In vitro 2D cell seeding on keratin‐PEG hydrogels. (a) Representative Live/Dead images of stained NIH/3T3 cells seeded on surfaces of keratin‐PEG hydrogels at days 1, 3, and 7 of culture (scale bar: 200 μm). Keratin‐PEG gels were produced from prepolymer solutions of a total 10% (w/v) concentration and 0.06 mM Eosin Y. (b) Representative images of phalloidin/DAPI stained NIH/3T3 cells seeded on hydrogels at days 1, 3, and 7 of culture (scale bar: 200 μm). (c) Quantification of cell viabilities at 1, 3, and 7 days of culture. (d) Measured relative degrees of metabolic activities of NIH/3T3 cells seeded on hydrogels using PrestoBlue assay at days 1, 3, and 7 of culture. (e) Quantification of areas of seeded NIH/3T3 cells obtained from F‐actin/cell nuclei stained images at days 1, 3, and 7 of culture. (f) Cell densities determined by counting the number of DAPI stained nuclei per given surface area of hydrogels at days 1, 3, and 7 of culture (*p < .05, **p < .01, and ***p < .001)