Friday, March 25, 2011

How can one maximize the chemical and physical stability of liposomes?

There are many ways to increase the chemical and physical stability of liposomes.

1. One way is to avoid using unsaturated phospholipids. Unsaturated phospholipids are subject to peroxidation. However this might not always be doable and the use of unsaturated lipids might be necessary for some liposomes formulations. If unsaturated phospholipids are used then it is important to do the following:

* Maintain an oxygen free environment during the manufacturing process and storage
* Add tocopherols or other membrane active antioxidants
* Limit the light exposure during the manufacturing process and storage

2. Store the liposomes in 4 C.

3. NEVER freeze the liposomes.

4. Buffer and maintain the pH of liposomes at 6-6.5 during the manufacturing and storage to avoid both acid- and base- catalysed hydrolysis.

5. Most buffers enhance hydrolysis; ensure minimal concentration of buffer sufficient to maintain pH.

6. Add ethylenediaminetetraacetic acid (EDTA) to ensure the absence of multivalent cations. The presence of multivalent cations may cause aggregation and bilayer destabilization.

7. Control the temperature or select lipids so that lipid phase transitions do not occur during storage.

8. Monitor the aggregation state of the liposomes and adjust the aqueous phase or lipid composition accordingly.

9. Avoid using lipid compositions which spontaneously fuse (i.e. DSPC SUV) or increase fusion activity upon accumulation of hydrolysis products.

10. Incorporation of cholesterol into liposomes can reduce destabilizing effects of hydrolysis products.

To see the original Q&A on Quora click on this link: