The Antibiofilm efficacy of nitric oxide on soft contact lenses

BACKGROUND To investigate the antibiofilm efficacy of nitric oxide (NO) on soft contact lenses. METHODS Nitrite (NO precursor) release from various concentrations (0-1000 μM) of sodium nitrite (NaNO2, NO donor) was measured by Griess Assay. Cell viability assay was performed using human corneal epithelial cell under various concentration (0-1000 μM) of NaNO2. Biofilm formation on soft contact lenses was achieved by adding Staphylococcus aureus or Pseudomonas aeruginosa to the culture media. Various concentrations of NaNO2 (0-1000 μM) were added to the culture media, each containing soft contact lens. After incubation in NaNO2 containing culture media for 1, 3, or 7 days, each contact lens was transferred to a fresh, bacteria-free media without NaNO2. The bacteria in the biofilm were dispersed in the culture media for planktonic growth. After reculturing the lenses in the fresh media for 24 h, optical density (OD) of media was measured at 600 nm and colony forming unit (CFU) was counted by spreading media on tryptic soy agar plate for additional 18 h. RESULTS Nitrite release from NaNO2 showed dose-dependent suppressive effect on biofilm formation. Most nitrite release from NaNO2 tended to occur within 30 min. The viability of human corneal epithelial cells was well maintained at tested NaNO2 concentrations. The bacterial CFU and OD showed dose-dependent decrease in the NaNO2 treated samples on days 1, 3 and 7 for both Staphylococcus aureus and Pseudomonas aeruginosa. CONCLUSIONS NO successfully inhibited the biofilm formation by Staphylococcus aureus or Pseudomonas aeruginosa on soft contact lenses in dose-dependent manner.