DiOC6 has shorter hydrocarbon "tails" than DiI. This feature makes it
more soluble but also more "promiscuous". It is very easy to label
living cells - just add a microliter of 10mg/ml DiOC6 in ethanol to a
milliliter of cell suspension (at 10super7 cells per ml). As quickly
as you can get a slide ready, the cells are labeled. However, the
DiOC6 doesn't stay in the membranes as DiI does. If we wash cells
out of excess DiOC6, and add unlabeled cells, all the cells become
labeled. We think that what we see represents an equilibrium of dye
moving in and out of various lipophilic compartments in the cell. The
nice thing about this equilibration is that the labeling is quite
stable. When a dye molecule is bleached, another from the external
pool can exchange with it.
Let us know how the staining goes.