OCT Of Brain Organoids in acoustic Levitation – OCTOBOL

Currently, the biophysics communities are facing two challenges: first, building relevant self-organized and structurally controlled 3D cell structures that can be cultured in a fully controllable microenvironment handled over days or weeks, second having access to the inner organizations and biological activity of the 3D cellular assemblies. Recently, in a close collaborative work between the PMMH and the NPS teams, we have started to actively explore a new approach, based Acoustic Radiation Force, for structuring and growing brain cells assemblies in 3D environment. Using this technique, we can grow layered cortico-striatal spheroids in acoustic levitation over days. Moreover, we can apply time-dependent acoustic pressure to stimulate the brain spheroids. To go further, informations on the spatial inner organizations of the cells as well as on their activity while in levitation are needed. Label free Optical Coherence Tomography (OCT) appears like the only technique allowing to reach theses goals. It consists in using the intrinsic optical properties of biological structures - instead of external probes like fluorophores - and monitoring how they dynamically change, in order to characterize samples. Using the various configurations (SD-OCT, FF-OCT), coupled to fluorescence microscopy, we should be able to have access to detailed informations on the cellular organization inside the spheroids at low time scale as well as cellular activity at short time-scale. Moreover, we plan to use nanoparticles as imaging contrast agents to access small deformations induced by acoustic pressure variations as well as monitoring of a tightly regulated cellular process such as axonal transport. A specific microscopy platform, mutualized between the three partners, will be developed during the project. This project should lead to ground-breaking experiments revealing the activity and organizations of cells inside 3D neuronal organoids cultured in acoustic levitation.