MTT Assay
Cell viability was measured using MTT assay according to manufacturer’s instruction. Briefly, the MTT solution was added to cells at the final concentration of 1 mg/mL and incubated at 37°C for 2 hours. Then, an equal volume of the extraction buffer (20% (w/v) of SDS was dissolved in 50% DMF – 50% H20 solution) was added to each well and incubated at 37°C for 20 hours. The absorbance at 595 nm wavelength was measured using a microplate reader (Bio-Rad). The results were expressed as percentage of viability versus vehicle (absorbance sample/absorbance vehicle x 100).