Sensitive impedimetric immunosensing of kidney injury molecule 1 using carboxyethylsilanetriol modified indium tin oxide polyethylene terephthalate electrodes

Kidney Injury Molecule-1 (KIM-1) is a transmembrane glycoprotein identified as a sensitive and specific biomarker for kidney injury. KIM-1 is significantly expressed in renal tissue following injury, making it a valuable marker for the early detection of kidney damage. In this study, an electrochemical immunosensor was designed for the determination of the KIM-1 biomarker. The ITO-PET (indium–tin oxide–coated polyethylene terephthalate) electrode was employed as the working electrode. Using disposable ITO-PET electrodes offers advantages such as cost-effectiveness, practicality, and enhanced convenience. The electrode surface was modified with carboxyethylsilanthriol to form a self-assembled monolayer. The silanized surface provided terminal carboxyl groups, which were activated through EDC/NHS chemistry to enable covalent immobilization of the anti-Kidney Injury Molecule-1 antibody. The stepwise surface functionalization and immunorecognition events were monitored by electrochemical impedance spectroscopy via changes in charge transfer resistance. The parameters of the biosensor were meticulously optimized and characterized. Reproducibility, repeatability, regeneration, storage stability, and selectivity studies were conducted to evaluate its performance. Additionally, Kramers–Kronig analysis and applicability assessments using commercially available urine samples were performed. EIS (electrochemical impedance spectroscopy) and CV (cyclic voltammetry) techniques were used throughout the experimental studies. Atomic force microscopy (AFM) was employed to examine morphological changes on the electrode surface. Owing to its high sensitivity, the biosensor response was evaluated over a working concentration range of 0.01–2.5 ng/mL, while the quantifiable analytical range was defined as concentrations ≥ 0.22 ng/mL based on the calculated limit of detection. Furthermore, it exhibits an LOQ (limit of quantification) of 0.74 ng/mL. Despite the promising analytical performance, further studies are required to assess long-term storage stability and to validate the biosensor using a larger set of clinical samples. Besides, further studies may be required to adapt the disposable ITO-PET electrode platform to routine clinical workflows, particularly in terms of standardization, large-scale fabrication, and operational robustness.