A Green Photoregulated Quadruple‐Action Selenium Nanozyme Platform for Rapid and Ferroptosis‐Like‐Enhanced Photodynamic Bacterial Killing with Integrated Biosensing Capabilities

The rise of bacterial infections globally necessitates alternatives to traditional antibiotic therapy. Herein, a photoregulated quadruple‐action selenium nanozyme platform (LG‐CS@SeNPs), synthesized sustainably using food‐grade lauryl gallate‐modified chitosan (LG‐ g ‐CS) as a stabilizer is developed. The LG‐CS@SeNPs exhibit uniform spherical morphology (54 nm), and high colloidal stability (ζ‐potential: +32 mV). Under visible light (420 nm), LG‐CS@SeNPs completely eradicates both bacteria and biofilms within 5 min. This high efficiency is attributed to a unique four‐pronged antibacterial mechanism involving rapid bacterial capture and contact‐killing, synergistic ROS generation from photo‐activated oxidase‐mimicking enzymatic activity and photodynamic inactivation, and ferroptosis‐like bacterial death induction. Additionally, LG‐CS@SeNPs seamlessly switch from potent, light‐driven antibacterial activity to robust antioxidant and wound‐healing functionalities in darkness, enhancing clinical adaptability. Moreover, their intrinsic fluorescence and catalytic properties ( K m = 0.11 m m , V max = 2.48 µ m min −1 ) enable sensitive and rapid biosensing, including detection of total antioxidant capacity in saliva, on‐off‐on sensing of Fe 3 ⁺ (limit of detection: 2.3 µ m ) and ascorbic acid (limit of detection: 2.59 µ m ). This light‐empowered, ferroptosis‐like‐enhanced selenium nanozyme thus establishes a new paradigm for rapid, multimodal antibacterial action integrated with diagnostic capabilities for intelligent healthcare and personalized medicine.