Chitosan and sodium alginate-coated liposomes as a novel delivery system for apple peel polyphenols: Preparation, characterization, stability, bioactivity, and in vitro digestion

Apple peel polyphenols (APPs) have high bioactivity, but are susceptible to pH and temperature changes and have low bioavailability. In this study, liposomes encapsulating APPs were prepared from reverse evaporation, and surface-modified with chitosan (CS) and sodium alginate (SA) to enhance the physicochemical stability, gastrointestinal stability, and bioactivity of APPs. Liposomes were characterized using DLS, FTIR, SEM, and TEM. After layer-by-layer modification, the particle size of the liposomes increased from 267.03 ± 1.04 to 421.86 ± 3.84 nm. The encapsulation rate increased from 86.52 ± 0.60 to 92.04 ± 0.13, and polydispersity index was 0.29 ± 0.01. Double-layered modified liposomes exhibit excellent encapsulation efficiency and form nanoscale spheres. SA-CS-APPL demonstrates significantly enhanced in vitro antioxidant, hypoglycemic, and antibacterial activities compared to CS-APPL and APPL. SA-CS-APPL exhibits superior physicochemical stability over CS-APPL and APPL under various storage conditions, pHs, and temperatures. In vitro digestion experiments indicate SA-CS-APPL exhibits higher stability and a slower release rate of APPs compared to CS-APPL and APPL. The bioavailability of SA-CS-APPL is 39.63 %, representing a 28.28 % increase compared to free APPs. Therefore, SA-CS double-layered modified nanoliposomes can serve as a potential nanocarrier for APPs, aiding in the development of more effective bioactive substance release systems.