UV-activated green-synthesized ZnO NPs from Camellia sinensis extract: a potent antimicrobial strategy

This study provides valuable insights into the structural and chemical characteristics of zinc oxide nanoparticles (ZnO NPs), enhancing their antimicrobial efficacy against Gram-positive bacteria and fungi. Structural and optical analyses of ZnO NPs synthesized via a green route revealed a floral morphology at 450 °C with petal sizes averaging ~ 20.56 nm. Size and strain characteristics were extensively investigated using mathematical techniques such as the Scherrer and Williamson–Hall methods. The influence of key parameters, including nanoparticle concentration and UV exposure, on the antimicrobial efficacy of UV-irradiated ZnO nanoparticles was examined. Biochemical assays suggest that the synthesized ZnO nanoparticles hold potential as novel antimicrobial agents for effectively controlling microbial infections. Notably, oxidative stress markers showed a significant increase in protein carbonyl formation in Staphylococcus aureus (31,237 nmol/mg) and Candida albicans (29,109 nmol/mg). Additionally, the time-dependent antimicrobial effect revealed reduction in microbial growth over specified periods, indicating prolonged antimicrobial activity. The molecular-level study demonstrates that the antimicrobial activity of ZnO NPs, particularly upon UV activation, is mediated through the production of ROS, leading to oxidative stress, protein damage, enzymatic activity disruption, and membrane integrity compromise, ultimately resulting in microbial cell death.