23 Octobre – Thesis defense - Nelson Hélaine

14 h Amphi - Institut d'Optique d'Aquitaine (Talence)

Optofluidic analyzer for cellular capsules.

This work consists in the design and use of a micro-device dedicated to the analysis of multicellular aggregates based on the measure of light attenuation. The celllular capsule technology, which was patented by the host team, can generate several thousand spheroids/organoids in a few seconds. Our objective is to characterize these submillimetric samples encapsulated in a transparent shell by measuring their radius and extinction coefficient without resorting to an inherently slow and low throughput imaging technique. To exploit the high throughput capabilities of the technique, we propose to develop a fluorescence-free optofluidic analyzer inspired from classical cytometers. We first simulated the interaction of a Gaussian laser beam with a sphere of known radius and extinction coefficient and developed the optical detection module. Experimental measurements were compared with simulations to validate our approach. Then, we designed a microfluidic device aimed at conveying the heavy cellular capsules through the beam using a 3D printing approach. Finally, our optical system was combined with the fluidic module and modified to determine the displacement speed of each conveyed capsule as it interacts with the laser beam. We provide a proof of concept that the high throughput of such an instrument allows the analysis of a very large number of samples (several thousands) in a short time (a few hours). The instrument was then used to determine the growth curves of two tumor lymphocyte cell lines ("liquid" tumors), as well as the modifications in the extinction coefficients when cancer cells are fixed and when adipose stem cells undergo differentiation into adipocytes that store lipid droplets. The sensitivity of our instrument is compatible with a further use in pre-clinical trials on tumour cell aggregates to estimate the efficacy of chemotherapy treatments for instance. Finally, an "open source" dimension was integrated into the design of the electronic and software parts of the project to promote copying and improvement, e.g through the addition of a sorting module.

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