MDA-MB231 cells and problems - (Sep/07/2004 )

I have handled MDA-MB 231 (breast cancer) cell line for the past 8-9 months. It grows like weeds, plentiful. However for the last month or so, they simply refuse to become confluent. Moreover I see black debris like particles floating. I tested it for Mycoplasma contamination, bacterial contamination- All negative!! Have checked media, FCS etc. has anyone experienced a similar problem with MDA-MB 231 cells or another cell line?

Thanks a lot!

how about fungus. it only takes one spore...