Near‐Infrared‐Responsive Black Calcium Carbonate With Oxygen Vacancies: Anchored Hydrogel Enhances Wound Healing via Photothermal Sterilization and Bio‐Activated Reaction

ABSTRACT The utility of calcium carbonate (CaCO 3 ) in photo‐activated scenarios has been severely restricted by the inherent lack of near‐infrared (NIR) absorption capability. Herein, we present a defect engineering strategy to modulate nanosized CaCO 3 and successfully synthesize boron‐doped black CaCO 3 nanocube ( b ‐CaCO 3‐x ) with oxygen vacancies (OVs) via a thermal reduction approach employing sodium borohydride as a reducing agent. The existence of OVs is confirmed by Spherical Aberration‐Corrected Transmission Electron Microscope (STEM). b ‐CaCO 3‐x exhibits remarkable NIR absorption characteristics. Acting as an anchoring core, b ‐CaCO 3‐x is used to construct a composite hydrogel via cross‐linking between on its surface Ca 2 + and carboxyl groups of sodium alginate (SA). By further incorporating glucose oxidase (GOx) and catalase (CAT), this multifunctional hydrogel is developed for accelerate diabetic wound healing via photothermal sterilization and bio‐activated reaction. Notably, the b ‐CaCO 3‐x component endows the hydrogel with NIR‐responsive photothermal sterilization to efficiently suppress wound infection. More importantly, the hydrogel can oxygenate endothelial cells to activate the extracellular signal‐regulated kinase (Erk1/2) and heme oxygenase 1 (HO‐1) signaling pathways for accelerating wound healing via in situ bio‐activated dual reaction: the overexpressed hydrogen peroxide (H 2 O 2 ) is catalyzed to generate oxygen (O 2 ), and the acidic microenvironment decomposes b ‐CaCO 3‐x to manufacture carbon dioxide (CO 2 ). Collectively, this work provides a viable approach to tailor the absorption characteristics of CaCO 3 , expanding its potential in photo‐activated biomedical applications.