Designing a label-free electrochemical aptasensor based on polypyrrole-l-cysteine-reduced graphene oxide nanocomposite for detection of 25-hydroxyvitamin D₃

Reliable and precise quantification of 25-hydroxyvitamin D-3 in clinical samples is vital because vitamin D-3 deficiency lead to several disorders, such as mental illness, osteoporosis, and coronavirus disease. Herein, we report the fabrication of a novel electrochemical aptasensor using a nanocomposite, including reduced graphene oxide, pyrrole, and l-cysteine, for the sensitive detection of 25-hydroxyvitamin D-3. Subsequently, the aptamer of 25-hydroxyvitamin D-3 was immobilized on the surface of the modified electrode. Differential pulse voltammetry signals were utilized for studying the binding and measurement of 25-hydroxyvitamin D-3 based on the oxidation peak. Under the optimum conditions, the designed electrochemical aptasensor exhibited a linear detection range of 0.001-150 nM, with a limit of detection of 0.006 nM. Furthermore, the proposed aptasensor selectively detected 25-hydroxyvitamin D-3 compared to other analogs. Moreover, this aptasensor was successfully applied for the detection of 25-hydroxyvitamin D-3 in human serum samples, which were quantified by the enzyme-linked immunosorbent assay method. The acceptable recoveries of 82.67%-111.07% demonstrated that this proposed electrochemical aptasensor can be a promising alternative for clinical methods of vitamin D determination.