielectrophoretic behavior of particles and cells and to choose parameters such as electric conductivity of the medium and frequency before performing laboratory experiments. Different designs for cell trapping are proposed and simulated in 2D with FEM using Comsol Multiphysics. Their fabrication implied the development of a reproducible method for μm precision alignment of microchannels in a polymer called polydimethylsiloxane (PDMS) with coplanar titanium/platinum electrodes deposited on glass, using a conventional mask aligner. It is based on the use of a silicon mold in combination with a Poly(methyl methacrylate) (PMMA) sarcophagus for precise control of the parallelism between top and bottom surfaces of molded PDMS. The trapping design based on coplanar electrodes was successfully tested experimentally on human embryonic kidney cells (HEK) with an automated setup. It proves its capability to create aggregates of a controlled number of cells with DEP. The cell aggregates proved to be stable (no disruption) after only 5 minutes of cell-cell contact. An impedance-based sensor design was proposed for characterizing single cells and cells aggregates before and after the trapping chamber. This sensor was successfully tested experimentally to detect particle passage in combination with the dielectrophoretic trapping design.

Keywords :
Dielectrophoresis, Cell trapping, Cell aggregates, Microfluidics, Bottom-up assembly, PDMS Alignment, Dielectric modelling, Impedance spectroscopy

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