Dear Sakthivel,

Usual methods involve rehydration of lipid films followed by a sonication or extrusion step.

Of course the approriate preparation methods depends on the nature of the lipid you are using.

More information for the case of phospholipid (DPPC and DOPC) may be find in these publications:

[1]. Michel, R.; Gradzielski, M. Experimental Aspects of Colloidal Interactions in Mixed Systems of Liposome and Inorganic Nanoparticle and Their Applications. Int. J. Mol. Sci. 2012, 13, 11610-11642. (open source)

[2]. Michel, R.; Plostica, T.; Danino, D.; Gradzielski, M. Control of Stability and Structure of Liposomes by Means of Nanoparticles. Soft Matter 2013, 9, 4167 - 4177.

I hope this helps,

with best regards,

I have recently prepared formulations of liposomes with encapsulated nanoparticles (NPs) of various sizes for similar applications. The process of encapsulating NPs is fairly simple - getting liposomes to reach the BBB & then release NPs for transport across is not so simple.

I found extrusion methods gave uniform sized, monodisperse liposomes with encapsulated NPs. TEM is the best option to confirm size & extent of NP loading whilst DLS & Zeta can give you insight into stability, size and dispersity.

You will need to consider how you will administer the formulation, how to "stealth" liposomes & how NPs will gain access through BBB (NP size is critical!)

Good Luck!!

Dear Sakthivel,

You will find a typical preparation of liposomes with all the details and many references in the following document:

Liposil, a Promising Phospholipid/Silica Composite Material

by Begu Sylvie, Aubert-Pouessel Anne, Lerner Dan A and Devoisselle Jean-Marie

In "Advances in Composite Materials for Medicine and Nanotechnology, Brahim Attaf (Ed.), ISBN: 978-953-307-235-7, InTech, 2011". Available freely from:

http://www.intechopen.com/articles/show/title/liposil-a-promising-phospholipid-silica-composite-material

I hope this will also help.

Dan

Read some papers of Moreira JN (U. Coimbra) or Cruz E (University of Lisbon)

I agree with Raphael. Formation of liposome depends on the kind of lipids you are using, typically the Mn of hydrophobic tails. For filming-rehydration method, you need first get one thin layer of lipid film by rotary evaporation of lipid solution in organic solvent, and then add appropriate amount of water, followed by sonication for a few minutes until suspension appears milky blue. In my experience, passing through BBB is not easy for nanoparticles, maybe you should make the size of particles as small as possible (e.g. 10-50nm) and also you can modify your liposome surface with specific transporters (e.g. transferrin) to increase the delivery ability across the BBB.

The lower size limit for liposomes is about 50 nm. Lposomes containing only

phospholipids are usually "rigid" while some mixed lipids liposomes are flexible and may cross barriers through holes of a diameter smaller than their own diameter.

Here are references to typical articles analysing these aspects.

Int J Pharm. 2003 Jun 4;258(1-2):141-51.

Particle size of liposomes influences dermal delivery of substances into skin.

Verma DD, Verma S, Blume G, Fahr A.

Ultradeformable lipid vesicles can penetrate the skin and other semi-permeable barriers unfragmented. Evidence from double label CLSM experiments and direct size measurements.

Cevc G, Schätzlein A, Richardsen H. Biochim Biophys Acta. 2002 Aug 19; 1564(1):21-30.

Dan Lerner

Thank you so much for all your suggestions and ideas.

Open the attached file for the protocol for preparation of the liposomes from book (liposomes, second edition a practical approach). It will be helpful for you.