Hello Xinyuan Ding

Yes, you are right. Too many dead cells can interfere with the normal growth of live cells. Without removal, dead cell will accumulate risking the viability of the remaining live cells.

These clumps of dead cells can induce further cell death through inflammation, nutrient competition, environmental changes, and exponential contamination. Dead cell debris releases proteins, nucleic acids, and metabolites which can affect other cells in culture. These waste components accumulate and interact with the available nutrients, depriving living cells of growth and survival factors. Over time, this contamination will affect the entire culture environment, changing the pH of the media and increasing the culture’s risk for outside contamination that thrives on dead cellular debris, such as bacteria and fungi.

So, you should avoid all these by separating the dead cells from the live ones. The quickest possible way would be to carry out centrifugation of the cell suspension at low speed, at 100g for 10 mins. Dead cells and cellular debris, being less dense and fractured, tend to remain in the supernatant, while the live cells form a pellet at the bottom of the centrifuge tube. Discard the supernatant and culture the live cells which is formed as a pellet.

Another way out would be to use a density gradient, typically created with reagents like Ficoll, to separate cells based on density. Ficoll of the appropriate density may be underlayered beneath suspension of cells in culture medium in 15- or 50-ml centrifuge tube as needed. The volume of Ficoll used is dependent upon the cell density and total volume of cell culture medium, but is usually 3-5 ml in a 15 ml tube or 10-15 ml in a 50 ml tube. Tubes may be spun at 1500 rev/min for 20 min at room temperature. Viable cells are collected at the medium-Ficoll interface and non-viable cells may be collected from the pellet. After washing, the cells may be resuspended in appropriate maintenance media. Cells may be counted using hemocytometer with trypan blue to determine viability.

You may want to refer to the article below for more information.

https://www.researchgate.net/publication/15761984_A_rapid_and_efficient_procedure_for_the_removal_of_nonviable_cells_from_suspension_culture_of_lymphoid_cell_lines

If you wish to be more accurate, then FACS is the method of choice. FACS uses fluorescent dyes to label dead cells, allowing them to be sorted and removed from the live cell population. However, this method can be more time-consuming and expensive.

Best,