Undenatured type II collagen nanofibrils with sodium alginate coating: Structural characterization, physicochemical properties and capability to load curcumin

In this study, the structural design and physicochemical property enhancement of undenatured type II collagen (UC-II) nanofibrils with sodium alginate (SA) coating induced by calcium ions (Ca2+) were investigated. The research aimed to elucidate the impact of Ca2+ concentration on the morphology, thermal stability, and digestive resistance, as well as to assess the potential of UC-II/SA nanofibrils as a delivery system for curcumin (Cur). A series of Ca2+ concentrations (1-9 mM) were methodically applied to optimize the condition that maintains the triple -helical structure of UC-II, thereby enhancing its functional properties. It was found that the Ca2+ level up to 5 mM effectively preserved the structural integrity and improved thermal stability of UC-II, with the added benefit of ensuring the substantial delivery of active fragment to small intestine (70.7 %), which was 3.43 times greater than that of uncoated UC-II. Moreover, incorporating Cur into the UC-II/SA nanofibrils resulted in a 300 times increase in Cur solubility and showcased the superior dispersion stability, antioxidant activity, and sustained release profile during simulated digestion. These findings underscored the dual functionality of the UC-II/ SA system as both a stabilizing agent for UC-II nanofibrils and an efficient carrier for Cur delivery.