Fabrication of Microalgae Oil Vesicles for Drug Delivery Applications

In this study, it is demonstrated that natural microalgae oils, which contain fatty acid components including docosahexaenoic acid (DHA), could be directly applied to fabricate vesicular structures in aqueous phase through a forced formation process. The microalgae oil vesicles had initial average diameters of 170- 230 nm with negative charges apparently caused by dissociation of the fatty acid components. The vesicles possessed excellent stability with lifetimes for at least 450 days. The formation of the vesicular structures with hydrophilic cores/regions was confirmed by the transmission electron microscopy (TEM) image and successful encapsulation of a hydrophilic material. For encapsulation of a hydrophobic material, lutein, the vesicle size was increased probably due to the insertion of lutein into the hydrophobic vesicular bilayer structures. The analysis of Fourier transform infrared (FTIR) spectroscopy suggested that the vesicular bilayer fluidity was decreased by encapsulating lutein. However, the lutein-encapsulating microalgae oil vesicles still possessed high stability and the vesicular structures could maintain intact even at an environmental temperature up to 60℃. Applicability of the microalgae oil vesicles as drug delivery carriers was also demonstrated by successful encapsulation of curcumin. However, when the loaded curcumin was increased to a certain amount, physical stability of the microalgae oil vesicles was significantly reduced. This is probably because the vesicular structures with only limited spaces for accommodating hydrophobic materials were strongly affected by encapsulating a large amount of curcumin. It is interesting to note that by adding egg L-α-phosphatidylcholine, the curcumin encapsulation-induced instability of the microalgae oil vesicles could be alleviated. The results indicated that vesicular structures could be fabricated from microalgae oils and the microalgae oil vesicles were capable of encapsulating hydrophilic or hydrophobic materials for drug delivery applications. The findings lay a background for further dosage form development of nutritional supplements encapsulated by natural microalgae oils.