Formation of mucus-permeable nanoparticles from soy protein isolate by partial enzymatic hydrolysis coupled with thermal and pH-shifting treatment

Modulating the size and surface charge of nanocarriers provides an efficacious strategy to enhance bioavailability of encapsulated cargos through increased mucus penetration. In this study, mucus-permHeable soy protein nanoparticles (SPNPs) were successfully fabricated via gastrointestinal proteolysis coupled with heating and pHshifting treatment. Results showed that treatment at 65.C and 75.C after proteolysis induced the assembly of a, a, ' and ss subunits, forming a relatively loose structure. This facilitated further assembly upon pH-shifting, forming smaller-sized and less electronegative nanoparticles, which showed enhanced mucus permeability. However, treatment at 85. C and 95. C promoted stronger hydrophobic interactions and induced disulfide bond crosslinking between B and ss subunits, forming compact macro-aggregates with high ss-sheet structure. These larger-sized aggregates were less influenced by pH-shifting treatment, demonstrating limited mucus diffusion. This study provides a potential alternative to fabricate mucus-permeable nanoparticles, and established a relationship between protein subunit assembly behavior and its mucus permeability.