Physicochemical Properties of Seed Oil Blends and Their Potential for the Creation of Synthetic Oleosomes with Modulated Polarities

There is an increasing demand within the pharmaceutical and cosmetic industries for biofriendly lipid-based active ingredient delivery systems. Micelles, liposomes, and lipid nanoparticles are currently the most used systems despite their limitations. Oleosomes, also known as lipid droplets, are promising alternatives to the existing strategies. Oleosomes are typically found in plant cells and are characterized by a nonpolar triacylglycerol core surrounded by a phospholipid monolayer punctuated with the protein oleosin. Producing oleosomes synthetically allows the customization of their lipid content, size, protein content, and oil core characteristics, expanding their versatility. Herein we demonstrate a proof of concept for the use of synthetic oleosomes to sequester polar molecules by modulating their core polarity with blends of sunflower and castor oils. The physical properties (density, refractive index, and permittivity) of the oil blends are characterized and demonstrate ideal mixing of the oils, which is supported by molecular dynamics simulations. Spectroscopic examination of the oil blends using fluorescent probes shows that the polarity of oil blends increases as the fraction of castor oil increases. Finally, we show that the uptake of a polar fluorescent probe (NBD-glucose) into synthetic oleosomes is enhanced by increasing the polarity of the oil core, but large charged molecules are excluded from the core regardless of polarity. These experiments show that synthetic oleosomes with tunable oil cores can expand the range of molecules that can be loaded into a biofriendly package as desired for biotechnology applications.