My colleagues and I are trying to embed very small tumor spheroids and the major limitation has been actually seeing them to transfer them from culture to Histogel.

We have read several reports of using stains such as Erythrosine dye or Nuclear Fast Red prior to embedding to allow them to be seen easier, but I've seen mixed information about whether or not these dyes are, themselves, fluorescent. We are looking to do three-channel immunofluorescence following sectioning, so dyes which fluoresce would not be helpful.

Can anyone with experience in this area advise? We are not limited to the dyes listed above - we are just looking for a dye that will be visible to the eye, but "invisible" for downstream staining.

Thank you!

~ Kate