Enhanced antibacterial actiwity of nanocrystalline ZnO due to increased ROS-mediated cell injury

An innovative study; aimed at understanding the influence of the particle size of ZnO (from the microscaie down to the nanoscale) on its antibacterial effect is reported herein. The antibacterial activity of ZnO has been found Us be due to a reaction of the ZnO surface with water. Electron-spin resonance measurements reveal that aqueous suspension of small nanoparticles of ZnO produce increased levels of reactive oxygen species, namely hydroxyl radicals. Interestingly, a remarkable enhancement of the oxidative stress, beyond the level yielded by the ZnO itself, is detected following the antibacterial treatment. Likewise, an exposure of bacteria to the small ZnO nanoparticles results in an increased cellular internalization of the nanopartit:les and bacterial cell damage. An examination of the antibacterial effect is performed on two bacterial species: Escherichia coii (Cram negative) and Staphytococcus: auraus (Gram positive). The nanocrystaMine particles of ZnO are synthesized using ultrasonic irradiation, and the particle sizes are controlled using different solvents during the sonication process. Taken as a whole, it is apparent that the unique properties (i.e., small size and corresponding large specific surface area) of small n;tnometer-scale ZnO particles impose several effects that govern its antibacterial action. These effects are size deperident and do not exist in the range of rnicroscale particles,