In order to take advantage of CF processing while avoiding the use of severe working conditions, we have developed a procedure based on the DELOS method for the production of unilamellar nanovesicles. This method, DELOS‑SUSP, involves the depressurization of a CO2-expanded liquid solution of lipids and/or surfactants into an aqueous phase using milder conditions of pressure and temperature. Lower temperatures allow the processing of heat-labile compounds, while milder pressures reduce the capital cost of a high-pressure plant when scaling up the process.
Incorporation of cholesterol in the lipid membrane of vesicles is sometimes required in order to reduce their permeability and avoid leakage of the encapsulated active molecule. Owing to the low aqueous solubility of cholesterol, the preparation of cholesterol-rich vesicles by conventional hydration procedures is problematic. Using DELOS‑SUSP is possible to prepare cholesterol-rich vesicles also composed by phospholipids, leading to nanoliposomes, or cationic surfactants, leading to Quatsuvs.
The potential of DELOS‑SUSP for the encapsulation of biologically active compounds has been shown in several drugs and biomolecules (peptides, proteins and nucleic acids). The simplicity of the method allows the one-step preparation of loaded or unloaded vesicles on a broad range of scales. DELOS-SUSP is very robust to produce these vesicles with narrow particle size distributions and high homogeneity concerning properties such as unilamerallity.