Microencapsulation and characterization of liposomal vesicles using a supercritical fluid process coupled with vacuum-driven cargo loading

•An ecofriendly process for liposomal microencapsulation has been developed.•Supercritical carbon dioxide was used as the sole lipid-dissolving solvent.•Aqueous cargo loading was driven by vacuum without additional energy input.•No solvent residue due to rapid CO2 evaporation in ambient pressure.•Unilamellar and multivesicular vesicles were generated as the resultant liposomes.

A new technique of liposomal microencapsulation, consisting of supercritical fluid extraction followed by rapid expansion of the supercritical solution and vacuum-driven cargo loading, was successfully developed. It is a continuous flow-through process without usage of any toxic organic solvent. For use as a coating material, the solubility of soy phospholipids in supercritical carbon dioxide was first determined using a dynamic equilibrium system and the data was correlated with the Chrastil model with good agreement. Liposomes were made with D-(+)-glucose as a cargo and their properties were characterized as functions of expansion pressure, temperature, and cargo loading rates. The highest encapsulation efficiency attained was 31.7% at the middle expansion pressure of 12.41 MPa, highest expansion temperature of 90 °C, and lowest cargo loading rate of 0.25 mL/s. The large unilamellar vesicles and multivesicular vesicles were observed to be a majority of the liposomes produced using this eco-friendly process.

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