Direct Evidence for Hydroxyl Radical Scavenging Activity of Cerium Oxide Nanoparticles

Cerium oxide (CeO2) nanoparticles have been considered as excellent antioxidants and have become a focus of numerous studies. However, the mechanism behind the antioxidant role in the complex biological system has not been well-understood. In this work, direct evidence for the hydroxyl radical (•OH) scavenging activity of CeO2 nanoparticles was established by a simple photometric system in vitro. When methyl violet (MV) reacted with hydroxyl radical, the absorbance change indicated the hydroxyl radical level. The presence of CeO2 nanoparticles protected MV by competitively reacting with the •OH, so their hydroxyl radical scavenging activity was directly seen through the absorbance change. This activity was also proved to be size-dependent and was believed to have a close correlation with Ce3+ at the surface of the particles.