RADA peptides were dissolved in water at a concentration of 1.0%, placed in culture inserts (0.4 μm) in 24-well plates, and incubated for at least 1 h at 37°C to allow gelation. DMEM-HG medium was then added at a volume double that of the hydrogel volume and the mixture was left overnight in an incubator (5% CO2 at 37°C). Human primary dermal fibroblasts were seeded on the hydrogels, at a density of 50,000 per insert and in DMEM-HG medium with 2% FBS, and incubated under standard conditions. The medium was changed every 2 days. After 3 days of incubation, cells were stained with carboxyfluorescein succinimidyl ester (CFSE) (10 μM) and propidium iodide (100 µM) for 3 min. and then analyzed by fluorescence microscopy to assess their viability.