Background: Staphylococcus aureus  biofilms contribute significantly to the recalcitrant nature of chronic rhinosinusitis. In previous studies, it has been shown that silk fibroin–nano silver solution can eliminate S. aureus  biofilms in vitro, which suggests a potential role of this novel agent in the treatment of biofilm-associated diseases, such as sinusitis.
Objective: The aim of this study was to investigate the efficacy of silk fibroin–nano silver solution as a topical anti-biofilm agent in a rabbit model of sinusitis.
Methods: Biofilm-associated sinusitis models were established in 24 New Zealand White rabbits by gelatin sponge placement and S. aureus  inoculation through a hole drilled into the anterolateral wall of the right maxillary sinus. After 4 weeks, indwelling catheters were placed into the maxillary sinus. Different concentrations of silk fibroin–nano silver solution or normal saline were irrigated slowly into the maxillary sinus via the indwelling catheters. After 7 days of irrigation, the rabbits were sacrificed. The sinus mucosa was harvested and examined for biofilm biomass as well as morphological integrity of the epithelium by scanning electron microscopy.
Results: Silk fibroin–nano silver solution was found to be most effective in reducing the biomass of the S. aureus  biofilms at a concentration of 384 mg/L, followed by the concentration of 153.6 mg/L, when compared with saline. After treatment with 384 mg/L silk fibroin–nano silver solution, the biofilms were completely eliminated and the injured epithelium was almost restored with regenerated cilia on the surface.
Conclusion: Silk fibroin–nano silver solution was found to be an effective topical agent against S. aureus  biofilms in the rabbit model of sinusitis, and its effect was concentration-dependent.
Keywords: chronic rhinosinusitis, nasal irrigation, maxillary sinus, biomass, scanning electron microscopy, animal