DEVELOPMENT OF A SEMI-DISTRIBUTED INTERFEROMETER BASED OPTICAL FIBER BIOSENSOR FOR URINE BIOMARKER DETECTION

Abstract

Scientists recognize the renal damage marker KIM-1 as a dependable indicator for detecting and tracking AKI alongside CKD. Medical intervention at the proper time and enhanced patient results demands early identification of these disorders. Standard diagnostic approaches through enzyme-linked immunosorbent assay (ELISA) and lateral flow assays face multiple disadvantages when used for sensitive and specific detection at low cost and real-time point-of-care systems. This innovative research develops an advanced fiber-optic biosensor incorporating a semi-distributed interferometer (SDI) to provide sensitive non-invasive KIM-1 detection capability in human urine samples. The biosensor detection system employs a specific single-mode optical fiber with KIM-1 ligands to perform precise interferometric detection. Surface modification of the optical fiber made it more specific with lower non-specific binding which resulted in precise detection. The biosensor achieved exceptional detection performance through systematic evaluation of artificial, abnormal artificial urine samples while detecting concentrations from 1 attomolar (aM) up to 100 nanomolar (nM). The detection system delivered exceptional precision by establishing an ultralow limit of detection (LOD) at 13.6 aM while outshining all current diagnostic methods. A series of extensive tests evaluated how well the sensor performed for response time stability and robustness under real urine sample conditions. The experimental results showed the KIM-1-functionalized SDI biosensor had superior performance over controls through its specific and strong binding properties toward KIM-1 across complex urinary solutions. Results from clinical tests proved that the biosensor exhibited excellent discrimination abilities because it revealed weak cross-reactivity with other urinary components. Multiple measurements showed that the sensor exhibits both stability and repeatability properties due to which it demonstrates potential use in long-term diagnostic applications. The presented research brings important progress to non-invasive biosensing technology with its sensitive yet inexpensive and expedited diagnostic technique that replaces traditional methods. The SDI-based fiber-optic biosensor demonstrates the capability to become integrated into portable diagnostic testing platforms which aid point-of-care disease assessments and continuous patient kidney disease monitoring. The next phase of research includes work to refine the size of sensors and develop methods for detecting several kidney biomarkers and advance the sensor's clinical usefulness in healthcare settings.