Composition influence on pulmonary delivery of rifampicin liposomes

The effects of lipid concentration and composition on the physicochemical properties, aerosol performance and in vitro toxicity activity of several rifampicin-loaded liposomes were investigated. To this purpose, six liposome formulations containing different amounts of soy phosphatidylcholine and hydrogenated soy phosphatidylcholine, with and without cholesterol and oleic acid, were prepared and fully characterized. Uni- or oligo-lamellar, small (~100 nm), negatively charged (~60 mV) vesicles were obtained. Lipid composition affected aerosol delivery features of liposomal rifampicin; in particular, the highest phospholipid concentration led to a better packing of the vesicular bilayers with a consequent higher nebulization stability. The retention of drug in nebulized vesicles (NER%) was higher for oleic acid containing vesicles (55% ± 1.4%) than for the other samples (~47%). A549 cells were used to evaluate intracellular drug uptake and in vitro toxicity activity of rifampicin-loaded liposomes in comparison with the free drug. Cell toxicity was more evident when oleic acid containing liposomes were used.