| Summary: | The aim of the study was to develop a sustained-release varnish (SRV) containing chlorhexidine (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 <i>Staphylococcus aureus subsp. aureus</i> ATCC 25923 or <i>Pseudomonas aeruginosa</i> ATCC HER-1018 (PAO1). Anti-bacterial effects were assessed by disc diffusion assay and planktonic-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-diphenyl-2H-tetrazolium bromide (MTT) method. Disc diffusion assay showed that SRV-CHX-coated SNS segments inhibited bacterial growth of <i>S. aureus</i><i>subsp. aureus</i> ATCC 25923 for 26 days and <i>P. aeruginosa</i> 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 <i>S. aureus</i><i>subsp. aureus</i> ATCC 25923 for 22 days and <i>P. aeruginosa</i> ATCC HER-1018 for 24 days. The MTT assay showed a reduction of biofilm growth on the coated SNS by 69% for <i>S. aureus</i><i>subsp. aureus</i> ATCC 25923 and 40% for <i>P. aeruginosa</i> ATCC HER-1018 compared to the placebo stent after repeated exposure to planktonic growing bacteria. 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 <i>S. aureus</i><i>subsp. aureus</i> ATCC 25923 and <i>P. aeruginosa</i> ATCC HER-1018 for approximately 3 weeks.
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