Hello Chaima Fadhloun

The optimal cell density for HeLa (or any cell line) for any surface area would have to be determined by performing the cell titration assay, which will give you an idea about the ideal seeding density to be used for the experiments.

Generally, for cell-based assay, the cells must be 80% confluent before treatment. So, you will have to perform this pilot experiment by seeding a number of cell densities in the desired vessel (multi-well plate or petri dish), and select that cell density which gives you 80% confluency after 24 hours. This chosen seeding density could be termed as the optimal cell density for that particular surface area.

Best.

Thank you for this informative answer Malcolm Nobre . I will eventually proceed with the cell titration assay.

Best.