2.6.2. Cell Viability Assay

The MTT assay was used to measure MCF-7 breast cancer cells’ viability after incubation with Ser NPs and Ser NPs + DOX at a final concentration of 20 mg/mL Ser NPs ± Dox. Briefly, MCF-7 cells were seeded at an initial density of 2 × 10⁵ cells/cm² in 96–well culture plates and treated with 20 mg/mL Ser NPs and Ser NPs + DOX for 6 and 24 h. At each time point, the culture media was discarded and replaced with a freshly prepared solution of MTT (1 mg/mL). The samples were further incubated for 4 h in standard cell culture conditions to allow the metabolically active cells to form formazan crystals, which were dissolved in DMSO. The absorbance of the resulting solutions was measured at 550 nm using a Flex Station III multimodal reader (Molecular Devices).