Copper-loaded ZIF-8-based immunosensor for early diagnosis of chronic kidney disease by detecting neutrophil gelatinase-associated lipocalin (NGAL) biomarker

Metal-organic frameworks (MOFs) is a promising contender among the nanomaterials for biosensors due to their special properties, including high surface area, tunable porosity, and adaptable functionalization competences. Zeolitic imidazolate frameworks (ZIFs), a subclass of MOFs, have drawn precise attention for their excellent chemical stability and ease of synthesis. This study, for the first time, concentrates on the preparation and characterization of a Cu-loaded ZIF-8-based immunosensor for the detection of neutrophil gelatinase-associated lipocalin (NGAL), a crucial biomarker for chronic kidney disease (CKD). Loading copper (Cu) into the ZIF-8 framework improves its electrochemical properties, conductivity, and surface area, leading it an ideal platform for antibody immobilization and NGAL detection. The immunosensor utilized Staphylococcal Protein A (SPA) IgG binding protein for antibody immobilization, providing an alternative to traditional crosslinking chemistry, enhancing biosensor functionality. Structural analysis, morphological assessment, elemental mapping, and stoichiometric analysis confirmed the successful synthesis of Cu-loaded ZIF-8 nanocomposite. Assessment of the electrochemical performance of the immunosensor demonstrated sufficiently low limit of detection (80 pg mL⁻¹) over a wide range of 0.1 ng mL⁻¹ to 1000 ng mL⁻¹ of NGAL along with superior selectivity, reproducibility, stability, and clinical feasibility. This advancement contributes to the rising knowledge on MOF-based biosensors and holds promise for future applications in disease diagnosis and healthcare monitoring.