The influence of liposomal formulation on the incorporation and retention of PNA oligomers.

Liposomal formulations composed of phospholipids with different unsaturation degrees, head groups and at different cholesterol content have been tested for the encapsulation of Peptide Nucleic Acid (PNA) oligomers. The best loading capability (177μg, ER%=87.2) was obtained for pure liposomes of phosphatidylglycerol (DOPG) with negatively charged head group. The insertion of a 10-20% of cholesterol in DOPG based liposomes provides a slight decrease (∼160μg) of the PNA loading. On the other hand, the cholesterol addition (20-30%) slows down the PNA's release (∼27%) in fetal bovine serum from the liposomal formulation. Based on the encapsulation and the release properties, PEGylated DOPG liposomes with a percentage of cholesterol of 10-20% are the optimal formulation for the loading of PNA-a210.