**3.1 Mechanisms of antimicrobial activity**

There are findings about the potential mechanisms of action, where it attempts to explain the bactericidal effect of metal oxide NPs [10, 24–27]. Some of these include the action of reactive oxygen species (ROS), the electrostatic interaction, accumulation, ions delivered and contact by itself of NPs, that induce a several effects from outside and into the bacteria, and that it will be described below (**Figure 1**).
