Fabricationof a Flexible Dual-Ion-Modified SERS Sensorand Its Application in Rapid, Trace Detection of Kidney Injury Biomarkers

Abstract To mitigate the interference from the complex composition of urine from patients with kidney injury and the challenging urinary environment, this study addresses the need for early screening of medium-sized molecular biomarkers in urine. To enable dynamic monitoring of multiple dialysis biomarkers, we propose developing a surface-enhanced Raman scattering (SERS) sensing system using bacterial cellulose modified with two types of ionic groups. By sequentially treating the bacterial cellulose membrane (BCM) with quaternary ammonium cations and tannic acid anions through layer-by-layer (LbL) self-assembly, we created a flexible SERS sensor featuring an asymmetric charge distribution and a porous hierarchical structure. This design effectively harnesses localized surface plasmon resonance effects, boosting signal detection and enhancing the selective recognition of medium-sized molecular biomarkers in complex urine samples. The enhancement factor for the QBCM@Ag NPs sensor is 1.51 × 102, while the TABCM@Ag NPs sensor achieves 9.15 × 102. The detection limits for kynurenic acid and spermidine in urine are as low as 1.056 μM and 1.456 μM, respectively. This research represents a significant advancement in the targeted adsorption and SERS-based detection of medium- and small-sized molecules within complex biological urine samples.