Context: Zinc oxide nanoparticles (ZnO Nps) have potential application in piezoelectric nanogenerator and in biotechnology.
Objective: The antibacterial activity of ZnO Nps on Klebsiella pneumoniae (ATCC 70068) and mode of action of ZnO Nps was investigated.
Methods: ZnO Nps was synthesized by a precipitation method and characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. In vitro susceptibility of K. pnumoniae of the ZnO Nps was detected using the disk diffusion method, and the minimum inhibitory concentration (MIC) value was determined using the serial dilution method. The chemical and physical interaction between the cell envelope of K. pneumonia and ZnO Nps was investigated. The effect of ZnO Nps on the cytotoxic activities of K. pneumonia was investigated using a HEp-2 cell line.
Results: The MIC of ZnO Nps was found in 40 µg/ml. The standard growth curve showed that ZnO Nps of 0.75 mM inhibited K. pneumoniae after 4 h. The interaction with outer membrane protein (OMP) and lipoploysacharride (LPS) residues showed modulation in ∼66 kDa and ∼29 kDa proteins with the use of increasing concentrations of ZnO Nps. The amount of nucleic acid and protein released from the cells increased with the ZnO Nps concentration used. Importantly, the OD of the ZnO Nps-treated cells decreased within 30 min of incubation in the presence of SDS. ZnO Nps-treated K. pneumoniae were five-fold less infectious in the HEp-2 cell line at doses between 0.50 and 0.75 mM.
Discussion: These results suggest the potential antibacterial use of ZnO Nps against K. pneumoniae infections.
Keywords: Agar diffusion assay; HEp-2 cells; growth curve; lipoploysaccharride; metal oxide nanoparticle; minimum inhibitory concentration; outer membrane protein.