Antiviral efficacy of cerium oxide nanoparticles

Nanomaterials are prospective candidates for the elimination of viruses due to their multimodal mechanisms of action. Here, we tested the antiviral potential of a largely unexplored nanoparticle of cerium dioxide (CeO₂). Two nano-CeO₂ with opposing surface charge, (+) and (-), were assessed for their capability to decrease the plaque forming units (PFU) of four enveloped and two non-enveloped viruses during 1-h exposure. Statistically significant antiviral activity towards enveloped coronavirus SARS-CoV-2 and influenza virus was registered already at 20 mg Ce/l. For other two enveloped viruses, transmissible gastroenteritis virus and bacteriophage φ6, antiviral activity was evidenced at 200 mg Ce/l. As expected, the sensitivity of non-enveloped viruses towards nano-CeO₂ was significantly lower. EMCV picornavirus showed no decrease in PFU until the highest tested concentration, 2000 mg Ce/l and MS2 bacteriophage showed slight non-monotonic response to high concentrations of nano-CeO₂(-). Parallel testing of antiviral activity of Ce³⁺ ions and SiO₂ nanoparticles allows to conclude that nano-CeO₂ activity was neither due to released Ce-ions nor nonspecific effects of nanoparticulates. Moreover, we evidenced higher antiviral efficacy of nano-CeO₂ compared with Ag nanoparticles. This result along with low antibacterial activity and non-existent cytotoxicity of nano-CeO₂ allow us to propose CeO₂ nanoparticles for specific antiviral applications.