A Wide Dynamic-Range Polarization-Controlled SPR Imaging Method for High-Throughput Biomolecular Detection

A surface plasmon resonance (SPR) enables label-free real-time biomolecular detection but is hindered by low throughput, limited sensitivity, and narrow dynamic range. Here, we report a polarization-controlled intensity-modulated SPR imaging (SPRi) system integrated with a 12-channel microfluidic chip to address these limitations. The working mechanism exploits the phase difference between s- and p-polarized light upon SPR excitation: p-polarized light induces SPR with an additional phase shift, whereas s-polarized light does not participate, converting incident linearly polarized light into elliptically polarized light. By incorporating a polarizer, a quarter-wave plate, and an analyzer, refractive index (RI) changes are transduced into multistage amplified signals: from phase difference to polarization state variation and finally to light intensity change, thereby significantly enhancing the sensitivity. The system achieves an RI sensitivity of 24,300 ± 426 au/RIU over the linear range of 1.337-1.370 RIU, a resolution of (9.96 ± 0.32)×10-7 RIU across a dynamic range of 1.331-1.410 RIU, and a baseline drift of 0.63 ± 0.02 RU/min (1 RU = 10-6 RIU). Real-time self-referencing effectively suppresses noise, yielding an RMS value of 0.0242. Biomolecular assays demonstrate a sensitivity of 0.06586 au/(μg/mL) for mouse immunoglobulin G (IgG) and a detection limit of 1.56 pg/mL for D-biotin. This platform offers a robust solution for high-throughput applications in biomedicine, environmental monitoring, and pharmaceutical development.