Simultaneous detection of inflammatory process indicators via operando dual lossy mode resonance-based biosensor

Detecting multiple analytes simultaneously, crucial in disease diagnosis and treatment prognosis, remains challenging. While planar sensing platforms demonstrate this capability, optical fiber sensors still lag behind. An operando dual lossy mode resonance (LMR) biosensor fabricated on a D-shaped single-mode fiber (SMF) is proposed for quantification of clinical indicators of inflammatory process, like in COVID-19 infection. Dual LMRs, created via two-step deposition process, yield a nanostructure with distinct SnO₂ thicknesses on the flat surface of the fiber. Theoretical and experimental analyses confirm its feasibility, showing a sensitivity around 4500 nm/RIU for both LMRs. A novel insight in spatially-separated biofunctionalization of the sensitive fiber regions is validated through fluorescence assays, showcasing selectivity for different immunoglobulins. Real-time and label-free detection of two inflammatory markers, C-reactive protein and D-dimer, empowers the platform capability with a minimum detectable concentration below 1 μg/mL for both biomolecules, which is of clinical interest. This proof-of-concept work provides an important leap in fiber-based biosensing for effective and reliable multi-analyte detection, presenting a novel, compact and multi-functional analytical tool.