4.2.2. Vero Cell Cytotoxicity Assay

The Vero cell cytotoxicity assay was done as described previously [19]. Briefly, Vero cells (10⁵ cells/mL) were seeded into 96-well plates, then overlaid with toxin samples the following day. After 48 h of incubation, the plates were fixed in formalin, stained with crystal violet, washed with water, dried; then the absorbance read at 590 nm. The CD₅₀ for each sample was the inverse of the dilution that caused 50% cell killing relative to untreated cells.