Ultrasound-triggered chitosan interfacial crosslinking for core–shell nanoemulsions with enhanced salidroside bioaccessibility

Abstract

An ultrasound-driven strategy developed to construct chitosan–tripolyphosphate ionic crosslinked shells of lecithin-stabilized nanoemulsions, enhancing salidroside encapsulation. Ultrasound accelerated phosphate mass transfer toward chitosan-adsorbed layers, homogenizing crosslinking density, increasing the degree of crosslinking to 0.78 and yielding a compact interfacial gel network with the highest encapsulation efficiency of 69.21%. Nanoemulsion transformed from a viscous fluid into viscoelastic weak hydrocolloids with narrowed relaxation time distribution. Coupled hydrogen bonding and ionic interactions between phosphate and chitosan hydroxyl/amino groups formed, while 1H NMR revealed restricted oil molecular mobility and C2—H downfield shifting indicative of –NH3+/phosphate ion-pair formation. In vitro simulated digestion demonstrated high salidroside bioaccessibility (25%) and facilitated mixed micelle formation, while post-digestion micelles significantly attenuated hypoxia-induced oxidative damage in RAW264.7 macrophages, reducing ROS/NO levels, restoring ATP production, and downregulating HIF-1α signaling. These findings establish ultrasound-driven interfacial ionic crosslinking as an effective approach for engineering robust core–shell nanoemulsions to enhancing bioactivity of food ingredients.