*2.3. MTT Assay*

Before adding 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT), 3D cultures were transferred to clean cell culture wells. MTT 0.5 mg/mL was prepared in a cell medium and added to the 3D cultures. To measure the percentage of cells that did not attach to the scaffold, MTT was also added to the wells where cells were initially seeded (Figure S1). The MTT solution was incubated for 2 h at 37 ◦C, 5% CO2. After removing the MTT solution, DMSO was added and the absorbance of formazan was measured at 595 nm using a microplate spectrophotometer VICTOR3 V Multilabel plate-reader (PerkinElmer, Wellesley USA). The sum of the two respective absorbance values, the first deriving from the primary wells used during the seeding and the second deriving from the scaffolds, were considered as 100%.
