Multilayered Sandwich Structure Sensor: Confinement‐Mediated H ₂ O ₂ Enrichment Strategy for Ultrasensitive and Long‐term Stable Prostate Cancer Biomarker Detection

Sarcosine (Sar), a critical potential biomarker for prostate cancer (PCa), is primarily detected via enzyme cascade reactions involving sarcosine oxidase (SOx) and peroxidase. Nevertheless, the intermediate product hydrogen peroxide (H₂O₂) tends to diffuse to the bulk solution phase without entering subsequent reaction, leading to suboptimal detection sensitivity and compromised analytical performance. To tackle this challenge, a multilayered sandwich nanozyme cascade sensor (designated as Cu-MOF/Rf@BDC) is proposed through a confinement-mediated H₂O₂ enrichment strategy. Its innovative architecture spatially restricts the H₂O₂ diffusion while maintaining optimal reaction proximity, thereby enhancing the utilization efficiency of H₂O₂ by local concentration effects. The confined microenvironment ultimately achieves the ultrasensitive Sar detection with a 3.31 nmol L^-1 detection limit (1-2 orders lower than previously reported methods). In clinical urine samples tested for Sar detection, the sensor exhibits strong consistency with commercial enzyme-linked immunosorbent assay (ELISA) kits, confirming the reliability of its analytical performance. Significantly, the sensor demonstrates a 3.6-fold shorter preparation time and 6.0-12.0-fold longer signal duration compared to ELISA kits. These dual advantages accelerate the detection process and improve efficiency for large-scale clinical screening of PCa biomarkers. Furthermore, the developed sensor exhibits exceptional selectivity and repeatability, underscoring its potential practicality in complex analytical matrices.