Antibacterial activity of ultra-small copper oxide (II) nanoparticles synthesized by mechanochemical processing against S. aureus and E. coil

In this paper, ultra-small CuO nanoparticles (NPs) were synthesized through a mechanochemical method using two different Cu-containing precursors (i.e. CuSO4 center dot 5H(2)O and CuCl2 center dot 2H(2)O), and their structure and antibacterial activity were studied. From the microstructural studies, it was observed that CuO NPs have a spherical morphology and a narrow size distribution with 7 and 14 nm median particle sizes for CuCl2 center dot 2H(2)O and CuSO4 center dot 5H(2)O precursors, respectively. The CuCl2 center dot 2H(2)O derived nanoparticles showed more antibacterial activity than CuSO4 center dot 5H(2)O derived nanoparticles. The minimum inhibitory concentration (MIC) of the synthesized nanoparticles (derived from both precursors) against E. coli and S.aureus were 3.75 and 2.50 mg/ml, respectively, which are higher than those reported in the literature for CuO NPs synthesized by other methods. This difference may be originated from ultra-small size of the synthesized nanoparticles, high bandgap energy and Fe inclusion entering from milling media and their effect on oxidative stress-mediated cytotoxicity of CuO NPs. The higher MIC value reported in this work indicates that the synthesized NPs not only show good antibacterial activity, but also they yield lower cytotoxicity, which extends their applications in the biomedical field.