Sinonasal stent coated with slow‐release varnish of chlorhexidine has sustained protection against bacterial biofilm growth in the sinonasal cavity: An in vitro study

The aim of the study was to develop a sustained‐release varnish (SRV) containing chlor-hexidine (CHX) for sinonasal stents (SNS) to reduce bacterial growth and biofilm formation in the sinonasal cavity. Segments of SNS were coated with SRV‐CHX or SRV‐placebo and exposed daily to bacterial cultures of Staphylococcus aureus subsp. aureus ATCC 25923 or Pseudomonas aeruginosa ATCC HER‐1018 (PAO1). Anti‐bacterial effects were assessed by disc diffusion assay and plank-tonic‐based activity assay. Biofilm formation on the coated stents was visualized by confocal laser scanning microscopy (CLSM) and high‐resolution scanning electron microscopy (HR‐SEM). The metabolic activity of the biofilms was determined using the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphe-nyl‐2H‐tetrazolium bromide (MTT) method. Disc diffusion assay showed that SRV‐CHX‐coated SNS segments inhibited bacterial growth of S. aureus subsp. aureus ATCC 25923 for 26 days and P. aeruginosa ATCC HER‐1018 for 19 days. CHX was released from coated SNS segments in a pH 6 medium up to 30 days, resulting in growth inhibition of S. aureus subsp. aureus ATCC 25923 for 22 days and P. aeruginosa ATCC HER‐1018 for 24 days. The MTT assay showed a reduction of biofilm growth on the coated SNS by 69% for S. aureus subsp. aureus ATCC 25923 and 40% for P. aeruginosa ATCC HER‐1018 compared to the placebo stent after repeated exposure to planktonic growing bac-teria. CLSM and HR‐SEM showed a significant reduction of biofilm formation on the SRV‐CHX-coated SNS segments. Coating of SNS with SRV‐CHX maintains a sustained delivery of CHX, providing an inhibitory effect on the bacterial growth of S. aureus subsp. aureus ATCC 25923 and P. aeruginosa ATCC HER‐1018 for approximately 3 weeks.