4.3. MTT Assay

For a cell viability assay with MTT, cells were seeded at a density of 1 × 10⁴ cells/well and grown for 2 days in a 24-well plate at 37 °C and treated with vehicle or various concentrations of BZ or CFZ alone or in combination for 2 days in the culture medium (n = 4 for technical replicates, n = 3 for biological replicates). Cells were washed once with 1 mL PBS and incubated with 500 μL MTT stock solution (5 mg/mL in PBS) for 1 h at 37 °C in the dark. The medium was removed and 200 μL DMSO was added to dissolve the formazan in each well. The level of formazan salts was measured at 570 nm using a plate reader (VICTOR³, PerkinElmer, Turku, Finland).