(5A)Fluorescent images MEFs encapsulated in 5% 8-arm PEG-VS and PEG-Ac without NVP (A,B), respectively and 5% 8-arm PEG-VS, PEG-Ac, and PEG-Mal with .1% v/v NVP (C,D,E), respectively. Cells were stained with calcein AM and ethidium homodimer-1 for 30 minutes. Magnification 10×. (F)Quantification of cell viability in PEG-VS, PEG-Ac, and PEG-Mal hydrogels (n=3). “*” indicates statistical significance (p<0.05). “X” indicates the hydrogel did not form. (5B) Brightfield and fluorescent images of MEFS seeded on 5% 8-arm PEG-VS, PEG-Ac, and PEG-Mal hydrogels without RGD modification (A,B,E,F,I,J) and 5% 8-arm PEG-VS, PEG-Ac, and PEG-Mal hydrogels incubated in a 5mM RGD solution after polymerization (C,D,G,H,K,L). Magnification 20×, inset magnification 10×.