Green synthesis and morphology dependent antibacterial activity of copper oxide nanoparticles

Cupper oxide nanoparticle (CuO-NPs) has been widely utilized in biomedical application due to their antibacterial function. It is well known that antibacterial characteristics of ma-terials could be controlled using the size, shape and composition of the particles. The aim of this paper is to green synthesis CuO-NPs with various morphologies, using Aloe Vera extract as reducing agent and investigate the effect of particle size and shape on the anti-bacterial properties. Results demonstrated the formation of pure CuO-NPs with crystallite size in range of 9-23 nm, depending on the precursor type and concentration as well as aging time. Furthermore, increasing the concentration of copper precursor from 6 mM to 1M altered the morphology from rod shape to spherical. We also examined the inhibitory effects of CuO-NPs toward the gram-negative bacterium, Escherichia coli and a gram-positive bacterium, Staphylococcus aureus cultures throughout a 24 hr period. Based on our data, while CuO-NPs had significant growth inhabitation, this property depended on the morphology and size of particles. Rod shape CuO-NPs with smooth surface were the most effective morphology due to the largest surface area contacting and highest reactivity in contact with bacteria. Results also demonstrated that St aureus was more resistant to CuO-NPs samples because it was a Gram positive bacteria and Gram-negative ones like E. coli were more susceptible, while all particles were toxic to both organisms. Together, these results suggest that the difference between the surface free energy may be a cause for their morphology-dependent antimicrobial activity.