I agree with Eva. She gave you a detailed answer. You can use also lower speeds (longer time), but not higher than 1500g.

Beware that DOPC:DPPC in a 1:1 ratio will phase separate in domains.

Density differences will help centrifuge the liposomes, but large sugar concentrations might change the membrane properties, I would try to stay below 0.1 M.

In our lab working with liposomes as drug carriers we found that also the size of vesicles pays the role. Liposomes of about 100 nm in diameter can be easily centrifuged even at 30000g without their disruption/aggregation/fusion. MLVs sediment freely even without centrifugation. But we were never working with such a mixture of lipids.

The real problem is the lipid's mixture DOPC and DPPC is the perfect mixture showing phase separation. Without trials there will be no simple answer. This imples also the effect of temperature on such liposomes during centrifugation.

It may happen that they will loose integrity and will start aggregation/fusion. Why not to try more "soft" technique as gel filtration(?) and for concentration of them some kind of lyophiilization (even RT evaporation of part of the solvent/solution under reduced pressure). It should not to much affect the properties of liposomes.

But evaporation at RT of part of the solvent/solution under reduced pressure should work without problem.

I think Mr. Arkadiusz Kozube answer are spot on. The separation method depends on the size of liposomes. For LUVs of size less than 100 nm is required speeds of 30 000g. It should be noted centrigugación temperature.

According to WAYNE E. MAGEE, et al. in an article published in THE JOURNALOF CELL BIOLOGY VOLUME 63, 1974 . pages 492-504. They recomend 60.000g x 30 min to pelletize liposomes

If you need to pellet all liposomes you have in preparation the 60 000g is better than 30 000g. But did authors say anything about the integrity of them? I do not have the access to this yournal.This is already quite old paper.

Liposomes of 150 nm do no really form a pellet in a 30 min, 14000 rpm centrifigue.

Without knowing the rotor geometry, RPM is useless. RCF is the preferred unit when reporting centrifugation forces. 

With that said, Ghosh lab at UC Riverside uses 60,000 g for 1-2 hours to pellet 100 nm liposomes.

My own lab has erythrocyte-derived vesicles, so I will try 60 kRCF for 1 hour. Then, I will use DLS on the supernatant to see if there are any unpelleted particles.

Hi,

Have a look at below text and attached paper describing our experience with centrifugation of liposomes:

Separation of free DNA from the

complexes was carried out by centrifugation at 30,000 g for

30 min at 4 ◦ C (90 XL, Ultracentrifuge, Beckman, USA).

If you want just to concentrate the solution perhaps the best option is to use a speed vac, you will evaporate the H2O without alter the liposomes.

Could you please answer my questions?

I want to do amperometric recording of liposome loaded with some neurotransmitterssuch as dopamine and serotonin. 

Please let me know :

Which kind of lipids are better to load and trap those neurotransmitters without leakage and also for releasing on the surface of electrodes with applying potential?

DOPC, DOPE and Cholesterol? 

DPPC and Cholesterol? 

Or if you have other suggestions. And also say molar ratio?

I have had a lot of studying about transition temperature(Tc) of phospholipids, because it semms so important for my answers. (( that Liposome membrain transit from gel phase to liquid phase and encapsulate drugs are released from vesicles))

Tc of DOPC, DOPE are about - 20. And DPPC is 41. 

I have studied some papers that said "to form a rigid membrain, should Tc>37". So DPPC should be better!? Also avanti Polar Lipids saya "the temperature of hydration buffer should be kept above the phase transition temperature"  If I used DPPC(Tc: 41)and Cholesterol, I am worried about leakage before applying potential. If I use DOPC, DOPE with low Tc, how can I use them?

Actually I don’t know to have amperometric spikes as apply potential , should I have gel phase or liquid phase? According to Tc. 

I have a lot of challengin with them.

Let me know which buffer is better. And pH?

Let me know the speed of centrifuge to have a  good pellet without leakage?

Please attention norotransmiters can oxide easily and it is another challenge. 

Afetr using vacuum lipids stick at the bottom of flask, how can I dissolve them with hydration buffer. Is it possible to use vortex or centrifuge? Attention I want to have 2 size big and small liposome , in one experiment big, in another one small. and I want to compare them. 

I think choosing the kind of lipids bace on their Tc is really important. 

Sorry for long and a lot questions!

Thanks a lot!

Dear Farzaneh Asadpour

The combination:

DPPC : DOPE : Chol

or

DPPC : DCP : Chol (for example in a 7:2:1 molar ratio) should give you sufficiently stable liposomes.

Regarding importance of Tc in liposome formulation, check out the attached papers.

The other parameter to consider seriously is liposome preparation method (also explained in the attached papers).