High-sensitivity multilayer SPR biosensor based on ZnO/Graphene/Ag/MXene architecture for simultaneous detection of leptospirosis, malaria, and glucose imbalance

Infectious diseases and metabolic disorders remain major global health challenges, especially in areas with limited diagnostic infrastructure. Conventional diagnostic methods are often costly, complex, and restricted to detecting a single analyte. This study presents a multilayer surface plasmon resonance (SPR) biosensor composed of zinc oxide (ZnO), graphene, silver (Ag), and MXene layers for simultaneous, label-free detection of leptospirosis, malaria, and glucose imbalance. The combined material system improves plasmonic field confinement, increases surface electron density, and strengthens biomolecular interaction sensitivity. The sensor uses a Kretschmann configuration with p-polarized light excitation and is analyzed through the transfer matrix method. Systematic optimization of layer thickness and refractive index variation improves optical performance across several biomarkers. Numerical simulations show that the sensor achieves 1240°/RIU sensitivity with a 1.5° resonance shift for polyuria detection, 2° angular tuning for oliguria, a 2.5° resonance shift for glucose detection, and a 10° shift with 271.43°/RIU sensitivity for malaria biomarkers. Quality factors range from 19.76 to 24.03, and detection limits vary between 0.006 and 0.134 RIU across analytes. Regression-based machine learning analysis verifies the model’s predictive accuracy, with R² values above 0.995 for refractive index variation.