Is Hoechst toxic to cells? In general, it is known as non-toxic. I am working with dsRED MDA-MB-231 cell line. I applied it for my PDMS-based microfluidic platform, for this reason, I incubated for 1h and my stock solution is 10mg/mL before applying the dye I imaged the cells to be sure that they are alive. After staining when I imaged my cells are dead. What should I do?