Hi, I am culturing monocyte derived macrophages from human blood. For my assay I need to stain MDMs with Cell tracker green. Recently I get toxicity- cells literary turn secondary necrotic while staining or just after staining when I add complete media (staining done in serum free media). This would indicate some osmolarity/ pH problem so I made all new reagents, new vial of CTG with other source of DMSO and I still get this toxicity. I should add that cells are perfectly happy before and were not treated with anything. Anybody encounter something similar or have an idea what can be a problem? I run out of ideas... thanks