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Neuropeptide Y (NPY) is one of the most abundant neuropeptides in the human brain, and its levels in the blood change in neurodegenerative and neuroimmune disorders. This indicates that NPY may serve as a diagnostic and monitoring marker for associated disorders. In this paper, an electrochemical immunosensor was created to detect NPY biomarkers using a novel immobilization technique. The proposed biosensor system enables accurate, specific, cost-effective, and practical biomarker analysis. Indium tin oxide-coated polyethylene terephthalate (ITO-PET) sheets were treated with hexamethylene diisocyanate (HMDC) to covalently immobilize antibodies. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used to analyze each step of the biosensors. The proposed NPY biosensor has a broad linear detection range (0.01–100 pg mL−1), a low limit of detection (LOD) (0.02968 pg mL−1), and a low limit of quantification (LOQ) (0.0989 pg mL−1). Atomic force microscopy (AFM) was used to support in the optimization process, study the surface morphology, and visualize it. Studies of repeatability, reproducibility, storage, and Kramers–Kronig transformation were conducted during electrochemical characterization. After analytical experiments, the biosensor’s responses to human serum samples were evaluated. According to the obtained data, the error margin is small, and the created biosensor offers a great deal of promise for the clinical measurement of NPY.

Parathyroid hormone (PTH) is a polypeptide containing 84 amino acids secreted by cells of the parathyroid glands. Imbalances of parathyroid levels cause medical problems such as osteoporosis, mental disorders, pancreatitis, kidney stones, cancer, and other symptoms. In this study, we aimed to design an ultrasensitive electrochemical immunosensor for PTH detection. Indium tin oxide (ITO) was used as an electrode for electrochemical impedance spectroscopy (EIS) measurements. ITO sheets were modified by using 3-cyanopropyltrimethoxysilane (3-CPTMS) selfassembled monolayers (SAMs) for immobilizing the anti-PTH antibody via covalent interactions. Cyclic voltammetry (CV) and EIS methods were applied to characterize immobilization steps. Therefore, 1% was selected for an optimal concentration of silane, 10 ng/mL was selected as an optimal concentration of anti-PTH, and 30 and 45 min were selected as optimal incubation times for anti-PTH and PTH, respectively. PTH antigen was determined in the concentration range from 0.05 fg/mL to 150 fg/mL. To detect the analytical characterization of the 3-CPTMS modified immunosensor, linear range, repeatability, reproducibility, Kramers-Kronig transform, and regeneration studies were performed. Also, the shelf life of the developed biosensor was investigated. Finally, real human serum samples were analyzed with the PTH immunosensor. The results showed that the designed biosensor system has high potential for early detection for medical treatments.

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