Size-Dependent Effect of Nanoceria on Their Antibacterial Activity Towards Escherichia coli

Cerium oxide nanoparticles (CeO₂ or nanoceria) have found numerous applications in the biomedical industries due to their unique properties. In this study, we employed hydrothermal approach to synthesize four different types of nanoceria of defined size and tested their antibacterial properties. Characterization of these nanoceria was performed using X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Our XRD and Raman studies revealed that these nanoceria were composed of fluorite-structured ceria crystallites with average diameters from 3.5 nm to 6.5 nm. The antibacterial activities of these four different sized nanoceria were tested against gram negative Escherichia coli (E. coli) strain HB101 K-12 by measuring their optical density as a function of time. The results showed that all four sizes of nanoceria significantly inhibited the growth of E. coli when compared with controls. The rates of bacterial growth inhibition were found to depend on the average sizes and concentration of these novel nanoceria and indicate that these nanoceria exhibit antibiotic properties that could be potentially useful for medical applications.