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

Iron oxide nanoparticles are utilized as a novel iron supplement due to their low irritancy and high bioavailability. In this study, FeCl₂·4H₂O and FeCl₃·6H₂O (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 Fe²⁺ was only 2.0 μg/mL, which effectively increased the bioavailability of iron and reduced the irritation of Fe²⁺ to the gastrointestinal mucosa. Fe-WPF prepared at a 1:1 ratio of FeCl₂·4H₂O and FeCl₃·6H₂O exhibits better bioavailability than FeSO₄ in vitro without observable cytotoxicity. Therefore, the Fe-WPF composite can become a novel iron oxide delivery system with high loading capacity and bioavailability.