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AFM characterization of gel particles - Application to living cells

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This study is part of the ANR CellDance project which explores a new approach combining nanophotonics and microfluidics to measure the mechanical response of individual cells for diagnostic purposes. Indeed, the deformability of individual cells is an indicator of certain diseases such as malaria. In this master project, we propose a first study on the mechanical measurement of gel beads whose mechanical properties mimic those of red blood cells.

We will use agarose gels to model the red blood cell (RBC). First it is important to characerize their mechanical properties using AFM. Elasticity measurements and viscoelasticity are proposed [1] to find the Young modulus (E) and the dynamic shear moduli (G’ and G’’, Fig. 1) in terms of frequency. Various geometries and AFM probes will be used. Comparisons with RBCs will be made to find the best system to model RBCs. For instance, changing the constituents concentrations will be a possible choice. Once the choice is made, a theoretical rheology model will be used.
This study will continue through a collaboration with our partners in Lyon (INL) in order to trap objects on metasurfaces. A few experiments using gel beads and RBCs will be carried out in order to trap them close to the surface. The resonant cavity will allow the measurement of the reflectivity (Fig. 2) and the object deformation (gel or RBC), in order to find its rheology. Finally the two methods will be compared.

Figure 1. Gel rheology parameters

Figure 2. Trapping of a deformable object on a metasurface

Candidates : We are looking for a candidate with interest for experimentation and he/she will interact with both teams. Physicist/Mechanic profile. Strong motivation

Contact : Claude VERDIER (04 76 63 59 80)

Collaboration : INL Lyon (Taha Benyattou, Magalie Faivre)

Cadre : ANR « CellDance » project

Possible continuation towards PhD : possible and recommended

References :

[1] Y. Abidine, V.M. Laurent, R. Michel, A. Duperray, L.I. Palade, C. Verdier, Physical properties of polyacrylamide gels probed by AFM and rheology, Europhys. Letters, 109, 38003 (2015)