In situ construction, characterization, and bioavailability of nano-iron oxide-whey protein isolate amyloid fibrils carriers

Iron oxide nanoparticles are utilized as a novel iron supplement due to their low irritancy and high bioavailability. In this study, FeCl 2 ·4H 2 O and FeCl 3 ·6H 2 O (3,1, 2,1, 1,1, 1,2, and 1:3) were dissolved in a whey protein isolate amyloid fibrils (WPF) solution, followed by reaction under alkaline conditions at 60 °C for 50 min to form an iron oxide-WPF complex (Fe-WPF) with high bioavailability. The WPF binds to iron oxide via van der Waals forces, and iron oxide predominantly existing in the ferrous state. And, in vitro digestion indicated that the fibril of the Fe-WPF remained intact and the release of free Fe 2+ was only 2.0 μg/mL, which effectively increased the bioavailability of iron and reduced the irritation of Fe 2+ to the gastrointestinal mucosa. Fe-WPF prepared at a 1:1 ratio of FeCl 2 ·4H 2 O and FeCl 3 ·6H 2 O exhibits better bioavailability than FeSO 4 in vitro without observable cytotoxicity. Therefore, the Fe-WPF composite can become a novel iron oxide delivery system with high loading capacity and bioavailability.