Shriners Hospitals for Children-Boston 2 articles published in JoVE Bioengineering Bulk Droplet Vitrification for Primary Hepatocyte Preservation Reinier J. de Vries1,2,3, Peony D. Banik1,2, Sonal Nagpal1,2, Lindong Weng1,2, Sinan Ozer1,2, Thomas M. van Gulik3, Mehmet Toner1,2, Shannon N. Tessier1,2, Korkut Uygun1,2 1Center for Engineering in Medicine, Harvard Medical School, Massachusetts General Hospital, 2Shriners Hospitals for Children, Boston, 3Department of Surgery, University of Amsterdam This manuscript describes an ice-free cryopreservation method for large quantities of rat hepatocytes whereby primary cells are pre-incubated with cryoprotective agents at a low concentration and vitrified in large droplets. Bioengineering Layer-by-layer Collagen Deposition in Microfluidic Devices for Microtissue Stabilization William J. McCarty1,2, Ljupcho Prodanov1,2, Shyam Sundhar Bale1,2, Abhinav Bhushan1,2, Rohit Jindal1,2, Martin L. Yarmush1,2, O. Berk Usta1,2 1Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, 2Shriners Hospitals for Children-Boston The creation of functional microtissues within microfluidic devices requires the stabilization of cell phenotypes by adapting traditional cell culture techniques to the limited spatial dimensions in microdevices. Modification of collagen allows the layer-by-layer deposition of ultrathin collagen assemblies that can stabilize primary cells, such as hepatocytes, as microfluidic tissue models.