Cell labelling - How can I label 2 cell populations? (no transgenes) (Jan/31/2011 )

Hello all, I wanted to ask you for some ideas about how can I label 2 different cell populations (that are in close proximity). The idea is to maintain the cells in culture for at least 5 days. I have tried some lipophilic tracers, but the component diffuses among cells from both populations. I have also read about fluorescent microspheres, but have never used them. If someone could share with me some ideas/products I would appreciate it a lot, as I am running out of ideas and it would be nice not to have to use transgenes. Thanks!



PS. Sorry my English.

Finally I decided to use Qtrackes (if you wanna know)