Preparation, characterization, and binding mechanism of pH-driven gliadin/soy protein isolate nanoparticles

Protein nanoparticles have attracted significant attention due to their low cost and high bioavailability; however, their poor stability limits their functional applications. To address this challenge, hydrophobic gliadin (G) and hydrophilic soy protein isolate (SPI) were co-assembled using the pH-driven method to evaluate the impact of different G/SPI ratios on their structural and functional properties. The results revealed that at G/SPI ratios between 1:1 and 1:8, the nanoparticles exhibited smaller particle sizes and higher zeta potentials. Spectroscopic analysis showed that protein interactions, primarily hydrogen bonding, hydrophobic interactions, and electrostatic interaction, led to a more compact spatial structure. Functional analysis identified a 1:3 ratio as optimal, offering excellent emulsifying properties (EAI: 28.95 m²/g; ESI: 90.53%) and superior foaming properties (FC: 837.46 %; FS: 87.62 %). Additionally, this ratio significantly enhanced solubility by 75.6 % and improved physical stability compared to gliadin nanoparticles (GNPs). Mechanistic analysis revealed that the assembly of G/SPI nanoparticles was primarily driven by hydrogen bonding, hydrophobic interactions, and electrostatic interactions, with hydrophobic interactions playing a dominant role. Notably, a key turning point in protein folding was identified as the pH shifted from 10 to 9. Molecular docking further pinpointed the binding site, elucidating the assembly process at the molecular level. These findings establish a solid foundation for the development of dual-protein nanoparticles with tailored properties, opening new possibilities for their application in bioactive compound delivery.