A green pH-shifted cottonseed protein-shellac complex for improved solubility and curcumin delivery

This study developed a pH-shifting assisted assembly strategy to construct soluble cottonseed protein isolate (CPI)-shellac complexes (CPS), achieving remarkable improvements in both protein functionality and nutraceutical delivery. First, a dramatic enhancement in solubility was accomplished: the CPS system reached a near-complete solubility of 94.5% at neutral pH, compared to only 6.8% for native CPI. Furthermore, the underlying solubilization mechanism was systematically deciphered through a multi-scale approach: physicochemical characterization confirmed effective shielding of hydrophobic regions by shellac; proteomics revealed a more homogeneous and stable protein state; and molecular dynamics simulations visually demonstrated that shellac molecules selectively patch key hydrophobic residues, thereby inhibiting aggregation. Notably, the CPS exhibited excellent performance as a curcumin delivery vehicle, achieving a high encapsulation efficiency (EE) of 75% and significantly improving the photothermal stability, cellular uptake, and anti-migration bioactivity of curcumin. This work provides a green, scalable, multi-scale strategy for developing high-performance nutraceutical carriers from plant proteins.