Properties of DHA algal oil liposomes coated with different deacetylation degrees chitosan: preparation, physicochemical characterization and in vitro release

This study investigated the effects of chitosan coating with varying deacetylation degrees (DD) on the physicochemical properties, stability, in vitro release of DHA algal oil liposomes, through multiple characterization techniques. With chitosan coating, the encapsulation rate of liposomes increased significantly to 92.87%, exceeding that of unmodified liposomes (89%). Transmission electron microscopy revealed the more uniform dispersion and more regular morphology of chitosan-coated liposomes. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses confirmed the successful adsorption of chitosan onto the liposomal surface, with enhanced adsorption at higher deacetylation degrees. Antioxidant assays demonstrated that compared with unmodified liposomes, those coated with 90% DD chitosan exhibited 1.2 times greater scavenging activity against DPPH and ABTS radicals. Liposomes coated with 90% DD chitosan showed superior stability under acidic, ionic, and thermal stressors. After 28 days of storage at 4°C, the encapsulation efficiency remained at approximately 87%. In contrast, the liposomes coated with 50%, 70%, and 80% DD chitosan showed a significant increase in particle size and a decrease in encapsulation efficiency. Furthermore, the stability of the liposomes decreased under alkaline conditions due to chitosan deprotonation. In vitro release experiments showed that the chitosan coating could delay the release of DHA algal oil, as evidenced by the 60.87% release rate of the 90% DD group after 48 h, and all liposomes conformed to the first-order kinetic model. In vitro simulated gastrointestinal digestion experiments indicated that chitosan coating significantly improved the liposome bioaccessibility, e.g., the 90% DD achieved bioaccessibility 2.5 times that of uncoated liposomes. These findings indicate that coating DHA algal oil liposomes with 90% deacetylated chitosan significantly enhances their stability, providing a theoretical basis and technical support for the efficient delivery and stabilization of functional bioactive components.