Matrix-Mediated Delivery of Silver Nanoparticles for Prevention of Staphylococcus aureus and Pseudomonas aeruginosa Biofilm Formation in Chronic Rhinosinusitis

TL;DR

A silk-elastinlike protein (SELP-815K) thermoresponsive hydrogel with hyaluronic acid and silver nanoparticles was developed as an antibacterial dressing for chronic rhinosinusitis. In vitro, the formulation released silver over 3 days, killed planktonic S. aureus and P. aeruginosa, prevented biofilm formation, and remained cytocompatible at the selected 625 µg/mL AgNp dose.

Key findings

• SELP/HA/AgNps (625 µg/mL) showed sustained, non-burst Ag+ release in simulated nasal fluid: cumulative release at 6 h was 8.31 ± 1.10% and at 72 h was 18.29 ± 2.86%; SELP/AgNps released 11.58 ± 1.82% at 6 h and 26.16 ± 4.68% at 72 h.
• The hydrogel produced complete bactericidal effect against planktonic S. aureus and P. aeruginosa, comparable to ciprofloxacin; SELP/HA without AgNps did not reduce CFU/mL. MIC for both strains was 7.8 µg/mL, and the highest MBC was 125 µg/mL, guiding selection of 625 µg/mL (5× MBC) for formulation development.
• In the colony biofilm assay, SELP/HA/AgNps (625 µg/mL) significantly prevented biofilm formation for S. aureus (p < 0.0001) and P. aeruginosa (p < 0.0001), with SEM showing absence of biofilm and bacterial growth.
• Cytocompatibility: free AgNps at 625 and 1250 µg/mL reduced HNEpC viability to 7.36 ± 0.37% and 8.21 ± 0.45%, respectively; SELP/HA/AgNps at 625 µg/mL gave 77.89 ± 5.12% viability (p = 0.008), while 1250 µg/mL gave 59.76 ± 10.05% (p = 0.0215). Rheology showed SELP/HA/AgNps viscosity increased from 1.02 ± 0.86 Pa s at 4 °C to 1.31 ± 0.41 Pa s at 23 °C to 5.01 ± 0.87 Pa s at 34 °C, with gelation <60 s at 34 °C.

Methods

• In vitro formulation characterization: PVP-coated AgNps were characterized by UV-Vis, TEM (6.2 ± 1.4 nm diameter), DLS, and ICP/MS. MIC/MBC were determined by macro dilution against S. aureus ATCC 25923 and P. aeruginosa ATCC 27853. HA concentration was optimized using LPS-stimulated THP-1 macrophages and IL-6/IL-8 ELISA, selecting 2 mg/mL.
• Efficacy and compatibility assays: HNEpC cytocompatibility was measured by CCK-8; antibacterial effect by viable count assay; biofilm prevention by colony biofilm assay on polycarbonate membranes with CFU counts and SEM. Ag+ release was measured in simulated nasal fluid over 72 h by ICP/MS.
• Rheology and statistics: viscosity was measured from 4 °C to 34 °C, and storage/loss moduli were measured at 34 °C by oscillatory sweep. Statistical comparisons used one-way ANOVA with Tukey’s multiple comparison tests; p < 0.05 was significant. Biological replicates were N = 2 and technical replicates n = 3 unless otherwise noted.

Limitations

• Stated: bactericidal effects were tested against single bacterial species, not multi-bacterial or patient-derived resistant strains; biofilm disruption was not studied; release kinetics could be further optimized by altering SELP and HA concentrations; other non-antibiotic antibacterial agents were not included; HA’s wound-healing/mucosal-regeneration effects require in vivo study; and free HA release and its interactions with the hydrogel network and silver nanoparticles need detailed analysis.
• Evident from the text: all reported antibacterial, antibiofilm, cytocompatibility, release, and rheological data are in vitro only, with no in vivo or clinical efficacy/safety data. The release study covers only 72 h, so longer-term release and biofilm prevention are not established.