Fiber-optic SPR sensor with layer-by-layer hydrogel-entrapped enzymes for specific glyceryl tributyrate detection.

Glyceryl tributyrate holds considerable promise for applications in intestinal health regulation and adjuvant therapy. However, conventional enzymatic assays are susceptible to lipase deactivation and environmental perturbations, often leading to signal drift and compromised analytical reliability. Accordingly, it is of considerable significance to develop a detection platform that integrates high sensitivity, robust stability, and strong resistance to interference. In this work, we propose an Ag-coated no-core fiber (NCF) surface plasmon resonance (SPR) sensor for glyceryl tributyrate quantitative detection, which is achieved by a layer-by-layer (LbL) assembled hydrogel biointerface SPR that encapsulates lipase. The hydrogel microenvironment is used to help preserve the integrity and activity of the enzymes, in addition to enhancing the robustness of the interface, which reduces the deviation of the measured results from non-target effects. In addition, the hydrogel overlayer also retards the oxidation of the Ag in air, thus prolonging the usable lifetime of the sensing region. By comparing resonance responses with different numbers of LbL layers, the three-layer configuration is found to be optimal. Over 0.5-10 mmol/L glyceryl tributyrate, the three-layer enzyme modified sensor has a sensitivity of 2.40 nm/mM, which is enough to meet the detection requirements of anticancer-related use scenarios. In addition, further stability and selectivity evaluations confirm the excellent operational stability and robust reusability of the sensor. The proposed approach provides a low-cost and simple pathway towards the reliable fiber-optic SPR enzymatic sensing for health monitoring and food safety screening applications.