Zinc oxide-gold nanocomposite as a proper platform for label-free DNA biosensor

In this study, a simple and cost-effective electrochemical DNA biosensor was developed for sensitive detection of mycobacterium tuberculosis (TB). Nanocomposite of zinc oxide (ZnO) and gold nanoparticles (AuNPs) was used as a platform for immobilizing thiolated TB DNA (probe DNA). ZnO was electrodeposited on a glassy carbon electrode by potentiostat electrolysis of Zn (NO₃)₂ solution at -1.0 V (vs. Ag/AgCl), then AuNPs were loaded as the second layer at -0.4 V from HAuCl₄ solution. Thiolated probe DNA was then covalently attached to AuNPs. Anodic peak current of Fe (CN)₆^3-/4- was followed in hybridization experiments and a linear calibration curve was obtained in concentration range of 2.5-250 pM and limit of detection (LOD) of 1.8 pM for target DNA. The label-free TB biosensor exhibited high selectivity, suitable stability, and reproducibility.