Cerium Oxide Nanoparticles and Their Efficient Antibacterial Application In Vitro against Gram-Positive and Gram-Negative Pathogens

Abstract

In this study, the antibacterial activity of cerium oxide nanoparticles on two Gram-negative and three Gram-positive foodborne pathogens was investigated. CeO₂ nanoparticles (CeO₂ nps) were synthesized by a Wet Chemical Synthesis route, using the precipitation method and the Simultaneous Addition of reactants (<i>WCS-SimAdd</i>). The as-obtained precursor powders were investigated by thermal analysis (TG-DTA), to study their decomposition process and to understand the CeO₂ nps formation. The composition, structure, and morphology of the thermally treated sample were investigated by FTIR, Raman spectroscopy, X-ray diffraction, TEM, and DLS. The cubic structure and average particle size ranging between 5 and 15 nm were evidenced. Optical absorption measurements (UV-Vis) reveal that the band gap of CeO₂ is 2.61 eV, which is smaller than the band gap of bulk ceria. The antioxidant effect of CeO₂ nps was determined, and the antibacterial test was carried out both in liquid and on solid growth media against five pathogenic microorganisms, namely <i>Escherichia coli</i>, <i>Salmonella typhimurium</i>, <i>Listeria monocytogenes</i>, <i>Staphylococcus aureus</i>, and <i>Bacillus cereus</i>. Cerium oxide nanoparticles showed growth inhibition toward all five pathogens tested with notable results. This paper highlights the perspectives for the synthesis of CeO₂ nps with controlled structural and morphological characteristics and enhanced antibacterial properties, using a versatile and low-cost chemical solution method.