Biosynthesis, Characterization, and Augmented Anticancer Activity of ZrO₂ Doped ZnO/rGO Nanocomposite

Fabrication of ZnO nanoparticles (NPs) via green process has received enormous attention for its application in biomedicine. Here, a simple and cost-effective green route is reported for the synthesis of ZrO₂-doped ZnO/reduced graphene oxide nanocomposites (ZnO/ZrO₂/rGO NCs) exploiting ginger rhizome extract. Our aim was to improve the anticancer performance of ZnO/ZrO₂/rGO NCs without toxicity to normal cells. The preparation of pure ZnO NPs, ZnO/ZrO₂ NCs, and ZnO/ZrO₂/rGO NCs was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), photoluminescence (PL), and dynamic light scattering (DLS). XRD spectra of ZnO/ZrO₂/rGO NCs exhibited two distinct sets of diffraction peaks, ZnO wurtzite structure, and ZrO₂ phases (monoclinic + tetragonal). The SEM and TEM data show that ZrO₂-doped ZnO particles were uniformly distributed on rGO sheets with the excellent quality of lattice fringes without alterations. PL spectra intensity and particle size of ZnO decreased after ZrO₂-doping and rGO addition. DLS data demonstrated that green prepared samples show excellent colloidal stability in aqueous suspension. Biological results showed that ZnO/ZrO₂/rGO NCs display around 3.5-fold higher anticancer efficacy in human lung cancer (A549) and breast cancer (MCF7) cells than ZnO NPs. A mechanistic approach suggested that the anticancer response of ZnO/ZrO₂/rGO NCs was mediated via oxidative stress evident by the induction of the intracellular reactive oxygen species level and the reduction of the glutathione level. Moreover, green prepared nanostructures display good cytocompatibility in normal cell lines; human lung fibroblasts (IMR90) and breast epithelial (MCF10A) cells. However, the cytocompatibility of ZnO/ZrO₂/rGO NCs in normal cells was better than those of pure ZnO NPs and ZnO/ZrO₂ NCs. Augmented anticancer potential and improved cytocompatibility of ZnO/ZrO₂/rGO NCs was due to ginger extract mediated beneficial synergism between ZnO, ZrO₂, and rGO. This novel investigation emphasizes the significance of medicinal herb mediated ZnO-based NCs synthesis for biomedical research.