Hemocytometer chamber

The trypan blue dye exclusion assay was performed to measure viability and proliferation of HeLa cells in the presence of As⁺³ (sodium meta arsenite, Sigma Aldrich, MO, USA). Dead cells are stained blue as a result of perforations in the cell membrane, whereas the intact membranes of viable cells prevent the dye from entering and the cells remain unstained. HeLa cells were seeded in six-well plates in the maintenance medium at a density of 1.5×10⁴ cells per well. The cells were grown overnight. The following day, cells from one well were trypsinized, stained with 0.2% trypan Blue Solution (Nalgene Packing, Life Technologies, Thermo Fisher Scientific, USA), and the number of viable cells and total cells were counted in a hemocytometer chamber (Hausser Scientific, PA, USA) as the Day 0 count. The other wells were washed and fresh maintenance medium was added, excluding the control well. All wells, except the control, were treated with different concentrations of sodium meta arsenite for 24 h. The next day, the cells were trypsinized and stained with 0.2% trypan blue, and the viable cells were counted in a hemocytometer.