As the title suggest, we want to image BBB permeability in the living mouse brain using two-photon microscopy. We were thinking of injecting fluorescently labelled dextrans into the tail vein and imaging the animal over a time course of ~3h. I'm now wondering if there is someone who could share his/her experience with me concerning the use of fluorescent dextrans in vivo? What concentrations can you recommend for mice? Should I expect bleaching? How long does it take until fluorescent dextrans are metabolised and would a second - or even regular injections every hour - be necessary? Thanks a lot for your thoughts on this!
As far as FITC (green) dextran is concerned it's pretty imagable and stable with two-photon with in vivo. I have not used it in mice. I have used it to visualise blood vessels in vivo in chicken CAM model. I don't know if it can answer your question.
I used 1 ul/g in mice routinely. There is no need to consider bleaching in my view. I never had problems. It depends on how big your dextran is. I used 2 MDa and I can image for 10 hours without a problem. However, when I used 10 kDa, the dextran would be broken up and dye molecules would leak out from vessels. You cannot image deep regions anymore. People say 70 kDa is better in mice. I haven't tested out for long term imaging.
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