**3.4 Zinc and copper**

ZnO appears to restrain the growth of strongly resistant bacteria. There are some reports about the significant antibacterial activity of ZnO, which is credited to the production of reactive oxygen species [ROS], causing the production of oxide substances.

Since olden times, Copper has been used for manufacturing utensils as it is a powerful natural biocidal metal. When bacteria encounter copper, there will be cell wall deformation which causes the death of bacteria. To deal with bacteria, many researchers have developed a method where a polymeric matrix was supported with copper by electro-spinning [24]. Ahire and his research team used electrospinning of Poly-D and PEO, L-lactide method to combine Cu nanoparticles into nanofibers. Due to the presence of copper nanofibers, *S. aureus* and *P. aeruginosa* were reduced by 50% and 40%, respectively after two days [25].
