Silicon nitride (Si₃N₄) is a promising biomaterial, currently used in spinal fusion implants. Such implants should result in high vertebral union rates without major complications. However, pseudarthrosis remains an important complication that could lead to a need for implant replacement. Making silicon nitride implants more bioactive could lead to higher fusion rates, and reduce the incidence of pseudarthrosis. In this study, it was hypothesized that creating a highly negatively charged Si₃N₄ surface would enhance its bioactivity without affecting the antibacterial nature of the material. To this end, samples were thermally, chemically, and thermochemically treated. Apatite formation was examined for a 21-day immersion period as an in-vitro estimate of bioactivity. Staphylococcus aureus bacteria were inoculated on the surface of the samples, and their viability was investigated. It was found that the thermochemically and chemically treated samples exhibited enhanced bioactivity, as demonstrated by the increased spontaneous formation of apatite on their surface. All modified samples showed a reduction in the bacterial population; however, no statistically significant differences were noticed between groups. This study successfully demonstrated a simple method to improve the in vitro bioactivity of Si₃N₄ implants while maintaining the bacteriostatic properties.

Preventing pathogen transmission and treating pathogen-associated diseases remain major public-health challenges. Recent epidemics and pandemics, key amongst them being the pandemic caused by the coronavirus disease (COVID-19), have highlighted the devastating effects that viral infections can have on society. Uncovering and utilising materials for the protection from and treatment of virus-induced diseases can considerably alleviate the load imposed on healthcare systems worldwide. Silicon nitride is a biocompatible ceramic material used in orthopedic implants that is effective in the inactivation of single-stranded RNA viruses. However, the effect of the material on the more resilient DNA viruses remains unknown. This study aimed to investigate the antiviral behaviour of the material, in powder and bulk form, against DNA viruses, and more specifically the human adenovirus. The results of the study indicated that silicon nitride dramatically reduces adenoviral infectivity in powder ($>$98% reduction in infective virus compared to the untreated control) and bulk form ($>$73% reduction in infective virus compared to the untreated control). In both cases, inactivation was achieved rapidly, in one minute for powders and 10 minutes for bulk surfaces. The findings of this study strengthen the potential of silicon nitride to be used as an antiviral agent, aiding the fight against the spread of both DNA and RNA virus diseases.