Production of PEG-coated liposomes using a continuous supercritical assisted process

Liposomes are spherical vesicles, characterized by spontaneous aggregation tendency. To overcome this problem, in this work, liposomes coating was attempted, using polyethylene glycol (PEG), at different polymer to lipid ratios (1, 5, 10 % w/w) and proposing two experimental protocols, based on a supercritical assisted process. Only one protocol was successful; in that case, size and SEM analysis confirmed that vesicles did not aggregate thanks to the repulsion created by PEG surface, as confirmed by zeta potential measurements (about -25 mV). Liposomes with mean size ranging between 134 ± 30 and 166 ± 45 nm, stable for at least 70 day, were produced. The efficiency of SuperLip to produce PEG-coated liposomes was also tested, entrapping artesunate, obtaining encapsulation efficiencies up to 92 %. Drug release tests for standard and PEG-coated liposomes were compared: PEGylated vesicles produced a controlled release at least three times longer, without a significant initial burst release.