2.7. MTT assay

Cell proliferation was quantified on day 3 and 7 by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, 5 mg/mL). For intrascaffold-cultured cells, 100 µL of cell-gel composites were incubated in 1 mL of culture medium with 200 µL of MTT. Then, supernatants were discarded and the cell-gel composites were cool pulverized using a tissuelyser (Shanghai Jinxin Industrial Development Co. Ltd., Shanghai, China). For cells cultured on the gel surfaces, 1 mL of cultured media containing 200 µL of MTT were dropped into each well (6-well plate). After 4 h of incubation at 37°C, MTT formazan crystals were dissolved by 1 mL of Dimethyl sulfoxide (DMSO, Solarbio, Beijing, China). Then absorbance was evaluated with a microplate reader (Thermo, Shanghai, China) at 490 nm.