Hello V H Krishna Prasad

It is not contamination. In mammalian cell culture, dead cells generally appear darker and less refractile (shiny) under a microscope compared to healthy, live cells. They may also detach from the growth surface and round up. This change in appearance is due to alterations in the cell membrane. So, these shiny or cluster of cells are not dead but healthy cells.

Healthy cells are often described as "refractile" because they reflect light and appear bright under a microscope. Dead cells lose this bright appearance and become less reflective, appearing darker. The shiny appearance of cells in culture can be due to the stage of growth. It is often a sign of healthy cell activity.

Buccal cells have a high turnover rate, and these cells which you term as dead could be growing cells, a sign of cell proliferation.

Best,

Hi Mr. V H Krishna Prasad,

Some cancer cell lines tend to grow on top of each other, defying contact inhibition. I think the shiny aspect is due to dense cluster of cells that is refracting light. I would suggest - split the cells again, resuspending it several times during splitting, to break these clusters. Maybe use more trypsin? Good luck!

Thank you, Malcolm Nobre and Souradip Sinha for your insights. As suggested, I had split the cells and seeded them in a lower density, which seems to have reduced the clusters by a considerable amount. However, compared to other cancer cell line at my disposal, only these are growing over each other.