An Antibody-Free, Silver-Silver Oxide-Carbon Nanotube Nanocomposite-Based Impedimetric Sensor for the Nanomolar Detection of 25-Hydroxyvitamin D₃

Abstract

Vitamin D deficiency in the body is a worldwide health concern with major consequences on bone health. It is also related to cardiovascular diseases, depression, infectious diseases, autoimmune disorders, cancer, and recently even to COVID-19. In the present work, we have developed a silver-silver oxide nanoparticles-decorated carbon nanotube-modified glassy carbon electrode (AgCNT/GCE) based sensor for antibody-free, nanomolar detection of 25-hydroxyvitamin D (25OHD). The impedimetric technique was utilized to achieve high sensitivity. The sensor exhibited a linear response in the range of 20 to 100 nM. A remarkably low limit of detection of 7.9 nM was observed, which is lower than the deficiency level defined at 30 nM for human serum. The sensor exhibited excellent response stability, repeatability, reproducibility, and minimal interference. Excellent recovery of ~102 % was also observed in real serum samples. The sensing mechanism and the AgCNT-25OHD interaction have also been explored by electrochemical impedance spectroscopy, cyclic voltammetry, Fourier transform infrared spectroscopy, and UV-Vis spectroscopy.