Polarization light-sheet microscopy and tomography (PLμTo) for flow-based imaging of 3D microcarrier mesenchymal stem cell culture

Light-sheet microscopy is an increasingly popular imaging tool for studying biological processes, however, it generally requires the use of exogenous fluorescent contrast agents which can be toxic to live cells. Light-sheet tomography is the label-free analog of light-sheet microscopy, utilizing elastic scattering contrast to visualize the structure of the biological sample. Here, we present a multi-modal polarization light-sheet microscopy and tomography (PL{micro}To) system for on-line, non-destructive, and non-invasive volumetric imaging of human mesenchymal stem cells, also referred to as mesenchymal stromal cells, attached to spherical gelatin methacryloyl microcarriers for image analysis-based quantitative monitoring of adherent stem cell culture expansion. The PL{micro}To system, which is built on an inverted selective plane illumination configuration, is compatible with standard horizontal sample mounting and microfluidics for multimodal volumetric data acquisition. This work is the first demonstration of scattering-based volume optical imaging flow cytometry.