{Silk@Hyaluronic-Acid} Hybrids: Efficient Antioxidants Against DPPH● With Resilience Against ●OH

Antiradical, antioxidant agents are of great importance in health, materials, and technology applications. Usually, DPPH^● are the radicals typically used as probes in the evaluation of antioxidant materials and technologies. Hydroxyl radicals (^●OH) are also omnipresent; however, assessment of their pervasive role on DPPH^●-antioxidants remains challenging. In this study, we introduce novel hybrid antioxidant materials with enhanced durability as DPPH^●-scavengers, demonstrating high resistance to ^●OH. The hybrid antioxidants were synthesized by immobilizing the two monomers of hyaluronic acid (D-Glucuronic Acid [GLA], and N-Acetyl-D-Glucosamine [GLAM]) onto the surface of degummed silk fibers. Hyaluronic acid, a prominent product widely utilized in cosmetics and medical applications, is renowned for its biochemical and therapeutic properties. Silk, commonly known as the “queen of textiles,” possesses remarkable structural and mechanical attributes. The hybrid materials' hydrogen atom transfer antioxidant activity was evaluated through their reactivity toward DPPH^● radicals. GLA@SFd@GLAM, exhibited the highest performance, effectively scavenging a total amount of 11 μmol of DPPH radicals per gram of material. All three hybrid materials demonstrated reusability, maintaining their efficacy in scavenging DPPH radicals over multiple cycles. The resilience of the hybrids, against hydroxyl radicals (^●OH), was evaluated in-situ using Electron Paramagnetic Resonance spectroscopy. The materials SFd@GLA, SFd@GLAM, and GLA@SFd@GLAM retained their DPPH-antioxidant activity after exposure to ^●OH radicals for up to two consecutive cycles of use. We discuss the physicochemical basis and mechanisms of the interactions of the {Silk@Hyaluronic-Acid} hybrids with DPPH^● and ^●OH radicals.