Novel formulations of nanocomposites derived from ZnO nanoparticles have provided potential biomedical applications as a new strategy for treatment of breast cancer. In this research, two types of ZnO nanomaterials were synthesized by sol-gel hydrothermal process and co-precipitation containing fast quenching and also surface modification methods. The cytotoxic effects on growth of the breast cancer cell lines MCF-7 were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cell viability of the breast cancer cell line MCF-7 was reduced with increasing ZnO nanofluid concentrations at 48 and 72 h of treatment. The IC value of MCF-7 cells after 72 h of treatment with the first product ZnO (a) and second one ZnO