[Felix]

Hello everybody,
I'm currently trying to dissolve a carotenoid (Astaxanthin). I did it in ethanol, DMSO and Polyethylene glycol.
But the problem is that these 3 solvents interfere with the subsequent analyses I'm trying to do.
Does anybody have an idea what other solvent I could test?
It should be miscible in water and not have any toxic effects on cells and membranes.

Thanks in advance for any suggestion

Have a nice weekend

[Corribus]

It would be helpful to know what kind of intereference you are running into, but DMF (dimethylformamide) is a solvent that has very similar solubility properties to DMSO. 

Though, I don't know its toxicity profile to isolated cells.

[Felix]

The interference is : These solvents inhibit  mitochondrial activity. No respiration detected.

[Corribus]

I see, well I'm assuming you are using solvent-water mixtures, not pure solvent, correct? 

What about acetonitrile or acetone? 

I'm just kind of ticking off solvents miscible with water.  Have no idea about what is compatible with mitochondria.

[Felix]

Thanks a lot.
The problem with these solvents is that they also solubilize Lipids. This will most certainly be a problems for m membranes which are Lipid bilayers.

[Arkcon]

Large amounts (or heck, even moderate amounts) of solvents are likely toxic withing a living cell.  Even phospholipid vesicles are prone to causing cell damage. I have never heard of this before, but can you possibly dissolve the carotenoid in some sort of biological lipid?  I don't know if the cells are guaranteed to take it up, however.

[Corribus]

Unfortunately a carotenoid is not altogether different than a lipid.  My guess is that anything which can dissolve your carotenoid is also going to dissolve lipids involved in membrane structure, at least to some extent.

Encapsulation or micellization, as indicated by the last poster, may be something worth trying.  There is actually quite a bit of precedent for incorporation of nonpolar chromophores within phospholipid micelles or other self-assembled nano- and microstructures.

[Babcock_Hall]

I have occasionally worked with carotenoids myself, but your specific application is new to me.  Methanol is a possibility, although it is pretty polar.  However, it seems to me that if you must have an organic solvent present, you might want to learn the maximum solubility of astaxanthin in that solvent ahead of time and then make the solution as concentrated as possible, so as to minimize the volume of solvent that you add.  There is a lipid database (hosted somewhere in Japan) that has a great deal of information about carotenoids on-line.  I have not looked for solubility information there, however.

[Felix]

Maximum solubility in DMSO seems to be 1mM. But even small doses of DMSO has negative effects on the mitochondria. THe biological Lipid solution is what I will try to find out right now.
It doesn't have to be an organic solvent.
On the lipid database in Japan they don't talk about solubility procedures.
Thanks everyone for you help. This really is appreciated.