2.9. Determination of the Cell Viability by the MTT Method

The effect of the obtained drug delivery systems on cancer cell survival was determined by MTT test according to Mosmann [32] and Laville et al. [33]. This test is based on the ability of living cells to convert the water-soluble yellow substrate [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-teyrazolium bromide] into the purple formazan product. The amount of insoluble formazan is directly proportional to the number of live cells [34]. In brief, the cells were trypsinized according to standard trypsinization procedure using trypsin/EDTA solution, then counted and re-suspended in 96-well microplates (a density of 8 × 10³ cells/well), in the same temperature and humidity conditions. For each samples, the total volume media was 300 μL/well. After monolayer formation (24 h), the cells were treated for 24 and 48h with unloaded and drug-loaded NPs in different doses ranging from 100 to 500 μg/mL. Likewise, the cells were treated with Cis in a corresponding dose with the highest one used in the case of NPs (500 μg/mL). After treatment, the samples were processed by MTT assay, the absorbance being measured at 570 nm using the Biochrom EZ Read 400 microplate automatic reader. The cell viability percentage was calculated according to Equation (4)