Phosphatidylcholine solubility in supercritical carbon dioxide: Experimental data, thermodynamic modeling, and application in bioactive-encapsulated liposome synthesis

Abstract

The solubility of phosphatidylcholine (PC) in supercritical-CO2 (SC-CO2) was measured experimentally using a dynamic system for the pressure and temperature range of 12.4–17.2 MPa and 313−353 K, respectively. The data were used to model the solubility using three cubic equations of state (EOS) combined with the conventional one parameter mixing rule: Soave–Redlich–Kwong (SRK); Peng–Robinson (PR); and van der Waals EOS, modified with Soave’s approach (MvdW). MvdW EOS demonstrated the best fit with experimental data. The optimal solubility condition was used to synthesize liposomes by using a venturi-based rapid expansion of supercritical solutions technique (Vent-RESS). Three model bioactives were simultaneously co-encapsulated into synthesized liposomes: one lipophilic bioactive, vitamin E; and two hydrophilic bioactives, vitamin-C and iron sulfate. Vitamin E, vitamin C, and iron sulfate demonstrated an average encapsulation efficiency of 95.1, 77.8, and 63.3 %, respectively.