Encapsulation of phytosterols and phytosterol esters in liposomes made with soy phospholipids by high pressure homogenization

The objective of this work is to design liposomal vesicles for the encapsulation of phytosterols and phytosterol esters (PEs), and to understand the encapsulation mechanism of phytosterols and PE in these vesicles. A commercial blend of free phytosterols and phytosterol esters were incorporated into liposomes by microfluidization using native mixtures of soy phospholipids. The average diameter of the liposomes increased with increasing amounts of encapsulated phytosterols, especially with increasing free sterol content. The phytosterol content, liposome size, and phytosterol encapsulation efficiency started to plateau when liposomes were prepared with more than 4% commercial PE blend at soy phospholipid content of 50 mg/ml, suggesting a saturation of phytosterol encapsulation. We propose an encapsulation mechanism of free sterols and PEs in liposomes, where free sterols were mainly encapsulated within the lumen of these liposomes as crystals, and PEs and some free sterols were incorporated within the phospholipid bilayer of the liposomal membrane. Results from this work could provide the pharmaceutical and nutraceutical industries a practical method to produce loaded liposomes using inexpensive phospholipid mixtures for the delivery of bioactive ingredients.