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

Abstract

IntroductionViral 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 antibacterial 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. Immunostaining and Raman spectroscopy were used as additional probes to investigate the cellular responses to virions exposed to the respective materials. ResultsAll 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. ConclusionsSilicon 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.

Silicon Nitride Inactivates SARS-CoV-2in vitro

“…The remarkable finding in the present study is that a one-minute exposure to a 5% solution of Si3N4 resulted in 85% inactivation of SARS-CoV-2, while Vero cell viability was minimally impacted even after a 48 hour exposure to a 20% concentration of the same material. This finding is consistent with previous work showing that Si3N4 exerts a fortuitous dual effect, whereby the material can inactivate viruses 12,26 and inhibit bacterial biofilm formation 29 without negatively impacting mammalian cell viability. The present study is also consistent with a recent investigation that showed the rapid inactivation of SARS-CoV-2 upon exposure to 15% (w/v) Si3N4, 12 and related data showing that the antiviral effect of Si3N4 may be generally applicable to other single-strand RNA viruses such as Influenza A, Feline calicivirus, and Enterovirus.…”

“…This finding is consistent with previous work showing that Si3N4 exerts a fortuitous dual effect, whereby the material can inactivate viruses 12,26 and inhibit bacterial biofilm formation 29 without negatively impacting mammalian cell viability. The present study is also consistent with a recent investigation that showed the rapid inactivation of SARS-CoV-2 upon exposure to 15% (w/v) Si3N4, 12 and related data showing that the antiviral effect of Si3N4 may be generally applicable to other single-strand RNA viruses such as Influenza A, Feline calicivirus, and Enterovirus. 26 Taken together, these studies suggest that Si3N4 may be a suitable material platform for the development of fabrics for personal protective equipment such as masks, and also to manufacture commonly-touched surfaces where viral persistence may encourage the spread of disease.…”

“…The antiviral effect of Si3N4 is related to several probable mechanisms that have been hypothesized previously. 12 One mechanism is the viral RNA fragmentation by reactive nitrogen species derived from a slow and controlled elution of ammonia from the surface of Si3N4; and the subsequent formation of ammonium, with the release of free electrons and negatively charged silanols in aqueous solution. Also, as reported previously, the similarity between the protonated amino groups, Si-NH3 + at the surface of Si3N4 and the N-terminal of lysine, C-NH3 + on the virus triggers a competitive binding that leads to SARS-CoV-2 inactivation.…”

“…Unlike Si3N4, Cu exhibited toxicity to mammalian cells. 12 The present study hypothesized that exposure to Si3N4 would not elicit a toxic response from mammalian cells under experimental conditions while demonstrating a time-and dose-dependent inactivation of SARS-CoV-2.…”

“…Some materials, notably metals such as copper (Cu), zinc (Zn), iron (Fe), and silver (Ag) have also been shown to rapidly inactivate viruses, including SARS-CoV-2. 7,12,13 Incorporation of Cu alloy surfaces in health care facilities reduces the microbial burden and the incidence of nosocomial infections. [14][15][16] Quaternary ammonium compounds such as ammonium chloride are also capable of inactivating viruses by deactivating the protective lipid coating that envelopes viruses like SARS-CoV-2 rely on; these compounds are used as disinfectants to clean surfaces and remove persistent viral particles.…”