Our best results have been from using sucrose (isotonic) as the solvent.
The DiI  is made up in EtOH or another solvent and then diluted 1:100 into
300mM sucrose.  The cells an be soaked in this without death. Remember to
rinse unbound DiI away with sucose solution before returning to normal
medium.
 
a couple of references:
Serbedzija, G.N., S. Burgan, S.E. Fraser, and M. Bronner-Fraser  (1991).
Vital dye labelling demonstrates a sacral neural crest contribution to the
enteric nervous system of chick and mouse embryos.  Development 111,
857-866.
 
Serbedzija, G.N., S.E. Fraser, and M. Bronner-Fraser  (1990).  Pathways of
trunk neural crest cell migration in the mouse embryo as revealed by vital
dye labelling.  Development 108, 605-12.
 
>   We are having problems maintaining cell viability following DiI
>labelling using the Molecular Probes proceedure.  Does any one
>have any suggestions, or a good, detailed reference.
 
 
 
Scott Fraser  ([log in to unmask])
Caltech, Beckman Institute (139-74)
Pasadena,  CA  91125
818 395-2790 telephone
818 449-5163 fax