Fraunhofer Institute for Silicate Research ISC 1 article published in JoVE Bioengineering Recombinant Collagen I Peptide Microcarriers for Cell Expansion and Their Potential Use As Cell Delivery System in a Bioreactor Model Melva Suarez Muñoz1, Davide Confalonieri1, Heike Walles1,2, Elisabeth M. W. M. van Dongen3, Gudrun Dandekar1,2 1Department Tissue Engineering and Regenerative Medicine, University Hospital Wuerzburg, 2Translational Center Regenerative Therapies (TLC-RT), Fraunhofer Institute for Silicate Research ISC, 3Fujifilm Manufacturing Europe B.V. We propose a cell expansion protocol on macroporous microcarriers and their use as delivery system in a perfusion bioreactor to seed a decellularized tissue matrix. We also include different techniques to determine cell proliferation and viability of cells cultured on microcarriers. Furthermore, we demonstrate functionality of cells after bioreactor cultures.