3D LENSFREE MICROSCOPY FOR 3D CELL CULTURE

National audienceNew microscopes are needed to help realize the full potential of 3D organoid culture studies by gathering large quantitative and systematic data over extended period of time while preserving the integrity of the living sample. In order to reconstruct large volume while keeping the ability to catch every single cell, we propose new imaging platforms based on lensfree microscopy, a technic which is addressing these needs in the context of 2D cell culture, providing label-free and non-phototoxic acquisition of large datasets. We have built lensfree diffractive tomography setups performing multi-angle acquisitions of 3D organoid culture embedded in Matrigel ® and developed dedicated 3D holographic reconstruction algorithms based on the Fourier diffraction theorem. Nonetheless, holographic setups do not record the phase of the incident wavefront and the biological samples in Petri dish strongly limit the angular coverage. These limitations introduces numerous artefacts in the sample reconstruction. We developed several methods to overcome them, such as multi wavelength imaging or iterative phase retrieval. The most promising technic currently developed is based on a regularized inverse problem approach directly performed on the 3D volume to reconstruct. 3D reconstructions were realized on several complex samples such as 3D networks or spheroids embedded in capsules with large reconstructed volumes up to ~25 mm^3 while still being able to identify single cells. To our knowledge, this is the first time that such an inverse problem approach is implemented in the context of lensfree diffractive tomography enabling to reconstruct large volume of unstained biological samples