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Hello Dear Listers,

We have run into a conundrum regarding live, semi-long term and fixable 
labelling of two population of mouse ES cells for aggregation/sorting 
out studies.
We would like to fix label cells (two cell strains), let them aggregate, 
fix the aggregates after 3-4 days and be able to make them out with either
am ancient Bio-Rad MRC 600 Krypton/Argon (488, 568 and 647 nm) or
a prehistorical Zeiss Photomicroscope (DAPI/Hoechst @ ~350 nm, FITC @ 
~390 nm and TRITC (~440 nm) ot Texas Red (~620 nm).

Invitrogen/Molecular Probes 
(http://www.invitrogen.com/site/us/en/home/References/Molecular-Probes-The-Handbook/Fluorescent-Tracers-of-Cell-Morphology-and-Fluid-Flow/Membrane-Permeant-Reactive-Tracers.html#head2) 
offer quite few cell tracking probes but figuring out what does what is 
difficult (for me, at least).
They say that CellTracker Green CMFDA (5-chloromethylfluorescein 
diacetate) labels cells that are both fluorescent and viable for at 
least 24 hours after loading.
We need three-four days, though.
Orange-fluorescent CellTracker Orange CMRA  - ditto.

CellTrace Oregon Green 488 Carboxylic Acid Diacetate Succinimidyl Ester 
is highly recommended but nothing is said of its fixability.
It is said that CellTrace Far Red DDAO-SE is a fixable, 
far-red–fluorescent tracer for long-term cell labelling but from the 
literature given I am not sure of its longevity.

Sigma 
(http://www.sigmaaldrich.com/img/assets/8200/PKH_LinkerKit_web_version.pdf) 
sells PKH26 and PKH67 that (Sigma says) are stable for up to 100 days in 
vivo (PKH26), but I do not see them heavily used in cell tracking other 
than FACS.

/Ergo/,
Any practical suggestion shall be greatly appreciated!

Greetings,

Michal

PS
Obviously (and to my chagrin) I have no financial association with 
neither company.
M.O.