This question is part of the following Ask The Expert session:
I suspect you are using adherent cells. Do you see debris in your cell suspension (from trypsinization) from which you freeze the cells. If you are pelleting cells from a large volume containing debris in it you may be pelleting the debris and effectively concentrating it. Do you do a viability stain before and after freezing. If you see debris but very high viability then that is probably the origin of the debris. Also I have noticed that growing fibroblasts tend to produce more debris or bits of membranes than other cell types. If these are reasons for the debris then don’’t worry about it. One way to remove some of the debris is to allow your cells to attach then wash them with a balanced salt solution or media to wash away some debris if it bothers you.