Antibacterial Properties of Wurtzite-hydrozincite Mixed-phase Phyto-synthesized ZnO Particles

Abstract

In this study, wurtzite-hydrozincite mixed-phase nanoparticles were prepared using a Mentha arvensis leaves extract as a stabilizing/reducing agent, followed by hydrothermal treatment at 180 °C. The resulting powder samples were characterized by X-ray diffraction (XRD) phase analysis and by Transmission Electron Microscopy (TEM). The existence of biphasic zinc oxide nanoparticles with hydrozincite and wurtzite crystallographic phases was proven. The particles sizes of biosynthesized oxide powders decreased upon the increase in the Mentha arvensis extract concentration. The antibacterial properties of the nanoparticles were investigated under dynamic contact conditions and the resazurin microplate method, using test strains with diverse structural and biochemical features. The effect of mixed-phase ZnO nanoparticles on the animal pathogens Erysipelothrix rhusiopathiae and Aeromonas caviae is studied for the first time. It was established, that the three powders exert significant antibacterial activity, which is higher against Gram-negative test microorganisms, whereupon the sample with the smallest particle sizes (G-Z3) exhibits the most effective inhibition. It could be supposed that the combination of factors: the presence of two phases, reactive oxygen species formation; small particles sizes and surface defects have beneficial effect on enhancement of their antibacterial properties.