Production and optimization of lipid-based “stealth nanocarriers” by supercritical technology

Conventional liposomes are highly biocompatible thanks to the membrane structure that resembles the cellular one; but they are visible to the immune system. The addition of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-mPEG2000) to the surface of liposomes (forming PEGylated or stealth liposomes) can prevent their uptake by the reticuloendothelial system (RES) and improve and prolong the action of the lipid-based carrier. In this work, liposomes were produced by a continuous process assisted by supercritical CO2 (SuperSomes) at 100 bar and 40 °C; then, PEGylation of liposomes by post-modification method was performed. The best formulation to produce stealth liposomes was obtained pre-heating the liposomal suspension to 45 °C, then, adding 1.5 % w/w of DSPE-mPEG2000 and stirring the system at 100 rpm for two hours. The resulting liposomes were stable, exhibiting a −24.1 ± 4.2 Zeta-potential, and were characterized by a mean diameter of 175 ± 27 nm. PEGylated liposomes were loaded with vancomycin, used as a model drug; the encapsulation efficiency was 89 % and, in the case of PEGylated liposomes, the drug release was prolonged up to 20 h, with an increase of 10 h with respect to the non-PEGylated ones.