Rapid Inactivation of SARS-CoV-2 by Silicon Nitride, Copper, and Aluminum Nitride

Introduction: Viral disease spread by contaminated commonly touched surfaces is a global concern. Silicon nitride, an industrial ceramic that is also used as an implant in spine surgery, has known anti-bacterial activity. The mechanism of antibacterial action relates to the hydrolytic release of surface disinfectants. It is hypothesized that silicon nitride can also inactivate the coronavirus SARS-CoV-2. Methods: SARS-CoV-2 virions were exposed to 15 wt.% aqueous suspensions of silicon nitride, aluminum nitride, and copper particles. The virus was titrated by the TCD50 method using VeroE6/TMPRSS2 cells, while viral RNA was evaluated by real-time RT-PCR. Immunostain-ing and Raman spectroscopy were used as additional probes to investigate the cellular responses to virions exposed to the respective materials. Results: All three tested materials showed >99% viral inactivation at one and ten minutes of exposure. Degradation of viral RNA was also observed with all materials. Immunofluorescence testing showed that silicon nitride-treated virus failed to infect VeroE6/TMPRSS2 cells without damaging them. In contrast, the copper-treated virus suspension severely damaged the cells due to copper ion toxicity. Raman spectroscopy indicated differential biochemical cellular changes due to infection and metal toxicity for two of the three materials tested. Conclusions: Silicon nitride successfully inactivated the SARS-CoV-2 in this study. The mechanism of action was the hydrolysis-mediated surface release of nitrogen-containing disinfectants. Both aluminum nitride and copper were also effective in the inactivation of the virus. However, while the former compound affected the cells, the latter compound had a cytopathic effect. Further studies are needed to validate these findings and investigate whether silicon nitride can be incorporated into personal protective equipment and commonly touched surfaces, as a strategy to discourage viral persistence and disease spread.