Cell encapsulation. Collagen furan hydrogels (r2) were prepared according to the same protocol mentioned above, except for using cell media instead of PBS. Cells were trypsinized and resuspended in a minimal amount of cell growth medium. For encapsulation experiments, cells (either hfcMSC or HUVEC) were mixed into the hydrogel by gentle pipetting to yield the final cell concentration in the hydrogel of 200,000 cells/200μL and 300,000 cells/200μL, respectively, and transferred into a syringe. Cell-laden hydrogels were cast into 48 well plates and cured for 1 h at 37 °C in cell culture incubator, followed by adding the appropriate cell growth medium. Media was changed every 2 days.