Effect of gum Arabic coating on release behavior of curcumin-loaded kafirin and zein composite nanoparticles

Prolamins extracted from cereal crops have shown promise as delivery vessels for hydrophobic bioactives. Kafirin, the main prolamin in sorghum, is more hydrophobic than its better known relative, zein, which makes kafirin an interesting candidate for encapsulation applications. Our aim was to find effective ways to fabricate kafirin-based nanoparticles with excellent encapsulation and release properties in simulated gastrointestinal fluids. We introduced gum Arabic (GA), a food-grade polysaccharide to stabilize kafirin by collectively forming nanoparticles. We measured encapsulation and release properties of the resulting nanoparticles using curcumin as a model drug, and compared them to zein-based nanoparticles. Electrostatic, hydrogen bonding and hydrophobic interactions drove the formation of curcumin-loaded GA-kafirin and GA-zein nanoparticles. The presence of GA coating improved encapsulation efficiency and pH stability of curcumin-loaded nanoparticles over a wide pH range of 3-8, and markedly slowed down curcumin release in simulated gastrointestinal fluids, especially for kafirin nanoparticles compared to zein-based ones. Regarding the release mechanism, binding forces between kafirin and curcumin played a more significant role in the slow-release rate in gastric fluid compared to the digestibility resistance characteristics of zein. These results indicate that GA-coated kafirin nanoparticles can significantly improve the bioavailability of hydrophobic nutrient molecules, such as curcumin. Our results provide a foundation for their application in sustained-release delivery systems and nutritious drinks, thereby expanding the range of prolamin species for encapsulation applications.