I synthesized DOTA-Gd contrast agent. After completion when I tried to make stock solution (1mg/ml) in DMSO, it’s insoluble in DMSO. I need to make stock solution so that I can further do my work such as partition coefficient, incubation assay, MTT assay and cell localization. But for all this I need to dissolve my compound in organic solvent which is compatible to all these assays. Can you please suggest an alternative solvent to use in my work-up?
Depends on the charge of contrast agent. If it is ionic, try DMF or DMA or benzonitrile (the advantage of latters is their higher boiling point). If it is neutral, try arena solvents like toluene. Good luck!
Can you try tween solution? (http://www.sigmaaldrich.com/catalog/product/sigma/p9416?lang=en®ion=US&gclid=CKDFqO68mcYCFVMsjgodNBQAAA)
Perhaps something weakly basic (you don't want a strong base fighting for the Gd ion!) would help to coordinate the four acetates - maybe in the ethanolamine line?
Dear all many thanks for your comments. could you please let me know whether these solvent effects the further testing of my compound in cells.
From OECD (http://www.oecd.org/chemicalsafety/testing/50108781.pdf): "Solvents/vehicles
13. The solvent/vehicle should be chosen to optimize the solubility of the test agent without adversely impacting the assay conduct, i.e., cell growth, integrity of the test material, reaction with culture vessels, metabolic activation system, etc. (Ref. to add). It is recommended that, wherever possible, the use of an aqueous solvent should be considered first. Well established solvents/vehicles are for example water, cell culture medium, dimethyl sulfoxide). Generally organic solvents should not exceed 1% (v/v) and aqueous solvents should not exceed 10% (v/v) in the final treatment medium.
If other than well established solvents are used, their use should be supported by data indicating their compatibility with the test substance and their lack of genetic toxicity. In the absence of that supporting data, it is important to include untreated controls (see Glossary) to demonstrate that no deleterious or mutagenic effects are induced by the chosen solvent. "
-- So, DMSO still may be the stock solvent of choice, despite its immunomodulatory effects (it quenches free radicals, hence is anti-inflammatory).
Hi,
You can use solvents whose solubility in water is similar to DMSO (DMF and acetonitrile), you could also use ethanol. The elected solvent should have similar behavior to DMSO in working conditions.
Best regards.
Hi again Sunil,
Are you sure you must have exclusively organic stock solvent? The polarity of water is unique; with a little basic buffer to ionize the carboxylates, you might be OK. Don't mistake speed of dissolution with equilibrium concentration; grinding the initial solid, warming and sonication may speed up the rate of dissolution for you. Also a complication: little bits of impurities (e.g., uncomplexed DOTA) present may dissolve and interfere with the dissolution of the complex.
Alternative solvent to DMSO cam be Dimethyl formamide or Trifluoroacetic acid.
The similar solvents to DMSO are Dimethylformamide (DMF), gamma-Butyrolactone (GBL), N-Methyl-2-pyrrolidone (NMP), Dimethylacetamide (DMAc). If your compound is still not soluble then, use anti solvents like Chloroform, Toluene, Chlorobenzene, IPA, Acetone, etc.,
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