Antiviral efficacy of cerium oxide nanoparticles (preprint)

ABSTRACT

Nanomaterials have been proposed as good candidates for the elimination of viruses due to their multimodal mechanisms of action. Here, we tested the antiviral potential of cerium dioxide (CeO 2 ) nanoparticles which is largely unexplored.Two types of nano-CeO 2 particles with opposing surface charge, nano-CeO 2 (+) and nano-CeO 2 (-), 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 of nano-CeO 2 towards enveloped coronavirus SARS-CoV-2 and influenza virus A/WSN/1933 was registered already at 20 mg Ce/l. Significant decrease in PFU of other two enveloped viruses, transmissible gastroenteritis virus TGEV and bacteriophage φ6 was evidenced at 200 mg Ce/l. For all the enveloped viruses the maximum reduction of PFU after 1 h exposure to nano-CeO 2 exceeded 2 logs, that has been considered as the lowest biologically meaningful activity in antiviral applications. For most of the enveloped viruses, 1 h exposure to nano-CeO 2 resulted in ≥ 4 log reduction in PFU. As expected, the sensitivity of non-enveloped viruses towards nano-CeO 2 was significantly lower than that of enveloped viruses. Until the highest tested concentration, 2000 mg Ce/l neither of the nano-CeO 2 showed an effect on picornavirus EMCV and only nano-CeO 2 (-) caused a slight non-monotonic response in MS2 bacteriophage.Parallel testing of antiviral activity of Ce 3+ ions and SiO 2 nanoparticles allows to conclude that nano-CeO 2 activity was due to neither released Ce 3+ ions nor nonspecific effects of any nanosized particulate. Interestingly, we did not evidence any significant antiviral activity of Ag nanoparticles at 1 h exposure. This result referred to notably higher antiviral activity of nano-CeO 2 compared with nanosilver that has been generally considered as active against viruses. Although exhibiting antiviral effects, the antibacterial activity of nano-CeO 2 was very low. These results along with non-existent cytotoxicity nano-CeO 2 allow us to propose nano-CeO 2 for specific antiviral applications.