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 mm, V_max = 2.48 µm min^-1) enable sensitive and rapid biosensing, including detection of total antioxidant capacity in saliva, on-off-on sensing of Fe³⁺ (limit of detection: 2.3 µm) and ascorbic acid (limit of detection: 2.59 µm). 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.