Preparation and characterization of metal-polyphenol networks encapsulated in sodium alginate microbead hydrogels for catechin and vitamin C delivery

A novel encapsulation system was designed, utilizing sodium alginate (SA) polysaccharide as the matrix and easily absorbed Fe 2+ as the metal-organic framework, to construct microbead scaffolds with both high catechins (CA) and vitamin C (Vc) loading and antioxidant properties. The structure of microbead hydrocolloids was investigated using SEM, XPS, FTIR, XRD and thermogravimetry, and the antioxidant activity , in vitro digestion and the release of CA and Vc were evaluated. These results revealed that the microbead hydrocolloids SA-CA-Fe and SA-CA-Vc-Fe exhibited denser and stronger cross-linking structures, and the formation of inter- and intramolecular hydrogen and coordination bonds improved thermal stability . Moreover, SA-CA-Fe (44.9 % DPPH and 47.8 % ABTS) and SA-CA-Vc-Fe (89.9 % DPPH and 89.3 % ABTS) displayed strong antioxidant activity . Importantly, they were non-toxic in Caco2 cells. The SA-CA-Fe and SA-CA-Vc-Fe achieved significantly higher CA (56.9 and 62.7 %, respectively) and Vc (42.2 %) encapsulation efficiency while maintaining higher CA and Vc release in small intestinal environment. These results suggested that SA polysaccharide-based encapsulation system using Fe 2+ framework as scaffold had greater potential for delivery and controlled release of CA and Vc than conventional hydrocolloids, which could provide new insights into the construction of high loading, safe, targeted polyphenol delivery system.