Cell Viability MTT Assay

MTT assay measures cell proliferation and cytotoxicity. ^{28 29} When MTT is taken up by a viable cell, it is enzymatically reduced to formazan crystals, which is directly proportional to the number of these cells. Briefly, the culture medium was discarded, and the dermal matrix, along with the attached fibroblasts, was transferred to a new well in the same 96-well plate. MTT (ThermoFisher Scientific, United States) solution in culture medium (0.5 mg/mL) was added in each well and then incubated for 3 hours at 37°C. At the end of the incubation period, the MTT solution was discarded and formazan granules were dissolved by incubation in solvent solution (dimethyl sulfoxide:isopropanol at 1:1). After 30 minutes’ incubation, the solution was transferred to a new well, and the optical density was assessed by microplate spectrophotometer (SpectroStar Nano, BMG Laboratory) at 570 nm.