Development of zein-soy protein isolate-rutin supramolecular nanoparticles via pH-ultrasound-shifting method: Structural characterization, stability, and gastrointestinal bioaccessibility.

Rutin, a natural flavonoid, has limited applications in functional foods due to its low aqueous solubility. To address this, this study fabricated zein-soy protein isolate-rutin supramolecular nanoparticles using the pH-ultrasound-shifting method (ZS-R-P-U), achieving a high encapsulation efficiency (89.06 ± 2.16%). Multispectral analysis confirmed that rutin-protein binding was driven primarily by hydrogen bonding, van der Waals forces, and hydrophobic interactions. Additionally, ZS-R-P-U exhibited a uniform, regular spherical structure, with significantly enhanced stability, apparent solubility, and antioxidant activity. In vitro simulated digestion studies revealed that the bioaccessibility of ZS-R-P-U was 20.77% (simulated gastric fluid phase) and 52.90% (simulated intestinal fluid phase) higher than free rutin, respectively. Release followed first-order kinetics, governed by Fickian diffusion. The formation of a protein corona during digestion further enhanced nanoparticle stability and sustained release. Compared to traditional delivery systems, ZS-R-P-U demonstrated significant advantages in improving rutin solubility, antioxidant activity, and bioaccessibility, showing great potential for application in functional foods.