Triple-optimization fiber-optic endotoxin-sensing strategy utilizing Limulus Amebocyte Lysate (LAL)

Rapid and reliable detection of lipopolysaccharide(LPS) is critical for the clinical management of sepsis. While the Limulus Amebocyte Lysate (LAL) assay remains the clinical gold standard for endotoxin detection, its heavy reliance on horseshoe crab blood has intensified ecological pressures as wild crab populations decline. Moreover, current alternatives still face challenges in sensitivity, speed, and reagent efficiency. Here, we present a fiber-optic biosensing platform integrating tapered and Er/Yb co-doped Fiber Bragg Gratings (FBGs) within a microfluidic capillary, establishing a "Triple Optimization" strategy to reconcile environmental and clinical demands. The system quantifies LPS by monitoring refractive index changes induced by the adsorption of unreacted LAL, achieving label-free detection with a sensitivity of <0.001 EU/mL, which is 10-fold superior to chromogenic methods. Closed-loop photothermal incubation accelerates reaction kinetics to 10 min, while microfluidic integration reduces LAL consumption by 95 % (<5 μL per test). A competitive binding-based regeneration protocol enables multiple reuses without performance decay. By synergistically addressing sensitivity, speed, and sustainability, this technology bridges critical gaps between biodiversity conservation and global healthcare needs, offering a scalable blueprint for ethical endotoxin monitoring.