Silicon Nitride Inactivates SARS-CoV-2in vitro

ABSTRACT Introduction Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, remains viable and therefore potentially infectious on several materials. One strategy to discourage the fomite-mediated spread of COVID-19 is the development of materials whose surface chemistry can spontaneously inactivate SARS-CoV-2. Silicon nitride (Si 3 N 4 ), a material used in spine fusion surgery, is one such candidate because it has been shown to inactivate several bacterial species and viral strains. This study hypothesized that contact with Si 3 N 4 would inactivate SARS-CoV-2, while mammalian cells would remain unaffected. Materials SARS-CoV-2 virions (2×10 4 PFU/mL diluted in growth media) were exposed to 5, 10, 15, and 20% (w/v) of an aqueous suspension of sintered Si 3 N 4 particles for durations of 1, 5, and 10 minutes, respectively. Before exposure to the virus, cytotoxicity testing of Si 3 N 4 alone was assessed in Vero cells at 24 and 48 hour post-exposure times. Following each exposure to Si 3 N 4 , the remaining infectious virus was quantitated by plaque assay. Results Vero cell viability increased at 5% and 10% (w/v) concentrations of Si 3 N 4 at exposure times up to 10 minutes, and there was only minimal impact on cell health and viability up to 20% (w/v). However, the SARS-CoV-2 titers were markedly reduced when exposed to all concentrations of Si 3 N 4 ; the reduction in viral titers was between 85% - 99.6%, depending on the dose and duration of exposure. Conclusions Si 3 N 4 was non-toxic to the Vero cells while showing strong antiviral activity against SARS-CoV-2. The viricidal effect increased with increasing concentrations of Si 3 N 4 and longer duration of exposure. Surface treatment strategies based on Si 3 N 4 may offer novel methods to discourage SARS-CoV-2 persistence and infectivity on surfaces and discourage the spread of COVID-19.