Cell viability assay

MTT assays were carried out following the recommended protocols from Sigma-Aldrich (Cat. No. 11465001001). First, the cells were seeded in a 96-well tissue culture plate with 100 µL medium to grow until the confluency reached 40-60% of the plate surface. Peptides and proteins were added and incubated for 84 h, followed by the addition of 10 µL of MTT I to each well before incubating further for approximately 4 h. Next, MTT II was added and incubated at 37 °C overnight to solubilize the purple crystals. Spectrophotometric absorbance measurements of the samples were carried out using a microplate reader (Biotek, citation 5) at a wavelength of 575 nm; the reference wavelength was 670 nm.