Antibacterial efficacy of zinc oxide nanoparticles synthesized by green and chemical methods

Background: Zinc oxide (ZnO) as an antimicrobial and non-toxic agent has been widely explored in comparison with other materials. The green manufacturing of mineral nanoparticles using plant extracts has outperformed other manufacturing methods due to many advantages. Methods: ZnO nanoparticles (ZnO NPs) were synthesized using two distinct methods: chemical synthesis and a green method involving lemon leaf extract. The synthesized ZnO was characterized using UV-Vis, X-ray diffraction (XRD), scanning electron microscope (SEM) , and Fourier transform infrared spectroscopy (FTIR) analyses. The antibacterial activity of the resulting ZnO NPs was evaluated against two gram-negative bacterial strains, Escherichia coli and Pseudomonas aeruginosa, and one gram-positive strain, Staphylococcus aureus, using the etching diffusion method. Results: In this study, ZnO NPs were synthesized using a green method from an inexpensive and readily available source, lemon leaf extract, and compared with those synthesized by a chemical method. The results showed that ZnO NPs obtained via the green synthesis method had a semi-spherical shape with an average size of 14.25 nm, which is smaller than the average size of chemically synthesized ZnO NPs at 34 nm. The effectiveness of the ZnO NPs varied depending on the bacterial strain tested. Grampositive bacteria were more sensitive than gram-negative bacteria. Conclusion: ZnO NPs produced from lemon leaf extract were most effective against S. aureus. Chemically synthesized ZnO NPs were more effective against gram-negative bacteria.