Demonstration of a Si 3 N 4 Microring Resonator-Based Aptasensor for Human Urokinase-type Plasminogen Activator (uPA) Detection in Point-of-Care Diagnostics *

This study introduces the first demonstration of an aptasensor utilizing photonic integrated silicon nitride (Si3N4) microring resonators (MRR) for the detection of human Urokinase-type Plasminogen Activator (uPA), a biomarker in cancer diagnostics. The sensor integrates the sensitivity of Si3N4-based photonic integrated circuits (PICs) with the selectivity of a uPA-targeted aptamer. The Si3N4PIC exhibits a bulk sensitivity of 109 nm/RIU and achieves a system limit of detection (LOD) of 1.7•10-5. Multichannel experiments validated successful biofunctionalization. uPA concentrations ranging from 216 ng/µl down to 27 ng/µl were tested, demonstrating the capability to detect different levels of the biomarker. In clinical settings, this sensor system could be suitable for point-of-care diagnostics, particularly for early cancer detection and monitoring. Its design supports single-use or reusable operation, depending on the application and receptor coating. Furthermore, the proposed sensor technology enables flexible adaptation to different analytes.