Fabrication of surfactant-stabilized zein nanoparticles: A pH modulated antisolvent precipitation method

Zein nanoparticles were fabricated by a pH-modulated antisolvent precipitation method using a food-grade non-ionic surfactant (Tween 80) as a stabilizer. The nanoparticles formed had a core-shell structure consisting of a zein core with a diameter around 78nm and a surfactant shell with a thickness around 4nm. The electrical charge on the nanoparticles was mainly determined by zein, going from positive at low pH to negative at high pH with a point of zero charge near pH5. The nanoparticles were stable to aggregation from pH2 to 4.5 (high positive charge) and from pH6.5 to 8 (high negative charge), but they aggregated from pH5 to 6.5 due to weak electrostatic repulsion. The nanoparticles were susceptible to aggregation at high ionic strengths (≥50mM NaCl) at both pH4 and 7. They also exhibited some aggregation upon heating (90°C for 120min) at pH4, but were relatively stable at pH7. The core-shell nanoparticles formed in this study have potential as food-grade delivery systems for encapsulating, protecting, and releasing bioactive molecules in food and pharmaceutical formulations.