Fabrication and growth mechanism of ZnO nanostructures and their cytotoxic effect on human brain tumor U87, cervical cancer HeLa, and normal HEK cells

Abstract

ZnO nanostructures of diverse shape were grown via a solution process with different precursors and conditions. Morphological investigation of the nanostructures was carried out using field emission scanning electron microscopy and transmission microscopy observations and revealed that the nanostructures exhibit a wurtzite phase with an ideal lattice fringe distance of approximately 0.52 nm. The powder crystallinity was examined via X-ray diffraction spectroscopy. Screening results from anticancer studies of the effects on human brain tumor U87, cervical cancer HeLa, and normal HEK cells of ZnO nanostructures of diverse shape were obtained and indicate promising activity that varies with changes in the structure and the size of the particles. Treatment-induced cell death [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and survival assay], growth inhibition, cytogenetic damage (formation of micronuclei), and apoptosis were studied as parameters for the cellular response. Treatment with nanostructures enhanced growth inhibition and cell death in a concentration-dependent manner in both U87 and HeLa cell lines. At higher concentrations (above 15.6 μg/ml) the cytotoxic effects of the nanoparticles were highly synergistic and mainly mediated through apoptosis, implying the possible interactions of lesions caused by the agents. The enhanced cell death due to nanoparticles was accompanied by a significant increase (2-3 fold at 31.25 μg/ml) in the formation of micronuclei in U87 cells. The increase in the formation of micronuclei observed after treatment indicates that these structures may interfere with the rejoining of DNA strand breaks. Among all the nanostructures, nanoparticles and sheets exhibited potent activity against both HeLa and U87 cells. However, despite potent in vitro activity, all nanostructures exhibited diminished cytotoxicity against normal human HEK cells at all effective concentrations.

Developing a Novel Embryo–Larval Zebrafish Xenograft Assay to Prioritize Human Glioblastoma Therapeutics

“…7 and 8), which is the opposite of what we hypothesized would occur based on the in vitro data. However, the exposure concentrations used in the zebrafish xenograft assay were lower than the effective inhibitory concentrations in in vitro studies, 23,39,40 and we also identified that the ZnO NP agglomerated and underwent considerable dissolution (*47%-50%) when prepared in water (data previously published 28 ). Therefore, we cannot distinguish whether this increase in glioblastoma proliferation is due to a low-exposure NP effect, an ionic effect, or a combination of both.…”

“…Our short, 3-day assay allowed us to identify that this ZnO NP is unstable and slightly enhances glioblastoma growth in vivo. These results, in addition to evidence that ZnO NPs seem to only be effective at extremely high concentrations (*62 and 814 mg/L for instance) in in vitro assays, 39,40 suggest that these ZnO NPs in their current state are not a good candidate for future preclinical assessment against glioblastoma in mammalian models. These results illustrate how this short assay successfully combines the rapid economy of in vitro assays with the relevance of slower in vivo rodent assays to aid advances in drug and nanotherapeutic development.…”

“…These ZnO NPs were selected for our assay because of *28-to 35-fold preferential toxicity to cancerous T cells relative to normal peripheral blood mononuclear cells in vitro 23 and existing literature demonstrates that other ZnO NPs selectively inhibit glioblastoma proliferation in culture. 39,40 However, these in vitro anticancer effects are often seen at high exposure concentrations (mg/L or mM levels), which may call into question the relevancy of the results. Yet, it was not known if this selective toxicity would be conserved in vivo.…”

“…The high ZnO NP exposure concentrations used in the in vitro studies 23,39,40 caused toxicity in the embryo-larval zebrafish assay. At lower, nontoxic exposure concentrations (0.156-1.25 mg/L), the ZnO NPs slightly enhanced glioblastoma proliferation and migration/invasion compared with the vehicle control (Figs.…”

Zinc Oxide Nanoparticles: Opportunities and Challenges in Veterinary Sciences

“…ZnO NPs were found to be toxic to all human or rodent cells when the concentration was above 15 ppm [145]. ZnO NPs have been studied extensively and they affect different cell types and animal systems [146][147][148][149][150][151]. They are toxic to animals after intra tracheal instillation [152] inhalation [153] and after oral administration [154,150].…”