Nanoparticle metal oxides represent new classes of important materials that are increasingly being developed for use in research and health-related applications. Highly ionic metal oxides are interesting not only for their wide variety of physical and chemical properties but also for their antibacterial activity. Although the in vitro antibacterial activity and efficacy of regular zinc oxides have been investigated, little is known about the antibacterial activity of nanoparticles of ZnO. In this work, the antibacterial activity of ZnO nanofluids was tested against Staphylococcus aureus (ATCC:25923) at different concentration and broad range of pH. Antibacterial tests were performed by measuring the growth curve of S.aureus in the TSB broth medium in the presence of nanofluids containing 1.5, 0.75, 0.375, 0.187,and 0.09 2g/ml of ZnO nanoparticles (ZnO NP) and pH range of 7-10. Antibacterial activity increased with increasing nanoparticle concentration . Also, it seems that basic pH improves antibacterial activity of ZnO NP.

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