A core-sheath fiber based on europium alginate/methacryloyl gelatin: Integrating fluorescence monitoring with enzyme-triggered drug release

The real-time monitoring of the wound microenvironment, coupled with on-demand and precise drug release, presents a key challenge in the development of next-generation smart dressings. Conventional dressings are often inadequate for addressing the complex pathological environment of chronic wounds. Herein, we designed and constructed a core-sheath fiber integrating environmental sensing, fluorescent signal feedback, and enzyme-responsive drug delivery. This was achieved through an integrated fabrication strategy combining wet spinning, dip-coating, and photocuring. The core, an interpenetrating polymer network (IPN) of europium-crosslinked sodium alginate and sodium polyacrylate (Eu@SA/PAAS), functions as the fluorescent sensing component. Leveraging the coordination chemistry of Eu 3 + , the core exhibits a dual fluorescence response to pH and Fe 3+ . The high concentration of Fe 3+ during hemostasis leads to fluorescence quenching, whereas the alkaline milieu of the inflammatory phase triggers stable red emission. This mechanism enables visual, real-time monitoring of the wound healing process. The therapeutic function is imparted by the sheath layer, composed of photo-cured methacryloyl gelatin (GelMA) loaded with ceftriaxone sodium (CEFNa). This layer undergoes specific enzymatic degradation by matrix metalloproteinase-9 (MMP-9), which is overexpressed in chronic wounds, thereby triggering the on-demand release of the antibiotic. Consequently, the released CEFNa demonstrated potent antibacterial activity against E. coli , S. aureus , and P. aeruginosa , with inhibition zone radii of 6 ± 0.3 mm, 8 ± 0.4 mm, and 9 ± 0.4 mm, respectively. This core-sheath architecture establishes an autonomous closed-loop system of “microenvironment sensing → fluorescent feedback → enzyme-triggered drug release,” offering a novel strategy for the intelligent and personalized management of chronic wounds.