Antibacterial activities of zinc oxide nanoparticles: a mini review

Highly reactive oxygen species (ROS) are released from the surface of zinc oxide nanoparticles (ZnO NP_s) which cause damage to the microorganisms. ROS may break down the cell wall and cell membrane of the bacteria leading to the leakage of cell contents causing their death. Antibacterial effect of ZnO NP_s synthesized from plants' extracts has been seen against several grampositive (Bacillus coagulans, Staphylococcus aureus, Bacillus subtilis) and gramnegative bacteria (Shigella dysenteriae, Sphingomonas paucimobilis, Salmonella typhimurium, Escherichia coli, Bacillus pumilus, Salmonella typhi). Zinc ions (Zn²⁺) freed from ZnO NP_s may attack DNA and proteins of the cell, thus hindering the growth of the bacteria. The negative charge on the surface of some bacteria (E. coli, S. typhi) interacts with positively charged particles in ZnO NP_s inhibiting the growth of these bacteria. The rate of antibiotic activity of ZnO NP_s depends on size, the concentration of ZnO NPs, and the type of surfactant used in the synthesis of these ZnO NP_s. Due to their antibiotic property, ZnO NP_s can be used as antibacterial coating of inner surfaces of refrigerators and dishwashers, plastic food containers, in the lining of food cans used for packaging and preservation of food to prevent their spoilage.