Hi Tsao,

These may be debris from cells dying due to overcrowding. Sometimes dead cells remain adhered before starting to float as suspended debris. Also, it might be a good idea to run a mycoplasma test for your cell culture to check possible contamination.

Hello Ta Tsao

Cancer cells don’t have contact inhibition, which means that when they’re 100% confluent, they’ll squeeze together, and crowding will cause cells to reduce to half of their original size. If these cells aren’t split at the required time, they’ll start detaching from the substratum, finally leading to cell death.

In cell culture, many cells round up during mitosis, forming very refractile (bright) spheres that may float freely if the culture is physically disturbed. However, dead cells often round up and become detach from the substratum and are usually not refractile.

So, this phenomenon is basically a result of cell overcrowding.

Best.