Natural polysaccharide-modified oral pH-sensitive ZIF-8 delivery system for targeted release of lutein liposomes in the gastrointestinal tract.

Lutein, a bioactive compound with anti-inflammatory, antioxidant, and vision-enhancing properties, suffers from poor stability and low bioavailability. To address this, three anionic polysaccharide-coated ZIF-8@lutein liposomes were developed as pH-responsive delivery systems and compared with uncoated ZIF-8@lutein liposomes. The polysaccharides formed a "smart switch" via ligand bonds with zinc ions, enhancing stability and enabling targeted release under gastrointestinal conditions. Among them, ZIF-8@Lu-lip@soy hull polysaccharide exhibited the highest stability and an encapsulation efficiency of 86.16%. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analyses confirmed the successful assembly of the composites, revealing characteristic molecular structure, and amorphous nature. In vitro release studies demonstrated pH sensitivity: lutein release (<10%) was suppressed at acidic pH 2.0 and 4.0 due to polysaccharide protonation, while sustained release occurred at neutral/alkaline pH (6.8 and 7.4) attributed to the slow degradation of polysaccharide. These results indicate that polysaccharide-coated nanoparticles are promising controlled-release carriers for sensitive bioactive compounds.