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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