Single/co-encapsulation capacity and physicochemical stability of zein and foxtail millet prolamin nanoparticles

In the last few decades, zein has been extensively studied owing to its wide commercial availability and the ability to self-assemble into nanosphere structure to encapsulate biologically active substances for targeted delivery. This work emphasized on comparing the encapsulation efficiency of hydrophobic active biomolecules and the physicochemical stability of composite nanoparticles (NPs) made up of zein- and foxtail millet prolamin (FP) -caseinate. Puerarin, resveratrol, diosmetin, and curcumin with various LogP values were selected as model drugs to study the single/co-encapsulation capacity, storage stability, and in vitro release profiles. Both LogP values (polarity) and specific structure are the main factors affecting the encapsulation efficiency. FP-based NPs could entrap more resveratrol, which may be related to the lower hydrophobic amino acid content of FP in comparison with that of zein. Co-encapsulation, in vitro release and long-term storage stability experiments confirmed that the model drugs were encapsulated in different NP regions mediated by polarity. Moreover, co-encapsulation changed the environment of curcumin from relatively polar microenvironment to hydrophobic regions. These hydrophobic regions retained significantly more curcumin during long-term storage stability. Overall, our results suggest that the hydrophobic amino acid composition of prolamin affects the encapsulation capacity. Various bioactives were encapsulated in the prolamin-based NPs via polarity mediation, and co-encapsulation could effectively retain the active molecules during storage.