Interrelationships between the structural, spectroscopic, and antibacterial properties of nanoscale (< 50 nm) cerium oxides

Bone healing is a complex process, and if not managed successfully, it can lead to non-union, metal-work failure, bacterial infections, physical and psychological patient impairment. Due to the growing urgency to minimise antibiotic dependency, alternative treatment strategies, including the use of nanoparticles, have attracted significant attention. In the present study, cerium oxide nanoparticles (Ce(4+), Ce(3+)) have been selected due to their unique antibacterial redox capability. We found the processing routes affected the agglomeration tendency, particle size distribution, antibacterial potential, and ratio of Ce(3+):Ce(4+) valence states of the cerium oxide nanoparticles. The antibacterial efficacy of the nanoparticles in the concentration range of 50–200 µg/ml is demonstrated against Escherichia coli, Staphylococcus epidermis, and Pseudomonas aeruginosa by determining the half-maximal inhibitory concentration (IC(50)). Cerium oxide nanoparticles containing a more significant amount of Ce(3+) ions, i.e., FRNP, exhibited 8.5 ± 1.2%, 10.5 ± 4.4%, and 13.8 ± 5.8% increased antibacterial efficacy compared with nanoparticles consisting mainly of Ce(4+) ions, i.e., nanoparticles calcined at 815 °C.