Shalom, Nicole, I'm not sure that your surfactant is soluble in water, since it has a double long-chained hydrophobic tail. Also for the double chain, it must be diffult for its arrangement as a micell. Those lipids, like Phophatedidyl choline, more favourable form lamellar phases. I would guess your cloudy dispersion may contain some liposomes, instead of micelles. To get a clear dispersion of liposomes, you'll need to lower the concentration, increase the dispersive energy or simply filtrate your cloudy dispersion. Btw. I work at a CRO company, e g with customers and representatives in your country, too. /  Johan Carlfors at:  www.ontargetchemistry.com, Uppsala, Sweden.

Hello Nicole,

I think that your glycolipid is not soluble in PBS. Since your 'solution' is still opaque after 30 min of sonication it is quite possible that other aggregates than micelles are formed, e.g. liposomes but also lamellar sturctures are possible. To check the size of your aggregates you can perform dynamic light scattering experiments (DLS) - with this, you can decide whether you have micelles, liposomes or larger stuff. Filtration is - in my opinion - not an option because you did not no the exact concentration after filtration. In case you have liposomes, extrusion might be an option ...

Kind regards, Simon.

Hi!

I'd say that you could first check which gluc ceramide you bought, as they may have different properties (such as different solubility). You can also contact Avanti...

What caught my attention in your text was the sonication time. AFAIK 30min sonication is not a good idea. You may end up with hydrolized or oxidated lipids and this would mean getting a much smaller number of good molecules into the cell (changed concentration) or getting the oxidized/hydrolized parts inside and getting a different response (assuming they get in). I think that most protocols sonicate max 5 min, with intervals, as the samples heat up.

Hi Nicole,

Do you specifically need to have glucosylceramide as micelles, or do you just need a uniform suspension in aqueous media to add to the cells? Judging by the structure of this phospholipid at standard physical conditions it will be prone to form lammelar phases - imagine an onion-like structure where each layer is a lipid bilayer. This structure will appear white and opaque in the solution, and may tend to settle out - do you observe anything like this before sonication? Also, you don't mention in what volume of PBS you are re-suspending your solution - what is your final lipid concentration?

As Ana Rita rightly says, such prolonged sonication may oxidize the phospholipid, and you may be getting a mixture of micelles from lipid biproducts and different forms of the starting material. 

If you don't need micelles but just a method to deliver a uniform aqueous suspension of this phospholipid, then extrusion would be your best bet. It's straightforward and easy (Avanti's are good), and will produce single unilamellar vesicles (SUVs) of a size determined by the extruder pore size. SUV suspension in water should be of see-through clarity and uniform. In principle you should be able to achieve SUVs from sonication as well, but if you're having difficulty with it extrusion will be more reliable. 

Sonication in a bath sonicator would be unlikely to break down multi-lamellar liposomes to single shelled liposomes. The latter would give a clear/translucent suspension of the lipid.. Either use the extrusion method as mentioned above or use a probe sonicator, which will input more energy. Sonication will remove dissolved gases, but as a precaution to avoid oxidation it is a good idea to sonicate under an inert atmosphere and degas your PBS.