To dissolve the acidic fluorophore, you will have to adjust the pH with base to keep it deprotonated. I don't know how high a concentration you can make this way, but I agree with Peter Kapusta, that such a high concentration is not usually needed for a fluorophore.

I made up a 170mM Calcein solution as a graduate student in 1985.  The procedure is on p. 22-23 (see also Fig 4-5) of my dissertation from UC-Irvine, 1986.  “Fusion of vesicles with planar bilayers: Membrane fusion and content release”  http://search.proquest.com/docview/303399830?accountid=4488.  Email me if you cannot access the online version: [email protected].

Hi Leland,

Instead of “mary-go-round”, let me mention a clear-cut answer to your question, namely the paper of Dr. Glavas-Dodov and this colleagues “The effects of lyophilization on the stability of liposomes containing 5-FU”, published in International Journal of Pharmaceutics, Volume 291,  Pages 79–86 (2005). Thus multilamellar liposomes containing 5-fluorouracil (5-FU) were prepared by modified lipid film hydration method and were lyophilized with or without saccharose as cryoprotectant. The effect of lyophilization on the stability of liposomes was evaluated by comparing the vesicle size, encapsulation efficiency and the drug release rate before and after lyophilization/rehydration. The process of lyophilization, without cryoprotectant, resulted in particle size increase and significant content leakage. By the addition of saccharose, the lipid bilayers become more stable and less permeable to the encapsulated drug, saccharose imparted 5-FU retention of about 80% after lyophilization/rehydration. Freeze-drying did not affect the particle size of liposomes containing saccharose as cryoprotectant. The drug release profiles of rehydrated liposomes followed Higuchi's square root model. Also, the obtained release profiles were all biphasic: a rapid initial drug release phase (burst release of the portion of the drug that leaked out of liposomes during the lyophilization) was followed by a slower, approximately constant drug release phase (zero-order kinetics).

Anyway, Leland, be ready to use LESS than a 0.1M aqueous solution of 5-FU.

Best wishes,

Ilya

Not sure what the "trick" was, but the details are attached in Chapter 2 of my dissertation (see pages 22-23). Final concentration was determined based on osmolarity measurements. See also Figures 4&5 in Chapter 3. 

Hi Marta,

It's been awhile since I did this, but I believe I settled for an 80mM calcein solution.  If you dissolve calcein disodium salt and then adjust the pH, you can get a fully quenched solution at physiological pH and osmolarity.  I couldn't get CF to dissolve at this concentration, but hopefully calcein is a decent substitute for you!

In looking back on the way I loaded vesicles with Calcien 30 years ago, I note that even though I prepared vesicles in a solution that I report as "~170mM Calcein" I also report that the actual content of the vesicles was in the "10-100mM" range.  Earlier in this thread I gave the reference as my dissertation, but I also just check and found that some additional details are in the paper we published (but some details are only in the dissertation).  The reference is: Biophysical Journal 1988 Vol.54 pp. 1053-1063.  James Hall was the co-author.