Control of liposomes diameter at micrometric and nanometric level using a supercritical assisted technique

Supercritical assisted Liposome formation process (SuperLip) allows one-shot, continuous and reproducible production of liposomes. In this work, the optimization of Gas to Liquid Ratio of the Expanded Liquid (GLR-EL); i.e., the ratio between carbon dioxide flow rate and ethanol flow rate, is presented. It allows to control liposomes diameter from micrometric to nanometric range and the amount of Solvent Residue (SR) in the final suspension. Working at a GLR-EL lower than about 1.8, resulted in the production of micrometric and sub-micrometric L-α-phosphatidylcholine (PC) liposomes, with mean diameters ranging from 1729 ± 733 nm to 878 ± 170 nm; whereas, working at larger GLRs-EL nanometric liposomes, with diameters down to about 139 ± 49 nm were produced. Liposomes produced at GLR-EL 6.0 were loaded with a hydrophilic compound: an antibiotic, vancomycin, or a lipophilic antioxidant, farnesol. Liposome diameters were again nanometric down to 126 ± 35 nm for farnesol loaded vesicles and encapsulation efficiencies (EE) were up to 76.7 ± 1.9%. The mean size of vancomycin loaded liposomes was 250 ± 93 nm and EE up to 74.0 ± 1.1% were obtained. SR down to 10 ppm were obtained on loaded vesicles, improving the possibility of their use for pharmaceutical applications.