Fabrication of electrochemical immunosensor based on GCN-β-CD/Au nanocomposite for the monitoring of vitamin D deficiency

• A label-free sensing probe is developed for 25(OH)D 3 determination. • A low limit of detection, and a wide linear range were obtained. • The developed sensor is clinically acceptable to identify serum 25(OH)D 3 . • First impedimetric determination of 25(OH)D 3 using GCN-β-CD@Au nanocomposite. Serum 25-hydroxyvitamin D (25(OH)D) has been clinically considered as a novel biomarker for vitamin D deficiency. The current standard technologies for the detection of 25(OH)D are performed in sophisticated laboratories exhibiting the practical limitations for onsite and affordable testing. Therefore, the development of a cost-effective device for Vitamin D is extremely necessary to provide an earlier diagnosis. Herein, for the first time, we propose a novel label-free impedimetric immunosensor for the detection and quantification of 25-hydroxyvitamin D 3 (25(OH)D 3 ) biomarker in serum samples based on the Au nanoparticles functionalized GCN–β-CD nanocomposite. To fabricate the sensing probe, Ab-25(OH)D 3 antibodies were covalently immobilized on GCN–β-CD@Au/GCE using carbodiimide chemistry. The surface morphology and structural properties of constructed immunosensor were confirmed by different analytical techniques. Electrochemical impedance spectroscopy technique (EIS) has been selected as the main detection method to measure the Antibody (Ab) and Antigen (Ag) interaction at the immunosensor surface because it is label-free, less destructive to the activities of the biomolecule, and highly sensitive. The as-prepared immunosensor exhibited an excellent concentration range from 0.1 ng/ml to 500 ng/ml with the lowest limit of detection of 0.01 ng/ml. Furthermore, the sensing probe was validated in serum samples and obtained results were compared with the standard CLIA technique. The results have revealed that the sensing probe could be used for clinical diagnosis of Vitamin D deficiency in the clinical laboratories.