Investigation of Self-Assembled Flexible Zein Nanoparticles and Their Sensitivity to Complex Environments

Zein was made flexible through acid-driven deamidation. This increased flexibility was confirmed by the higher release of water-soluble peptides during trypsin hydrolysis. Self-assembled flexible zein nanoparticles (FZNPs) were prepared using the anti-solvent precipitation method. To test the sensitivity of FZNPs to complex environment, ionic solutions (CaCl₂ and NaCl) at various concentrations were prepared. The morphology and particle size of FZNPs differed significantly from those of control zein nanoparticles (NZNPs). As the ionic concentration increased from 0 to 15 mmol/L, FZNPs showed higher electrical conductivity and adsorption capacity than NZNPs. This suggests that FZNPs are highly sensitive to complex environment. X-Ray Photoelectron Spectrum (XPS) results revealed that both FZNPs and NZNPs bound more Na⁺ than Ca²⁺. The enhanced sensitivity of FZNPs to complex environments may be due to their greater tendency for structural changes. These conformational changes are likely caused by the altered amino acids in flexible zein, which result from deamidation. This study offers a practical approach to designing novel nanoparticles as functional materials for delivering bioactive compounds.