Preparation of liposomes using the supercritical anti-solvent (SAS) process and comparison with a conventional method

Two methods to produce liposomes encapsulating a fluorescent marker were compared: the supercritical anti-solvent (SAS) method and a conventional one (Bangham). Liposome size and encapsulation efficiency were measured to assess the methods. Micronized lecithin produced by the SAS process was characterized in terms of particle size, morphology and residual solvent content in order to investigate the influence of experimental parameters (pressure, CO2/solvent molar ratio and solute concentration). It appears that when the lecithin concentration increases from 15 to 25 wt.%, at 9 MPa and 308 K, larger (20–60 μm) and less aggregated lecithin particles are formed. As concerns liposomes formed from SAS processed lecithin, size distribution curves are mainly bimodal, spreading in the range of 0.1–100 μm. Liposome encapsulation efficiencies are including between 10 and 20%. As concerns the Bangham method, more dispersed liposomes were formed; encapsulation efficiencies were about 20%, and problems of reproducibility have been raised.

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► Liposomes were produced from lecithin processed with the supercritical anti-solvent (SAS) method and a conventional method.
► Pressure and CO2/solvent molar ratio have little effect on micronized lecithin unlike solute concentration.
► Liposome size distribution is included in the narrow range of 0.1–10 μm (>80 cvol.%) and encapsulation efficiency is about 20%.
► Liposome stability in suspension form remains a challenging issue.