Abstract
Kidney injury molecule 1 (KIM-1) is a promising biomarker for early diagnosis of various kidney diseases such as acute kidney injury and chronic kidney disease. This study introduces a fiber-optic biosensor based on a semi-distributed interferometer (SDI) designed for direct measurement of KIM-1 in human urine specimens. The biosensor demonstrated exceptional sensitivity and specificity to KIM1 protein, and the KIM-1-functionalized sensor significantly surpassed the control sensors with optimal responses in both artificial and abnormal urine samples. The response of the SDI biosensor to KIM-1 in clinical samples showed a linear range from 10 aM to 1 nM, covering concentrations between 1 aM and 100 nM. The lowest limit of detection is 13.6 aM with an exceptional accuracy. Clinical testing confirmed the biosensor's high selectivity, sensitivity, and stability, positioning it as a promising non-invasive diagnostic tool for early detection and monitoring of kidney diseases.