2.4. Cell viability assay

MTT and SRB assay was used to analyze cellular viability³⁴. For MTT assay, a total of 5000 cells per well were cultured in a 96-well plate. At the indicated incubation time points after the addition of the tested drugs, the medium was replaced by 100 μL fresh medium containing 20 μL MTT solution (5 mg/mL) for each well. After additional 4 h incubation, the medium was discarded and 150 μL dimethylsulfoxide (DMSO) was added into each well to solubilize the converted formazan. Blank wells were set at the same time. The absorbance was read at 490 nm with a microplate reader (elx800, BioTek, USA). Survival (%) was calculated at each concentration, and the IC₅₀ values were calculated by SigmaPlot. For SRB assay, cells were seeded in 6-well plates for adherence. Then the medium was changed to LMPt or OXA containing medium suspension for 48 h incubation. Then cells were fixed with 10% (w/v) trichloroacetic acid and stained with SRB for 30 min, after which the excess SRB was removed by washing with 1% (v/v) acetic acid. SRB staining was recorded by digital images and then dissolved in 10 mmol/L tris base solution for absorbance determination at 570 nm using a microplate reader for survival calculation.