A Functionalized Chitosan with Unsaturated Aldehyde Conjugated Moiety for UV‐Shielding and Antioxidation

ABSTRACT To address the critical issues of poor biocompatibility and phototoxicity in traditional UV‐shielding materials, a functionalized chitosan derivative (CS‐MCD) featuring unsaturated aldehyde conjugated moieties was successfully prepared by covalently grafting trans‐4‐methoxycinnamaldehyde (MCD) onto chitosan (CS) via a Schiff base reaction. The conjugated structure of MCD enables CS‐MCD to exhibit strong UV absorption in the range of 280‐350 nm, thereby delivering efficient UV‐shielding performance. Meanwhile, CS not only improves the water dispersibility of the composite but also mitigates the potential toxicity of MCD while enhancing its biocompatibility. Furthermore, CS‐MCD displays prominent antioxidant activity and broad‐spectrum antibacterial activity against both Staphylococcus aureus and Escherichia coli . This simple, green preparation strategy endows CS‐MCD with great application potential in skin protection, implant surface modification, wound dressings, and packaging materials.