evidence: To date, numerous topical agents have been tested and although some have shown anti-biofilm activity (Chiu et al., 2008; Le et al., 2008; Alandejani et al., 2009; Jardeleza et al., 2011; Jervis-Bardy et al., 2012; Paramasivan et al., 2014; Richter et al., 2016, 2017a,b), none have been widely accepted as a treatment option in recalcitrant CRS. Recent evidence suggests that colloidal silver (CS) may be effective against bacterial biofilms. We have previously shown that CS showed significant anti-biofilm activity in vitro and in vivo against S. aureus (Goggin et al., 2014; Rajiv et al., 2015), and against methicillin-resistant S. aureus (MRSA) and P. aeruginosa biofilms. Spherical nanoparticles were also shown to be non-toxic in human cell culture (THP-1, Nuli-1) (Richter et al., 2017c) and safe in a sheep sinusitis model (Rajiv et al., 2015). Moreover, they were physically stable for over 6 months in storage with no observed loss in anti-biofilm activity (Richter et al., 2017c). [...] Richter, K., Facal, P., Thomas, N., Vandecandelaere, I., Ramezanpour, M., Cooksley, C., et al. (2017c). Taking the silver bullet colloidal silver particles for the topical treatment of biofilm-related infections. ACS Appl. Mater. Interfaces 9, 21631–21638. doi: 10.1021/acsami.7b03672