Injection marker - Looking for a long term dye (Nov/05/2009 )

I'm working on developing vectors for injection into the peripheral nervous system. The injection is somewhat error-prone, so we don't always know whether a negative result is due to the vector not working or the injection not getting into the nerve. Does anyone know of a dye that could be added to the injectate as a marker so we know that the injection went into the nerve when we dissect the tissue 10-14 days later? Ideally it would be visible to the naked eye, though a fluorescent label might work as well.

Thanks for any ideas.

maybe You can try Congo Red or it`s derivates

Ivaguely remember "biocytin"for labelling neurons, although I must say I have no idea whether it would be suitable for your purposes. You might want to check it though.