Ferritin-alginate oligosaccharide shell core complex for co-encapsulation and synergistic stabilization of astaxanthin and zinc ions

Abstract

Ferritin is a natural cage-like protein with multiple interfaces that can be used for encapsulation delivery of bioactive substances. With the increasing demand for nutrients containing multiple bioactive substances, it is important to study the co-encapsulation of bioactive substances with different properties using ferritin as a carrier. In this study, two different bioactive substances, hydrophobic astaxanthin (AST) and mineral Zn²⁺ ions, were encapsulated in the ferritin cavity to fabricate the ferritin-AST-Zn²⁺ complex, and the alginate oligosaccharides (AOS) were further bound to the ferritin to form a ferritin-AST-Zn²⁺-AOS complex. Results showed that each ferritin could load (30.02 ± 1.22) AST and (64.62 ± 0.38) Zn²⁺ ions, and AST could form a complex with Zn²⁺ ions in the ferritin cage. The AST in ferritin-AST-Zn²⁺ complex showed higher thermal, light, and iron ion stabilities and the Zn²⁺ ions in ferritin-AST-Zn²⁺ complex had higher pH and thermal stabilities, showing a synergistic stabilization effect between AST and Zn²⁺ ions. This effect improved the antioxidant properties of ferritin-AST-Zn²⁺ complex. In addition, the binding of AOS on the ferritin facilitated the stability of AST and Zn²⁺ ions. Moreover, the in vitro simulated digestion exhibited that the ferritin-AST-Zn²⁺-AOS complex could sustain the release of AST and Zn²⁺ ions compared with ferritin-AST and ferritin-Zn²⁺ complex, respectively. Ferritin cage is applied as a shell core architecture to deliver bioactive substances with different properties, providing a feasible scheme for ferritin to synergistically stabilize bioactive substances.