2.7. Lactate Dehydrogenase (LDH) Assay

The LDH amount released in culture medium was assessed as a measure of cell membrane integrity using the In Vitro Toxicology Assay Kit, Lactic Dehydrogenase-Based (TOX7, Sigma-Aldrich, St. Louis, MO, USA). According to the manufacturer’s instructions, volumes of 50 µL of culture supernatants removed from the same 96-well plates used for MTT test, were incubated with 100 µL mix composed from equal parts (1:1:1) of dye, substrate, and cofactor for 30 min in dark. The reaction was stopped by adding 15 µL of 1 N HCl, and the absorbance was read at 490 nm using a microplate reader.