Toxicity of some charged lipids used in liposome preparations.

The inhibition of 3H-thymidine incorporation into DNA of L1210 cells in culture by liposomes was used as an index of liposome toxicity. Inhibition of 3H-thymidine incorporation appeared to be dose dependent for some lipid compositions tested. The commonly used neutral lipids, phosphatidylcholine and cholesterol did not appear to inhibit 3H-thymidine incorporation. Phosphatidic acid, an adjunct for preparing anionic liposomes, appeared to be non-toxic compared to phosphatidylserine and dicetylphosphate (alternative adjuncts for preparing anionic liposomes). Stearylamine, a synthetic lipid which continued to dominate the preparation of cationic liposome was the most toxic of the lipids tested.