Optically Transparent Anionic Nanofibrillar Cellulose Is Cytocompatible with Human Adipose Tissue-Derived Stem Cells and Allows Simple Imaging in 3D oleh Jonathan J. Sheard, Mesude Bicer, Yiming Meng, Alessia Frigo, Rocío Martínez Aguilar, Thomas M. Vallance, Donata Iandolo, Darius Widera