Although I am not an expert in in vivo imaging, the use of cyanine dyes (e.g. Cy5) might be an option. See here for a reference http://dx.doi.org/10.1016/j.copbio.2007.01.003

Hey Christian,

I am not imaging live animal, I wish to analyze harvested organs using fluorimeter.

I need a fluorophore to "survive" for a few days in the animals to give a detectible signal.

cy5 could work if it is stable and there is no high auto fluorescence the same wavelength

Thank you

Does anyone have any experience working with cy5 conjugates in vivo ?

You could use so called up-converting nanoparticles - i.e. luminophores, which absorb in NIR (basically 980nm) radiation and emit in Vis (e.g. narrow bands at 470nm (tulium), 540 (erbium), 650 nm(Erbium), 800 nm (thulium). They are perfectly photostable, basically non-toxic, provide background free detection (due to NIR excitation and long luminescence lifetimes, which are suitable for time rosolved techniques) etc. You can find many interesting research articles and reviews on this topic (e.g. a review of my own http://www.sciencedirect.com/science/article/pii/S1748013212001223). There are a few problems that are faced with this technology : bioconjugation and dedicated instrumentation, which is not commercially available yet. good luck

Dear Ehud,

your question sounds interesting and valuable to be answered. BUT you must write in your question THE KIND OF PARTICLES. Why?

When you inject the conjugated particles in mice veins you MUST HAVE an idea (previous references ...) about the TRANSPORT of them in ORGANS (liver, blood brain barrier, bladder, urine excretion e.g. urinanalysis...)

Without THESE IDEAS you are working ALONE in the DARK!!!

It is important because the surface of your particles MUST have a group reacting with your fluorescent reactive group ( p.e sulfochloride, isothiocyanate, cynurchloride a.s.o....) The steric hindrance on your particles can lead to undesirable effects and you must WASH your particle-conjugate prior to injection. Please note that your particles can be stored in LYZOSOMES in living tissues of organs and leads to accumulation .

The molecular weight of your fluorochrome plays an important role . The M.W. of CY5 is different from a pyrene dye with reactive group.

Concerning the autofluorescence of tissues :

xxxxxxx

The fluorescent molecule needs to be stable and not bleach in live tissue for few days, and needs to overcome the tissue auto-fluorescence

xxxxxxx

you must choose a FILTER for cutting it when you work with a fluorecence microscop or a fluorimeter. What a kind of fluorimeter are you using at this time. What a lot of filters have you ?

The bleaching of fluorescence occurs with light (p.e. UV) but not in the dark

At what a temperature do you want to store the harvested organs prior to work with your fluorimeter?

As you see you must GIVE MORE INFOS concerning your fluorimeter and your particles.

JRG