Effects of Surface Charge of Inhaled Liposomes on Drug Efficacy and Biocompatibility

Objectives: Liposomes are a promising drug carrier for inhaled delivery systems and their physical parameters could influence therapeutic efficacy significantly. This study was designed to answer the specific question of the proper surface charge of liposomes in pulmonary inhalation, as well as to study the synergistic anti-inflammation efficacy between drugs. Methods: In this work, a series of drug-loaded liposomes with different surface charges (from negative to positive) were prepared, and several in vitro and in vivo assays, including cytotoxicity, hemolysis assay, mucus penetration and lipopolysaccharide (LPS)-induced pneumonia model test, were adopted to evaluate the anti-inflammation efficacy and biocompatibility of the above liposomes. Results: Compared with cationic liposomes, anionic liposomes are capable of better mucus penetration and good biocompatibility (low cytotoxicity, better blood compatibility and mild tissue inflammation), but with poor cellular uptake by immune cells. In specific, even when the liposome surface charge was only +2.6 mV, its cytotoxicity and blood hemolysis reached around 20% and 15%, respectively. Furthermore, there was no significant difference in biocompatibility between anionic liposomes (-25.9 vs. -2.5 mV), but a slightly negative-charged liposome exhibited better cellular uptake. Conclusions: Thus, slightly negative-charged liposomes (-1~-3 mV) could be a well inhaled drug carrier considering both efficacy and biocompatibility. In an LPS-induced pneumonia mouse model, the drug-loaded liposomes achieved better anti-inflammatory efficacy compared with free drugs.